BIL 161 Research Project: Biodiversity in Local Ecosystems and Microhabitats

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1 BIL 161 Research Project: Biodiversity in Local Ecosystems and Microhabitats The responsibility and rush of every day life sometimes distracts us from the natural world. The diversity of non-human species is immense and all around us, and yet most people rarely notice it. During the course of this first research project, we hope you will begin to gain a naturalist s perspective of the world around you. The species you encounter--small and large, simple and complex--are the working cogs of that living machine we call the biosphere. Biodiversity is defined as the degree of variation of living organisms within a particular ecosystem (or the entire planet). In this first research project of this semester, you will explore the biodiversity in microhabitats of local ecosystems. I. Biodiversity The biological definition of a species is a group of organisms able to interbreed in nature to produce fertile, viable offspring. A population is defined as all the individual organisms of a single species living in a defined area. All the populations in a given area comprise that area s community. And the communities interacting with the non-living components of the environment make up the ecosystem. (Figure 1) Figure 1. The ecological hierarchy, from individual organism to biosphere. Ecosystems are as varied as the surface of the earth. Within each ecosystem, microhabitats smaller systems characterized by specific physical factors determine what lives there. For example, a pond ecosystem might have microhabitats such as (1) the interstitial space (i.e., empty gaps between living matter) of pond plants, (2) the bottoms of stones, (3) the water column, (4) the sediment at various depths, and (5) the pond s surface. Biodiversity1-1

2 Every species has evolved its own tolerance limits for environmental factors, such as temperature, light, humidity, nutrients, etc. Different ecosystems and microhabitats have different levels and combinations of each of these factors, so the species composition and diversity of each ecosystem differs accordingly. The abiotic (non-living) components of any given habitat determine the composition and abundance of the biotic (living) components of that habitat, and the biotic components, in turn, affect each other's abundance and diversity. A. Measures of Biodiversity Ecologists use specific terms to describe the number, density, and variety of species living in a particular ecosystem. When you devise your study, be sure to use this vocabulary appropriately. Biodiversity1-2

3 The simplest measure of biodiversity in an ecosystem is species richness (S). This is no more than a count of the number of different species found in a collected sample, and it does not take into account the abundance of each species. One index used to represent species richness is Menhinick s Index (D): the number of species in the sample divided by the square root of the number of individuals in the sample. in which s = the number of different species in your sample N = equals the total number of individual organisms in the sample In ecology, the term abundance is used to describe the relative representation of species in an ecosystem. If you collect a sample from an ecosystem, the abundance of a particular species is simply the number of individuals per unit area or volume of your sample. The relative abundance of a particular species refers to how common or rare that species is in comparison to other species in the same locality or ecosystem. The relative abundance of any given species can be calculated as the number of individuals of that species divided by the total number of individuals of all species combined. For example, if you collected a one milliliter (ml) sample of pond water and found the following numbers of each of three species: 100 diatoms (Neidium pseudodensestriatum) 50 nematodes (Psilenchus hilarulus) 5 mosquito larvae (Aedes aegypti) Then the relative abundance of each species would be: Neidium pseudodensestriatum: 100/155 = 0.64 Psilenchus hilarulus): 50/155 = 0.32 Aedes aegypti 5/155 = 0.03 Many other measures of biodiversity are important in studies of community ecology; you might encounter them during the literature search you will perform in preparation to designing your research project. For now, review the indices above and be ready to use them, as appropriate, for your project. Your team may wish to determine whether there is a significant difference in species richness between two different types of ecosystems, or from two different microhabitats in the same ecosystem. Or perhaps you would like to determine whether certain taxonomic groups are more abundant in one ecosystem (or microhabitat) than another, and determine why. It is up to your team, with your inquiring minds, to decide on an interesting, relevant project. B. Aquatic Environmental Factors and Biodiversity Unlike last semester, you will NOT be doing any sort of treatment versus control experimentation. This time, your data collection will be best classified as a survey. In this project, your task will be to identify two (or more, if you really insist) different, naturally occurring aquatic habitats/microhabitats that you predict will have different biodiversity for a specific, logical reason. The next section will explain what sorts of variables might affect biodiversity in aquatic habitats. 1. Salinity Aquatic environments harbor many living organisms, and the biodiversity of an aquatic system depends, in part, on the salinity of the water. Fresh water is defined as having less than 0.5 grams dissolved salts per liter. It is hypoosmotic with respect to the cytosol of a Biodiversity1-3

4 typical living cell. Hence, a freshwater environment presents a challenge to living cells, which must expend energy pumping water out to maintain proper osmotic balance. Conversely, today s seawater is hyperosmotic with respect to a typical cell s cytosol. Marine water contains between grams of dissolved salts per liter. Thus, many (though not all) marine organisms must expend energy to retain water in the cytosol. Finally, brackish water is defined as having between grams of dissolved salts per liter. This wide range means that the term brackish is not precise. Still, the biodiversity of brackish environments can vary with the salinity of the water, and many brackish habitats have wide variations in salinity over the course of a day due to tidal flux. 2. Other Natural Abiotic Factors Ecosystems are complex, with many variables. Aquatic habitats throughout southern Florida can differ in light level, temperature, chemical composition, and any number of other factors. One difficulty faced by every ecologist is controlling for multiple variables. When you select the two habitats you wish to compare, you and your team should list all possible differences between the two habitats that could affect biodiversity. It s okay if there are multiple factors. Your project will essentially be a pilot study that will tell you whether there is a difference in biodiversity between your habitats. It will then be up to your team to devise additional studies that could allow you to pinpoint the exact factor(s) causing the difference, and explain the mechanism(s) by which it/they does/do so. 3. Anthropogenic Factors Anthropogenic (from the Greek anthropos, meaning human and genesis, meaning origin ) factors are those generated by humans. Suburban areas are subjected to human disturbance such as pesticide and fertilizer runoff, physical disruption, sanitation/clearing efforts, etc. How might these factors affect species diversity and species composition of a nearby aquatic ecosystem? Consider various factors that might affect biodiversity, and use these as keywords in your literature search to find background information about this area. C. Local Environments and Their Biodiversity Close to the center of campus lies brackish Lake Osceola, which contains more species (many microscopic or very small) than you might guess at a glance. It is connected to the ocean by a long network of canals, so species from both fresh water and marine environments have access to the lake. Until recently, there was a small, isolated freshwater pond, the Gifford Arboretum Pond just behind the Cox Science Building. Before the demolition of the area commenced to make way for the new Cox Annex, we were able to sample the pond and save some of the microscopic biota for your examination. It can be found in the small aquarium on the window ledge of each lab. (Note that the species living in the water column itself, those in the algae, and those living in the sludge at the bottom might not be the same.) Coral Gables and surrounding communities are dotted with many man-made ponds and canals. Some are connected to each other, and some are closed systems. Some are freshwater, and some are brackish. Some of our faculty have ponds on their properties, and those are of various sizes and condition. Your research project is limited only by your imagination. You can choose what to ask about biodiversity. Does it differ between two different ecosystems? Two different types of water? Nighttime and daytime? Polluted or unpolluted? Consider interesting, relevant possibilities, and use these as keywords in the literature search assignment described below. Biodiversity1-4

5 II. Assignment: Literature Search and Review An essential part of undertaking a research project is to find out what is already known about your area of interest, why it is important and relevant. Previous research might give you ideas about what questions still need to be addressed in this area. For example, you might be interested in finding out if a particular environmental factor (e.g., ph) affects biodiversity, but it s quite possible that research in this area already has been done. In order to conduct a study that is not simply a repeat of someone else s work, it is important to conduct a literature search and review before embarking on your experimental project. (While it is often important to replicate published studies to validate them, your team should design a study that might be similar to one already published, but not exactly the same.) A literature search is an organized search for published material on a selected topic. You will be required to use databases that retrieve academic sources of high quality and reliability. Literature databases allow you to search a wide array of journals and other sources, and enable you to collect scholarly references. Some of these may be in the form of an abstract, whereas others might be the full text of a journal article. You can usually save these to your own computer for future reference. An effective literature search takes an organized approach: 1. Decide on a search topic With your team, formulate a question to narrow and define the topic. For example, if you wished to determine the effect of ph on biodiversity, you might ask Do two ecosystems with consistently different ph exhibit differences in biodiversity that can be explained by ph? From such a question, you can then develop hypotheses and predictions. 2. Use appropriate keywords to use in your search Identify important keywords. In the example above, you might include biodiversity, ph, ecosystem, acid, alkaline, or any number of terms related to this area. Also consider: When to use broad terms, and when to use narrower terms to refine your search Use synonyms for your keywords to find every possible variant of the vocabulary used in the research on this topic. Use dictionaries to check spelling and find keyword synonyms Using online encyclopedias (e.g., Wikipedia) to find initial background information that might help you refine your search or choose an area for your research topic. 3. Choose a Database GoogleScholar is an excellent place to start, but there are other databases available through the UM library system that you may wish to use, as well. 4. Perform your Search Use Boolean operators (always use them un upper case) to combine search keywords. Truncate (shorten) your keywords to make your search broader. If you are not sure how to spell a keyword, use wildcards. To narrow your search, use phrases enclosed on quotation marks. For example, ph effect on species richness. Use the database to search for keywords in different places, such as title or abstract. If you find a useful article by a particular author, search that author s name to find papers on the same topic. If you find a useful article, search its Literature Cited section to find additional, related sources. Biodiversity1-5

6 Make sure the literature you are citing is recent and current. Make sure the literature you use is from a peer-reviewed, scientific journal. Make sure to identify whether your source is a journal article, a book, a thesis, etc. 5. Determine the availability of the material you wish to reference. If the paper you wish to read is not available online, you may be able to get a copy by contacting the people at the UM Richter Library Help Desk. If our library does not have the paper you need, they may be able to get it via interlibrary loan. Since this requires turnaround time, this is one very good reason to start this assignment immediately, and not find yourself hamstrung by time constraints. Each student will be assigned the task of finding at least one relevant paper from a peerreviewed scientific journal on the topic of biodiversity, and preferably narrowed to an area discussed in advance by your team. Once you find a paper of interest, read it completely and analytically. Your assignment is to turn in (1) a copy of the scientific paper and (2) a one-page summary and review of the paper to your instructor. At the end of your summary, include at least three questions that the research paper has inspired you to ask. One or more of these could lead your team to an interesting and unique research project of your own design. Your laboratory instructor will give you additional details about this assignment. Biodiversity1-6