topic 2.5: investigating ecosystems
To a large extent it is the physical (abiotic) conditions within any environment that controls the plant and thus the animal (biotic) community that develops. In terrestrial ecosystems physical conditions in the atmosphere, at the surface and within the soils all interact to create the conditions that give rise to vegetation that develops. To make links between the physical environment and the biotic communities, ecologist and environmental scientist need to be able to measure the abiotic conditions.
Remember that biotic components of an ecosystems consists of all of the living organisms in the ecosystem. Measuring the biotic component can be a challenge at times. Especially if the organism you are trying to sample is traveling over 50km per hour. It can also be a challenge trying to find out how many anthills are in a 100 square kilometers.
In this unit you will learn how to make dichotomous keys to identify organisms and various sampling techniques. This unit is a minumum of 4.5 hours.
Significant ideas:
Remember that biotic components of an ecosystems consists of all of the living organisms in the ecosystem. Measuring the biotic component can be a challenge at times. Especially if the organism you are trying to sample is traveling over 50km per hour. It can also be a challenge trying to find out how many anthills are in a 100 square kilometers.
In this unit you will learn how to make dichotomous keys to identify organisms and various sampling techniques. This unit is a minumum of 4.5 hours.
Significant ideas:
- The description and investigation of ecosystems allows for comparisons to be made between different ecosystems and for them to be monitored, modelled and evaluate over time, measuring both natural change and human impacts.
- Ecosystems can be better understood through the investigation and quantification of their components.
Knowledge & Understanding:
2.5.U1 The study of an ecosystem requires that it be named and located; for example, Deinikerwald in Baar, Switzerland—a mixed deciduous–coniferous managed woodland.
Ecosystem ecology is the study of these and other questions about the living and nonliving components within the environment, how these factors interact with each other, and how both natural and human-induced changes affect how they function.
Understanding how ecosystems work begins with an understanding of how sunlight is converted into usable energy, the importance of nutrient cycling, and the impact mankind has on the environment. Plants convert sunlight into usable forms of energy that are carbon based. Primary and secondary production in populations can be used to determine energy flow in ecosystems. Studying the effects of atmospheric? CO2 will have future implications for agricultural production and food quality
Understanding how ecosystems work begins with an understanding of how sunlight is converted into usable energy, the importance of nutrient cycling, and the impact mankind has on the environment. Plants convert sunlight into usable forms of energy that are carbon based. Primary and secondary production in populations can be used to determine energy flow in ecosystems. Studying the effects of atmospheric? CO2 will have future implications for agricultural production and food quality
2.5.U2 Organisms in an ecosystem can be identified using a variety of tools including keys, comparison to herbarium or specimen collections, technologies and scientific expertise.
Proper identification of species is important to biologists if they want to compare their study area to other regions. Knowing the organisms that live in your region can help you to learn about their function within the ecosystem
and why it is important to protect them
and why it is important to protect them
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2.5.U3 Sampling strategies may be used to measure biotic and abiotic factors and their change in space, along an environmental gradient, over time, through succession, or before and after a human impact (for example, as part of an EIA).
Investigations in to ecosystems are very complicated since there are so many different factors that need to be considered. We can broadly group factors influencing ecosystems in to: biotic factors are living factors affecting an organism, such as food, competition or disease and abiotic factors, non-living factors.
Know the methods for measuring any three significant abiotic factors and how these may vary in a given ecosystem with depth, time or distance.
- Marine—salinity, pH, temperature, dissolved oxygen, wave action
- Freshwater—turbidity, flow velocity, pH, temperature, dissolved oxygen
- Terrestrial—temperature, light intensity, wind speed, particle size, slope, soil moisture, drainage, mineral content.
image from en.wikipedia.org
Methods and changes should be selected appropriately for the human activity chosen. Suitable human impacts for study might include toxins from mining activity, landfills, eutrophication, effluent, oil spills and overexploitation. This could include repeated measurements on the ground, satellite images and maps.
Example of human activity
Chernobyl 1986, Russia:
Nuclear reactor blew up
This caused an increase in thermal power which lead to more explosions. This contaminated soil, plants and animals.
Respond:
Example of human activity
Chernobyl 1986, Russia:
Nuclear reactor blew up
- design drawback
- human errors due to poor supervision
This caused an increase in thermal power which lead to more explosions. This contaminated soil, plants and animals.
Respond:
- Fire fighters tried to turn it off, it took 5000 tonnes of sand, lead and clay.
- The UN gave £75 million to make it safe and it was fixed by an international team ten years later.
- People had to evacuate 30km away
- The town was cleared of everything
- 15cm of soil depth was removed
- land washed away and dams were built
- wall built around it
- food was contaminated
2.5.U4 Measurements should be repeated to increase reliability of data. The number of repetitions required depends on the factor being measured.
Reliability, like validity, is a way of assessing the quality of the measurement procedure used to collect data in a dissertation. In order for the results from a study to be considered valid, the measurement procedure must first be reliable. Reliability in research data refers to the degree to which an assessment consistently measures whatever it is measuring.
There are many forms of reliability, all of which will have an effect on the overall reliability of the instrument and therefore the data collected. Reliability is an essential pre-requisite for validity. It is possible to have a reliable measure that is not valid, however a valid measure must also be reliable.Below are some of the forms of reliability that the researcher will need to address
Inter-Rater or Inter-Observer Reliability
Used to assess the degree to which different raters/observers agree when measuring the same phenomenon simultaneously.
Test-Retest Reliability
Compares results from an initial test with repeated measures later on, the assumption being that the if instrument is reliable there will be close agreement over repeated tests if the variables being measured remain unchanged.
Parallel-Forms or Alternate-Forms Reliability
Used to assess the consistency of the results of two similar types of test used to measure the same variable at the same time.
There are many forms of reliability, all of which will have an effect on the overall reliability of the instrument and therefore the data collected. Reliability is an essential pre-requisite for validity. It is possible to have a reliable measure that is not valid, however a valid measure must also be reliable.Below are some of the forms of reliability that the researcher will need to address
Inter-Rater or Inter-Observer Reliability
Used to assess the degree to which different raters/observers agree when measuring the same phenomenon simultaneously.
Test-Retest Reliability
Compares results from an initial test with repeated measures later on, the assumption being that the if instrument is reliable there will be close agreement over repeated tests if the variables being measured remain unchanged.
Parallel-Forms or Alternate-Forms Reliability
Used to assess the consistency of the results of two similar types of test used to measure the same variable at the same time.
2.5.U6 Methods for estimating the biomass and energy of trophic levels in a community include measurement of dry mass, controlled combustion and extrapolation from samples. Data from these methods can be used to construct ecological pyramids.
Dry weight measurements of quantitative samples could be extrapolated to estimate total biomass. Biomass is calculated to indicate the total energy within in a living being or trophic level. The greater the mass of the living material the greater the amount of energy present.
2.5.U7 Methods for estimating the abundance of non-motile organisms include the use of quadrats for making actual counts, measuring population density, percentage cover and percentage frequency.
Counts
Coverage
Frequency
- Number of species in an individual area
- The number of individuals per unit area
- D=ni/A (D = density; n = number of individuals in species, A = sampling area)
Coverage
- The proportion of ground that is occupied or area covered by the plant/species
- Ci=ai/A
Frequency
- The number of times a given event occurs
2.5.U8 Direct and indirect methods for estimating the abundance of motile organisms can be described and evaluated. Direct methods include actual counts and sampling. Indirect methods include the use of capture–mark–recapture with the application of the Lincoln index.
– n1 is the number caught in the first sample
– n2 is the number caught in the second sample
– nm is the number caught in the second sample that were marked
– n2 is the number caught in the second sample
– nm is the number caught in the second sample that were marked
t is impossible for you to study every organism in an ecosystem. The number of organisms can be overwhelming. Limitations must be put on how many plants and animals you study. In order to study the animals there are trapping methods which help obtain more samples, like:
Sample methods must allow for the collection of that is scientifically representative and appropriate, and allow the collection of data on all species present. Results can be used to compare ecosystems.
IT is important to take into consideration that the marking methods are not harmful to the animal and clear so that they do not become easy targets for prey.
- pitfall traps
- small mammal traps
- light traps
- tullgren funnels
Sample methods must allow for the collection of that is scientifically representative and appropriate, and allow the collection of data on all species present. Results can be used to compare ecosystems.
IT is important to take into consideration that the marking methods are not harmful to the animal and clear so that they do not become easy targets for prey.
2.5.U9 Species richness is the number of species in a community and is a useful comparative measure.
Biological diversity can be quantified in many different ways. The two main factors taken into account when measuring diversity are richness and evenness. Richness is a measure of the number of different kinds of organisms present in a particular area. For example, species richness is the number of different species present. However, diversity depends not only on richness, but also on evenness. Evenness compares the similarity of the population size of each of the species present.
2.5.U10 Species diversity is a function of the number of species and their relative abundance and can be compared using an index. There are many versions of diversity indices, but students are only expected to be able to apply and evaluate the result of the Simpson diversity index as shown below. Using this formula, the higher the result (D), the greater the species diversity. This indication of diversity is only useful when comparing two similar habitats, or the same habitat over time.
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
– 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:
When we consider ecosystems, diversity is sometimes used to mean how may different species there are in a community.
Species diversity is best describe as a combination of richness and evenness. Ecologists have developed various formula to measure species diversity.
When using the Simpson's diversity index, D is a measure of species richness. A high value of D suggests a stable and ancient site, and a low value of D could suggest pollution, recent urbanization or agricultural activity. The index is normally used in studies of vegetation but can also be applied to comparisons of animal or species diversity.
One of the most common indices of species diversity is the Simpson’s index. In Environmental Systems and Society we use a derivative of the index with the formula
- 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.
Species diversity is best describe as a combination of richness and evenness. Ecologists have developed various formula to measure species diversity.
When using the Simpson's diversity index, D is a measure of species richness. A high value of D suggests a stable and ancient site, and a low value of D could suggest pollution, recent urbanization or agricultural activity. The index is normally used in studies of vegetation but can also be applied to comparisons of animal or species diversity.
One of the most common indices of species diversity is the Simpson’s index. In Environmental Systems and Society we use a derivative of the index with the formula
Applications and skills:
2.5.A1 Evaluate sampling strategies.
Sampling Techniques
It is not possible to survey an entire area, so small areas called samples are taken, these are two methods used.
Quadrat sampling takes small areas, randomly chosen from an ecosystem, these areas are bounded by a metal frame called a quadrat. Where to place the quandrat is usually decided by dividing an area in a grid, and then randomly selecting co-ordinates (throwing isn't scientific enough!). For instance, below point (2,3) has been chosen to be sampled.
It is not possible to survey an entire area, so small areas called samples are taken, these are two methods used.
Quadrat sampling takes small areas, randomly chosen from an ecosystem, these areas are bounded by a metal frame called a quadrat. Where to place the quandrat is usually decided by dividing an area in a grid, and then randomly selecting co-ordinates (throwing isn't scientific enough!). For instance, below point (2,3) has been chosen to be sampled.
Quadrats are more useful for comparing species in two different areas, and for practical purposes are used in ecosystems without tall vegetation - such as meadows or shores.
A problem is when counting plants, but they grow in clumps; this is overcome by calculating the density or the percentage of ground covered.
A second method is transect sampling, this is used to measure the change from one area to another. It is carried out by laying a line along an area, and then recording species the line touches, or placing a quadrat at regular intervals.
A slightly different method is a belt transect, where two parallel lines are laid and the conditions between these measured.
A problem is when counting plants, but they grow in clumps; this is overcome by calculating the density or the percentage of ground covered.
A second method is transect sampling, this is used to measure the change from one area to another. It is carried out by laying a line along an area, and then recording species the line touches, or placing a quadrat at regular intervals.
A slightly different method is a belt transect, where two parallel lines are laid and the conditions between these measured.
Statistical Methods
Once you have performed an ecological investigation, you will have a lot of data and need to represent and interpret it somehow; to do this we use statistics.
One method of interpreting the mean that you may be familiar with, is the standard deviation. This is a measure of how spread out the data is. For instance, 10, 11 ,12, 13, 14 have a mean of 12, but 1, 1, 1, 1, 56 also have a mean of 12, this is where the standard deviation is useful.
The equation for standard deviation is:
Once you have performed an ecological investigation, you will have a lot of data and need to represent and interpret it somehow; to do this we use statistics.
One method of interpreting the mean that you may be familiar with, is the standard deviation. This is a measure of how spread out the data is. For instance, 10, 11 ,12, 13, 14 have a mean of 12, but 1, 1, 1, 1, 56 also have a mean of 12, this is where the standard deviation is useful.
The equation for standard deviation is:
2.5.A2 Evaluate methods to measure at least three abiotic factors in an ecosystem
2.5.A3 Evaluate methods to investigate the change along an environmental gradient and the effect of a human impact in an ecosystem
The distribution of organisms in a habitat may be affected by physical factors, such as temperature and light. Transects and quadrats are used to collect quantitative data.
An environmental gradient is a gradual change in abiotic factors. Environmental gradients can be related to factors such as altitude, temperature, depth, ocean proximity and soil humidity. Species abundances usually change along environmental gradients in a more or less predictive way. However, the species abundance along an environmental gradient is not only determined by the abiotic factor but, also by the change in the biotic interactions, like competition.
When measuring these changes, all parts of the gradient needs to be sampled. A transect is usually used. The simplest one is when a line of tape is layed down across the area wanted to be measured then to take samples of all the organisms touching the tape. Many transects should be taken to obtain quantitative data. A belt transect is used for bigger samples
When measuring these changes, all parts of the gradient needs to be sampled. A transect is usually used. The simplest one is when a line of tape is layed down across the area wanted to be measured then to take samples of all the organisms touching the tape. Many transects should be taken to obtain quantitative data. A belt transect is used for bigger samples
2.5.A4 Evaluate methods for estimating biomass at different trophic levels in an ecosystem
Biomass - The mass of organic matter present in organisms or ecosystems, usually per unit area.It is taken as the mass of an organism minus the water content (dry weight biomass). This is because water varies from organism to organism. Additionally, it has no energy nor is it organic. The process of obtaining dry weight biomass is the same as the soil moisture process. The sample is heated at a temperature (80 degrees C) which is hot enough to evaporate the water, but not hot enough to burn tissue. This is left for a specific period of time and re-weighed. The process is then repeated until no further weight loss is recorded. Biomass is usually represented per unit area so that comparisons can be made between trophic levels. Dry-weight measurements can be extrapolated to estimate total biomass.
2.5.A5 Evaluate methods for measuring or estimating populations of motile and non-motile organisms
Measuring non motile species will include the use of quadrats for making actual counts, measuring population density, percentage cover and percentage frequency. Motile species can be sampled using the capture-mark-release-recapture method (with estimates based on the Lincoln index)
2.5.A6 Calculate and interpret data for species richness and diversity
Richness is the number of species per sample. The more species present in a sample, the 'richer' the sample. Species richness as a measure on its own takes no account of the number of individuals of each species present. It gives as much weight to those species which have very few individuals as to those which have many individuals.
Simpson's Diversity Index is a measure of diversity. In ecology, it is often used to quantify the biodiversity of a habitat. It takes into account the number of species present, as well as the abundance of each species.
Simpson's Diversity Index is a measure of diversity. In ecology, it is often used to quantify the biodiversity of a habitat. It takes into account the number of species present, as well as the abundance of each species.
2.5.S1 Design and carry out ecological investigations.
Methods of Investigation
- The Scientific Method
- Planning an Investigation
- Stages of an Investigation
- Making Investigations
- Transformations
- Constructing Tables and Graphs
- Descriptive Statistics
- Frequency Distributions
- Direct Methods
- Point Sampling
- Quadrat Sampling
- Transect Sampling
- Mark and Recapture
- Indirect Methods
- Equipment and Sampling Methods
- Keying Out Species
2.5.S2 Construct simple identification keys for up to eight species.
Keys called dichotomous keys are used to identify species. The key is written so that the identification is done in steps. At each step two options are given based on different possible characteristics of the organism you are looking at. You go through all the steps until the name of the species is discovered.
This is a key that divides macroinvertebrates into four categories.
For the exams you need to have at least eight species in the key you construct. This can also be shown graphically.
This is a key that divides macroinvertebrates into four categories.
For the exams you need to have at least eight species in the key you construct. This can also be shown graphically.
2.5.S3 Draw graphs to illustrate species diversity in a community over time, or between communities.
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Key Terms
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biodegradable
diversity Lincoln index small mammal trap dry weight overexploration |
dichotomous key
sustainable environmental impact physical characteristics duration species biomass genetic diversity capture light traps density index |
biotic
habitat diversity recapture tullgren funnel population density species richness |
mitigation
scoping competition index diversity quadrats catchable percentage frequency relative abundance secchi circle terrestrial |
correlation
species diversity pitfall trap release percentage cover evenness |
Classroom Materials
Quadrat Method Samping worksheet
Quadrate Method investigation
Quadrate Sampling Lab Simulation
A line transect
Measuring abundance
Capture / Mark / Release / Recapture practice
Lincoln Index Internal Assessment
Abiotic Systems Links
Marine Ecosystem
Woodland Ecosystem
Freshwater Ecosystem
Grassland Ecosystem
Quadrat Method Samping worksheet
Quadrate Method investigation
Quadrate Sampling Lab Simulation
A line transect
Measuring abundance
Capture / Mark / Release / Recapture practice
Lincoln Index Internal Assessment
Abiotic Systems Links
Marine Ecosystem
Woodland Ecosystem
Freshwater Ecosystem
Grassland Ecosystem
Powerpoint and Notes Adapted from Brad Kremer, P Brooks and Ms. McCrindle
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
2.5 Practical field work Part 1 - Niche Science
2.5 Practical Field Work Part 2 - Niche Science
How to Measure Abiotic Factors - eHow
Sampling and Measuring Abiotic and Biotic Factors from BBC
Abiotic Factors of Ecosystems - BBC Bitesize
Abiotic Tools - Educational Media Learning Centre
How to Measure Wind Speed - eHow
Ecological Sampling Methods - Offwell Woodland and Forest Trust
Measuring Biomass PDF Booklet - UN Food and Agriculture Organisation
Measuring Biomass - Global Greenhouse Warming
Cropland Capture - GeoWiki
Quadrat Sampling - Science Aid
All About Transects - PB Works
This Example from New Zealand is the model we use for the courtyard transect
Dichotomous Keys - Biology Junction
The Broads - Biology Junction
Using Dichotomous Keys - Oregon State University
Another Macro-Invertebrate Key - CVRB
Benthic Macro-invertebrates - EPA
Fieldguide to Freshwater Macro Organisms
Pond Organisms - Microscopy UK
Interactive Plant Key - Web World Wonders
Interactive Insect Key - About.com
Interactive Tree Key - Key Nature
All Kinds of Sampling Techniques - Field Studies Counsel
Terrestrial Measuring Techniques - Oregon State University
Ecological Surveys - Offwell Woodland and Forest Trust
Lincoln Index - Offwell Woodland and Forest Trust
Biotic Index - Water Action Volunteers
Simpson's index - Offwell Woodland and Forest Trust
Simpson's Diversity Index - Offwell Woodland and Forest Trust
Screencast of Simpson's index - Tiger Tube
Simpson Index Calculator - Al Young Studios
In The News
Biodiversity Articles from the Guardian
Biodiversity Articles from Earth Times
Terrestrial Primary Production: Fuel For Life from Knowledge Project
Secondary productivity from Knowledge Project
TOK:
How does the role of instrumentation circumvent the limitations of perception? Can environmental investigations and measurements be as precise or reliable as those in the physical sciences? Why is this, and how does this affect the validity of the knowledge? Applying similarly rigorous standards as are used in physics, for example, would leave environmentalists with very little they could claim as knowledge. But, by insisting on high degrees of objectivity, would we miss out on a useful understanding of the environment? Is a pragmatic or correspondence test of truth most appropriate in this subject area?
Video Clips
Line transects are used when you wish to illustrate a linear pattern along which plant or animl communities change. They are especially good for showing zonation. In this video I show you how to do both a continuous line transect and an interrupted line transect
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his chapter explains the concept of line transect sampling for estimating prey populations
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On June 30, 2010 a Harbor Porpoise (10-012) underwent satellite tagging at the University of New England's Marine Animal Rehabilitation Center and was released shortly after, a couple of miles off-shore in Biddeford, Maine.
Dr. Chris Jenkins of The Orianne Society demonstrates how to place an electronic transponder inside a live snake in order to track its movements in the wild over time. Data recovered from the electronic tracking device, called a PIT tag, are used by scientists in their efforts to save rare and endangered reptiles in their native habitats.
Paul Andersen explains the importance of biodiversity. He starts by describing how biodiversity can be species, genetic or ecosystem diversity. He explains the importance of keystone species in an environment and gives two examples; the jaguar and the sea otter. He finishes with a quote from the father of biodiversity, E.O. Wilson
Madagascar, the 4th largest island in the world and home to 5% of its plant and animal species, is designated as a "biodiversity hot spot." Hot spots are areas that are directly threatened by an expanding human population.
Wildlife biology students Brandon Davis, James Goerz and Tucker Seitz talk about their snowshoe hare research projects
This video clip shows how to use excel to calculate both Shannon-Wiener and Simpson Index for biodiversity. Only need to focus on Simpson Index
