Analyze the biodiversity of a stream ecosystem.
Overview: The experiment is located at Virtual Biology Lab website. You will analyze the biodiversity of a stream ecosystem. This lab addresses the challenge of quantifying biodiversity. After reviewing the various levels of biodiversity, the exercise will focus on estimating species diversity by simulating stream sampling for aquatic invertebrates.
As you work through the exercise, you will be required to answer questions. Compose the questions and answers in a separate document and then submit completed report in the Journal. There are four parts to this exercise. Itemize your responses per part.
Background: It is common to hear ecologists talking about biodiversity, particularly in terms of conservation biology. It is one of those terms that is used a lot, and is considered to refer to something important, yet, rarely is it clear exactly what is being discussed. In fact, ‘biodiversity’ can refer to many things, and has many specific definitions.
The most common definition of biodiversity refers to the number of different species in a given area or species diversity. The greatest biodiversity by this measure would be the number of different species found in tropical rain forests which is estimated to be in the millions. Sometimes biologists refer to the diversity within a particular taxon. For example, the southern Appalachians are the world’s ‘hotspot’ for salamander diversity. There are many indices of species diversity that we will explore later.
Biodiversity, in the broad sense, can also refer to variation within species, or among populations. Many species have populations which can be differentiated by morphology or behavior. Typically this occurs within species with large ranges. Consider for example, the extraordinary differences among human populations across the globe. This variation reflects underlying differences in allele proportions among populations and is called genetic diversity. Genetic diversity is of special concern to endangered species because small populations tend to lose genetic diversity through random genetic drift. Without genetic diversity, populations lose their ability to adapt to changing environments, and are more susceptible to be decimated by disease. In populations with normal genetic diversity there will a range of disease resistance among individuals. An extreme example of a species with low genetic diversity is the cheetah. Cheetah’s are so similar genetically that they can accept skin grafts from unrelated individuals without tissue rejection.
On a larger scale, we can consider ecosystem diversity. In this case we are not considering individual species, rather a species assemblage in a particular habitat. Ecosystem diversity is a broad concept, encompassing any level of ecological organization above species (e.g. habitat, community, and ecosystem). An example of a major threat to ecosystem diversity in the US is the loss of wetlands to development. It is not easy to quantify ecosystem diversity, as the edges of things like habitat and communities are hard to define. However, it can be argued that the most natural way to preserve all levels of biodiversity is to protect as much and as varied habitat as possible, and then let nature take care of the rest.
Procedure: Using the Model With a Java-enabled web-browser, go to:
Click ‘Biodiversity’ under the ‘Ecology’ tab from the Model Categories menu, and open the ‘Stream Diversity’ model.
When the model opens, you will see a section of stream with 16 containers lined up on the bank. Using the control buttons you can open a seine in the middle of the stream and catch any of the animals that float into it. Captured animals are then sorted into the appropriate containers.
Reset: Clears the graph, sets time to 0, removes the seine, releases animals
Go: Sets the stream in motion with animals drifting down
Pollution: Selects stream pollution level (None, Moderate, Severe)
Sampling_Time: The amount of time the seine will be open (simulated seconds)
Open Seine: Places the seine in the middle of the stream, starts sampling & plotting data
Close Seine: Removes the seine, stops plotting data
Release: Dumps captured animals downstream
Clear Plot: Clears lines from the plot, otherwise runs are overlaid
Speed: The slider above the world-view, controls the speed of the simulation
Individual Species Counts: The numbers of each species caught (row below world-view)
Total Catch: Number of all individuals caught
Total Species: Number of different species represented in sample
Sampling Time: The amount of time the seine has been open (simulated seconds)
Line Graph: Cumulative species vs. Sampling time
Procedure: Run the model several times to become familiar with how it works. You can speed things up with the speed slider, but be sure to slow it down now and then to admire your catch. When you are ready, use the simulation and the information above to answer the following questions. Type the questions and answers in your Journal for submission.
1) Having read the text of this learning journal, write a definition for each of the following reporters – ie what ecological measure does each of them represent?
Individual species counts
2) Which of the measure (or measures) of species diversity that you have described in question 1 reflects how evenly individuals are distributed among different species?
3) Which measure of species diversity that you have described in question 1 reflects the overall density of organisms in an area?
4) Run the simulation and set the sampling time = 200. Perform the experiment three times with no pollution and three times with severe pollution. Record counts in your journal for individual species, for total species and for total catch in each run. Create a table for easier recording and analysis and calculate the average (mean) values for each read out. Present your calculated results in a graphical format – you may choose which ever type of graph you think best displays your data (bar, line or pie).
5) Which species appear to be the most sensitive to pollution? Which species are the least sensitive?
6) Observe the cumulative species to sampling time plot. Explain what it represents and describe how it changes (if it does) in the presence and absence of pollution. Is it behaving as you would expect?
7) Briefly describe the effect of pollution on stream diversity using data to support your analysis and make some suggestions about why pollution could cause the changes you have observed.
Physical factors: The physical characteristics of the stream, such as temperature, flow rate, water depth, and substrate type, play a crucial role in determining the types of organisms that can live in the ecosystem. For example, certain fish species require cool, clear water with high oxygen levels, while others thrive in warmer, more turbid water.
Nutrient availability: The availability of
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Habitat complexity: The physical structure of the stream, including riffles, pools, and runs, can create diverse microhabitats that support different types of organisms. For example, riffles are typically characterized by fast-moving water and rocky substrate, which provides habitat for benthic macroinvertebrates such as mayflies and stoneflies.
Connectivity: Streams are often connected to other aquatic ecosystems, such as lakes, wetlands, and groundwater, which can increase biodiversity by allowing for the exchange of organisms and nutrients.
Disturbance: Natural disturbances such as flooding and drought, as well as human impacts such as pollution and habitat destruction, can have both negative and positive effects on biodiversity in stream ecosystems. For example, a flood event may create new habitat and increase nutrient availability, while pollution can reduce biodiversity by harming sensitive species and disrupting the food web.
In summary, the biodiversity of a stream ecosystem is influenced by a variety of factors, including physical characteristics, nutrient availability, habitat complexity, connectivity, and disturbance. Understanding these factors is important for managing and conserving stream ecosystems and the biodiversity they support.