Edited by Jessica E. Fultz for the Department of Biology.
Updated January 10, 2014
Concepts in Biology Laboratory
Please note that this manual is a work in progress and was compiled specifically for the ISU Biology department. It changes each semester/session depending on the interests of the instructors. It is
a free and unpublished manual that has not seen reviewers or editors; there are errors.
The first step in the acquisition of wisdom is silence, the second listening, the third memory, the fourth practice,
the fifth teaching others.
~Solomon ibn Gabirol (1021 -1058 AD)
Biol 1100L Ecology1 Lab 1
1. Define hypothesis using your textbook.
In lab this week you will gather observational data about arthropod distributions and ecol- ogy, describe their niches in terrariums, construct a hypothesis, make a prediction, and calculate the diversity (Shannon-Weiner Diversity Index) for each niche type. Arthropods are a major component of all terrestrial ecosystems and their behavior has been the object of many famous ecological studies. All arthropod species are in the Kingdom Animalia and Phylum Arthropoda but they are in many different classes, orders, and families. A large proportion of arthropods are plant detritivores, i.e. organisms that feed on dead and decaying plant material. These organisms hasten the conversion of biomass to soil, speed up rates of nutrient cycling, and as a result, increase the productivity of ecosys- tems. In this lab you will learn about three very important ecological concepts: diversity, niche and the competitive exclusion principle. Diversity can be measured in a number of different ways, and you will use the Shannon-Weiner Diversity Index. The niche is a set of environ- mental factors necessary to the continued existence of a species. The niche describes anything you might be able to think of that an organism requires. This includes what it eats, where it eats, when it eats, when it sleeps etc. The competitive exclusion principle states that two species with identical niches cannot coexist indefinitely (Gausse 1934). It makes sense that species that coexist will have different niches. If they didn’t they would either be in the process of going extinct or driving their competitor into extinction. The way species subdivide niche space has been called niche partitioning.
Figure 1-1. Diagram of an arthropod terrarium.
Part 1. Defining Niches
One of the members of your group will obtain a terrarium and poking / digging tools from the west end of the lab. Do not do anything to the terrarium yet. Note the overall structure of the terrarium ecosystem (Fig. 1-1). As a group talk about the different ways the species of arthropods could partition this niche space to avoid identical niches. Be prepared to present your group ideas to the class. Decide as a class on 4 distinct niches that would be good to use. All groups of students must use the same niches to continue with the exercise.
2. What is an example of a hypothesis (see textbook)?
Biol 1100L Ecology1 Lab 1
3. What are the niches you and your classmates identified for the terrarium? 1___________________ 2___________________ 3___________________ 4___________________
4. As a class construct a hypothesis about arthropod abundance and diversity of each niche.
Table 1-1. Abundance of arthropod types from ter- rarium #_____.
1 2 3 4 cricket isopod millipede bess beetle tenebrio beetle other 1 other 2 Total Abundance
5. As class make a prediction about arthropod abundance and diversity of each niche.
Part 2. Data Collection
Observe your terrarium. Carefully, without disturbing the other niches, search one niche for arthropods. Be gentle and care-
ful (we don’t want to harm any of the arthropods). As you find an arthropod place it in the plastic holding chamber.
6. Fill in the appropriate niche/arthropod cell in Table 1-1 with count data using tick marks. NOTE: do not count dead arthropods.