ESS Subtopic 2.2: Energy and Biomass

subtopic 2.2: Energy and biomass in ecosystems

Subtopic 2.2 focuses on the interactions among organisms and their environment, examining principles like food webs, trophic levels, and energy flow within ecosystems. This subtopic explores how ecological interactions shape the distribution and abundance of organisms, underlining the importance of biodiversity and the dynamics of populations and communities within ecosystems. T

he study of ecology in this context helps understand the scientific principles governing natural systems, providing a foundation for analyzing environmental issues and human impacts on these systems.

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This unit will take a minimum of 6 hours

Guiding Questions

How can flows of energy and matter through ecosystems be modelled?
How do human actions affect the flow energy and matter, and what is the impact on ecosystems?
What strategies can be employed to mitigate human impacts on the natural cycles of energy and matter in ecosystems?
How do changes in land use affect the biogeochemical cycles and what are the implications for ecosystem health and sustainability?

Understanding

Ecosystem Productivity and Energy Flow

2.2.1 Ecosystems are sustained by supplies of energy and matter.

List three components that make up an ecosystem
Outline the process of energy flow in an ecosystem.
Describe how matter is recycled within an ecosystem.
Explain why ecosystems are considered open systems

An ecosystem is a complex and interconnected system that includes all living organisms and their physical environment within a defined geographic area. The sustainability of ecosystems hinges on the continuous supply and exchange of energy and matter. To grasp how ecosystems function and thrive, it's essential to understand the dynamics of energy and matter flow within these systems.

https://www.e-education.psu.edu/geog3/node/1211

The Open System Nature of Ecosystems

Ecosystems operate as open systems, meaning they constantly exchange energy and matter with their surroundings. This exchange is crucial for maintaining the balance and health of the ecosystem. The concept of open systems in ecosystems is fundamental (section 1.2.2), as it explains how ecosystems remain dynamic and adaptable to changes in their environment.

https://www.bartleby.com/

Energy Flow in Ecosystems

Energy enters ecosystems primarily from sunlight, captured by producers like plants and algae through photosynthesis.
Producers convert solar energy into organic compounds, serving as food for various consumers including herbivores, carnivores, and decomposers.
Energy flows through the food chain, undergoing transformations but is never destroyed, following the law of conservation of energy.
Energy exits ecosystems in various forms, including heat during metabolic processes and through decomposition of dead organisms.
The continuous flow and transformation of energy are essential for sustaining life within ecosystems.

https://bioprinciples.biosci.gatech.edu/ecosystems-2/

Matter Cycling in Ecosystems

Unlike energy, matter is recycled within ecosystems.
Elements such as carbon, nitrogen, and phosphorus circulate through biogeochemical cycles, ensuring their availability to all organisms.
Carbon, for example, is taken up by plants during photosynthesis and converted into organic matter.
Herbivores consume this organic matter, passing it along the food chain.
Eventually, decomposers break down the organic matter, releasing carbon back into the atmosphere or soil for reuse by producers.

The Balance of Energy and Matter

For an ecosystem to remain stable and productive, the balance of energy and matter is crucial. Any disruption in the supply or flow of energy and matter can lead to ecological imbalances, affecting the health and survival of organisms within the ecosystem. Human activities, such as deforestation, pollution, and climate change, can significantly alter these natural flows, posing challenges to ecosystem sustainability.

2.2.2 The first law of thermodynamics states that as energy flows through ecosystems, it can be
transformed from one form to another but cannot be created or destroyed.

Outline the first law of thermodynamics
Explain how the first law of thermodynamics apply to a food chain and an energy production system. Use a systems diagram to aid in your explanation.

http://www.bradjbrennan.ca/13-energy-balanceequilibria.html

The first law of thermodynamics, also known as the law of conservation of energy, is a fundamental principle in understanding energy flow within ecosystems. This law states that energy can be transformed from one form to another but cannot be created or destroyed. In the context of ecosystems, this means that as energy moves through the various components of an ecosystem, it undergoes transformations but the total amount of energy remains constant.

Energy Transformations in Ecosystems

The majority of energy within ecosystems originates from the Sun.
Photosynthetic organisms capture solar energy and convert it into chemical energy through photosynthesis.
This chemical energy flows through food webs as organisms consume each other.
Energy is transformed and transferred at each trophic level, but some is inevitably lost as heat due to metabolic processes.
A systems approach is crucial for understanding energy flow in ecosystems, allowing us to visualize how energy moves from sunlight to its eventual exit as heat.
This approach emphasizes the interconnectedness of ecosystem components and the efficiency of energy transfer between trophic levels.

The Systems Approach to Energy Flow

A systems approach, outlined in section 1.2.2, is essential for visualizing and understanding energy flow in ecosystems.
By modeling ecosystems as open systems, we can track the path of energy from its entry point as sunlight to its eventual exit as heat.
This approach highlights the interconnectedness of ecosystem components and the efficiency of energy transfer between trophic levels.

For example, consider a simple food chain: sunlight is captured by plants (producers), which are eaten by herbivores (primary consumers). Herbivores are then consumed by carnivores (secondary consumers). At each stage, energy is transferred and transformed. While energy remains conserved according to the first law of thermodynamics, the usable energy decreases with each transfer due to heat loss.

Importance of the First Law of Thermodynamics in Ecosystems

Ecosystems rely on a constant input of solar energy to sustain life processes.
Without solar energy, the energy transformations supporting life would cease, leading to ecosystem breakdown.
The principle of conservation of energy dictates that energy cannot be created or destroyed but only transformed from one form to another.
Solar energy absorbed by plants is converted into stored chemical energy, which fuels ecosystem functioning.

2.2.3 Photosynthesis and cellular respiration transform energy and matter in ecosystems.

Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.

https://www.sciencefacts.net/photosynthesis-and-cellular-respiration.html

In ecosystems, the transformation of energy and matter is essential for sustaining life. Two critical processes that facilitate these transformations are photosynthesis and cellular respiration. These processes not only convert energy from one form to another but also transform matter through chemical reactions

Photosynthesis

the process by which photosynthetic organisms, such as plants, algae, and some bacteria, convert light energy from the Sun into chemical energy.
the transformation occurs in the chloroplasts of cells, where light energy is captured by chlorophyll and used to synthesize glucose from carbon dioxide and water. The word equation for photosynthesis is:

Carbon dioxide + Water + Light energy → Glucose + Oxygen

inputs:
- sunlight as energy resource, carbon dioxide and water
processes:
- chlorophyll traps sunlight; energy is used to split water molecules; hydrogen from water is combined with carbon dioxide to produce glucose.
outputs:
- glucose used as an energy source for the plant and as a building block for other organic molecules; oxygen is released to the atmosphere through stomata.
transformations:
- light energy is transformed to store chemical energy.

Cellular Respiration

the process by which organisms break down glucose to release the stored chemical energy for cellular activities. This process occurs in the mitochondria of cells and can be summarized by the following word equation:

Glucose + Oxygen → Carbon dioxide + Water + Energy

inputs:
- glucose and oxygen
processes:
- oxidation processes inside cells
outputs:
- release of energy for work and heat
transformations:
- stored chemical energy to kinetic energy and heat

Cellular respiration is essential for providing the energy required for growth, repair, and maintenance of cells. It is the complementary process to photosynthesis, ensuring a continuous flow of energy and recycling of matter within ecosystems.

The Interconnected Cycle of Photosynthesis and Cellular Respiration
Photosynthesis and cellular respiration are interconnected in the cycle of energy and matter within ecosystems. The oxygen produced during photosynthesis is used by organisms in cellular respiration, while the carbon dioxide produced during cellular respiration is used by photosynthetic organisms in photosynthesis. This cyclical relationship ensures the balance and flow of energy and matter in ecosystems.

During photosynthesis, energy from sunlight is stored in glucose molecules, and matter is assembled into organic compounds.
During cellular respiration, the energy stored in glucose is released for use by cells, and matter is broken down and recycled.

Application of skills: Create system diagrams from a set of data of ecosystems showing transfers and
transformations of energy and matter.

2.2.4 Photosynthesis is the conversion of light energy to chemical energy in the form of glucose,
some of which can be stored as biomass by autotrophs.

Define photosynthesis.
List the main products of the photosynthesis process.
Outline the role of chlorophyll in photosynthesis.
Describe how glucose produced in photosynthesis is used by autotrophs.
Explain the importance of photosynthesis in the flow of energy within an ecosystem.
Define the term "autotroph" and give two examples.

Basic inputs and outputs of the photosynthesis process. (Olha Pohorielova/iStock/Getty)

Photosynthesis is a fundamental process that supports life on Earth by transforming light energy from the Sun into chemical energy in the form of glucose. This process is carried out by autotrophs, such as plants, algae, and certain bacteria, which can produce their own energy through photosynthesis. Understanding the basics of photosynthesis is essential for grasping how energy flows through ecosystems and how biomass is formed.

Autotrophs, also known as primary producers, are the foundation of most ecosystems. By converting light energy into chemical energy through photosynthesis, they produce the organic matter that forms the base of the food web. This organic matter is consumed by herbivores and then passed along to higher trophic levels, such as carnivores and omnivores.

The Basics of Photosynthesis
Photosynthesis occurs in the chloroplasts of plant cells, where chlorophyll, the green pigment, captures light energy. This light energy is used to convert carbon dioxide from the air and water from the soil into glucose, a type of sugar that serves as a primary energy source for the plant. The word equation for photosynthesis is:

Carbon dioxide + Water + Light energy → Glucose + Oxygen

In this process:

Light energy from the Sun is converted into chemical energy stored in glucose.
Carbon dioxide and water are the raw materials that are transformed into glucose and oxygen.

Glucose and Biomass
The glucose produced during photosynthesis serves several important functions:

Immediate energy: It provides energy for the plant's cellular activities.
Storage: Some of the glucose is stored as starch, a complex carbohydrate that can be used later when the plant needs energy.
Biomass: Glucose can be converted into other carbon compounds, such as cellulose, proteins, and lipids, which are essential components of the plant's biomass. Biomass refers to the total mass of living matter within a given area, and it represents the stored energy and nutrients that can be passed through the food web.

Importance of Photosynthesis in Ecosystems

Energy Flow: It is the primary means by which solar energy enters the ecosystem, fueling all life processes.
Oxygen Production: It generates oxygen as a byproduct, which is essential for the respiration of most living organisms.
Carbon Cycle: It plays a key role in the carbon cycle, helping to regulate atmospheric carbon dioxide levels.

Energy Transfer and Efficiency

2.2.5 Producers form the first trophic level in a food chain.

Define the term "producer" in the context of an ecosystem.
List three types of producers found in ecosystems.
Outline the process of photosynthesis in producers.
Describe the role of producers in a food chain.
Explain why producers are essential for the sustainability of ecosystems.
Define the term "trophic level" and identify the trophic level at which producers are found.

Producers, also known as autotrophs, form the first trophic level in a food chain. These organisms are vital for the sustainability of ecosystems as they are the primary source of energy and organic matter for all other living organisms. Producers are typically plants, algae, and photosynthetic bacteria that create their own food through the process of photosynthesis.

Producers serve as the starting point for energy and nutrient flow in ecosystems.
Producers capture and store energy, which is then passed on to herbivores (primary consumers) as they consume the producers.
Energy continues to flow through the food chain as herbivores are consumed by carnivores (secondary and tertiary consumers).
Producers have the unique ability to convert light energy from the Sun into chemical energy via photosynthesis.
Photosynthesis involves using sunlight, carbon dioxide, and water to produce glucose and oxygen.
The chemical energy stored in glucose fuels producers' growth, reproduction, and life processes, serving as the foundation of the entire food web.

https://www.sciencefacts.net/autotrophs-primary-producer.html

Types of Producers

Plants: Terrestrial plants, ranging from grasses to large trees, are primary producers on land. They capture sunlight through their leaves and convert it into energy through photosynthesis.
Algae: Found primarily in aquatic environments, algae are crucial producers in both freshwater and marine ecosystems. They perform photosynthesis and provide food and oxygen for aquatic life.
Photosynthetic Bacteria: Certain bacteria, such as cyanobacteria, can also perform photosynthesis. These microorganisms are significant in some ecosystems, particularly in nutrient-poor environments where they contribute to primary production.

Importance of Producers

Energy Source: Producers are the primary source of energy for all other trophic levels. Without them, there would be no energy available for herbivores, carnivores, or decomposers.
Oxygen Production: Through photosynthesis, producers release oxygen into the atmosphere, which is essential for the respiration of most living organisms.
Carbon Dioxide Removal: Producers absorb carbon dioxide from the atmosphere for photosynthesis, helping to regulate atmospheric CO2 levels and mitigate climate change.
Foundation of Food Webs: Producers form the base of food webs, supporting a diverse array of life forms and contributing to the overall stability and biodiversity of ecosystems.
Regulating the Hydrological Cycle: through absorbing and releasing water into the atmosphere through transpiration
Habitats: creating diverse habitats for animal species while their roots secure the soil, preventing erosion.

https://www.scithrill.com/10-examples-of-producers-in-food-chain/

2.2.6 Cellular respiration releases energy from glucose by converting it into a chemical form that can easily be used in carrying out active processes within living cells.

Define cellular respiration.
List the main products of cellular respiration.
Outline the basic steps involved in cellular respiration.
Describe the role of glucose in cellular respiration.
Explain how cellular respiration contributes to energy release in living cells.
Define the term "aerobic organism" and explain its relevance to cellular respiration.

https://www.scithrill.com/10-examples-of-producers-in-food-chain/

The Basics of Cellular Respiration
Cellular respiration is the process by which glucose, a simple sugar produced during photosynthesis, is broken down to release energy. This process occurs in the mitochondria of cells, where the chemical bonds in glucose are broken, and the energy is extracted. The word equation for photosynthesis is:

Oxygen + Glucose → Energy+ Carbon Dioxide+Water

In this process:

Glucose is oxidized, meaning it loses electrons, and its chemical energy is released.
Oxygen is used to help break down the glucose, resulting in the production of carbon dioxide and water.
Energy is released and converted into a form that cells can use for various functions.
Heat is produced as a by-product. Heat generated within an individual organism cannot be transformed back into chemical energy and is ultimately lost from the organism

Transformation of Energy

Muscle contraction: Providing the energy needed for muscles to contract and move.
Cell division: Supplying energy for the complex process of cell replication and growth.
Active transport: Enabling the movement of molecules across cell membranes against their concentration gradient.
Biosynthesis: Fueling the synthesis of essential molecules like proteins and nucleic acids.

While the detailed biochemical mechanisms of cellular respiration involve specific molecules and reactions, it is sufficient to understand that this process efficiently converts the energy stored in glucose into a usable form.

The Importance of Cellular Respiration

Cellular respiration is essential for the survival of all aerobic organisms.
It provides cells with a continuous supply of energy to perform essential functions.
Without cellular respiration, cells would be unable to sustain life processes.
This would result in organisms being unable to grow, reproduce, or respond to their environment.

Connection with Photosynthesis
Cellular respiration is closely linked to photosynthesis, forming a cycle of energy transformation in ecosystems. Photosynthesis captures light energy and stores it in glucose molecules, while cellular respiration releases that energy to be used by cells. This cyclical relationship ensures a constant flow of energy through the ecosystem, supporting the life processes of producers, consumers, and decomposers.

2.2.7 Some of the chemical energy released during cellular respiration is transformed into heat.

List the main byproducts of cellular respiration.
Outline the reasons why heat is generated during cellular respiration.
Describe how heat produced during cellular respiration is used in warm-blooded animals.
Explain why cellular respiration is not 100% efficient in transferring energy from glucose.
Define the term "exergonic reaction" and explain its relevance to cellular respiration.

Cellular respiration is a vital process that allows organisms to release energy from substrates like carbohydrates. However, this process is not entirely efficient in transferring energy into a usable chemical form, resulting in the generation of heat. Understanding how heat is produced during cellular respiration and its implications for organisms is crucial for comprehending energy dynamics in living systems.

Inefficiency and Heat Production
During cellular respiration, glucose is broken down to release energy. This energy is primarily converted into a chemical form that cells can use for various activities. However, the process is not 100% efficient. Some of the energy released during the breakdown of glucose is transformed into heat.

In this process:

Chemical energy stored in glucose is released and used for cellular activities.
Heat is produced as a byproduct due to the inefficiencies in energy transfer.

Why Heat is Generated
The generation of heat during cellular respiration occurs because:

Energy Conversion: Not all the energy from glucose can be captured and stored in a chemical form (such as ATP). Some energy is inevitably lost as heat.
Metabolic Reactions: The biochemical reactions involved in cellular respiration are exergonic, meaning they release energy. Part of this released energy is in the form of heat.

Heat as a Non-Recoverable Energy Form
One important aspect of the heat generated during cellular respiration is that it cannot be transformed back into chemical energy. Once energy is lost as heat, it dissipates into the environment and is no longer available for biological work. This is a key principle in thermodynamics, highlighting the inefficiency of energy transformations and the ultimate loss of usable energy as heat.

Energy Flow: The energy flow through an ecosystem involves a continuous input (primarily from the Sun) and a gradual loss as heat. Producers capture solar energy and convert it into chemical energy, which is then passed through the food web. At each trophic level, some energy is lost as heat.
Thermodynamic Limits: The limitations in energy transfer efficiency underscore the need for a continuous input of energy to sustain life processes and ecosystems.

2.2.8 The second law of thermodynamics states that energy transformations in ecosystems are
inefficient.

Outline the second law of thermodynamics

The second law of thermodynamics is a fundamental principle that helps explain why energy transformations in ecosystems are inherently inefficient. This law states that when energy is transformed from one form to another, some of it must be degraded into a less useful form, such as heat. This concept is crucial for understanding the energy dynamics within ecosystems and the limitations of energy transfers.

The second law can be summarized as follows:

When energy is transformed, some of it is inevitably lost as heat, reducing the efficiency of the energy transfer.

Energy Inefficiency in Ecosystems
In ecosystems, energy transformations occur continuously as organisms obtain, convert, and use energy to sustain life processes. However, these transformations are never 100% efficient due to the second law of thermodynamics. The most significant energy losses in ecosystems occur during cellular respiration:

Cellular Respiration: When organisms break down glucose to release energy, not all of the chemical energy from glucose is converted into usable energy for cellular activities. A portion of this energy is inevitably lost as heat. This heat energy dissipates into the environment and cannot be reused by the organism.
Energy Transfers in Food Chains: As energy flows from one trophic level to the next in a food chain, only a fraction of the energy is transferred to the next level. Typically, only about 10% of the energy at one trophic level is passed on to the next level, while the remaining 90% is lost as heat during metabolic processes. This inefficiency limits the number of trophic levels that can be sustained in an ecosystem.

Implications of the Second Law of Thermodynamics

Energy Degradation: Energy becomes less useful as it is transformed and transferred through an ecosystem. The continual loss of energy as heat means that a constant input of energy (primarily from the Sun) is necessary to sustain life.
Energy Pyramids: The inefficiency of energy transfers results in the characteristic shape of energy pyramids, where energy diminishes at each successive trophic level. This pyramid structure reflects the decreasing amount of usable energy available to higher trophic levels.
Ecosystem Productivity: The primary productivity of an ecosystem is determined by the amount of solar energy captured by producers (plants, algae, and photosynthetic bacteria). The efficiency of energy conversion and transfer influences the overall productivity and biomass of the ecosystem.

image from faculty.ycp.edu

This occurs when energy is transferred between trophic levels as illustrated in a food chain When one animal feeds off another, there is a loss of heat (energy) in the process. Additional loss of energy occurs during respiration and movement. Hence, more and more energy is lost as one moves up through trophic levels. This fact lends more credence to the advantages of a vegetarian diet. For example, 1350 kilograms of corn and soybeans is capable of supporting one person if converted to beef. However, 1350 kilograms of soybeans and corn utilized directly without converting to beef will support 22 people!

Trophic Levels and Energy Efficiency

2.2.9 Consumers gain chemical energy from carbon (organic) compounds obtained from other organisms. Consumers have diverse strategies for obtaining energy-containing carbon compounds.

Define the term "consumer" in the context of an ecosystem.
List three types of consumers and provide one example for each type.
Outline the process by which herbivores obtain energy from plants.
Describe the role of detritivores in an ecosystem.
Outline the importance of saprotrophs in nutrient cycling.

Consumers are organisms that gain chemical energy from carbon (organic) compounds obtained from other organisms. They play a critical role in the flow of energy through ecosystems by transferring energy and nutrients from one trophic level to another. Consumers have developed diverse strategies for obtaining energy-containing carbon compounds, each adapted to their ecological niches. These strategies include herbivory, detritivory, predation, parasitism, saprotrophy, scavenging, and decomposition.

Types of Consumers and Their Energy Acquisition Strategies

https://www.activewild.com/examples-of-herbivores/

Herbivores
- Definition: Herbivores are consumers that feed primarily on plants and other photosynthetic organisms.
- Energy Source: Herbivores obtain energy by consuming leaves, stems, seeds, and roots of plants. The chemical energy stored in plant tissues, primarily as carbohydrates, is converted into usable energy through cellular respiration.
- Examples: Deer, rabbits, and caterpillars.

https://lizzieharper.co.uk/image/detritivores-soil-litter-invertebrates/

Detritivores
- Definition: Detritivores are consumers that feed on dead organic matter, particularly plant detritus
- Energy Source: Detritivores break down plant litter and other dead organic material, recycling nutrients and obtaining energy from decomposing matter.
- Examples: Earthworms, millipedes, and woodlice.

https://warnercnr.source.colostate.edu/apex-predators-not-quick-fix-for-restoring-ecosystems/

Predators
- Definition: Predators are consumers that hunt, capture, and kill other animals for food.
- Energy Source: Predators obtain energy by consuming the flesh of their prey, which provides proteins, fats, and carbohydrates necessary for their survival and reproduction.
- Examples: Lions, eagles, and spiders.

https://microbeonline.com/parasitic-infections-source-of-infection-mode-of-transmission-and-prevention/

Parasites
- Definition: Parasites are consumers that live on or inside a host organism, deriving nutrients at the host's expense.
- Energy Source: Parasites extract nutrients directly from the tissues or bodily fluids of their hosts, often causing harm but not immediately killing the host.
- Examples: Tapeworms, fleas, and mistletoe.

https://www.geeksforgeeks.org/saprophytes/

Saprotrophs
- Definition: Saprotrophs are organisms that feed on decaying organic matter by secreting digestive enzymes and absorbing the resulting nutrients.
- Energy Source: Saprotrophs decompose dead organic material, breaking it down into simpler substances and absorbing the released nutrients and energy.
- Examples: Fungi, bacteria, and molds.

Scavengers
- Definition: Scavengers are consumers that feed on dead animals and plant material.
- Energy Source: Scavengers consume carrion and decomposing organic matter, playing a vital role in cleaning the environment and recycling nutrients.
- Examples: Vultures, hyenas, and crabs.

https://newtondesk.com/why-bacteria-fungi-called-decomposers/

Decomposers
- Definition: Decomposers are organisms, primarily fungi and bacteria, that break down dead organic material into simpler inorganic substances.
- Examples: Mushrooms, soil bacteria, and actinomycetes.
- Energy Source: Decomposers obtain energy by breaking down complex organic compounds into simpler molecules, which are then returned to the soil and atmosphere, making nutrients available for primary producers.

Importance of Consumers in Ecosystems

Energy Transfer: They facilitate the flow of energy from primary producers to higher trophic levels, ensuring that energy captured by photosynthesis is distributed throughout the ecosystem.
Nutrient Recycling: By breaking down and consuming organic matter, consumers contribute to the recycling of nutrients, which are essential for the growth of primary producers.
Population Control: Predators and parasites help regulate the population sizes of other organisms, preventing overpopulation and promoting biodiversity.

2.2.10 Because producers in ecosystems make their own carbon compounds by photosynthesis, they are at the start of food chains. Consumers obtain carbon compounds from producers or other consumers, so form the subsequent trophic levels.

List the types of organisms that are typically considered producers in an ecosystem.
Outline the process of photosynthesis and its importance for producers.
Describe the role of primary consumers in a food chain.
Explain how energy flows from primary producers to tertiary consumers in a food chain.
Define the term "trophic level" and identify the trophic levels occupied by producers, primary consumers, secondary consumers, and tertiary consumers.
List the main differences between herbivores, carnivores, and omnivores in terms of their feeding strategies.

A food chain illustrates the sequential transfer of energy and nutrients among organisms within an ecosystem, showcasing how energy moves from one organism to another according to their feeding interactions. Arrows are employed to indicate the direction of energy flow.

Flow of Organic Matter in Food Chains
The flow of organic matter in a food chain follows a unidirectional path from producers to various levels of consumers. This can be summarized as:

Primary Producers: Capture light energy and convert it into chemical energy in the form of glucose. They form the base of the food chain.
Primary Consumers (Herbivores): Consume producers and obtain energy stored in plant tissues.
Secondary Consumers (Carnivores/Omnivores): Feed on primary consumers, transferring energy further up the food chain.
Tertiary Consumers: Higher-level predators that feed on secondary consumers, maintaining the balance of the ecosystem.
Decomposers: Break down dead organic matter from all trophic levels, recycling nutrients back into the ecosystem.

Importance of Food Chains in Ecosystems
Food chains are crucial for understanding the flow of energy and matter in ecosystems. They illustrate how energy captured by producers is transferred through different trophic levels, sustaining various forms of life. Additionally, food chains highlight the interdependence of organisms and the importance of each trophic level in maintaining the balance and health of an ecosystem.

Application of skills: Create a food chain from given data.

https://www.ahmadcoaching.com/2023/09/define-food-chain-in-science-ecology.html

2.2.11 Carbon compounds and the energy they contain are passed from one organism to the next in
a food chain. The stages in a food chain are called trophic levels.

Outline the process by which primary consumers obtain energy from primary producers.
List three roles of decomposers in an ecosystem.
Explain the significance of decomposers in maintaining the flow of energy and cycling of nutrients within an ecosystem.

In ecosystems, carbon compounds and the energy they contain are transferred from one organism to the next through a sequence of feeding relationships known as a food chain. The different stages in a food chain are referred to as trophic levels. Each trophic level represents a step in the transfer of energy and matter through the ecosystem.

https://raider.pressbooks.pub/biology2/chapter/16-trophic-interactions/

Trophic Levels in Food Chains

Primary Producers: These are the autotrophs, such as plants, algae, and photosynthetic bacteria, that produce their own food using sunlight through photosynthesis. They form the first trophic level and are the primary source of energy and carbon compounds for all other organisms in the ecosystem.
Primary Consumers: These are herbivores that feed directly on the primary producers. They occupy the second trophic level. Examples include deer, rabbits, and caterpillars.
Secondary Consumers: These are carnivores and omnivores that feed on primary consumers. They occupy the third trophic level. Examples include frogs, spiders, and lions.
Tertiary Consumers: These are higher-level carnivores that feed on secondary consumers. They occupy the fourth trophic level. Examples include eagles, sharks, and large predators.
Quaternary Consumers: In some ecosystems, there may be an additional trophic level consisting of apex predators that have no natural predators. Examples include orcas and large cats like tigers.

Role of Decomposers
Traditionally, decomposers are not included in linear food chains because they do not fit neatly into the sequence of primary, secondary, and tertiary consumers. Decomposers, such as fungi and bacteria, gain carbon compounds from a variety of sources, including dead plants, animals, and waste products. However, their role in energy transformations and nutrient cycling is crucial for the health and sustainability of ecosystems.

Energy Recycling: Decomposers break down dead organic matter, releasing energy and nutrients back into the ecosystem. This process ensures that energy is not lost entirely but is made available for primary producers to capture once again through photosynthesis.
Nutrient Cycling: By decomposing organic matter, decomposers convert complex organic compounds into simpler inorganic forms, such as nitrogen, phosphorus, and potassium, which are essential nutrients for plant growth. This nutrient recycling maintains soil fertility and supports plant life.
Detrital Food Webs: Decomposers form the base of detrital food webs, where energy and matter flow from dead organic material to detritivores and other organisms that consume decomposers. These detrital food webs are interconnected with traditional grazing food webs, creating a complex and interdependent ecosystem.
Breaking Down Toxins: Some decomposers can break down and detoxify harmful substances in the environment, contributing to the overall health of the ecosystem.

Energy Flow in Food Webs
Energy flows through an ecosystem in a unidirectional manner from the Sun to producers and then through the various trophic levels of consumers. The flow of energy along the food chain is in the direction of the arrows and points towards where the energy is going, and not where it has come from. Ecosystems are more complex than what is represented in simple food chains. In reality, organisms usually do not feed on only one other type of organism

2.2.12 There are losses of energy and organic matter as food is transferred along a food chain.

List the main reasons why not all food available at a given trophic level is harvested.
Describe how digestion and absorption contribute to energy losses in a food chain.
Explain why not all absorbed energy is stored as biomass in an organism.
Define the term "trophic efficiency" and explain its significance in an ecosystem.

In the intricate web of life within ecosystems, energy and organic matter are continuously transferred from one organism to another through food chains. However, this transfer is not perfectly efficient. At each step along the food chain, significant losses of energy and organic matter occur due to various biological and ecological processes. Understanding these losses is essential for comprehending the limitations of energy flow and the dynamics of ecosystems.

Energy and Organic Matter Transfer in Food Chains
A food chain represents the sequence of organisms through which energy and nutrients pass as one organism eats another. Despite the apparent straightforwardness of this process, not all the energy and organic matter available at one trophic level makes it to the next. The reasons for these losses can be summarized as follows:

Availability and Harvesting:
- Not All Food is Harvested: Within any given trophic level, not all potential food sources are accessed or consumed by organisms. For instance, some plants may not be eaten by herbivores because they are inaccessible, unpalatable, or defended by physical or chemical means.
- Predation and Competition: Predators and competitors also influence how much food is harvested from a given trophic level.
Consumption:
- Not All Harvested Food is Consumed: Of the food that is harvested, not all is ingested. Some parts of the food may be left uneaten due to being indigestible, such as bones, shells, or fibrous plant material.
- Waste Production: Animals often discard parts of their prey or food, contributing to organic matter that is not consumed.
Absorption and Digestion:
- Not All Consumed Food is Absorbed: Of the food that is consumed, not all nutrients are absorbed by the digestive system. Some portion of the ingested food passes through the digestive tract and is excreted as waste.
- Digestive Efficiency: The efficiency of digestion varies among organisms, influencing how much of the ingested food is converted into usable energy and organic matter.
Utilization and Storage:
- Not All Absorbed Energy is Stored: Of the nutrients that are absorbed, not all are stored as biomass. A significant portion of the absorbed energy is used immediately for metabolic activities and cellular functions.
- Loss as Heat: During cellular respiration, a process by which cells extract energy from organic compounds, a considerable amount of energy is lost as heat. This heat is a byproduct of metabolic processes and cannot be utilized by the organism.

Implications of Energy and Organic Matter Losses
The inefficiencies in the transfer of energy and organic matter have several important implications for ecosystems:

Trophic Efficiency: The concept of trophic efficiency refers to the percentage of energy that is transferred from one trophic level to the next. Typically, only about 10% of the energy at one trophic level is passed on to the next level. This low efficiency limits the number of trophic levels in an ecosystem.

productivity

2.2.13 Gross productivity (GP) is the total gain in biomass by an organism. Net productivity (NP) is the amount remaining after losses due to cellular respiration.

Define gross productivity (GP) and net productivity (NP).
List the main differences between GP and NP.
Outline the process by which net productivity is calculated from gross productivity.
Define the term "maximum sustainable yield" in the context of net productivity.
List the factors that could affect the gross productivity of primary producers in an ecosystem.

Understanding the concepts of gross productivity (GP) and net productivity (NP) is essential for analyzing the energy dynamics within ecosystems. These metrics help quantify the energy gain and loss by organisms, providing insights into the sustainability and efficiency of energy transfer across trophic levels.

https://old-ib.bioninja.com.au/standard-level/topic-4-ecology/42-energy-flow/ecological-productivity.html

Gross productivity (GP) refers to the total gain in biomass by an organism or trophic level over a specific period. It represents the total amount of energy captured through processes like photosynthesis in producers or the total food intake in consumers.

In Producers:
- GP is the total amount of energy captured from sunlight and converted into chemical energy through photosynthesis.
In Consumers:
- GP is the total amount of energy obtained from the ingestion of food.

Net productivity (NP) is the amount of biomass remaining after accounting for losses due to cellular respiration. It represents the energy available for growth, reproduction, and consumption by higher trophic levels.

Formula: NP = GP - R, where R represents the energy lost through respiration.
In Producers: NP is the energy remaining after the plants have used part of the captured energy for their metabolic activities.
In Consumers: NP is the energy remaining after the consumers have used part of the ingested energy for their metabolic activities.

Differences in GP and NP Between Producers and Consumers
The losses due to cellular respiration are typically greater in consumers than in producers. This difference is due to the higher energy requirements of consumers, who need energy for activities such as movement, thermoregulation, and complex metabolic processes. In contrast, producers primarily use energy for growth and basic metabolic functions.

Producers: Plants, algae, and photosynthetic bacteria have lower respiration rates relative to their GP, resulting in a higher NP.
Consumers: Animals and other heterotrophs have higher respiration rates relative to their GP, resulting in a lower NP.

Importance of NP in Ecosystems
The net productivity of any organism or trophic level is crucial for understanding the sustainability of ecosystems. NP represents the maximum sustainable yield that can be harvested without diminishing the availability of resources for the future. It indicates how much biomass can be removed (e.g., through grazing, predation, or harvesting) without negatively impacting the ecosystem's ability to regenerate and maintain its functions.

Application of GP and NP Values
When analyzing ecosystem data, it is essential to consider both GP and NP values to understand the efficiency and sustainability of energy transfer. For instance:

High GP and NP in Producers: Indicates a healthy and productive primary producer base, supporting a robust food web.
Low NP in Consumers: Suggests high energy losses due to metabolic activities, highlighting the need for efficient energy transfer and conservation strategies.

Example Calculation: If a plant captures 100 units of energy through photosynthesis (GP) and uses 40 units for respiration (R), the NP would be:

NP = GP - R = 100 - 40 = 60 units.
This 60 units represent the energy available for growth, reproduction, and consumption by herbivores.

2.2.14 The number of trophic levels in ecosystems is limited due to energy losses.

List the main reasons why energy is lost at each trophic level in a food chain.
Describe how cellular respiration contributes to energy losses in a food chain.
Explain why only a small percentage of energy is transferred from one trophic level to the next.
Define the term "food chain" and explain why the length of food chains is limited in ecosystems.

Energy flow in ecosystems is subject to the second law of thermodynamics, which states that energy transformations are inefficient, resulting in energy losses. As energy moves through trophic levels—from primary producers to primary consumers, and then to secondary and tertiary consumers—a significant amount of energy is lost at each step, primarily as heat during metabolic processes.

Energy Flow and Losses in Trophic Levels
Energy enters an ecosystem through primary producers, such as plants, algae, and photosynthetic bacteria, which capture solar energy and convert it into chemical energy through photosynthesis. This energy is then transferred through the ecosystem via consumers at various trophic levels. However, at each trophic level, a significant portion of energy is lost due to the following processes:

Cellular Respiration: Organisms use energy to fuel their metabolic activities, such as growth, reproduction, movement, and maintaining homeostasis. During cellular respiration, a considerable amount of energy is converted into ATP to power these processes. However, a significant portion of this energy is lost as heat, which dissipates into the environment and is no longer available for biological work.
Heat Loss: The second law of thermodynamics dictates that energy transformations are inefficient, resulting in the loss of energy as heat. This heat is a byproduct of metabolic processes and cannot be recaptured by organisms.

Calculating Energy Efficiency
To illustrate how energy is transferred and lost in an ecosystem, consider the hypothetical example. The Sun provides 20,000 units of energy to primary producers. However, as energy flows through the food chain, significant amounts are lost, leaving progressively less energy available at higher trophic levels.

In our example, the primary producers transfer 2,500 units of energy to the primary consumers. To calculate the ecological efficiency, which is the percentage of energy received by the producers that is passed on to the next trophic level, we use the following formula:

This calculation shows that approximately 12.5% of the energy received by primary producers is transferred to primary consumers. This is slightly higher than the commonly cited figure of 10%, which is a generalized approximation. In reality, the efficiency of energy transfer between trophic levels can vary widely depending on the ecosystem, the species involved, and specific environmental conditions.

Impact on Trophic Levels and Food Chain Length
Due to these losses, typically only about 10% or less of the energy available at one trophic level is passed on to the next level. This is known as the 10% rule.

The limited transfer of energy between trophic levels explains why food chains rarely exceed four or five levels. With each successive trophic level, less energy is available to sustain organisms, restricting the number of viable levels in the food chain. As a result, top predators at the highest trophic levels are fewer in number and have larger energy requirements, which are met by consuming a substantial biomass of organisms from lower levels.

Application of skills: Work out the efficiency of transfer between trophic levels.

2.2.15 Food webs show the complexity of trophic relationships in communities.

Define the term "food web" and explain how it differs from a food chain.
List the different trophic levels that can be found in a food web and provide an example organism for each level.
Outline the role of arrows in a food web and what they represent.
Describe how energy flows through a food web, starting from primary producers to top predators.
Explain why species in a food web may feed at more than one trophic level.

https://blog.desertmuseum.org/

Food webs provide a detailed and interconnected representation of the trophic relationships within ecological communities. Unlike simple food chains, which depict a linear sequence of energy transfers from one organism to another, food webs illustrate the complex network of feeding interactions among various species in an ecosystem. Understanding food webs is crucial for grasping the intricate dynamics of ecosystems and the flow of energy and biomass.

Understanding Food Webs

Complexity of Relationships:
- Multiple Interactions: In a food web, each species is connected to multiple other species through feeding relationships. This complexity reflects the reality of natural ecosystems, where organisms often have varied diets and interact with multiple other species.
- Interconnectedness: The interconnected nature of food webs highlights the dependence of species on one another for energy and nutrients, demonstrating the ecosystem's resilience and stability.
Direction of Energy Flow:
- Arrows Indicating Flow: In both food chains and food webs, arrows are used to indicate the direction of energy flow and the transfer of biomass. The arrows point from the food source to the consumer, showing the pathway of energy as it moves through the ecosystem.
- Energy Transfer: The direction of the arrows also signifies the transfer of organic matter and energy from producers to various levels of consumers, ultimately reaching decomposers.
Feeding at Multiple Trophic Levels:
- Variable Trophic Positions: Many species in a food web can feed at more than one trophic level. For example, omnivores can act as both primary consumers (eating plants) and secondary consumers (eating herbivores).
- Flexibility in Diet: This flexibility allows species to adapt to changes in food availability, contributing to the stability and resilience of the ecosystem. It also means that the same species can appear at multiple points within the food web.

Importance of Food Webs in Ecosystems

Energy Dynamics:
- Comprehensive View: Food webs provide a more comprehensive view of energy dynamics compared to simple food chains. They reveal the complex pathways through which energy and nutrients flow in an ecosystem.
- Ecosystem Stability: The interconnected nature of food webs helps stabilize ecosystems. If one species is removed or its population changes, the impact can be mitigated by the presence of alternative food sources and pathways for energy flow.
Biodiversity and Ecosystem Health:
- Indicator of Biodiversity: The complexity of a food web is an indicator of biodiversity. A more complex food web generally signifies a more diverse and healthy ecosystem.
- Impact of Changes: Food webs help ecologists understand the potential impact of changes in species populations, such as the introduction or extinction of species, on the overall ecosystem.
Management and Conservation:
- Ecosystem Management: Food webs are valuable tools for ecosystem management and conservation efforts. They allow scientists and policymakers to predict the consequences of environmental changes and human activities on ecosystems.
- Conservation Strategies: Understanding the roles and interactions of different species within a food web can inform strategies to protect endangered species and maintain ecological balance.

Example of a Simple Food Web
Consider a terrestrial ecosystem consisting of plants, herbivores, carnivores, and decomposers:

Primary Producers: Grass, plants, trees (convert solar energy into biomass through photosynthesis)
Primary Consumers: Rabbits, deer, insects (herbivores that eat plants)
Secondary Consumers: Frogs, birds, small mammals (carnivores and omnivores that eat herbivores)
Tertiary Consumers: Hawks, foxes, snakes (top predators that eat secondary consumers)
Decomposers: Fungi, bacteria, earthworms (break down dead organic matter, recycling nutrients back into the ecosystem)

Application of skills: Create a food web from given data.

2.2.16 Biomass of a trophic level can be measured by collecting and drying samples.

Define the term "biomass" in the context of an ecosystem.
Outline the process of drying samples to measure biomass.
Describe how the dry mass of samples approximates the biomass of an organism.

Biomass, the total mass of living or recently living organisms within a given trophic level, is a key metric in understanding ecosystem productivity and energy flow. Accurate measurement of biomass and the energy it contains provides valuable insights into the functioning and health of ecosystems. There are several methods to measure biomass and the energy it contains, including collecting and drying samples and using combustion techniques.

Measuring Biomass

Collection and Drying of Samples:
- Sample Collection: To measure the biomass of a particular trophic level, representative samples of organisms are collected from the ecosystem. This can include plants, herbivores, carnivores, and decomposers, depending on the trophic level of interest.
- Drying Samples: The collected samples are then dried to remove all water content. Drying is typically done in an oven at a constant temperature until the samples reach a stable weight, indicating that all moisture has been evaporated.
- Dry Mass: The dry mass of the samples is approximately equal to the mass of organic matter, or biomass, since water represents the majority of inorganic matter in most organisms. By eliminating water content, the dry mass provides a more accurate measure of the actual organic material present.
- Calculating Biomass: Once the dry mass of the samples is determined, the biomass of the entire trophic level can be estimated by extrapolating the sample data to the total area or volume of the ecosystem being studied.

Measuring Energy in Biomass

Combustion of Samples:
- Energy Content: The energy content of biomass can be measured by burning the dried samples in a process known as combustion. This process releases the chemical energy stored in the organic matter as heat.
- Calorimetry: The heat produced during combustion is measured using a calorimeter, a device designed to capture and quantify the amount of heat released. The calorimeter measures the temperature change of a known quantity of water, which can then be used to calculate the energy content of the sample.
Extrapolation:
- Extrapolating Data: The energy content measured from the combustion of samples can be extrapolated to estimate the total energy content of the biomass in the entire trophic level. This involves scaling up the sample data based on the total biomass previously calculated.

Importance of Biomass and Energy Measurements

Ecosystem Productivity:
- Measuring biomass and energy content provides insights into the productivity of different trophic levels. High biomass and energy content at the primary producer level, for example, indicate a productive ecosystem capable of supporting a diverse and abundant array of consumers.
Energy Flow:
- Understanding the distribution of biomass and energy across trophic levels helps ecologists study energy flow within ecosystems. It reveals how much energy is available at each trophic level and how efficiently energy is transferred from one level to the next.
Conservation and Management:
- Accurate measurements of biomass and energy content are essential for effective ecosystem management and conservation efforts. They inform decisions about resource allocation, habitat protection, and the sustainability of harvesting practices.

2.2.17 Ecological pyramids are used to represent relative numbers, biomass or energy of trophic levels in an ecosystem.

Define the term "ecological pyramid" and explain its purpose in studying ecosystems.
List the three types of ecological pyramids and describe the main characteristic of each type.
Outline the process of constructing a pyramid of biomass.
Describe how a pyramid of energy differs from a pyramid of number.
Define the term "standing crop" and explain its significance in pyramids of number and biomass

Ecological pyramids are graphical representations that illustrate the relative amounts of different parameters—such as numbers, biomass, or energy—across the various trophic levels within an ecosystem. These pyramids help visualize the structure and function of ecosystems, making it easier to understand the distribution of organisms and the flow of energy.

Types of Ecological Pyramids

Pyramids of Number:
- Definition: Pyramids of number display the number of individual organisms at each trophic level in an ecosystem.
- Characteristics: These pyramids can vary greatly in shape. For example, in some ecosystems, there may be a large number of primary producers (e.g., grasses), followed by fewer herbivores (e.g., insects), and even fewer predators (e.g., birds).
- Example: In a grassland ecosystem, the base of the pyramid would be broad, representing numerous grasses, while the top would be narrow, representing fewer top predators like hawks.
- Shape Variations in Pyramids of Number:
  - Inverted Pyramids: Some pyramids of number can be inverted. For instance, a single tree (one primary producer) can support numerous herbivorous insects, which in turn support fewer predators.
  - Irregular Pyramids: Variations occur due to the size and reproductive rate of organisms. For example, a large number of small insects feeding on a single plant.

https://byjus.com/question-answer

Pyramids of Biomass:
- Definition: Pyramids of biomass represent the total dry mass of all organisms at each trophic level at a specific time.
- Characteristics: These pyramids typically have a more regular shape, with a broad base representing a large biomass of primary producers and progressively narrower levels representing smaller biomasses of consumers.
- Example: In a forest ecosystem, the base might be wide, indicating a large biomass of trees, with narrower levels above representing the biomass of herbivores (e.g., deer) and even narrower levels for predators (e.g., wolves).
- Shape Variations in Pyramids of Biomass:
  - Inverted Biomass Pyramids: In some aquatic ecosystems, inverted pyramids of biomass can occur where the biomass of primary consumers (zooplankton) exceeds that of the primary producers (phytoplankton). This happens because phytoplankton reproduce rapidly and are consumed quickly, maintaining a lower biomass at any given time.
  - Regular Biomass Pyramids: Typically, in terrestrial ecosystems, pyramids of biomass have a broad base and narrow top, reflecting the accumulation of biomass at the producer level and decreasing biomass at higher trophic levels.

https://commons.wikimedia.org/wiki/File:Biomass_Pyramid.svg

Pyramids of Energy (Pyramids of Productivity):
- Definition: Pyramids of energy show the amount of energy flowing to each trophic level per unit area and per unit time, usually measured in kilojoules per square meter per year (kJ m⁻² year⁻¹).
- Characteristics: These pyramids always have a traditional pyramid shape because energy transfer between trophic levels is inefficient (approximately 10% efficiency), leading to a significant decrease in available energy at each successive level.
- Example: In any ecosystem, the base of the pyramid would represent the primary producers with the highest energy capture, and the top would represent tertiary consumers with the least energy available.
- Shape Variations in Pyramids of Energy:
  - Consistent Shape: Pyramids of energy are always upright and never inverted because energy transfer is unidirectional and inefficient. Energy is lost at each trophic level due to metabolic processes and heat loss.
  - Importance: These pyramids provide a clear picture of the energy dynamics and the efficiency of energy transfer within ecosystems.

https://old-ib.bioninja.com.au

Importance of Ecological Pyramids

Ecosystem Analysis: Ecological pyramids help ecologists analyze the structure and function of ecosystems by visualizing the distribution of organisms, biomass, and energy.
Conservation and Management: Understanding the flow of energy and distribution of biomass aids in ecosystem management and conservation efforts, helping to identify critical trophic levels and potential impacts of changes.
Educational Tool: These pyramids serve as effective tools for teaching ecological concepts and illustrating the principles of energy flow and trophic relationships.

Application of skills:

Create pyramids of numbers, biomass and energy from given data.
Follow experimental procedures on how to find biomass and energy from biological samples (plant material only).

Pollutants and Human Impact

2.2.18 Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification.

Define the term "non-biodegradable pollutant" and provide two examples.
Define the term "biomagnification" and explain its significance in an ecosystem.
Outline the differences between bioaccumulation and biomagnification.
List the processes through which non-biodegradable pollutants enter and persist in ecosystems.
List the potential ecological and health impacts of bioaccumulation and biomagnification.

Non-biodegradable pollutants are substances that do not break down naturally in the environment. They resist decomposition by natural processes and, as a result, can persist for long periods. These pollutants persist in the environment and can cause significant ecological harm through the processes of bioaccumulation and biomagnification

Polychlorinated Biphenyls (PCBs):
- Industrial chemicals used in electrical equipment, which are highly persistent and toxic.
Dichlorodiphenyltrichloroethane (DDT):
- A pesticide that, despite its ban in many countries, remains in the environment due to its stability and persistence.
Mercury:
- A heavy metal released from industrial processes and mining, which is highly toxic and accumulates in living organisms.

https://capemaywhalewatch.com/blog/biomagnification-and-persistence-of-chemical-marine-pollution/

Bioaccumulation refers to the gradual build-up of non-biodegradable pollutants in an organism or trophic level over time. This occurs because these pollutants are absorbed faster than they are excreted or metabolized. As a result, their concentration increases within the individual organism.

Process:
- Organisms absorb pollutants from their environment (water, soil, air) or through their diet. Since the pollutants are non-biodegradable, they accumulate in the tissues, especially in fat and other lipid-rich tissues.
Examples:
- Fish in contaminated waters may accumulate mercury in their tissues.
- Birds that ingest prey exposed to DDT may accumulate the pesticide in their bodies.

Biomagnification refers to the increasing concentration of non-biodegradable pollutants as they move up the food chain. This occurs because predators consume multiple prey items, each containing the pollutant, leading to higher concentrations in the predator's body.

Process:
- At each trophic level, organisms consume others that have accumulated pollutants. Since energy transfer between trophic levels is inefficient (only about 10% of energy is passed on), the biomass at higher levels is much lower. However, the pollutants are not metabolized or excreted effectively, resulting in higher concentrations in the predator's tissues.
Examples:
- Small aquatic organisms like plankton absorb pollutants from the water. Small fish eat large quantities of plankton, accumulating higher pollutant levels. Larger fish, birds, or mammals then eat these fish, leading to even higher concentrations.
- Top predators, such as eagles or polar bears, may exhibit extremely high levels of pollutants like PCBs or DDT in their tissues, affecting their health and reproduction.

https://www.researchgate.net/figure/Schematic-representation-of-contaminants-bioaccumulation-and-biomagnification-Image_fig2_367189213

Ecological and Health Impacts
The processes of bioaccumulation and biomagnification can have severe consequences for ecosystems and the organisms within them:

Health Effects:
- High concentrations of pollutants can cause toxic effects, including reproductive failure, immune system suppression, and developmental abnormalities in wildlife. For example, DDT exposure has been linked to eggshell thinning in birds, leading to reduced reproductive success.
Ecosystem Changes:
- Pollutant accumulation can alter species composition and abundance, disrupting food webs and ecosystem stability. Predators with high pollutant loads may experience population declines, affecting the entire ecosystem structure.

Mitigation and Management
Addressing the impacts of non-biodegradable pollutants requires comprehensive strategies, including:

Regulation and Bans:
- Many countries have banned or restricted the use of harmful chemicals like DDT and PCBs to reduce their release into the environment.
Cleanup Efforts:
- Contaminated sites, such as polluted rivers or industrial areas, require cleanup and remediation to remove or neutralize pollutants.
Monitoring and Research:
- Continuous monitoring of pollutant levels in the environment and research on their effects help inform policy decisions and conservation efforts.

2.2.19 Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain.

Define the term "microplastics" and explain their origin.
List the sources of microplastics in the environment.
Outline the process by which microplastics absorb non-biodegradable pollutants.
Describe how microplastics are ingested by organisms in lower trophic levels.

Plastics are materials that can be shaped when soft and retain that shape when hardened. Plastic can be synthetic or naturally occurring and are polymers. A polymer is like a chain of individual components linked together.

Understanding Microplastics

Microplastics, tiny plastic fragments or particles less than 5 millimeters in diameter. They originate from a variety of sources, including the breakdown of larger plastic debris, microbeads in personal care products, synthetic fibers from clothing, and industrial processes.

Microplastics are non-biodegradable, meaning they do not break down easily and can persist in the environment for extended periods.Non-biodegradable pollutants are absorbed within microplastics, which increases their transmission in the food chain. Studies have illustrated the potential for plastic debris to sorb, concentrate and transport POPs in the marine environment as well as their ingestion by marine organisms.

Absorption of Non-Biodegradable Pollutants:

Pollutant Absorption: Microplastics can absorb non-biodegradable pollutants, such as heavy metals, PCBs (polychlorinated biphenyls), DDT (dichlorodiphenyltrichloroethane), and other toxic chemicals, from their surrounding environment. These pollutants adhere to the surface of microplastics or become embedded within them.
Transport and Transmission: Once absorbed, these pollutants can be transported along with the microplastics through water currents, wind, and other environmental pathways.

Microplastics in Food Chains

Ingestion by Organisms:
- Lower Trophic Levels: Small aquatic organisms, such as plankton and small fish, often mistake microplastics for food and ingest them. These organisms accumulate microplastics and the associated pollutants within their bodies.
- Higher Trophic Levels: Predators that consume these smaller organisms also ingest the microplastics and pollutants, leading to bioaccumulation and biomagnification up the food chain.

Ecological and Health Impacts

Ecological Effects:
- Toxicity: The absorbed pollutants can cause toxicity in organisms, leading to reduced growth, reproductive issues, and increased mortality rates. The physical presence of microplastics can also cause blockages and damage to the digestive systems of marine organisms.
- Biodiversity Loss: The combined effects of chemical toxicity and physical harm from microplastics can reduce biodiversity and disrupt ecosystem stability and function.
Human Health Concerns:
- Seafood Contamination: Humans who consume seafood are at risk of ingesting microplastics and associated pollutants. This can lead to potential health issues, including chemical exposure and digestive problems.
- Long-Term Impacts: The long-term health effects of microplastic and pollutant ingestion in humans are still being studied, but concerns include potential links to cancer, endocrine disruption, and other chronic health conditions.

Mitigation and Management

Pollution Control:
- Reducing Plastic Waste: Efforts to reduce plastic waste through bans on single-use plastics, improved waste management, and recycling can help decrease the input of microplastics into the environment.
- Cleanup Efforts: Initiatives to clean up plastic debris from oceans, rivers, and coastal areas can reduce the sources of microplastics.
Research and Monitoring:
- Monitoring Programs: Establishing monitoring programs to track microplastic pollution and its impacts on ecosystems and human health is crucial for informed decision-making.
- Scientific Research: Continued research on the effects of microplastics and associated pollutants will help develop effective mitigation strategies and policies.

Example of Microplastic Pollution:

Case Study: Marine Ecosystems:
- Primary Producers and Primary Consumers: In marine ecosystems, microplastics are ingested by small organisms like plankton and small fish. These primary consumers accumulate both the microplastics and the absorbed pollutants.
- Secondary and Tertiary Consumers: Larger fish, seabirds, and marine mammals that feed on the contaminated primary consumers accumulate higher concentrations of microplastics and pollutants. For instance, fish such as anchovies and sardines can ingest significant amounts of microplastics, which are then passed on to predators like tuna, seals, and seabirds.

https://www.sciencelearn.org.nz/images/4613-microplastics-in-the-food-web

2.2.20 Human activities, such as burning fossil fuels, deforestation, urbanization and agriculture, have impacts on flows of energy and transfers of matter in ecosystems.

Define the term "deforestation" and explain its impact on primary productivity in ecosystems.
List three human activities that affect the flows of energy and transfers of matter in ecosystems.
Outline the process by which burning fossil fuels can both increase and decrease primary productivity.
Describe the effects of urbanization on natural ecosystems and food webs.
Explain how agriculture can lead to the disruption of energy flows and matter transfers in ecosystems.

Human activities, including burning fossil fuels, deforestation, urbanization, and agriculture, significantly affect the flows of energy and transfers of matter within ecosystems. These activities disrupt natural processes, leading to changes in ecosystem structure, function, and productivity.

Burning Fossil Fuels

Burning fossil fuels releases CO2 into the atmosphere and causes global warming as well as air pollution

Increased CO2 for Photosynthesis:
- Positive Impact: Burning fossil fuels releases carbon dioxide (CO2) into the atmosphere, which can enhance the availability of CO2 for photosynthesis in plants, potentially increasing primary productivity.
- Negative Impact: Despite the potential increase in photosynthesis, the overall effects of burning fossil fuels are detrimental. The release of other pollutants, such as sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter, can harm plant health and reduce photosynthetic efficiency. Additionally, increased CO2 contributes to global warming, which can lead to extreme weather conditions, altering growing seasons and reducing primary productivity.

https://www.researchgate.net/figure/Atmospheric-CO2-level-and-Seawater-pH-in-the-North-Pacific-8_fig2_336813938

Global Warming:
- Climate Change: The enhanced greenhouse effect due to increased CO2 levels leads to global warming, causing shifts in climate patterns. This affects the distribution and health of ecosystems, potentially reducing the capacity for photosynthesis and primary productivity.
- Ocean Acidification: Increased CO2 levels also lead to ocean acidification, which can harm marine life, particularly organisms with calcium carbonate shells or skeletons, disrupting marine food webs and reducing biodiversity.

Deforestation

Deforestation involves removing trees from a wide area of land. The purpose could be to clear the land for farming, make way for mining activities, or to use the wood for timber or manufacturing

Loss of Biomass and Photosynthesis:
- Reduced Primary Productivity: Deforestation involves the removal of large areas of forest, leading to a significant loss of biomass and a decrease in the area available for photosynthesis. This reduces the overall primary productivity of the ecosystem.
- Carbon Sequestration: Forests act as carbon sinks, sequestering CO2 from the atmosphere. Deforestation reduces this capacity, leading to higher atmospheric CO2 levels and contributing to global warming.
Disruption of Food Webs:
- Habitat Loss: The removal of trees and other vegetation destroys habitats, leading to the displacement or extinction of species. This disruption of food webs affects the flow of energy and the transfer of matter, altering ecosystem dynamics and reducing biodiversity.

Urbanization

Urbanization involves the movement of people from rural to urban areas and the associated activities of building human settlements. This process involves removing or disrupting ecosystems to make space for human-construction

Alteration of Natural Landscapes:
- Land Conversion: Urbanization converts natural landscapes into urban areas, replacing vegetation with buildings, roads, and other infrastructure. This reduces the area available for photosynthesis and primary productivity.
- Fragmentation: Urbanization fragments habitats, creating isolated patches of ecosystems. This fragmentation disrupts animal movement, breeding, and feeding patterns, affecting food webs and energy flows.
Pollution and Waste:
- Air and Water Pollution: Urban areas generate significant air and water pollution, including emissions from vehicles and industrial activities. Pollutants can harm plant and animal health, reducing photosynthesis and disrupting food webs.
- Waste Generation: Urbanization leads to increased waste production, which can contaminate soil and water, further impacting ecosystems.

Agriculture

Agriculture involves growing crops for food or other purposes such as clothes. This usually involves clearing land to grow crops. The food webs and other plants that are native to the environment are removed and destroyed.

Land Use and Biomass:
- Conversion of Natural Ecosystems: Agricultural activities often involve clearing natural ecosystems to create farmland, leading to a loss of biomass and a reduction in primary productivity.
- Monoculture: The practice of monoculture (growing a single crop over a large area) reduces biodiversity, making ecosystems more vulnerable to pests, diseases, and extreme weather events.
Chemical Inputs:
- Fertilizers and Pesticides: The use of fertilizers and pesticides can lead to nutrient runoff and contamination of water bodies, causing eutrophication and harming aquatic life. These chemicals can also disrupt soil health and microbial communities, affecting nutrient cycling and energy flows.
Irrigation:
- Water Use: Irrigation practices can deplete water resources, affecting the availability of water for natural ecosystems. Over-irrigation can lead to soil salinization, reducing soil fertility and plant productivity.

HL Only

This unit will take a minimum of 2 hours

2.2.21 Autotrophs synthesize carbon compounds from inorganic sources of carbon and other elements. Heterotrophs obtain carbon compounds from other organisms.

Define the term "autotroph" and provide two examples.
Define the term "heterotroph" and explain how heterotrophs obtain their carbon compounds.
List the main differences between photoautotrophs and chemoautotrophs.
Outline the process by which autotrophs synthesize carbon compounds from inorganic sources.
Describe the role of heterotrophs in an ecosystem.
Explain how autotrophs contribute to the carbon cycle.

In ecosystems, all living organisms can be classified into two main categories based on their method of acquiring carbon compounds: autotrophs and heterotrophs. Understanding these classifications is essential for studying energy flow and nutrient cycling within ecosystems.

Autotrophs, also known as primary producers, are organisms that synthesize their own carbon compounds from inorganic sources of carbon and other elements. They utilize energy from the environment to convert these inorganic materials into organic molecules necessary for their growth and survival.

Types of Autotrophs:
- Photoautotrophs: These organisms use light energy to drive the process of photosynthesis, converting carbon dioxide (CO₂) and water (H₂O) into glucose and oxygen (O₂). Examples include:
  - Plants: Trees, grasses, and shrubs.
  - Algae: Both unicellular (e.g., phytoplankton) and multicellular (e.g., seaweeds).
  - Photosynthetic Bacteria: Cyanobacteria, also known as blue-green algae.
- Chemoautotrophs: These organisms obtain energy from the oxidation of inorganic molecules, such as hydrogen sulfide (H₂S) or ammonia (NH₃), to synthesize organic compounds. Examples include:
  - Sulfur Bacteria: Found in deep-sea hydrothermal vents.
  - Nitrifying Bacteria: Found in soil and involved in the nitrogen cycle.
Role in Ecosystems:
- Primary Production: Autotrophs form the base of the food web by producing organic compounds that serve as food for other organisms.
- Energy Conversion: They convert solar or chemical energy into a form that can be used by heterotrophs.
- Carbon Fixation: Autotrophs play a crucial role in carbon cycling by converting CO₂ into organic matter, helping to regulate atmospheric CO₂ levels.

Heterotrophs are organisms that cannot synthesize their own carbon compounds from inorganic sources. Instead, they obtain organic carbon by consuming other organisms or organic matter. Heterotrophs include all animals, fungi, and many bacteria and protists.

Types of Heterotrophs:
- Herbivores: Organisms that feed directly on primary producers (plants and algae). Examples include deer, rabbits, and caterpillars.
- Carnivores: Organisms that feed on other animals. Examples include lions, eagles, and sharks.
- Omnivores: Organisms that feed on both plants and animals. Examples include humans, bears, and pigs.
- Detritivores: Organisms that feed on dead organic matter (detritus). Examples include earthworms, millipedes, and woodlice.
- Saprotrophs: Organisms that decompose organic matter by secreting digestive enzymes and absorbing the resulting nutrients. Examples include fungi and many bacteria.
Role in Ecosystems:
- Energy Transfer: Heterotrophs transfer energy from one trophic level to the next by consuming other organisms.
- Nutrient Recycling: Detritivores and saprotrophs play a critical role in breaking down dead organic matter, recycling nutrients back into the ecosystem.
- Population Control: Predators and parasites help regulate the populations of other organisms, maintaining ecosystem balance.

Autotrophs vs. Heterotrophs

Energy Source:
- Autotrophs: Utilize solar or chemical energy to produce organic compounds.
- Heterotrophs: Obtain energy by consuming organic compounds produced by autotrophs or other heterotrophs.
Carbon Source:
- Autotrophs: Use inorganic carbon sources (e.g., CO₂) to synthesize organic molecules.
- Heterotrophs: Depend on organic carbon sources obtained from other organisms.
Role in Food Webs:
- Autotrophs: Form the base of the food web, providing energy and organic matter for all other trophic levels.
- Heterotrophs: Occupy higher trophic levels, including primary consumers (herbivores), secondary consumers (carnivores and omnivores), and decomposers (detritivores and saprotrophs).

https://www.sciencefacts.net/heterotroph.html

2.2.22 Photoautotrophs use light as an external energy source in photosynthesis. Chemoautotrophs use exothermic inorganic chemical reactions as an external energy source in chemosynthesis.

Define the term "photoautotroph" and provide two examples.
List the main differences between photoautotrophs and chemoautotrophs.
Outline the process of photosynthesis in photoautotrophs, including the key reactants and products.
Describe the role of chemoautotrophs in ecosystems where light is scarce or absent.

Photoautotrophs are organisms that use light as an external energy source to drive the process of photosynthesis. They convert light energy from the Sun into chemical energy stored in organic molecules such as glucose.

Process of Photosynthesis:
- Light Energy: Photoautotrophs capture light energy using pigments like chlorophyll.
- Carbon Dioxide and Water: They use carbon dioxide (CO₂) from the atmosphere and water (H₂O) from the soil.
- Glucose and Oxygen: Through a series of chemical reactions, they convert light energy, CO₂, and H₂O into glucose (C₆H₁₂O₆) and release oxygen (O₂) as a byproduct.
- Equation: The general equation for photosynthesis is:
  6 CO2+6 H2O+light energy→C6H12O6+6 O2\text{6 CO}_2 + \text{6 H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{6 O}_26 CO2+6 H2O+light energy→C6H12O6+6 O2
Examples of Photoautotrophs:
- Plants: All green plants, such as trees, shrubs, and grasses.
- Algae: Both unicellular (e.g., phytoplankton) and multicellular (e.g., seaweeds) forms.
- Photosynthetic Bacteria: Cyanobacteria, also known as blue-green algae.
Role in Ecosystems:
- Primary Producers: Photoautotrophs form the base of most terrestrial and aquatic food webs, providing energy and organic matter for heterotrophs.
- Oxygen Production: They produce oxygen, which is essential for the respiration of aerobic organisms.

https://www.mdpi.com/1996-1944/14/11/3027

Chemoautotrophs are organisms that use exothermic inorganic chemical reactions as an external energy source to drive the process of chemosynthesis. They convert inorganic molecules into organic molecules in environments where light is scarce or absent.

Process of Chemosynthesis:
- Chemical Energy: Chemoautotrophs obtain energy by oxidizing inorganic substances such as hydrogen sulfide (H₂S), ammonia (NH₃), or ferrous iron (Fe²⁺).
- Carbon Dioxide and Inorganic Molecules: They use CO₂ as a carbon source and inorganic molecules as electron donors to produce organic compounds.
- Equation: A general equation for chemosynthesis by sulfur bacteria is:
  CO2+O2+4H2S→CH2O+4S+3H2O\text{CO}_2 + \text{O}_2 + 4\text{H}_2\text{S} \rightarrow \text{CH}_2\text{O} + 4\text{S} + 3\text{H}_2\text{O}CO2+O2+4H2S→CH2O+4S+3H2O
Examples of Chemoautotrophs:
- Sulfur Bacteria: Found in deep-sea hydrothermal vents and hot springs.
- Nitrifying Bacteria: Found in soil, involved in the nitrogen cycle (e.g., Nitrosomonas and Nitrobacter).
- Iron-Oxidizing Bacteria: Found in environments with high levels of iron, such as acid mine drainage.
Role in Ecosystems:
- Primary Producers in Dark Environments: Chemoautotrophs are the principal source of energy in ecosystems where there is little or no light, such as deep-sea hydrothermal vents, underground caves, and sulfur-rich hot springs.
- Support Unique Food Webs: In these environments, chemoautotrophs support unique and diverse communities of organisms that rely on chemical energy rather than sunlight

Importance of Photoautotrophs and Chemoautotrophs

Energy Conversion:
- Photoautotrophs: Convert solar energy into chemical energy, making it accessible to other organisms in the ecosystem.
- Chemoautotrophs: Convert chemical energy from inorganic molecules into organic molecules, sustaining ecosystems in the absence of light.
Ecosystem Productivity:
- Both types of autotrophs are essential for the productivity and stability of ecosystems, providing the energy foundation for food webs.
Adaptation to Diverse Environments:
- Photoautotrophs thrive in environments with abundant light, such as forests, grasslands, and ocean surfaces.
- Chemoautotrophs are adapted to extreme environments with harsh conditions where light is unavailable, showcasing the diversity of life strategies on Earth.

2.2.23 Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.

Define the term "primary productivity" and explain its significance in an ecosystem.
Define the term "net primary productivity" and explain its role in energy transfer within an ecosystem.
List the differences between gross primary productivity (GPP) and net primary productivity (NPP).
Outline the process of measuring primary productivity in a laboratory setting using photosynthesizing samples.

Primary productivity is a critical ecological metric that quantifies the rate at which biomass is produced by autotrophs (primary producers) using external energy sources and inorganic materials. It provides insights into the energy available to support food webs and the overall health and functioning of ecosystems.

Primary Productivity refers to the rate at which primary producers, such as plants, algae, and some bacteria, convert inorganic carbon (CO₂) and other elements into organic compounds using an external energy source. This process is fundamental to the creation of biomass that fuels ecosystems.

Gross Primary Productivity (GPP): The total rate of photosynthesis, including the energy used by plants for respiration.
Net Primary Productivity (NPP): The rate of biomass accumulation after accounting for the energy expended on plant respiration. It represents the energy available to consumers in the ecosystem.

Units of Measurement:

Primary productivity is often measured in kg carbon m-2 yr-1. This unit quantifies the amount of carbon fixed into biomass over a specific area and time period.

Measuring Productivity

Laboratory Measurements:
- Photosynthesizing Samples: In a controlled laboratory environment, primary productivity can be estimated by measuring the rate of photosynthesis in samples of primary producers.
- Oxygen Production: One common method involves measuring the amount of oxygen produced by plants or algae, as oxygen is a byproduct of photosynthesis.
- Carbon Dioxide Uptake: Another approach is to measure the uptake of CO₂, which is directly related to the production of organic carbon.
Field Measurements:
- Biomass Change Over Time: In the field, primary productivity can be estimated by measuring the change in biomass of primary producers over time. For example, in a grassland ecosystem, researchers can measure the biomass of grass at the beginning and end of a growing season to estimate productivity.
- Harvest Method: This involves harvesting plant material from a known area, drying it to remove water content, and weighing it to determine the biomass produced.
- Non-Destructive Methods: These include measuring plant height, density, and coverage as proxies for biomass, allowing continuous monitoring without destroying the samples.

Importance of Productivity

Energy Availability:
- Productivity determines the amount of energy available to support all other trophic levels in an ecosystem. Higher productivity typically indicates a more robust and diverse ecosystem.
Ecosystem Health:
- Monitoring productivity helps ecologists assess the health and functioning of ecosystems. Declines in productivity can indicate environmental stress or degradation.
Carbon Cycling:
- Productivity plays a crucial role in the global carbon cycle, as it represents the rate at which CO₂ is removed from the atmosphere and fixed into organic matter.
Management and Conservation:
- Understanding productivity is essential for managing natural resources, conserving biodiversity, and predicting the impacts of environmental changes such as climate change.

https://www.quora.com/In-environmental-science-what-is-gross-primary-productivity

2.2.24 Secondary productivity is the gain in biomass by consumers using carbon compounds absorbed and assimilated from ingested food.

Define the term "secondary productivity" and explain how it is calculated.
Define the term "assimilation" and explain its significance in secondary productivity.
List the main processes involved in secondary productivity.
Outline the importance of secondary productivity in food webs.
Describe the role of faecal waste in the calculation of secondary productivity.
Explain how secondary productivity contributes to nutrient cycling within an ecosystem.

Secondary productivity is a key concept in ecology that refers to the gain in biomass by consumers (heterotrophs) through the absorption and assimilation of carbon compounds from ingested food. This process is essential for understanding how energy and nutrients flow through food webs, supporting higher trophic levels and maintaining ecosystem dynamics.

https://collegedunia.com/exams/productivity-in-ecosystem-biology-articleid-1356

Net secondary productivity (NSP) is the rate at which consumers produce biomass or energy per unit area per unit time remaining after accounting for respiratory losses

Net secondary productivity (NSP) is a more meaningful measure of productivity than gross secondary productivity because it also removes the amount of energy lost to cellular respiration.

Gross secondary productivity (GSP) in animals equals the amount of biomass assimilated or biomass eaten less feces. As in the case of plants herbivores and carnivores ingest the food material out of which a part gets assimilated and a part is egestion. A large part of the assimilated energy is consumed during metabolic process like respiration, growth, reproduction etc and the rest is available to be laid down as new biomass.

Units: Secondary productivity is expressed as mass per unit area per unit time (e.g. g m-2 yr-1).

Processes Involved in Secondary Productivity

Ingestion:
- Consumers ingest food containing carbon compounds from primary producers (plants and algae) or other consumers.
- The ingested food includes a variety of organic materials such as carbohydrates, proteins, and fats.
Absorption and Assimilation:
- During digestion, the ingested food is broken down into smaller molecules that can be absorbed through the gut lining into the bloodstream.
- These absorbed nutrients are then assimilated into the body’s cells and tissues, contributing to growth and maintenance.
Faecal Waste:
- Not all ingested food is digested and absorbed. The undigested and unabsorbed material is excreted as faecal waste.
- Faecal waste is excluded from the calculation of secondary productivity because it does not contribute to the gain in biomass.

Importance of Secondary Productivity

Energy Transfer:
- Secondary productivity represents the energy available to higher trophic levels, such as predators and scavengers.
- It is a measure of how efficiently consumers convert the energy and nutrients from their diet into new biomass.
Food Web Dynamics:
- Understanding secondary productivity helps ecologists study the flow of energy and matter through food webs.
- It provides insights into the health and sustainability of ecosystems, indicating how well energy is transferred from primary producers to consumers.
Nutrient Cycling:
- The processes of ingestion, digestion, absorption, and waste excretion are integral to nutrient cycling within ecosystems.
- Secondary productivity plays a role in the decomposition of organic matter and the recycling of nutrients back into the ecosystem.

https://old-ib.bioninja.com.au/standard-level/topic-4-ecology/42-energy-flow/ecological-productivity.html

Net primary productivity (NPP) is a fundamental concept in ecology that serves as the foundation for food chains. It represents the amount of biomass produced by primary producers that is available for consumption by primary consumers. Understanding NPP is crucial for comprehending energy flow, ecosystem dynamics, and sustainable resource management.

2.2.25 Net primary productivity is the basis for food chains because it is the quantity of carbon compounds sustainably available to primary consumers.

Define the term "net primary productivity" and explain its significance in an ecosystem.
List the main differences between gross primary productivity (GPP) and net primary productivity (NPP).
Outline the process by which NPP is calculated from GPP and respiration.
Describe the role of NPP in supporting primary consumers in a food chain

Units: Secondary productivity is expressed as mass per unit area per unit time (e.g. g m-2 yr-1).
Formula:

Importance of Net Primary Productivity

Basis for Food Chains:
- Energy Source: NPP provides the primary source of energy for herbivores (primary consumers) in natural ecosystems. This energy is transferred through the food chain as herbivores are consumed by secondary and tertiary consumers.
- Sustainable Yield: NPP represents the sustainable yield of biomass that can be harvested by primary consumers without depleting the primary producers. It ensures that ecosystems can maintain their productivity over time.
Sustainable Harvesting:
- Natural Ecosystems: In natural ecosystems, NPP can be thought of as the plant growth that herbivores can sustainably consume without damaging the ecosystem's health. It supports the populations of herbivores and, subsequently, the entire food web.
- Agricultural Systems: In agricultural systems, NPP is the basis for the sustainable yield of crops that farmers can harvest. It determines the amount of biomass available for food, feed, and other agricultural products.
- Silvicultural Systems: In forestry, NPP represents the sustainable yield of timber and other forest products that can be harvested without depleting forest resources. It is crucial for maintaining forest health and productivity.

Implications of Net Primary Productivity

Ecosystem Health:
- Indicator of Productivity: NPP is a key indicator of ecosystem productivity and health. High NPP values indicate robust primary production, supporting diverse and abundant populations of consumers.
- Impact of Environmental Changes: Changes in NPP can signal shifts in environmental conditions, such as climate change, nutrient availability, or disturbances like deforestation and pollution.
Resource Management:
- Sustainable Practices: Understanding NPP helps in developing sustainable practices for agriculture, forestry, and conservation. It ensures that biomass is harvested at rates that do not exceed the ecosystem's capacity to regenerate.
- Biodiversity Conservation: Maintaining high NPP supports biodiversity by providing sufficient energy and habitat for a wide range of species. It promotes resilient ecosystems capable of withstanding environmental stressors.
Global Carbon Cycle:
- Carbon Sequestration: NPP plays a crucial role in the global carbon cycle by sequestering carbon dioxide from the atmosphere and storing it as biomass. This process helps mitigate climate change by reducing atmospheric CO₂ levels.

Application of skills: Use laboratory and field techniques for measuring primary and secondary productivity and work out GP and NP from data.

2.2.26 Maximum sustainable yields (MSYs) are the net primary or net secondary productivity of a system.

Define the term "maximum sustainable yield" (MSY) and explain its significance in resource management.
List the differences between net primary productivity (NPP) and net secondary productivity (NSP) in the context of MSYs.
Outline the process of determining MSY in a forest ecosystem.
Describe how MSY is applied in fisheries management.
Explain the importance of environmental stability for maintaining MSY in natural ecosystems.

Maximum sustainable yields (MSYs) are a crucial concept in resource management and ecology. They represent the highest rate at which biomass can be harvested from an ecosystem without compromising its ability to regenerate. MSYs are applicable to both net primary productivity (NPP) in plant-based systems and net secondary productivity (NSP) in animal-based systems.

Maximum Sustainable Yield (MSY) refers to the largest yield (catch or harvest) that can be taken from a species' stock over an indefinite period under constant environmental conditions. It aims to balance resource extraction with the sustainability of the ecosystem.

Net Primary Productivity (NPP): MSY in primary productivity refers to the maximum biomass of plants or algae that can be sustainably harvested.
Net Secondary Productivity (NSP): MSY in secondary productivity refers to the maximum biomass of animals (such as fish, livestock, or other wildlife) that can be sustainably harvested.

MSYs in Natural Ecosystems

Forests:
- Timber Harvesting: In natural forests, MSY involves the sustainable harvest of timber. Forest managers must balance the rate of tree cutting with the forest's natural regeneration rate to ensure long-term productivity.
- Non-Timber Products: MSY also applies to non-timber forest products such as fruits, nuts, and medicinal plants, which must be harvested at rates that allow for continued reproduction and growth.
Wildlife:
- Game Management: MSY is used in the management of game species, where hunting quotas are set to ensure that populations remain stable. This prevents overhunting and ensures that wildlife populations can sustain themselves.
Fisheries:
- Fish Stocks: MSY in fisheries management involves setting quotas for fish catches that do not exceed the population's ability to replenish itself. This requires understanding the reproductive rates and growth patterns of fish species.
- Marine Ecosystems: Sustainable fishing practices help maintain the balance of marine ecosystems, ensuring that fish populations and other marine life remain healthy.

http://ib.bioninja.com.au).

MSYs in Agricultural Systems

Crop Production:
- Sustainable Harvesting: In agriculture, MSY refers to the maximum yield of crops that can be sustainably harvested without depleting soil fertility or causing long-term damage to the land. This involves practices like crop rotation, proper fertilization, and pest management.
- Soil Health: Maintaining soil health is essential for achieving MSY in crop production. Techniques such as conservation tillage, cover cropping, and organic amendments help preserve soil structure and nutrient content.
Livestock:
- Grazing Management: For livestock, MSY involves managing grazing pressure to ensure that pasturelands are not overgrazed. Rotational grazing and proper stocking rates are key practices.
- Animal Health: Ensuring the health and productivity of livestock involves providing adequate nutrition, healthcare, and living conditions.

MSYs in Silvicultural Systems

Timber Plantations:
- Sustainable Forestry: In managed timber plantations, MSY involves harvesting trees at a rate that allows for continuous replanting and growth. This ensures a steady supply of timber without degrading the forest ecosystem.
- Selective Logging: Techniques such as selective logging, where only certain trees are harvested, help maintain biodiversity and ecosystem health.
Non-Timber Forest Products:
- Sustainable Harvesting: MSY applies to the sustainable collection of products like resin, rubber, and other forest materials. Harvesting practices must allow for the regeneration of these resources.

Considerations for Determining MSYs

Environmental Conditions:
- MSYs depend on stable environmental conditions. Changes in climate, habitat quality, and resource availability can affect the sustainability of yields.
Ecosystem Dynamics:
- Understanding the complex interactions within ecosystems is crucial for setting MSYs. This includes predator-prey relationships, competition, and nutrient cycling.
Monitoring and Adaptation:
- Regular monitoring of resource stocks and environmental conditions is necessary to ensure that MSYs are not exceeded. Adaptive management practices allow for adjustments based on observed changes.
Socioeconomic Factors:
- MSYs must also consider the needs and impacts on local communities and economies. Sustainable practices should balance ecological health with human well-being.

2.2.27 Sustainable yields are higher for lower trophic levels.

List the environmental impacts associated with high levels of meat consumption and animal farming.
Describe the environmental benefits of consuming plant-based foods over animal-based foods from higher trophic levels.
Explain how land and water requirements differ between plant-based food production and animal-based food production.

Sustainable yields are the rates at which resources can be harvested without compromising the future availability of those resources. In the context of food production, sustainable yields are higher for organisms at lower trophic levels. This is particularly true for plant-based foods, and it has significant implications for achieving sustainability in food production.

Reasons for Higher Sustainable Yields at Lower Trophic Levels

Energy Efficiency:
- Energy Transfer: Energy transfer between trophic levels is inefficient. Only about 10% of the energy at one trophic level is transferred to the next level. This means that primary producers capture solar energy most efficiently, while higher trophic levels receive progressively less energy.
- Lower Energy Loss: Consuming organisms at lower trophic levels (e.g., plants) is more energy-efficient because less energy is lost in the process. More energy is available per unit area of land when humans consume plants directly rather than consuming animals that feed on plants.
Resource Use:
- Land and Water Requirements: Growing plants generally requires less land and water compared to raising animals. For example, it takes much more land to produce a kilogram of beef than a kilogram of vegetables.
- Feed Conversion Ratios: Animals, especially those at higher trophic levels, require significant amounts of plant-based food to grow. For instance, cows need large quantities of feed to produce meat, whereas plants can be consumed directly by humans with minimal processing.
Environmental Impact:
- Lower Greenhouse Gas Emissions: Plant-based food production typically results in lower greenhouse gas emissions compared to animal-based food production. Livestock, especially ruminants like cows, produce methane, a potent greenhouse gas.
- Reduced Pollution: Plant agriculture generally leads to less pollution in terms of runoff and waste compared to intensive animal farming, which can cause water contamination and other environmental issues.
Biodiversity and Ecosystem Health:
- Habitat Conservation: Lower trophic level food production, such as crop farming, can often be integrated with practices that support biodiversity and ecosystem health. For instance, agroforestry combines trees and crops to enhance biodiversity.
- Sustainable Practices: Practices like crop rotation, organic farming, and permaculture help maintain soil health and ecosystem services, contributing to higher sustainable yields.

Implications for Sustainable Food Production

Dietary Choices:
- Plant-Based Diets: Shifting towards plant-based diets can significantly reduce the ecological footprint of food production. It supports higher sustainable yields and reduces the strain on natural resources.
- Reducing Meat Consumption: Lowering the consumption of meat, particularly from higher trophic levels, can contribute to sustainability by conserving resources and reducing environmental impacts.
Agricultural Practices:
- Sustainable Farming: Emphasizing sustainable agricultural practices that maximize plant yields, such as organic farming, regenerative agriculture, and precision farming, can enhance productivity while preserving ecosystems.
- Innovations in Crop Production: Advancements in crop breeding, biotechnology, and sustainable irrigation practices can further increase the sustainable yields of plant-based foods.
Policy and Education:
- Promoting Sustainability: Policies that promote sustainable food production and consumption, such as subsidies for sustainable farming practices and public awareness campaigns, are crucial for achieving higher sustainable yields.
- Consumer Awareness: Educating consumers about the benefits of consuming lower trophic level foods can drive demand for sustainable products and support broader environmental goals.

2.2.28 Ecological efficiency is the percentage of energy received by one trophic level that is passed on to the next level.

Define ecological efficiency and explain its significance in energy flow within ecosystems.
Describe how ecological efficiency is calculated and discuss factors that may influence its value in different ecosystems.
Compare and contrast ecological efficiency in a terrestrial ecosystem with that in an aquatic ecosystem,

Ecological efficiency is a crucial concept in ecology that describes how energy is transferred between trophic levels within an ecosystem. It is the percentage of energy received by one trophic level that is passed on to the next trophic level. This efficiency varies widely among different ecosystems, trophic levels, and species.

Ecological Efficiency refers to the ratio of energy transferred from one trophic level to the next relative to the energy received by the lower trophic level. It is expressed as a percentage and is calculated using the following formula:

Variability in Ecological Efficiency
The efficiency of energy transfer between trophic levels is not constant and can vary significantly due to several factors:

Ecosystem Type:
- Aquatic Ecosystems: Often exhibit higher ecological efficiency compared to terrestrial ecosystems. For example, aquatic ecosystems may have efficiencies ranging from 10% to 20%.
- Terrestrial Ecosystems: Typically have lower ecological efficiencies, often around 5% to 10%.
Trophic Levels:
- Primary Producers to Primary Consumers: The efficiency of energy transfer from plants to herbivores is generally higher than the transfer between higher trophic levels.
- Higher Trophic Levels: Energy transfer between higher trophic levels, such as from herbivores to carnivores, is usually less efficient due to greater energy losses through metabolic processes and heat.
Species and Life Strategies:
- Metabolic Rate: Species with higher metabolic rates tend to have lower ecological efficiency because a larger proportion of the energy is used for maintenance and heat production.
- Feeding Habits: Herbivores that consume high-energy plant parts (e.g., seeds, fruits) may have higher ecological efficiency compared to those that consume lower-energy parts (e.g., leaves).

Calculating Ecological Efficiency
To calculate ecological efficiency, you need data on the energy received by one trophic level and the energy transferred to the next. Here’s an example calculation:

Given Data:
- Energy received by primary consumers (herbivores) from primary producers (plants): 1000 kJ
- Energy transferred to secondary consumers (carnivores) from primary consumers: 100 kJ
Calculation:

In this example, the ecological efficiency is 10%, indicating that 10% of the energy received by the herbivores is passed on to the carnivores.

Importance of Ecological Efficiency

Energy Flow:
- Ecological efficiency is a key factor in determining the flow of energy through an ecosystem. It influences the structure and dynamics of food webs and the distribution of biomass among trophic levels.
Ecosystem Productivity:
- High ecological efficiency can lead to higher productivity at higher trophic levels, supporting larger populations of consumers. Conversely, low efficiency can limit the abundance of higher trophic levels.
Biodiversity and Stability:
- Efficient energy transfer supports greater biodiversity by allowing a wider range of species to thrive. It also contributes to ecosystem stability by maintaining balanced energy flows.
Conservation and Management:
- Understanding ecological efficiency helps in the management and conservation of ecosystems. It informs decisions about sustainable harvesting, wildlife management, and habitat conservation.

Limitations and Considerations

Variability:
- The 10% rule, often cited as a general estimate of ecological efficiency, is not a fixed value. The actual percentage can vary widely depending on the specific conditions of the ecosystem and the species involved.
Energy Losses:
- Significant energy losses occur at each trophic level due to respiration, growth, reproduction, and heat production. These losses must be considered when assessing energy transfer and ecosystem health.
Data Accuracy:
- Accurate calculation of ecological efficiency requires reliable data on energy intake, assimilation, and transfer for each trophic level. Field studies and controlled experiments are essential for obtaining such data.

2.2.29 The second law of thermodynamics shows how the entropy of a system increases as biomass passes through ecosystems.

Define the term "entropy" and explain its significance in the context of the second law of thermodynamics.
Outline how the second law of thermodynamics affects energy transfer between trophic levels.
Describe how cellular respiration contributes to the increase in entropy in an ecosystem.
Explain how living systems maintain a high degree of organization despite the second law of thermodynamics.

The second law of thermodynamics is a fundamental principle in physics that has significant implications for understanding energy flow and entropy in ecosystems. It helps explain how energy is transformed and how the entropy, or disorder, of a system increases as biomass passes through different trophic levels in an ecosystem.

The Second Law of Thermodynamics states that in any energy transfer or transformation, the total entropy of a system and its surroundings always increases. Entropy is a measure of the amount of disorder or randomness in a system.

Entropy:
- Definition: Entropy is the degree of disorder or randomness in a system. High entropy indicates a high level of disorder, while low entropy indicates a high level of organization.
- Implications: As energy is transferred or transformed in an ecosystem, some of it is lost as heat, increasing the overall entropy.

Energy Transfer and Entropy:
- Energy Degradation: When energy is transferred between trophic levels, a significant portion is lost as heat due to metabolic processes like cellular respiration. This loss contributes to an increase in entropy.
- Efficiency of Transfer: Because of the second law, energy transfers are never 100% efficient. Typically, only about 10% of the energy at one trophic level is passed on to the next level, while the rest is lost as heat, contributing to increased entropy.

Entropy and Biomass in Ecosystems

Biomass and Energy Flow:
- Primary Producers: Plants and other autotrophs capture solar energy and convert it into chemical energy stored in biomass through photosynthesis. This process involves a decrease in entropy within the plant as it creates ordered structures from less ordered molecules.
- Primary Consumers: Herbivores consume primary producers and convert their biomass into energy for growth, reproduction, and maintenance. During this process, a significant amount of energy is lost as heat, increasing the entropy of the system.
- Secondary and Tertiary Consumers: Carnivores and omnivores that consume herbivores and other consumers continue this process, with each transfer of biomass resulting in further energy loss and increased entropy.
Cellular Respiration and Entropy:
- Energy Use: Living organisms use cellular respiration to convert the chemical energy in biomass into usable energy (ATP). This process is inherently inefficient and results in the release of heat.
- Increase in Entropy: The heat released during cellular respiration contributes to an increase in the overall entropy of the ecosystem. Despite this, living systems maintain low internal entropy by continuously importing energy from their environment (e.g., food, sunlight).

Maintaining Organization in Living Systems

High Degree of Organization:
- Living Systems: Despite the second law of thermodynamics, living systems maintain a high degree of organization (low entropy) within themselves. This organization is achieved through the constant input of energy.
- Energy Input: Autotrophs obtain energy from sunlight or chemical sources, while heterotrophs obtain energy from consuming other organisms. This continuous input of energy allows living systems to maintain their structured, low-entropy state.
Net Increase in Entropy:
- Entropy Export: While maintaining low entropy internally, living organisms export entropy to their surroundings through metabolic processes, primarily cellular respiration. The heat released during these processes increases the entropy of the environment.
- Balancing Act: This balance allows ecosystems to sustain complex and ordered structures, such as food webs and habitats, while adhering to the second law of thermodynamics.

Implications for Ecosystem Functioning

Energy Flow and Ecosystem Health:
- Energy Availability: The efficiency of energy transfer and the associated entropy increases determine the amount of energy available at each trophic level. Higher trophic levels receive less energy due to cumulative losses, limiting their population sizes and biomass.
- Productivity: Ecosystem productivity depends on the balance between energy capture (photosynthesis) and energy loss (respiration). Understanding entropy helps ecologists manage ecosystems sustainably.
Biodiversity and Stability:
- Diverse Systems: Ecosystems with diverse and complex food webs tend to be more stable because they can distribute energy more efficiently and buffer against disruptions.
- Adaptation: Organisms have evolved various strategies to maximize energy use and minimize entropy production, contributing to their survival and the resilience of ecosystems.

Correct use of terminology is a key skill in ESS. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Key Terms

Laws of Thermodynamics
photosynthesis
cellular respiration
conservation of energy

HL
heterotrophs
photoautotrophs
chemoautotrophs
secondary productivity
assimilated
net primary productivity
maximum sustainable yields
ecological efficiency
entropy

carbon compounds
organic matter
non-biodegradable
biomass

sustainability
energy transfer
trophic levels
bioaccumulation
autotrophs
producers

food chains
food webs
equilibrium
biomagnification.
energy

gross productivity
energy efficiency
ecological pyramids
energy transformation

Activities

Activity 1: Create system diagrams from a set of data of ecosystems showing transfers and transformations of energy and matter.
Activity 2: Individually brainstorm and select your own organisms to draw a food chain from given data. Include decomposers and detritivores in your food chains to illustrate the complete cycle of energy and nutrients in ecosystems
Activity 3: Draw a freshwater food web based on the following information
Activity 4: Using the provided data, each group will calculate the trophic efficiency between consecutive trophic levels.
Activity 5 : Using data, draw pyramids of numbers, biomass, and energy from the given data
Activity 6: Follow experimental procedures on how to find biomass and energy from biological samples (plant material only).
Activity 7: Bioaccumulation simulation. This experiment is based on a simulation that was generously developed and made available to all by Virtual Biology Lab, located on the web at virtualbiologylab.org

HL
Activity 8: Use laboratory and field techniques for measuring primary and secondary productivity and work out GP and NP from data
Activity 9: Graph the ecological efficiency between two trophic levels in both terrestrial and aquatic ecosystems

Classroom Resources

Energy Flow Diagram homework
Thermodynamics of Food Investigation

Subtopic 2.2 Energy and Biomass.pptx
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Subtopic 2.2 Energy and Biomass Workbook.docx
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Useful links

National Geographic - Ecosystem
Khan Academy - Energy Flow in Ecosystems:
Encyclopedia Britannica - Primary Productivity:
NOAA - Primary Productivity in the Ocean:
Photosynthesis and Cellular Respiration - Khan Academy
BBC Bitesize - Trophic Levels and Food Webs
University of Michigan - The Food Chain
houghtCo - Understanding Ecological Pyramids:
NOAA - Biomagnification:

In The News

Tracking the Impacts of Climate Change on Food Webs in High-Latitude Ecosstems:
The New Arctic: Amid Record Heat, Ecosystems Morph and Wildlife Struggle:
A Drowned Future for Coastal Ecosystems:
Energy Flow Through an Ecosystem:
Human Impacts on Energy Flow through Natural Ecosystems, and How to Mitigate Them:

International-Mindedness

Understanding the principles of energy flow and ecological efficiency in ecosystems highlights the interconnectedness of global environmental challenges. By recognizing the impacts of human activities such as deforestation, urbanization, and pollution on energy transfer and ecosystem sustainability, we can foster a sense of global responsibility and cooperation in developing sustainable practices to protect our planet's diverse ecosystems for future generations..

TOK:

To what extent does the second law of thermodynamics challenge the sustainability of ecosystems, and how do different ways of knowing influence our understanding and management of energy flow and entropy in these systems?

Video Clips

Biological processes depend on energy flow through the Earth system.

This video is about how we don't just need energy to power our lives, we need *low entropy* energy! This is also known as "free energy", and one way of thinking about entropy is as the lack of free energy. The sun provides us with useful, low entropy, energy in the form of photons of visible light, which are then absorbed and converted into plants, sugar, complex molecules, etc, before being radiated back into space as heat, which has much higher entropy.

This video explains the 1st and 2nd laws of thermodynamics as they relate to energy exchanges with environmental systems.

In this episode of Crash Course Chemistry, Hank goes over the ideas of keeping your life balance... well, your chemical life. Equilibrium is all about balance and today Hank discusses Chemical Equilibrium, Concentration, Temperature, and Pressure. Also, he'll chat about Le Chatalier's Principle and Fritz Habe

Watch the following video to learn about: -Positive feedback loops -Negative feedback loops -How competing feedback loops may influence climate change

Paul Andersen explains how ecosystems respond to disruptions. Disruptions can cause changes in the number and variety of organisms. It can also lead to migration, extinction or even speciation.

"A short animated film about the feedback loops likely to lead to catastrophic climate change, by Leo Murray."

From time to time, ecosystems are hit by storms, fires or other types of disturbance. Resilience is the ability of an ecosystem to resist or recover from these events. Resilience preserves ecosystem diversity, productivity and sustainability. Disturbance has more impact on ecosystems that have lost diversity.

For 10,000 years, our world seemed endless. The sky was the limit. But today's world looks much smaller. We've cleared, consumed and polluted our way across the globe. The planet is shrinking. Have we pushed Earth past the tipping point? That's a critical issue the University of Minnesota's Institute on the Environment explores in our second Big Question video. This three-minute multimedia feature draws on research from the article Planetary Boundaries: A Safe Operating Space for Humanity, published this past fall in the journal Nature, and discussed in the current Scientific America

Earth Could Reach Devastating Ecological Tipping Point by 2025

This segment deals with the main positive feedback loops in action in Gaia's complex ecosystems: melting of the ice caps, deforestation, melting of permafrost regions of the planet and the destruction of Ehux: a vital marine algae that is a key component of the earth's climate regulation system.

The scientific evidence appears (overwhelmingly) to indicate that earth (Gaia) may be inexorably approaching or perhaps PAST the tipping point and on it's way to a new climate regime not seen on earth for 55 million years. It will be a climate that is, on average, much hotter, more chaotic and violent than what we have experienced for the entire tenure of our species.

Rain Forest Tipping Point

In a remote fishing village in the Philippine archipelago, coastal fishers responded to falling fish stocks by working harder to catch them. The combination of dynamite, longer workdays, and more advanced gear caused stocks to fall faster. On the edge of crisis, this small community decided to create a no-take marine sanctuary on 10% of its coral-reef fishing grounds. This initiative sparked a renaissance of not only their fishery, but also their cherished way of life

Plenty of people have an opinion on whether the precautionary principle is good or bad, but what exactly is it?