subtopic 3.1: Biodiversity and evolution
https://www.bath.ac.uk/
Biodiversity is the variety of all life forms on earth - the different plants, animals and micro-organisms and the ecosystems of which they are a part.
In this unit focuses on biodiversity and the processes driving the evolution of life on Earth. Biodiversity includes the variety of genes, species, and ecosystems, which are crucial for ecosystem resilience. Evolution, through mechanisms like natural selection and speciation, explains how species change over time. The topic also covers the impact of mass extinctions, evidence from fossils, and how human activities are altering biodiversity, helping us understand the past and future of life on Earth.
This unit is a minimum of 3 SL hours.
In this unit focuses on biodiversity and the processes driving the evolution of life on Earth. Biodiversity includes the variety of genes, species, and ecosystems, which are crucial for ecosystem resilience. Evolution, through mechanisms like natural selection and speciation, explains how species change over time. The topic also covers the impact of mass extinctions, evidence from fossils, and how human activities are altering biodiversity, helping us understand the past and future of life on Earth.
This unit is a minimum of 3 SL hours.
Guiding questions:
- How can diversity be explained and quantified, and why is this important?
- How does the unsustainable use of natural resources impact biodiversity?
Understanding:
importance of biodiversity
3.1.1 Biodiversity is the total diversity of living systems and it exists at several levels.
- Define biodiversity and explain its three levels.
- Discuss the importance of habitat, species, and genetic diversity in maintaining ecosystem stability.
- Explain how genetic diversity within a population contributes to its long-term survival.
The term biodiversity refers to the variety of life on Earth at all its levels, from genes to ecosystems, and the ecological and evolutionary processes that sustain it. Biodiversity includes not only species we consider rare, threatened, or endangered, but every living thing—even organisms we still know little about, such as microbes, fungi, and invertebrates. Biodiversity is important everywhere; species and habitats in your area as well as those in distant lands all play a role in maintaining healthy ecosystems
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Biodiversity encompasses all forms of life on Earth and is categorized into three major levels: habitat diversity, species diversity, and genetic diversity. Each level contributes uniquely to the stability and functioning of ecosystems.
- Habitat diversity: The variety of physical environments, such as forests, wetlands, deserts, coral reefs, and tundra, where species live. Diverse habitats provide different niches and microclimates, allowing a wider range of species to coexist. A region with many distinct habitats, like rainforests or estuaries, often supports greater biodiversity.
- Species diversity: Species diversity is defined as the number of species and abundance of each species that live in a particular location. The number of species that live in a certain location is called species richness.
- Richness is a measure of the number of different species in an area; more species means a richer environment. However, no account is taken of how common or rare each species is.
- Evenness looks at the relative abundance of the species. It therefore takes into account the abundance or scarcity of each species and eliminates the problems of just analyzing species richness in an area.
- High species diversity allows ecosystems to function more effectively, as different species often fulfill various ecological roles (producers, consumers, decomposers). For example,
- If you were to measure the species richness of a forest, you might find 20 bird species, 50 plant species, and 10 mammal species. Abundance is the number of individuals of each species. For example, there might be 100 mountain beavers that live in a forest. You can talk about species diversity on a small scale, like a forest, or on a large scale, like the total diversity of species living on Earth
- Tropical rainforests exhibit high species richness, while temperate forests may have fewer species but still contribute to ecosystem services like carbon sequestration and nutrient cycling.
Genetic diversity: Genetic diversity refers to the variation of genes within both individuals and populations of a species. This diversity allows species to adapt to changing environmental conditions and increases their chances of survival over time. When genetic diversity is high, there are more options for beneficial traits that can help individuals or populations survive environmental changes.
- Low Genetic Diversity: Cheetahs
Cheetahs are an example of a species with very low genetic diversity. Due to historical population bottlenecks, cheetahs are genetically similar to one another, which makes them vulnerable to diseases and reduces their ability to adapt to environmental changes. Their low genetic diversity poses a significant threat to their long-term survival. - Genetically Identical: Bananas
Many commercial banana crops are genetically identical, as they are propagated through cloning. This uniformity makes bananas highly susceptible to pests and diseases, such as the Panama disease, because if one plant is vulnerable, the entire population is at risk. This lack of genetic diversity means that banana crops lack the resilience to adapt to new threats. - High Genetic Diversity: Coral Reefs
Coral reefs often show a high level of genetic diversity within species. Different populations of corals may have genetic variations that allow them to survive in slightly different conditions, such as varying water temperatures or levels of acidity. This diversity within coral species helps coral reefs adapt to changing ocean conditions, contributing to their resilience in the face of climate change.
Activity: Do something on species and richness
3.1.2 The components of diversity contribute to the resilience of ecological systems.
- Define ecosystem resilience and explain how biodiversity at all levels contributes to it.
Analyze the impact of reduced genetic diversity on an ecosystem’s resilience.
Describe how habitat diversity can help ecosystems recover from disturbances such as wildfires or floods.
Resilience refers to an ecosystem's ability to resist change and return to equilibrium despite disturbances. The health, suitability, and resilience of an ecosystem are closely intertwined and depend heavily on its biodiversity and complexity. Ecosystems with high biodiversity tend to have more species interactions and greater stability, allowing them to withstand disruptions more effectively.
Ecosystem diversity, species diversity and genetic diversity are embedded within ecosystems and are interdependent. For example, habitat diversity supports species diversity, which in turn relies on genetic diversity for long-term adaptability. Losses in any one of these levels can weaken the entire system, making ecosystems more vulnerable to collapse or less able to provide essential services such as clean air, water, and food.
An ecosystem with high biodiversity can absorb shocks, recover from disturbances, and continue to provide crucial services, such as climate regulation, nutrient cycling, and habitat for wildlife. This resilience is particularly important as ecosystems face increasing pressures from climate change and human activities.
Overall, biodiversity at all three levels enhances ecosystem resilience, productivity, and stability, ensuring that ecosystems continue to provide essential services such as water purification, pollination, and food production.
An ecosystem with high biodiversity can absorb shocks, recover from disturbances, and continue to provide crucial services, such as climate regulation, nutrient cycling, and habitat for wildlife. This resilience is particularly important as ecosystems face increasing pressures from climate change and human activities.
Overall, biodiversity at all three levels enhances ecosystem resilience, productivity, and stability, ensuring that ecosystems continue to provide essential services such as water purification, pollination, and food production.
Ecosystem Complexity and Resilience
An ecosystem’s complexity is largely determined by its biodiversity and the number of connections within its food web. High biodiversity means that ecosystems have more species, more niches, and more interactions between species. This diversity leads to greater stability because:
Greater genetic diversity within species also enhances resilience, as populations with more genetic variation are more likely to survive and adapt to environmental changes. For instance, in ecosystems with diverse genetic pools, species may have individuals better suited to survive drought, disease, or changes in temperature.
Stage of Succession and Resilience
The stage of succession—the process by which ecosystems develop over time—also influences resilience:
Limiting Factors and Ecosystem Health
Ecosystem health and resilience are also affected by limiting factors such as nutrient availability, water, and sunlight. High productivity, which occurs when limiting factors like sunlight and water are abundant, promotes high biodiversity and more complex food webs, further enhancing resilience. In contrast, ecosystems with limited resources often have lower biodiversity, making them more vulnerable to disturbances.
Human Impacts on Resilience
Human activities can reduce the resilience of ecosystems by simplifying their complexity. Activities like deforestation, agriculture, and urbanization often reduce biodiversity, shorten food chains, and disrupt species interactions. These changes:
However, humans can also enhance ecosystem resilience through positive interventions. Rewilding projects—such as the reintroduction of keystone species—can increase biodiversity and restore ecological balance. For example:
An ecosystem’s complexity is largely determined by its biodiversity and the number of connections within its food web. High biodiversity means that ecosystems have more species, more niches, and more interactions between species. This diversity leads to greater stability because:
- More connections: Species can shift between food sources when disruptions occur, maintaining the flow of energy and resources.
- Negative feedback loops: Complex ecosystems often have more feedback mechanisms that help restore balance after a disturbance. For example, if one species is removed, other species in the food web can adapt, limiting the impact on the entire system.
Greater genetic diversity within species also enhances resilience, as populations with more genetic variation are more likely to survive and adapt to environmental changes. For instance, in ecosystems with diverse genetic pools, species may have individuals better suited to survive drought, disease, or changes in temperature.
Stage of Succession and Resilience
The stage of succession—the process by which ecosystems develop over time—also influences resilience:
- Pioneer communities: In early stages of succession, ecosystems are simple, with short food chains and low biodiversity. These communities are less resilient to change because they have fewer species and interactions to buffer against disturbances.
- Climax communities: In contrast, mature ecosystems (or climax communities) tend to have longer food chains, more species interactions, and greater biodiversity. These factors make mature ecosystems more resilient, as they can better absorb shocks and return to equilibrium. However, climax communities in harsh environments (such as deserts or tundras) may still have low complexity and resilience, even if they are old.
Limiting Factors and Ecosystem Health
Ecosystem health and resilience are also affected by limiting factors such as nutrient availability, water, and sunlight. High productivity, which occurs when limiting factors like sunlight and water are abundant, promotes high biodiversity and more complex food webs, further enhancing resilience. In contrast, ecosystems with limited resources often have lower biodiversity, making them more vulnerable to disturbances.
- Examples: Tropical rainforests, which receive high insolation and precipitation, are highly productive and have complex ecosystems with many species interactions, making them more resilient to changes. In contrast, ecosystems like deserts, where water is a limiting factor, are less complex and more vulnerable to disturbances.
Human Impacts on Resilience
Human activities can reduce the resilience of ecosystems by simplifying their complexity. Activities like deforestation, agriculture, and urbanization often reduce biodiversity, shorten food chains, and disrupt species interactions. These changes:
- Weaken feedback loops: By simplifying ecosystems, human activity reduces the ability of negative feedback loops to restore balance, leaving ecosystems more vulnerable to disturbances.
- Reduce stability: As biodiversity decreases, species have fewer options for adapting to change, making the system less stable and more prone to collapse in the face of environmental stressors.
However, humans can also enhance ecosystem resilience through positive interventions. Rewilding projects—such as the reintroduction of keystone species—can increase biodiversity and restore ecological balance. For example:
- Reintroduction of wolves in Yellowstone National Park: The return of wolves helped restore the food web, leading to more stable populations of other species and improved ecosystem health.
- Sea otters in the Pacific Northwest: Sea otters help control sea urchin populations, which in turn protects kelp forests. This keystone species has a disproportionately large impact on ecosystem resilience by maintaining the balance between species.
Evolution and Biodiversity
3.1.3 Biodiversity arises from evolutionary processes.
- Outline the processes that lead to the evolution of new species.
Discuss the role of mutation, natural selection, and gene flow in generating biodiversity.
Explain how genetic drift differs from natural selection in shaping biodiversity.
image from www.lycaenid.org
Biodiversity has developed over millions of years through evolutionary processes, which result from genetic changes in populations over time. Several key mechanisms drive this process:
Evolutionary processes lead to the development of new species and adaptations that allow organisms to thrive in different environments. Biodiversity is thus the result of millions of years of evolutionary change, responding to shifts in climate, competition, and other selective pressures.
- Mutation: Mutations are random changes in the DNA of organisms. While most mutations are neutral or harmful, some provide advantageous traits that enhance survival and reproduction, introducing new genetic material into populations.
- Gene flow: Movement of genes between populations, typically through migration, increases genetic diversity. When individuals from different populations interbreed, they introduce new genetic combinations that may help populations adapt to environmental changes.
- Genetic drift: This refers to random changes in gene frequencies, especially in small populations. Over time, certain traits may become more common purely by chance, even if they do not provide a survival advantage. This process can lead to reduced genetic diversity.
- Natural selection: This is the process by which individuals with traits better suited to their environment tend to survive and reproduce more successfully. Over many generations, natural selection shapes the characteristics of populations, driving adaptation to specific environments.
Evolutionary processes lead to the development of new species and adaptations that allow organisms to thrive in different environments. Biodiversity is thus the result of millions of years of evolutionary change, responding to shifts in climate, competition, and other selective pressures.
3.1.4 Natural selection is the mechanism driving evolutionary change.
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Natural selection: is the where the organisms that are more adapted to the environment have an advantage over those that are less well adapted, and they survive, flourish and reproduce.
Natural selection refers to the survival of the fittest, with those species containing more favourable traits (strong defence mechanisms, diverse gene pool, can feed on variety of food resources) surviving and those less well suited to their environments not surviving or flourishing
Because of the varying environment both locally as well as globally. Each local environment presents different challenges at different time, if the species migrates to a new place it encounters a much rapid change. Different environmental challenges combined with the time scales involved, results in infinite number of selection criterions, thus leading to diverse selection. Which is repeated for eons. Thus the biodiversity.
Natural selection refers to the survival of the fittest, with those species containing more favourable traits (strong defence mechanisms, diverse gene pool, can feed on variety of food resources) surviving and those less well suited to their environments not surviving or flourishing
- Genetic Variation: Every species has individuals with slight differences. For instance, some moths may be lighter in color due to their genes.
- Survival of the Fittest: Certain traits give individuals an advantage in survival, especially when resources are limited. For example, lighter-colored moths may be harder for birds to spot on tree bark, increasing their chances of survival.
- Reproduction: Those that survive longer are more likely to reproduce. A moth that avoids predation can live longer, find mates, and produce offspring.
- Inheritance: The survivors pass their advantageous traits to their offspring. Over time, more moths inherit these beneficial traits, increasing their frequency in the population.
Because of the varying environment both locally as well as globally. Each local environment presents different challenges at different time, if the species migrates to a new place it encounters a much rapid change. Different environmental challenges combined with the time scales involved, results in infinite number of selection criterions, thus leading to diverse selection. Which is repeated for eons. Thus the biodiversity.
3.1.5 Evolution by natural selection involves variation, overproduction, competition for limited resources, and differences in adaptation that affect rates of survival and reproduction.
- Explain how variation, overproduction, and differential reproduction contribute to natural selection.
- Discuss the significance of variation within a population for natural selection to occur.
- Using an example, explain how competition for resources can lead to evolutionary change.
Natural selection occurs because genetic diversity within a population gives rise to variation among individuals. These variations can affect an individual’s ability to survive and reproduce. The key mechanisms involved in natural selection are:
For example, in a population of beetles, those with darker coloration may be better camouflaged from predators on dark surfaces. Over time, more dark-colored beetles survive and reproduce, increasing the frequency of the dark-color gene in the population. This process continues, shaping the population to better suit its environment.
- Variation: Genetic diversity within a population leads to differences in traits such as size, coloration, or behavior. These variations are essential for natural selection to occur. Individuals with traits that provide an advantage in their environment are more likely to survive and reproduce.
- Overproduction: Most species produce more offspring than can survive to adulthood. This leads to competition for limited resources such as food, water, and shelter.
- Competition: In the struggle for resources, individuals with traits that give them an advantage (e.g., speed, camouflage, resistance to disease) are more likely to survive and reproduce. Those without advantageous traits are less likely to survive.
- Differential survival and reproduction: Individuals with advantageous traits are more likely to survive and reproduce, passing these traits to their offspring. This means that the frequency of advantageous genes increases over generations, leading to a population better adapted to its environment.
- Heritability: Variation is heritable, meaning that traits that provide a survival advantage are passed down from parents to offspring. Over time, as more individuals inherit advantageous traits, these traits become more common in the population, driving evolutionary change.
For example, in a population of beetles, those with darker coloration may be better camouflaged from predators on dark surfaces. Over time, more dark-colored beetles survive and reproduce, increasing the frequency of the dark-color gene in the population. This process continues, shaping the population to better suit its environment.
Case Study: The Peppered Moth (Biston betularia) and Natural Selection
https://globalchange.umich.edu
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https://askabiologist.asu.edu/peppered-moths-game/kettlewell.html
The peppered moth is a classic example of natural selection in action, demonstrating how species can adapt to environmental changes over relatively short periods of time. This case study focuses on the evolutionary changes observed in the peppered moth population during the Industrial Revolution in England and how this provides evidence for natural selection.
Background: Peppered MothThe peppered moth exists in two main color forms:
Background: Peppered MothThe peppered moth exists in two main color forms:
- Light-colored (typica): Moths with light, speckled wings that blend in with the pale lichen-covered tree bark typical of rural environments.
- Dark-colored (carbonaria): Moths with dark, almost black wings.
Before the Industrial Revolution, the light-colored moth was more common because it blended in with the lichen-covered trees, protecting it from predators, particularly birds. The dark-colored moth was rare because it stood out against the lighter tree bark, making it easier for predators to spot.
Impact of the Industrial Revolution
During the late 18th and early 19th centuries, the Industrial Revolution brought widespread pollution to many parts of England. Factories burned coal, releasing large amounts of soot into the environment. This soot settled on trees, turning the previously light, lichen-covered bark dark.
As a result, the light-colored moths that once had a camouflage advantage became highly visible against the soot-darkened bark. Meanwhile, the dark-colored moths, which were previously rare, now blended in better with their surroundings. This environmental change triggered a shift in the population of peppered moths due to differential predation:
Over time, the proportion of dark-colored moths increased significantly in polluted areas—a phenomenon known as industrial melanism. The carbonaria form became more common in industrial regions, while the typica form remained dominant in rural areas with less pollution.
Evidence of Natural Selection
The peppered moth is one of the most famous examples of natural selection because it shows how a population's traits can change in response to environmental conditions.
Impact of the Industrial Revolution
During the late 18th and early 19th centuries, the Industrial Revolution brought widespread pollution to many parts of England. Factories burned coal, releasing large amounts of soot into the environment. This soot settled on trees, turning the previously light, lichen-covered bark dark.
As a result, the light-colored moths that once had a camouflage advantage became highly visible against the soot-darkened bark. Meanwhile, the dark-colored moths, which were previously rare, now blended in better with their surroundings. This environmental change triggered a shift in the population of peppered moths due to differential predation:
- Light-colored moths were more frequently preyed upon because they were easier to spot against the darker trees.
- Dark-colored moths had better camouflage, increasing their chances of survival and reproduction.
Over time, the proportion of dark-colored moths increased significantly in polluted areas—a phenomenon known as industrial melanism. The carbonaria form became more common in industrial regions, while the typica form remained dominant in rural areas with less pollution.
Evidence of Natural Selection
The peppered moth is one of the most famous examples of natural selection because it shows how a population's traits can change in response to environmental conditions.
- Adaptation: The shift from light-colored to dark-colored moths demonstrates how populations adapt to their environments. In this case, the moths’ survival depended on their ability to avoid predation, which was influenced by how well they blended in with their surroundings.
- Genetic Variation: The existence of both light and dark forms in the peppered moth population provided the variation necessary for natural selection to act. When environmental conditions changed, the genetic trait that provided better camouflage (dark coloration) became more favorable.
- Reversal After Pollution Control: In the mid-20th century, efforts to reduce pollution led to cleaner air, and lichen began to regrow on tree trunks, lightening their bark again. As a result, the light-colored form of the moth started to increase in frequency once more, as it regained its camouflage advantage in these less-polluted environments.
Activity: A natural selection case study Gorongosa National Park in Mozambique is an example of natural selection with the emergence of tuskless elephants
3.1.6 Speciation is the generation of new species through evolution.
- Define speciation .
image from evolution.berkeley.edu
Speciation is the process through which new species are generated by evolution. This occurs when populations of a single species become isolated and evolve separately, leading to significant genetic divergence. Over time, these populations develop distinct traits that make them incapable of interbreeding, resulting in the formation of new species.
Speciation will depended on:
Environmental change can create new conditions and challenges for species, driving the process of natural selection. When environmental factors shift—such as changes in climate, habitat, or resource availability—populations of a species may face different selection pressures. Those individuals with traits that make them better suited to the new conditions are more likely to survive and reproduce, gradually shifting the genetic makeup of the population.
In the Galápagos Islands an immigrant finch began breeding with a local female finch. This pairing established a new lineage of finches that bred only within that new lineage. Within three generations, they were completely reproductively isolated from other local finches.
Speciation will depended on:
- isolation of species:the process by which two populations become separated by
- change of environmental
- change of gene pool
Environmental change can create new conditions and challenges for species, driving the process of natural selection. When environmental factors shift—such as changes in climate, habitat, or resource availability—populations of a species may face different selection pressures. Those individuals with traits that make them better suited to the new conditions are more likely to survive and reproduce, gradually shifting the genetic makeup of the population.
In the Galápagos Islands an immigrant finch began breeding with a local female finch. This pairing established a new lineage of finches that bred only within that new lineage. Within three generations, they were completely reproductively isolated from other local finches.
Activity: Select a species known for its evolutionary history and speciation process. Some examples include:
Conduct research on the following aspects of the chosen species:
Write a research report detailing the evolutionary changes, speciation events, and environmental factors that contributed to the development of the new species
- Darwin's finches on the Galápagos Islands.
- Cichlid fish in African Great Lakes.
- Polar bears evolving from brown bears.
- Apple maggot flies and their divergence due to different host plants.
Conduct research on the following aspects of the chosen species:
- Original Population: What was the original species like? Describe its habitat, characteristics, and population before speciation occurred.
- Environmental Changes or Isolation: What environmental factors or isolation mechanisms led to the divergence of populations? For example, geographic isolation, differences in food sources, or climate changes.
- Adaptations and Evolution: What new traits or adaptations emerged in the isolated population? How did these traits help the species survive in its new environment?
- Speciation: How did these changes result in the formation of a new species? Did reproductive isolation occur? Can the new species still interbreed with the original population, or are they fully distinct?
- Present-Day Species: How does the new species differ from its ancestral species today? What role did natural selection and environmental pressures play?
Write a research report detailing the evolutionary changes, speciation events, and environmental factors that contributed to the development of the new species
- What were the main factors driving the speciation of the species?
- How did isolation play a role in the emergence of new traits?
- Are there similarities in the speciation process of different species?
measuring biodiversity
3.1.7 Species diversity in communities is a product of richness and evenness.
- Define species richness and species evenness and explain how they contribute to species diversity.
- Compare two ecosystems with high species richness but different levels of evenness. How might their stability differ?
- Explain why an ecosystem with both high species richness and high evenness is more resilient than one with low evenness.
Species diversity is an important indicator of ecosystem health and stability. It is composed of two key components:
High species diversity (richness and evenness combined) makes ecosystems more stable and resilient because it ensures that multiple species can perform similar ecological roles. For instance, in a coral reef ecosystem, a high diversity of fish species helps maintain balance within the food web and contributes to the overall health of the reef.
- Species richness: This refers to the number of different species present in an ecosystem. Richness alone, however, does not fully represent the diversity of an ecosystem.
- Species evenness: This is the relative abundance of individuals among the species present in an ecosystem. Evenness reflects how evenly distributed the species are. An ecosystem where one species dominates may have high richness but low evenness.
High species diversity (richness and evenness combined) makes ecosystems more stable and resilient because it ensures that multiple species can perform similar ecological roles. For instance, in a coral reef ecosystem, a high diversity of fish species helps maintain balance within the food web and contributes to the overall health of the reef.
Activity: Review the images representing different ecosystems to understand species richness and evenness.
- Examine the number and types of species visible in each ecosystem.
- Count the total number of different species you see in this ecosystem. (Estimate where exact numbers are not clear.)
- Compare the species richness of the three ecosystems. Which ecosystem has the highest species richness? Which has the lowest?
- Compare the species evenness of the ecosystems. Which ecosystem appears to have populations that are more balanced in number?
- Which ecosystem is most likely to have been disturbed by human activity?
https://digfir-published.macmillanusa.com/friedlandapes2e/asset/img_ch5/friedland_2e_fig14_02.html
3.1.8 Simpson’s reciprocal index is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored.
- Define Simpson’s reciprocal index and explain how it is used to measure biodiversity.
- Using the formula for Simpson’s reciprocal index, calculate the species diversity for an ecosystem with given species abundances.
- Compare the species diversity of two ecosystems using Simpson’s reciprocal index and explain what the results indicate about each ecosystem’s stability.
Simpson’s reciprocal index is a mathematical measure of species diversity in an ecosystem, taking into account both species richness and evenness. It is calculated using the formula:
- D is the Simpson diversity index
- – N is the total number of organisms of all species found
- – n is the number of individuals of a particular species
- Diversity is often considered as a function of two components:
- the number of different species
- the relative numbers of individuals of each species.
When we consider ecosystems, diversity is sometimes used to mean how may different species there are in a community.
- High index values: Ecosystems with a high Simpson’s index have a greater number of species and a more even distribution of individuals among species.
- Low index values: Low values suggest that a few species dominate the ecosystem, and diversity is lower.
This index is widely used in conservation biology to compare biodiversity between ecosystems or track changes in biodiversity over time. It helps identify areas of high biodiversity (hotspots) that may need protection and areas where biodiversity is declining, signaling a need for conservation efforts.
Sampling Strategies to Compare Biodiversity
Sampling strategies are essential when comparing biodiversity in different ecosystems, as it is often inefficient or impractical to count every species or individual in a given area. These strategies involve selecting representative samples to estimate the diversity and abundance of species. Random sampling is commonly used to ensure unbiased data collection, while transect sampling is ideal for studying changes across gradients or different zones. These methods can be applied to both terrestrial and aquatic ecosystems.
Sampling in Different Ecosystems
Sampling Techniques Overview
Sampling strategies are essential when comparing biodiversity in different ecosystems, as it is often inefficient or impractical to count every species or individual in a given area. These strategies involve selecting representative samples to estimate the diversity and abundance of species. Random sampling is commonly used to ensure unbiased data collection, while transect sampling is ideal for studying changes across gradients or different zones. These methods can be applied to both terrestrial and aquatic ecosystems.
Sampling in Different Ecosystems
- Grasslands To assess grass species diversity in a grassland, random sampling can be done using 1 m² quadrats within a larger area. The number of grass species and their abundance can be recorded. For small mammals like voles or mice, live traps (e.g., Sherman traps) can be placed systematically across the area to estimate population density and species diversity.
- Wetlands In a wetland ecosystem, you might sample amphibian diversity using drift fences and pitfall traps placed at different points around ponds or marshes to capture frogs, toads, or salamanders. For aquatic plants, random quadrats can be set up within the shallow water zones to count species like cattails, reeds, or water lilies.
- Forests In forest ecosystems, tree diversity can be studied by establishing a 100 m² quadrat and recording the species and size (diameter at breast height) of every tree within the plot. For bird diversity, point counts are often used—observers stay in designated spots and record all bird species seen or heard within a specific time frame. Alternatively, remote acoustic recorders can capture bird songs over a longer period.
- Streams Fish diversity in a stream can be assessed using electrofishing, where a small electrical current is used to temporarily stun fish, making them easier to count and identify before releasing them unharmed. For macroinvertebrates like stoneflies, mayflies, and caddisflies, kick sampling can be used, where the streambed is disturbed within a quadrat and the dislodged organisms are collected with a net downstream.
- Coastal Zones In coastal ecosystems, you can study shellfish diversity along a tidal gradient using transect sampling from the shore to deeper water. Quadrat samples are taken along the transect at regular intervals to assess the distribution and abundance of species like clams, oysters, or mussels. For seagrass beds, random sampling with underwater quadrats can help estimate the abundance of species living within the grass, such as shrimp or juvenile fish.
- Deserts In desert ecosystems, plant diversity can be measured by setting up quadrats to count drought-tolerant species like cacti and succulents. Reptile diversity can be assessed using pitfall traps or rock-flipping along transects to count species such as lizards and snakes. For nocturnal animals, camera traps can be used to capture images of species that are active at night, such as desert foxes or rodents.
- Lakes In lakes, fish diversity can be assessed by using gill nets at various depths to sample fish species. For plankton diversity, specialized equipment like plankton nets is used to sample different depths and distances from the shore. The collected plankton is then analyzed under a microscope to count and identify species.
- Mountains In mountainous ecosystems, you can study alpine plant diversity using transects along an elevation gradient. Quadrat sampling at different altitudes helps track how species composition changes with increasing altitude. For large mammals, scat surveys and camera traps placed along animal trails can provide data on species presence and population densities.
Sampling Techniques Overview
- Quadrat Sampling: Suitable for plants, small invertebrates, or ground-dwelling species.
- Pitfall Traps: Effective for ground-dwelling insects, reptiles, or amphibians.
- Sweep Nets: Used for insects in grasslands or wetlands.
- Mist Netting or Point Counts: Common for sampling bird diversity.
- Camera Traps and Scat Surveys: Used for sampling large mammals or nocturnal species.
- Electrofishing or Gill Nets: Used to sample fish populations in freshwater environments.
- Plankton Nets: Specialized equipment for collecting plankton in aquatic ecosystems.
Application of skills: Collect data in order to work out Simpson’s reciprocal index for diversity.
3.1.9 Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.
- Explain how knowledge of biodiversity can inform conservation strategies.
- Discuss the importance of identifying biodiversity hotspots in global conservation efforts.
- Explain how species recovery programs contribute to maintaining biodiversity.
The preservation of biodiversity requires detailed knowledge of species, ecosystems, and genetic diversity at both global and local scales. This knowledge forms the foundation for effective conservation strategies, guiding decisions that protect species and their habitats. Gathering biodiversity data involves a variety of methods, often combining scientific research with community-based efforts.
How Knowledge is Gathered
In many regions, particularly those with rich biodiversity, local knowledge is critical for conservation. Biodiversity data is collected through a combination of approaches:
How Knowledge is Gathered
In many regions, particularly those with rich biodiversity, local knowledge is critical for conservation. Biodiversity data is collected through a combination of approaches:
Citizen science:
- Involves volunteers from the general public in gathering biodiversity data. Participants might record sightings of specific species, monitor ecosystems, or contribute to large-scale projects like bird counts or plant surveys. Citizen science expands the reach of scientific studies, providing valuable data from across wide geographical areas, and encouraging community engagement in conservation efforts.
Voluntary and government-funded agencies:
Gorongosa National Park is a collaboration between the government of Mozambique and the Carr Foundation
- Organizations such as conservation NGOs, wildlife trusts, and government environmental agencies conduct regular biodiversity assessments. They may use remote sensing technologies, field surveys, and species monitoring programs to track changes in biodiversity and assess the effectiveness of conservation actions.
Gorongosa National Park is a collaboration between the government of Mozambique and the Carr Foundation
Training indigenous communities and parabiologists:
- Indigenous people, who have deep ecological knowledge of their lands, play a crucial role in biodiversity monitoring and conservation. Training indigenous groups to document biodiversity enhances conservation efforts by incorporating their traditional knowledge with scientific methods. Similarly, parabiologists (local people trained in biological data collection) provide valuable data to support biodiversity management. They can conduct species inventories, track endangered species, and report changes in ecosystems, aiding in conservation decisions that align with both scientific and cultural priorities.
Conservation Strategies
Knowledge of biodiversity allows conservationists to identify biodiversity hotspots, species at risk of extinction, and the ecological processes that sustain ecosystems. Key conservation strategies include:
By integrating scientific research, traditional knowledge, and community involvement, conservation efforts become more effective and equitable, ensuring the preservation of biodiversity for future generations.
Knowledge of biodiversity allows conservationists to identify biodiversity hotspots, species at risk of extinction, and the ecological processes that sustain ecosystems. Key conservation strategies include:
- Protected areas: Based on biodiversity data, regions of high ecological value are designated as national parks, nature reserves, or marine sanctuaries. These areas are managed to preserve habitats and protect species from human activities like logging, mining, and poaching.
- Sustainable resource management: Scientific knowledge informs practices that balance human use of natural resources with the need to conserve biodiversity. For example, sustainable forestry practices, fishing quotas, and water management policies are all informed by biodiversity data.
- Species recovery programs: Data on species populations and genetic diversity guides the development of recovery programs for endangered species. These programs may involve captive breeding, habitat restoration, or reintroduction efforts aimed at increasing population numbers and restoring ecosystems.
By integrating scientific research, traditional knowledge, and community involvement, conservation efforts become more effective and equitable, ensuring the preservation of biodiversity for future generations.
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3.1.10 Mutation and sexual reproduction increase genetic diversity.
- Explain how mutation and sexual reproduction increase genetic diversity in populations.
- Discuss the role of mutations in evolution and how they contribute to adaptation.
- Analyze the importance of genetic diversity for species survival in changing environments
Genetic diversity within a population is vital for adaptation and evolution, providing the raw material for natural selection.
Two key mechanisms contribute to this diversity: mutation and sexual reproduction.
Two key mechanisms contribute to this diversity: mutation and sexual reproduction.
DNA exists in every cell of every living organism. The DNA contains all of the information needed for an organism to develop, survive and reproduce. This code is called the genotype (the sequence). It determine the phenotype (the outward expression of the gene)
During sexual reproduction half of the DNA in the egg will combine with half of the DNA in the sperm. This means that there may be different combinations of alleles in the offspring. This is a source of genetic variation..
During sexual reproduction half of the DNA in the egg will combine with half of the DNA in the sperm. This means that there may be different combinations of alleles in the offspring. This is a source of genetic variation..
Mutation
Mutations are random changes in the DNA sequence that create new gene variants (alleles). They can occur spontaneously during DNA replication or due to environmental factors like radiation. Mutations provide genetic variation, essential for evolution:
Mutations constantly introduce new genetic material, ensuring populations have the potential to adapt to changing environments.
Mutations are random changes in the DNA sequence that create new gene variants (alleles). They can occur spontaneously during DNA replication or due to environmental factors like radiation. Mutations provide genetic variation, essential for evolution:
- Beneficial mutations improve survival or reproduction (e.g., disease resistance), and these traits may become more common over generations.
- Neutral mutations do not affect survival but add to the genetic pool.
- Harmful mutations reduce fitness and are often eliminated through natural selection.
Mutations constantly introduce new genetic material, ensuring populations have the potential to adapt to changing environments.
Sexual Reproduction
Sexual reproduction further increases genetic diversity by creating new combinations of genes. This occurs through:
These processes ensure that offspring are genetically diverse, enhancing the population’s ability to adapt to environmental changes and resist threats like disease.
Sexual reproduction further increases genetic diversity by creating new combinations of genes. This occurs through:
- Meiosis: Homologous chromosomes exchange genetic material (recombination), leading to new gene combinations.
- Fertilization: The fusion of genetically unique gametes from two parents results in offspring with a unique set of genes.
These processes ensure that offspring are genetically diverse, enhancing the population’s ability to adapt to environmental changes and resist threats like disease.
Importance of Genetic Diversity
Populations with high genetic diversity are better equipped to survive environmental changes. In contrast, populations with low diversity (e.g., due to inbreeding) are more vulnerable to extinction. For example, agricultural monocultures with low diversity are susceptible to widespread pest and disease outbreaks, whereas wild populations with greater diversity can adapt and survive.
Populations with high genetic diversity are better equipped to survive environmental changes. In contrast, populations with low diversity (e.g., due to inbreeding) are more vulnerable to extinction. For example, agricultural monocultures with low diversity are susceptible to widespread pest and disease outbreaks, whereas wild populations with greater diversity can adapt and survive.
3.1.11 Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioural differences.
- Define speciation and explain how geographical isolation can lead to the formation of new species, using bonobos and chimpanzees as an example.
- Explain how behavioral isolation can lead to speciation, with reference to the apple maggot fly.
- Discuss the factors that contribute to high rates of endemism on isolated islands, with examples like the Galápagos finches or Madagascar's lemurs.
Speciation occurs when populations become reproductively isolated, preventing gene flow and allowing them to evolve independently. Over time, genetic differences accumulate, resulting in the formation of new species.
https://puppeteer.cognitoedu.org/coursesubtopic/b3-alevel-cie_rLpHZapg
Modes of speciation are often classified according to how much the geographic separation of incipient species (a group of organisms that is about to become a separate species from other) can contribute to reduced gene flow. The demands of a different environment or the characteristics of the members of the new group will differentiate the new species from their ancestors.There are three basic ideas of speciation:
Allopatric speciation occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another. Each species develops differently based on the demands of their unique habitat or the genetic characteristics of the group that are passed onto offspring.
Sympatric speciation occurs when there are no physical barriers preventing any members of a species from mating with another, and all members are in close proximity to one another. A new species, perhaps based on a different food source or characteristic, seems to develop spontaneously. The theory is that some individuals become dependent on certain aspects of an environment—such as shelter or food sources—while others do not. Some scientist don't believe it exist.
Parapatric speciation occurs when a species is spread out over a large geographic area. Although it is possible for any member of the species to mate with another member, individuals only mate with those in their own geographic region. Like allopatric and peripatric speciation, different habitats influence the development of different species in parapatric speciation. Instead of being separated by a physical barrier, the species are separated by differences in the same environment.
- allopatric speciation
- sympatric speciation
- parapatric speciation
Allopatric speciation occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another. Each species develops differently based on the demands of their unique habitat or the genetic characteristics of the group that are passed onto offspring.
Sympatric speciation occurs when there are no physical barriers preventing any members of a species from mating with another, and all members are in close proximity to one another. A new species, perhaps based on a different food source or characteristic, seems to develop spontaneously. The theory is that some individuals become dependent on certain aspects of an environment—such as shelter or food sources—while others do not. Some scientist don't believe it exist.
Parapatric speciation occurs when a species is spread out over a large geographic area. Although it is possible for any member of the species to mate with another member, individuals only mate with those in their own geographic region. Like allopatric and peripatric speciation, different habitats influence the development of different species in parapatric speciation. Instead of being separated by a physical barrier, the species are separated by differences in the same environment.
Island Endemism
Isolated islands have high rates of endemism, where species are unique to that island. This is due to geographical isolation, limited gene flow, and unique ecological niches. Factors that contribute to island endemism include:
Isolated islands have high rates of endemism, where species are unique to that island. This is due to geographical isolation, limited gene flow, and unique ecological niches. Factors that contribute to island endemism include:
- Geographical Isolation: Species evolve independently, free from gene flow with mainland populations.
- Limited Gene Flow: Isolation reduces genetic mixing, allowing populations to diverge through genetic drift and natural selection.
- Ecological Niches: Islands often present new, unoccupied niches, allowing species to evolve into specialized roles.
- Example: Galápagos Finches: Finches on the Galápagos Islands evolved into different species, each with unique beak shapes adapted to specific food sources, due to the isolation and diverse ecological niches.
- Example: Hawaiian Honeycreepers: These birds evolved from a single ancestor but diversified into many species, each adapted to different food sources, due to the isolation and unique environments of the Hawaiian Islands.
Activity: Research two contemporary examples of speciation and their causes. (geographical separation, behavioral separation)
- apple maggott flies
- bonobos and common chimpanzees
- North Altaltic killer whatle
- Northern and Mexican Spotted owls
- Grand Canyon squirrels
- Caribbean Anoles
- Hawaiian Honeycreepers
human activity on biodiversity
3.1.12 Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered.
- Explain why biodiversity is unevenly distributed across the planet.
- Discuss the importance of biodiversity hotspots and why they are critical for global conservation efforts.
- Analyze the factors that contribute to high biodiversity in tropical regions compared to temperate regions
Biodiversity is not evenly spread across the Earth. Certain areas, called biodiversity hotspots, are home to a disproportionately high number of species, many of which are endemic (found nowhere else). These regions, such as tropical rainforests and coral reefs, are crucial for global biodiversity.
However, these biodiversity hotspots are under threat from human activities such as deforestation, habitat destruction, climate change, and pollution. Conservation efforts often focus on protecting these areas because they contain a large proportion of the Earth’s species in a small area.
- Tropical rainforests: These ecosystems support about 50% of the world’s species, despite covering only 7% of the Earth’s surface. The stable climate, abundant rainfall, and complex structure of rainforests provide a wide variety of niches for species to occupy.
- Coral reefs: Often referred to as the "rainforests of the sea," coral reefs support a vast array of marine life. The structural complexity of coral formations provides habitat for fish, invertebrates, and other marine organisms.
However, these biodiversity hotspots are under threat from human activities such as deforestation, habitat destruction, climate change, and pollution. Conservation efforts often focus on protecting these areas because they contain a large proportion of the Earth’s species in a small area.
https://www.tropicalconservationfund.org/biodiversityhotspots.html
Critics say that naming hotspots can be misleading:
- the focus is only on vascular plants. It ignores all animals
- hotspots do not represent the total species diversity and richness
- only focuses on regions where habitats have ben lost. It ignores whether that loss is still happening
- does not consider genetic diversity
- does not consider the value of services
3.1.13 Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species.
- Explain how human activities, such as hunting and climate change, have influenced natural selection in a species, using tuskless elephants in Gorongosa as an example.
- Discuss the impact of creating new habitats through urbanization or agriculture on the natural selection of local species.
- Using a named example, explain how selective pressures from human activities can lead to physical adaptations in species
Human activities have significantly altered natural environments, creating new selective pressures on species. These pressures often force species to adapt rapidly or face extinction. Key human activities that affect natural selection include:
Urbanization as a Selective Pressure
Agriculture as a Selective Pressure
- Urban environments present unique challenges, such as traffic and altered food sources. Species like urban squirrels adapt by developing road-crossing behaviors, while others, such as pigeons and raccoons, shift their diet to human-related food waste. Nesting behaviors also change, as some birds use buildings as substitutes for natural habitats.
Agriculture as a Selective Pressure
- Agricultural land use favors species that exploit crops or develop pesticide resistance. Some animals adapt by shifting their feeding strategies to cultivated plants, while pests evolve to survive chemical treatments, as seen in pesticide-resistant insects. Agriculture also fragments habitats, driving further adaptations in species behavior and movement.
Climate Change:
- The burning of fossil fuels has led to global warming, shifting ecosystems, and forcing species to migrate or adapt to new temperature and precipitation patterns. For example, species in polar regions and coral reefs are particularly vulnerable to the changes caused by rising temperatures.
Hunting, Poaching, and Harvesting:
- Targeted hunting or poaching of specific species can alter the traits within a population. Selective pressures favor individuals that avoid human detection, leading to changes in behavior or physical traits over generations.
- Example: Tuskless Elephants in Gorongosa, Mozambique
In response to heavy poaching for ivory during Mozambique's civil war, the population of tusked elephants in Gorongosa National Park dramatically decreased. As a result, elephants with the genetic trait for tusklessness had a survival advantage, since poachers targeted elephants with tusks. Over time, the frequency of tuskless elephants has increased, a clear example of human-driven selection favoring this trait.
Consequences of Human Activities on Species
Human-induced changes often occur more quickly than natural environmental shifts, requiring species to adapt at an accelerated pace. This rapid selection can lead to:
- Altered behavior: Species may change their feeding, mating, or migration behaviors to survive in human-modified environments.
- Physical adaptations: Traits such as body size, coloration, or reproductive strategies may shift as a response to selective pressures imposed by human activities.
- Population decline or extinction: Species unable to adapt may face rapid population decline or even extinction.
3.1.14 Artificial selection reduces genetic diversity and, consequently, species resilience.
- Explain the difference between natural and artificial selection, and discuss how artificial selection reduces genetic diversity. [6 marks]
- Using examples, explain why artificially selected species are more vulnerable to diseases or environmental changes. [5 marks]
- Discuss the economic and environmental importance of maintaining genetic diversity
Artificial selection is a deliberate process where humans choose specific traits in plants or animals for breeding, while natural selection is an unguided process driven by environmental pressures. Although artificial selection can increase productivity, it often reduces genetic diversity, making species more vulnerable to diseases, environmental changes, and other threats.
Natural vs. Artificial Selection
Natural vs. Artificial Selection
- Natural Selection:
Occurs naturally, favoring individuals with traits that help them survive and reproduce in their environment. It maintains genetic diversity by allowing a wide range of traits to persist in populations. - Artificial Selection:
Humans select individuals with desirable traits (e.g., high crop yields, fast-growing livestock) for breeding, reducing genetic diversity as only certain genes are passed on. This genetic uniformity increases the vulnerability of species to diseases and environmental changes.
Vulnerability of Artificially Selected Species
Artificially selected species, such as crops and livestock, often lack the genetic diversity needed for resilience:
Artificially selected species, such as crops and livestock, often lack the genetic diversity needed for resilience:
- Monocultures in Agriculture: Growing genetically uniform crops (monocultures) can increase yields but leaves them highly susceptible to pests or diseases, as seen in the Irish Potato Famine.
- Livestock Breeding: Selective breeding in livestock for traits like fast growth can make them less resistant to diseases or environmental stress, leading to greater risks for farmers.
The Importance of Genetic Diversity
Maintaining genetic diversity is crucial for resilience:
Maintaining genetic diversity is crucial for resilience:
- Economic Perspective:
- Diverse crops and livestock are better able to resist disease outbreaks, ensuring food security and reducing the need for chemical interventions.
- Environmental Perspective:
- Genetic diversity in natural populations supports ecosystem resilience and adaptability, helping species survive in changing environments and preserving biodiversity.
Artificial selection has both advantages and disadvantages
earth history
3.1.15 Earth history extends over a period of 4.5 billion years. Processes that occur over an extended timescale have led to the evolution of life on Earth.
- Outline the major geological events in Earth’s history and their impact on biodiversity.
- Explain how continental drift has influenced the distribution and evolution of species.
- Discuss the relationship between mass extinctions and biodiversity over Earth’s history
Key Geological and Biological Events
- Formation of Earth:
About 4.5 billion years ago, the Earth formed from a cloud of dust and gas surrounding the young sun. The early Earth was extremely hot and inhospitable, but as it cooled, the first oceans formed, and simple life began to emerge. - Origin of Life:
The earliest forms of life—simple, single-celled organisms—appeared around 3.5 billion years ago in Earth's oceans. These organisms evolved over billions of years into more complex life forms, with multicellular life appearing around 600 million years ago. - Cambrian Explosion:
About 541 million years ago, the Cambrian Explosion marked a period of rapid diversification of life forms. During this time, most major groups of animals evolved, and complex ecosystems began to take shape. Fossil evidence from this period shows the emergence of many of the body plans that still exist today. - Mass Extinctions and Evolution:
Earth has experienced five major mass extinctions, where a significant percentage of species were wiped out. These events were often followed by periods of rapid speciation, where new species evolved to fill the ecological niches left vacant by the extinctions. For example, the Cretaceous-Paleogene extinction 66 million years ago, which wiped out the dinosaurs, allowed mammals to become the dominant land animals.
Adapted from an original drawing by S. M. Stanley
Role of Fossils in Understanding Evolution
Fossils provide critical evidence for understanding the evolution of life over geological timescales. They offer a record of organisms that lived in the past, showing how life has changed and diversified over millions of years. Fossils help scientists:
Fossils provide critical evidence for understanding the evolution of life over geological timescales. They offer a record of organisms that lived in the past, showing how life has changed and diversified over millions of years. Fossils help scientists:
- Track the Progression of Life:
Fossils show the gradual changes in species over time. By studying different layers of rock, scientists can reconstruct a timeline of life’s evolution. For example, fossils of ancient fish help scientists understand the transition from aquatic to terrestrial life, as fish evolved into amphibians. - Link Major Evolutionary Changes:
Transitional fossils, like Tiktaalik (a fish with features of both aquatic and land-dwelling organisms), provide important evidence of how major evolutionary transitions occurred. These fossils bridge the gaps between large evolutionary steps, such as the evolution of tetrapods from lobe-finned fish. - Understand Extinctions and Radiations:
Fossil records also reveal periods of mass extinction and the subsequent recovery of ecosystems. For example, the fossil record following the Permian-Triassic extinction (252 million years ago) shows a sharp decline in biodiversity followed by the emergence of new species that adapted to the altered environment.
ib.bioninja.com.au
Fossils and Epoch Transitions
Fossils help scientists mark the boundaries between epochs, showing changes in species diversity and the appearance of new forms of life after mass extinctions.
Fossils help scientists mark the boundaries between epochs, showing changes in species diversity and the appearance of new forms of life after mass extinctions.
- Mass Extinctions: Many epoch transitions are linked to mass extinction events, where environmental changes cause a sharp decline in species, followed by the rise of new species.
- Example: End-Cretaceous Extinction
Around 66 million years ago, an asteroid impact caused the extinction of non-avian dinosaurs, marking the shift from the Cretaceous to the Paleogene period. Fossils show a decline in dinosaurs and the rise of mammals.
- Example: End-Cretaceous Extinction
- Evolutionary Radiations: After extinctions, new species rapidly evolve to fill vacant niches, as seen in the Cambrian Explosion, which marks the start of the Phanerozoic eon.
The Evolutionary Impact of Geological Changes
Earth’s geological history—shaped by tectonic activity, climate shifts, and asteroid impacts—has had profound effects on the evolution of life:
Earth’s geological history—shaped by tectonic activity, climate shifts, and asteroid impacts—has had profound effects on the evolution of life:
- Continental Drift: The movement of continents has isolated populations and created new habitats, driving speciation. For example, the separation of South America from Africa led to the evolution of distinct species on each continent.
- Climate Change: Ice ages, warming periods, and other climate shifts have forced species to adapt or migrate, contributing to natural selection and evolutionary change. For example, the repeated ice ages of the Pleistocene Epoch were a major factor in the evolution of modern humans.
3.1.16 Earth history is divided up into geological epochs according to the fossil record.
- Explain the significance of the Cambrian Explosion for the evolution of biodiversity.
- Discuss the impact of the Cretaceous-Paleogene extinction on the evolution of life.
- Using examples, analyze how mass extinction events have shaped Earth’s geological epochs.
The geological timescale divides Earth's 4.5 billion-year history into eons, eras, periods, and epochs, each marked by significant geological or biological events. Fossils are key to understanding these divisions, showing how life evolved or became extinct in response to environmental changes.
- Eons: The largest time divisions. For example, the current Phanerozoic Eon began around 541 million years ago and includes all complex life.
- Eras: Eons are divided into eras, such as the Mesozoic Era, which saw the rise and fall of dinosaurs.
- Periods and Epochs: Eras are further divided into periods and epochs, marked by major shifts in species and climate, such as the transition from the Cretaceous Period to the Paleogene Period.
https://www.australianenvironmentaleducation.com.au/education-resources/the-geologic-timescale/
Examples of Epochs
- Pleistocene Epoch (2.6 million to 11,700 years ago): Known for repeated ice ages and the evolution of modern humans. Large mammals, such as mammoths, became extinct as the epoch transitioned to the Holocene.
- Anthropocene (Proposed): A suggested epoch based on human impact on Earth's geology, including pollution and climate change.
The Importance of Geological Timescales
The concept of geological timescales allows scientists to divide Earth’s history into distinct periods, each characterized by significant changes in climate, geography, and life forms. These timescales include:
The concept of geological timescales allows scientists to divide Earth’s history into distinct periods, each characterized by significant changes in climate, geography, and life forms. These timescales include:
- Eons, Eras, and Periods: Earth's history is divided into major eons, such as the Precambrian and Phanerozoic eons. Each eon is subdivided into eras and periods, such as the Mesozoic Era, which saw the rise and fall of the dinosaurs.
- Epochs: Finer divisions, such as epochs, help pinpoint more specific geological and evolutionary events, such as the evolution of humans during the Pleistocene Epoch.
mass extensions
3.1.17 Mass extinctions are followed by rapid rates of speciation due to increased niche availability.
- Explain how mass extinctions create opportunities for speciation. [6 marks]
- Discuss the role of adaptive radiation in the evolution of new species after a mass extinction event. [6 marks]
- Analyze how the Permian-Triassic extinction led to significant changes in biodiversity.
Mass extinctions are catastrophic events that result in the loss of a significant portion of Earth’s species. Although devastating, these extinctions are often followed by periods of speciation, where new species evolve to fill the ecological niches left vacant by extinct species. Over Earth’s history, there have been five major mass extinctions, each caused by different natural factors. Today, however, scientists warn that a sixth mass extinction—driven by human activities—is underway.
Causes of Past Mass Extinctions
Causes of Past Mass Extinctions
- Tectonic Plate Movements: The shifting of continents can drastically alter climate and sea levels, creating environments that species cannot adapt to quickly enough. For example, the Permian-Triassic Extinction (around 252 million years ago) is believed to have been influenced by massive tectonic shifts, which led to climate change and habitat destruction, causing the extinction of over 90% of marine species.
- Super-volcanic Eruptions: Large volcanic eruptions release vast amounts of ash and gases, causing climate cooling and acidification of oceans. The End-Triassic Extinction (about 201 million years ago) may have been triggered by volcanic activity in what is now the Atlantic Ocean, leading to global climate disruption and mass extinction.
- Climatic Changes: Natural shifts in global climate can have extreme effects on biodiversity. For instance, the Ordovician-Silurian Extinction (about 444 million years ago) occurred due to an ice age that drastically lowered sea levels, destroying habitats and causing the extinction of marine species.
- Sea-level Changes: Fluctuations in sea levels, often driven by tectonic or glacial activity, can destroy coastal habitats or isolate populations. Sea-level drops during the Devonian Extinction (around 359 million years ago) reduced shallow marine habitats, leading to the extinction of many marine species.
- Meteorite Impacts: The most well-known mass extinction, the Cretaceous-Paleogene Extinction (66 million years ago), was caused by an asteroid impact near present-day Mexico. The resulting environmental upheaval, including fires, dust clouds blocking sunlight, and a "nuclear winter," wiped out about 75% of species, including non-avian dinosaurs.
The Sixth Mass Extinction
Unlike the previous five, the sixth mass extinction is driven by anthropogenic (human-caused) factors, including habitat destruction, climate change, pollution, overhunting, and the introduction of invasive species. The rapid pace of this extinction is unprecedented in Earth’s history:
- Habitat Destruction: Deforestation, urbanization, and agricultural expansion are eliminating ecosystems that species rely on for survival. Many rainforests, which are biodiversity hotspots, are being cleared at alarming rates.
- Climate Change: Human-induced global warming is causing shifts in temperature and precipitation patterns, forcing species to migrate or adapt quickly. For many species, these changes are happening too rapidly for natural adaptation.
- Overexploitation: Overfishing, hunting, and poaching are reducing populations of species at unsustainable rates. For example, the illegal poaching of elephants for ivory has drastically reduced their numbers, driving evolutionary changes such as the rise of tuskless elephants in certain populations.
- Pollution: Industrial pollution, plastic waste, and chemical runoff are poisoning ecosystems, leading to species declines, particularly in freshwater and marine environments.
Speciation After Mass Extinctions
Following mass extinctions, new species often evolve to fill the niches left by those that went extinct. These periods of adaptive radiation occur as surviving species diversify and adapt to new environments.
While mass extinctions reset ecosystems, they also create opportunities for rapid evolutionary change, driving speciation and the development of new biodiversity.
Following mass extinctions, new species often evolve to fill the niches left by those that went extinct. These periods of adaptive radiation occur as surviving species diversify and adapt to new environments.
- Example: Mammalian Radiation After the Cretaceous-Paleogene Extinction
After the dinosaurs were wiped out, mammals, which were previously small and relatively insignificant, quickly diversified to fill vacant ecological roles. This led to the rise of many mammalian species, including the ancestors of humans. - Example: Evolution of Marine Life Post-Permian Extinction
The Permian-Triassic Extinction, which decimated marine species, was followed by a period of rapid diversification of marine organisms. New groups of fish, mollusks, and corals evolved, leading to the modern marine ecosystems we see today.
While mass extinctions reset ecosystems, they also create opportunities for rapid evolutionary change, driving speciation and the development of new biodiversity.
image from https://www.nationalgeographic.org/media/mass-extinctions/
3.1.18 The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity.
- Define the Anthropocene and explain why it is considered a new geological epoch.
- Discuss the environmental changes that characterize the Anthropocene
- Explain how spherical fly ash particles and Carbon-14 markers can be used as evidence of the proposed beginning of the Anthropocene
The Anthropocene is a proposed geological epoch that highlights the profound impact humans have had on the Earth’s geology, ecosystems, and climate. Unlike previous epochs defined by natural geological events, the Anthropocene reflects the global changes caused by human activity. However, there is ongoing debate among scientists about whether the Anthropocene should be formally recognized and when exactly it began. Scientists are considering various 'golden spikes', or markers, to pinpoint its beginning
Debate on the Existence and Beginning of the Anthropocene
Some geologists argue that human impact on the planet has been so significant that it deserves its own epoch, while others believe these changes may not meet the strict criteria used to define geological time divisions. The key debate centers around identifying a clear starting point, or "golden spike," in the geological record that marks the beginning of the Anthropocene.
Various start dates have been proposed, based on significant human-driven changes:
Key Features of the Anthropocene
The Anthropocene is characterized by the unprecedented scale and speed of human-driven changes. Key features include:
Potential Markers of the Anthropocene in Geological Strata
If the Anthropocene is formally recognized, certain markers will serve as evidence of the epoch in the geological strata:
Debate on the Existence and Beginning of the Anthropocene
Some geologists argue that human impact on the planet has been so significant that it deserves its own epoch, while others believe these changes may not meet the strict criteria used to define geological time divisions. The key debate centers around identifying a clear starting point, or "golden spike," in the geological record that marks the beginning of the Anthropocene.
Various start dates have been proposed, based on significant human-driven changes:
- 1610 Dip in Carbon Dioxide:
Some scientists suggest that the Anthropocene began in 1610, following the arrival of Europeans in the Americas. The subsequent decline in indigenous populations due to disease and colonization led to the reforestation of vast areas of land, which caused a noticeable dip in atmospheric carbon dioxide levels. This event, visible in ice cores, marks a potential starting point for human-driven environmental change on a global scale. - 1950 Spherical Fly Ash Particles:
The mid-20th century is another proposed starting point, coinciding with the advent of the Industrial Revolution and the "Great Acceleration" of human activity. This period saw a sharp increase in fossil fuel consumption, pollution, and population growth. A distinct marker for this period is the appearance of spherical fly ash particles—tiny remnants from coal burning that are found in sediments worldwide, indicating industrial pollution. - 1964 Carbon-14 Markers from Nuclear Tests:
Another proposed marker for the Anthropocene is the 1964 Carbon-14 spike, caused by above-ground nuclear weapons testing during the Cold War. This period left a clear, global signature in the form of radioactive carbon isotopes, which can be detected in tree rings, sediments, and other geological records. This global event is considered one of the most visible and consistent markers of human impact on the planet.
Key Features of the Anthropocene
The Anthropocene is characterized by the unprecedented scale and speed of human-driven changes. Key features include:
- Climate Change:
Human activities, particularly the burning of fossil fuels, have led to rising levels of greenhouse gases like carbon dioxide, causing global warming, melting ice caps, and changing weather patterns. These changes are now visible in the geological record through increased carbon levels in ice cores and other sediments. - Habitat Destruction:
Deforestation, urbanization, and industrial agriculture have transformed large areas of land. These activities have driven species extinction rates to levels comparable to those seen in previous mass extinction events. Sediment layers now contain evidence of these changes, including pollen from introduced plant species and shifts in soil composition. - Pollution:
Human activities have introduced synthetic chemicals, plastics, and radioactive materials into the environment. Plastic particles, for example, are now found in sediments across the globe, marking a lasting and potentially permanent change in the Earth’s geological layers.
Potential Markers of the Anthropocene in Geological Strata
If the Anthropocene is formally recognized, certain markers will serve as evidence of the epoch in the geological strata:
- Plastics:
Non-biodegradable plastics are now embedded in sediment layers in oceans and rivers worldwide. Plastics, particularly microplastics, are likely to be a long-lasting marker of human activity in the Earth's strata. - Carbon-14 from Nuclear Tests:
The spike in Carbon-14 from nuclear weapons tests in the 1950s and 1960s provides a clear, globally distributed marker that can be detected in many natural archives, such as tree rings and ice cores. - Fly Ash from Coal Burning:
Spherical fly ash particles, a byproduct of industrial coal combustion, are now a prominent feature in sediment cores dating from the 1950s onward, signifying the global spread of pollution during the Industrial Revolution and beyond.
The epoch of the Anthropocene is likely to be announced in August 2024. In July 2023, Crawford Lake, Ontario, Canada was announced as the location for the golden spike which will mark the Global Boundary Stratotype Section and Point (GSSP) that is required for the citation of a new Epoch
The World Wide Fund for Nature produces a periodic report on the state of the world's ecosytems, called the Living Planet Report. The 2022 report showed an average decline of 69% decrease since 1970.
The Significance of the Anthropocene
If the Anthropocene is officially adopted, it would represent the first geological epoch defined by human activity. The concept raises important questions about the long-term effects of human actions on the Earth’s systems and our responsibility to manage these impacts. It also underscores the magnitude of the current biodiversity crisis, climate change, and widespread environmental degradation driven by human activities.
If the Anthropocene is officially adopted, it would represent the first geological epoch defined by human activity. The concept raises important questions about the long-term effects of human actions on the Earth’s systems and our responsibility to manage these impacts. It also underscores the magnitude of the current biodiversity crisis, climate change, and widespread environmental degradation driven by human activities.
3.1.19 Human impacts are having a planetary effect, which will be detectable in the geological record.
- Explain how human activities will leave a geological record that will be visible for millions of years.
- Discuss the significance of plastic pollution in the geological record of the future.
- Analyze how nuclear testing has left a distinct marker in the Earth’s geological strata
Human activities are leaving permanent marks on the Earth’s geological record, providing evidence that future geologists will be able to observe for millions of years. These changes, which are occurring at a scale and speed never before seen in Earth’s history, are a strong argument for recognizing the Anthropocene as a separate epoch from the Holocene.
Evidence for the Anthropocene in the Geological Record
Four key types of evidence support the notion that human activities are altering the planet in ways that will be preserved in the geological strata for millions of years:
Chemical Pollution
Human industrial activities have introduced a wide range of synthetic chemicals into the environment. These pollutants, including plastics, heavy metals, and pesticides, are accumulating in soils and ocean sediments. Over time, these chemical signatures will be preserved in geological layers. Microplastics, for example, have now been detected in sediments from remote areas of the ocean floor, and their persistence means they will likely form part of the future fossil record.
Plastics and Synthetic Compounds: Plastics, which are non-biodegradable, are being deposited worldwide in terrestrial and marine sediments. These materials, along with synthetic compounds like DDT and PCBs (polychlorinated biphenyls), are already being preserved in geological layers and could serve as lasting markers of human activity.
Mixing of Native and Non-Native Species
The widespread movement of species due to human activities, whether intentional (e.g., agriculture, landscaping) or unintentional (e.g., through global trade), has led to the mixing of native and non-native species in ecosystems around the world. This biological mixing, also known as biotic homogenization, will be evident in the fossil record. Fossils of non-native species found in areas where they previously did not exist will serve as a marker of human-driven ecological change.
Deposits from Nuclear Testing
The advent of nuclear weapons testing during the mid-20th century left a distinct signature in the form of radioactive isotopes, such as Carbon-14 and Plutonium-239. These isotopes, released during atmospheric nuclear tests, are now present in soils, glaciers, and sediments across the globe. This radioactive layer will persist for thousands of years, creating a clear boundary in the geological record that corresponds to human nuclear activity.
Modification of Terrestrial and Marine Sedimentary Systems
Human activities have significantly altered natural sedimentary processes. Urbanization, deforestation, agriculture, and dam building have disrupted the flow of rivers, modified coastlines, and changed the deposition of sediments in marine and terrestrial environments. These changes have accelerated erosion in some areas and sediment buildup in others, leading to layers of human-modified sediments that will be preserved in geological records.
Minerals Created Solely by Human Activity
Human activities have also led to the creation of new minerals and rocks that did not exist naturally before industrialization. These "anthropogenic minerals" include materials such as steel slag, aluminum alloys, and certain types of glass and ceramics. These human-made materials are already being embedded in sediments and rocks, and they will become part of the Earth's geological layers in the far future.
Evidence for the Anthropocene in the Geological Record
Four key types of evidence support the notion that human activities are altering the planet in ways that will be preserved in the geological strata for millions of years:
Chemical Pollution
Human industrial activities have introduced a wide range of synthetic chemicals into the environment. These pollutants, including plastics, heavy metals, and pesticides, are accumulating in soils and ocean sediments. Over time, these chemical signatures will be preserved in geological layers. Microplastics, for example, have now been detected in sediments from remote areas of the ocean floor, and their persistence means they will likely form part of the future fossil record.
Plastics and Synthetic Compounds: Plastics, which are non-biodegradable, are being deposited worldwide in terrestrial and marine sediments. These materials, along with synthetic compounds like DDT and PCBs (polychlorinated biphenyls), are already being preserved in geological layers and could serve as lasting markers of human activity.
Mixing of Native and Non-Native Species
The widespread movement of species due to human activities, whether intentional (e.g., agriculture, landscaping) or unintentional (e.g., through global trade), has led to the mixing of native and non-native species in ecosystems around the world. This biological mixing, also known as biotic homogenization, will be evident in the fossil record. Fossils of non-native species found in areas where they previously did not exist will serve as a marker of human-driven ecological change.
- Example: Invasive Species: Fossils of species introduced by humans, such as certain plants, insects, or marine organisms, may be found in areas far outside their natural ranges. For example, species such as the zebra mussel (introduced to North America) or the cane toad (introduced to Australia) will leave fossil evidence of their spread across ecosystems.
Deposits from Nuclear Testing
The advent of nuclear weapons testing during the mid-20th century left a distinct signature in the form of radioactive isotopes, such as Carbon-14 and Plutonium-239. These isotopes, released during atmospheric nuclear tests, are now present in soils, glaciers, and sediments across the globe. This radioactive layer will persist for thousands of years, creating a clear boundary in the geological record that corresponds to human nuclear activity.
- Nuclear Fallout as a Marker: The Carbon-14 spike from nuclear testing in the 1950s and 1960s is visible in ice cores, tree rings, and lake sediments. These isotopic markers, found worldwide, serve as a clear and globally synchronized signal of human activity.
Modification of Terrestrial and Marine Sedimentary Systems
Human activities have significantly altered natural sedimentary processes. Urbanization, deforestation, agriculture, and dam building have disrupted the flow of rivers, modified coastlines, and changed the deposition of sediments in marine and terrestrial environments. These changes have accelerated erosion in some areas and sediment buildup in others, leading to layers of human-modified sediments that will be preserved in geological records.
- Example: Coastal Changes: Coastal cities and industrial developments have led to the deposition of artificial materials, such as concrete, asphalt, and other building materials, in sediments. Additionally, the construction of dams has changed the flow of rivers, trapping sediments that would normally be carried to the ocean, altering sediment deposition patterns in coastal areas.
Minerals Created Solely by Human Activity
Human activities have also led to the creation of new minerals and rocks that did not exist naturally before industrialization. These "anthropogenic minerals" include materials such as steel slag, aluminum alloys, and certain types of glass and ceramics. These human-made materials are already being embedded in sediments and rocks, and they will become part of the Earth's geological layers in the far future.
- Example: Technofossils: Future geologists may find evidence of human-made structures and materials—known as technofossils—such as concrete, bricks, and metals, embedded in sedimentary layers. These will serve as physical markers of the Anthropocene, distinct from any natural geological formations.
Activity: Data sowing the number of species that are under thret of extension or that have become extinct. produce an activity.
Key Terms
|
biodiversity
speciation behaviour evolution stability adaptation mutation survival of the fittest jump dispersal |
genetic diversity
species fertile Charles Darwin Theory of Evolution succession Galapagos Islands island population diffusion |
species diversity
inbreed offspring physical barrier habitat finch secular migration interbreeding over population |
habitat diversity
lithosphere isolation plate tectonics land bridge resilience competition geographic isolation climax community |
natural selection
asthenosphere population gene pool diversity inertia limited resources fitness speciation |
Classroom Materials
| Subtopic 3.1 Biodiversity and Evolution Presentation.pptx |
| Subtopic 3.1 Biodiversity and Evolution Workbook.docx |
Biodiversity and Conservation Project
Consequence of Change Article
Island Foxes May be 'Least Variable' of all Wild Animals Article
Natural Selection Virtual Lab - Gene frequency
pHet Natural Selection Simulation
Peppered Moth Simulation
pHet Simulation: Plate Tectonics
Case Studies
- Examples of speciation of an organism
- Speciation of Camels
- Speciation of Spotted Owls
- 5th Mass Extinction Activity
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.
Useful Links
Map Maker: Biodiversity Hotspots
National Geographic: Types of Biodiversity
NWF Why is Diversity Important?
Natural History Museum site
Global Issues with Biodiversity - Global Issues
Biodiversity Science
Island Biogeography from Stanford University, USA
Another good island biogeography animation showing the physical migration, real-time data, and a graph.
Biodiversity and Ecosystem Stability - Nature
Millennium seed bank
Natural History Museum site
Darwin's full works - Darwin Online
Biodiversity Science
Charles Darwin and evolution - Natural Selection animation for CSU
Natural Selection - Charles Darwin and Evolution
Evolution 101 on natural selection and speciation - Berkeley
Important Dates and Cool Creatures In Earths History - University of Kentucky
Plate tectonics
Plate tectonic - PBS
Island Biogeography from Stanford University, USA
Another good island biogeography animation showing the physical migration, real-time data, and a graph.
Millennium seed bank
Map Maker: Biodiversity Hotspots
National Geographic: Types of Biodiversity
NWF Why is Diversity Important?
Natural History Museum site
Global Issues with Biodiversity - Global Issues
Biodiversity Science
Island Biogeography from Stanford University, USA
Another good island biogeography animation showing the physical migration, real-time data, and a graph.
Biodiversity and Ecosystem Stability - Nature
Millennium seed bank
Natural History Museum site
Darwin's full works - Darwin Online
Biodiversity Science
Charles Darwin and evolution - Natural Selection animation for CSU
Natural Selection - Charles Darwin and Evolution
Evolution 101 on natural selection and speciation - Berkeley
Important Dates and Cool Creatures In Earths History - University of Kentucky
Plate tectonics
Plate tectonic - PBS
Island Biogeography from Stanford University, USA
Another good island biogeography animation showing the physical migration, real-time data, and a graph.
Millennium seed bank
In The News
Global Biodiversity Outlook - Convention on Biological Diversity
Mechanics of speciation: Model examines factors that contribute to emergence of new species - Science Daily June 27, 2011
The Looming Mass Extinction by Humans - BBC News 1 Nov 2013
Global Biodiversity Outlook - Convention on Biological Diversity
Mechanics of speciation: Model examines factors that contribute to emergence of new species - Science Daily June 27, 2011
The Looming Mass Extinction by Humans - BBC News 1 Nov 2013
TOK
- "Theories of evolution and biodiversity rely on evidence from the natural world, but our understanding of these processes is continually shaped by new discoveries and evolving scientific perspectives."
International-mindedness:
- "Biodiversity is a global resource that transcends national borders, and the conservation of ecosystems and species requires international collaboration to address shared environmental challenges and protect the planet's biological heritage."
The theory of evolution explains how the enormous variety of life could come into existence. How it is possible for primitive life forms to spawn the millions of different creatures, that exist today. Unfortunately, evolution is often misunderstood, because it's mechanisms seem counter intuitive
Biologists teach that all living things on Earth are related. Is there any solid evidence to back this claim?
Discover natural selection as a mechanism of evolution with the Amoeba Sisters. This video also uncovers the relationship of natural selection and antibiotic resistance in bacteria and emphasizes biological fitness.
There is a dizzying diversity of species on our planet. From genetic evidence we know that all of those species evolved from a single ancient ancestor. But how does one species split in to many? Through the evolutionary process of speciation — which begins when populations become isolated by changes in geography or by shifts in behavior so that they no longer interbreed. This video illustrates the speciation process in birds to help you understand the basis of earth's biodiversity.
In this video you will learn how weird and wonderful animals are formed in the process of speciation and the formation of new species
Hank guides us through the process of natural selection, the key mechanism of evolution
Hank explains specification - the evolutionary process by which new biological species arise - in terms of finches, ligers, mules, and dogs.
Mr. Andersen describes how plate tectonics shapes our planet. Continental and oceanic platers are contrasted and major plate boundaries are discussed
Visualization of asteroid impact that killed dinosaurs 65 million years ago, based on accurate research and scientific fact. Created by Radek Michalik ([email protected]) at the Science Institute of Columbia College Chicago
According to the United Nations, we are losing about 200 species per day--a thousand times the normal background rate of extinction. How does this stack up to previous mass extinctions?
Hank takes us on a trip through time to revisit the 5 major mass extinction events that have impacted species over the Earth's history, and leaves us with some thoughts about what could possibly be the sixth event - the one caused by human activities.
"Medea Hypothesis" author Peter Ward argues that most of Earth's mass extinctions were caused by lowly bacteria. The culprit, a poison called hydrogen sulfide, may have an interesting application in medicine.
