Part 3. Data Analysis
To calculate diversity biologists use indices that are based on mathematical equations. For this lab you will use the diversity spreadsheet linked to Moodle to calculate the Shannon-Wiener Index (H’) which is calculated as -Σ(pi ln pi). This index is an indicator of the evenness and richness (i.e. number of arthropod species and the abundance within each species) within an environment. H’ ranges upwards from 0. The 0 value indicates a single species and increases as richness and evenness increases. When you have completed your observations, each group will provide their niche totals from Table 1-1 to the class.
Biol 1100L Ecology1 Lab 1
7. Calculate a class average using the Excel spreadsheet linked to Moodle for each arthro- pod type in each niche and enter that average into Table 1-2.
8. Using the class averages, cal- culate Shannon- Wiener Diver- sity Index (H’) for each niche using the Ex- cel spreadsheet provided and fill in Table 1-3.
Table 1-2. Average abundance of arthropod types from all terrariums studied.
1 2 3 4 cricket isopod millipede bess beetle tenebrio beetle other 1 other 2 Total Average Abundance
Table 1-3. Shannon-Wiener Diversity Index (H’) for each niche.
Niche H’ 1 2 3 4
9. In a complete sentence and in your own words define the Shannon-Wiener Index (H’). What two important factors are taken into account by the Shannon-Wiener Diversity Index?
10. Did you conclude that your prediction was true or false for the diversity of arthropods per niche?
11. Did you accept or reject your hypothesis?
12. In retrospect would you have modified your selection/distinction of niches?
13. Did the taxonomic descriptions in the appendix appear to agree with the niches you saw the arthro- pods in?
Biol 1100L Ecology1 Lab 1
Cricket Class: Insecta Order: Orthoptera Family: Gryllidae
Bess Beetle Class: Insecta Order: Coleoptera Family: Passalidae
Darkling Beetle Class: Insecta Order: Coleoptera Family: Tenebrionidae
Isopod (Pill bug) Class: Malacostraca Order: Isopoda Family: Armadillidiidae and Porcellionidae
Millipede Class: Diplopoda Order: Spirobolida Family: Spirobolidea
This group of insects is closely related to grasshoppers that are in the Family Acrididae. Most species of crickets overwinter as eggs. All crickets have auditory organs on their front tibia. The male cricket rubs its wings together to make a chirping sound. The young cricket, or nymph, looks like an adult except that it is smaller and not sexu- ally developed. Crickets are generally scavengers that will eat essentially anything.
These are large (32-36 mm long) shiny black beetles. The mouth is adapted for chewing wood. Passalids are somewhat social and their colonies live in decaying logs. The adults can produce a squeaking sound by rapidly rubbing their third legs against their fifth abdominal sec- tion. All beetles undergo larval and pupal stages before emerging as adults.
These dark brown flying beetles are also known as dark- ling beetles. Most tenebrionids feed on plant matter of some kind and often live in cornmeal, dog food, cere- als, and dried fruits. The Tenebrionidae is the fifth larg- est family of beetles with over 1000 species in North America.
These organisms are actually crustaceans and are closely related to crabs and lobsters. The name isopod literally means equal-legs. Individuals in this group are often found under boards and decaying wood. They eat wood and logs as they decay. Isopods breathe with gills so they must live in an area that is constantly moist.
Millipedes are elongate wormlike animals with many legs. Most millipedes have 30 or more pairs of legs. They tend to avoid light since they have eyespots on their heads that are sensitive to light. They live on dead leaves or other decaying material.
14. Do you feel you have made an adequate description of niche space of these arthropods? Why or why not?
15. Which niche was most diverse? Why do you think this is the case?