Purpose:
Biodiversity is both an important factor to, and key indicator of, ecosystem health. This investigation is designed to give you the opportunity to calculate the biodiversity of one taxonomic group of organisms that are an important piece of the overall biodiversity puzzle: arthropods. The hope is that you begin to recognize the relationship between organism type and number to specific habitat.
Procedures:
Data:
- Retrieve organisms from the alcohol by forceps and/or pipette and place in Petri dishes.
- Identify and count under the dissecting microscope.
- Use one of the arthropod identification guides in order to attempt identification of species.
- Once all counts have been completed, calculate the biodiversity using Simpson's Index of Diversity
- Finally your team should share its findings with the rest of the class.
Biome Description: Collected on 9/20 @ 5 pm
Type of Biome: Deciduous Forest
Location: Near Falls Lake
Description of Weather Conditions:
Type of Biome: Deciduous Forest
Location: Near Falls Lake
Description of Weather Conditions:
- Air Temperature: 74 degrees Fahrenheit
- Humidity: 52
- Wind Speed: 10 mph (N)
Analysis:
About 90% of the biomass produced by a forest returns to the soil. There is approximately 1.5 times as much energy stored in the soil and leaf litter of a forest as there is in the trees. Mites and springtails may recycle almost 30% of the leaves and wood on the forest floor. Indirectly, their feeding breaks litter into smaller pieces, increasing the surface area where decomposition by bacteria and fungi actually take place. Their feeding also coats the pieces with fungal spores and bacteria. Both of these may double or even triple the rate of decomposition by fungi and bacteria ("Role of Leaf Litter Arthropods" 1). In the sample studied by group 5, there was only one type of species found, which was the araneae. So the araneae had the lowest relative abundance of 1. According to the Life in the Leaf Litter by Elizabeth Johnson, the spiders feed primarily on insects and play an important role controlling the insect population. Mites and springtails made up 0% collectively of group 5's sample. The spider had the greatest absolute abundance of two and had the greatest relative abundance of 1 (100%). Because group 5 only collected one type of species, the spider is also considered to have the lowest absolute abundance of two and the lowest relative abundance of 1 (100%). The Simpson's Index of Diversity for group 5's sample was zero. This indicates a low level of diversity. Reasons for low diversity could be that the spider population was low in the area and the spiders could have consumed other insects in the sample before data was collected. The different diversity index amongst the different lab groups was not very different except group 5 with a diversity index of 0. This is not very surprising because the sample was collected in the same area, so the biodiversity should be similar. Negative phototaxis occurs when organisms moves away from a source of light (Masterson 2015). This affects the type and number of arthropods in the alcohol-filled beaker because most arthropods would try to stay away from the surface of the ground and instead prefer to stay lower. This means there are generally more arthropods deeper in the Earth than closer to the surface. Yes, the biodiversity values give a general idea of which sites were supposedly more stable. Areas with a high Index of Diversity will generally be more stable than one’s with lower biodiversity. An abiotic factor that may increase diversity in a specific area is water. An area closer to a body of water will have higher biodiversity because it is easier to support multiple organisms. Another abiotic factor that may increase or decrease diversity is the amount of sunlight because certain species of plants and animals, like those which have positive phototaxis, will thrive in sunlight and organisms like arthropods will thrive under the surface, where little sunlight is received. Biotic factors, such as keystone species, may also affect biodiversity positively in an ecosystem because they change the habitat to make it more suitable for other species. If an ecosystem loses its keystone species, then the biodiversity of the ecosystem will decrease because other organisms are dependent on keystone species. For example, the food web of that particular ecosystem would be disrupted with the absence of a keystone species because keystone species usually play several important roles in food webs. Cryptobiosis is a physiological state in which an organism goes essentially into a dormant state when environmental conditions are unfavorable. This is very beneficial to arthropods because whenever the experience distress from the outside they can go into this state until the environment returns to a more favorable state. Cryptobiosis is useful to arthropods in surviving extreme, lethal conditions. All of the organisms found in the leaf litter play different roles in the temperate forest ecosystem. Worms are decomposers in temperate forests. They eat dead plants and animals and other organic matter, and release nutrients such as nitrogen, potassium, and carbon into the soil. These nutrients are then taken up by living plants and animals. A snail’s role in a temperate forest is that of a herbivore and it usually feeds on rotting vegetation and moist leaf litter. Its diet is rich in calcium and other nutrients. A snail also acts as prey to birds and larger animals; the snail helps these predators get their nutrients and thus plays an vital role in the functioning of a food web. Spiders are consumers in temperate forests. They mainly consume different types of insects. Therefore they play a vital role in controlling the population of insects. Biological Diversity is necessary for an ecosystem because it allows for the sustainability of all organisms in an ecosystem. A more diverse ecosystem, then the more variety of food there is for the organisms that live there. Also an ecosystem that is more diverse will not be easily wiped out by sudden changes in the environment. For example if spiders became extinct in an ecosystem there would be other organisms that could take over its role/niche. Deciduous forests and tropical rain forests support a large amount of organisms with a variety of producers. Rain forests have higher rates of precipitation compared to deciduous forests. Also, rain forests have a large amount of tall trees, creating a canopy, so sunlight rarely reaches to the surface of the forest. Deciduous forests have four distinct seasons and the plants and animals must adapt to the seasons.
Bibliography
Hutchison, LeeAnn. “Arthropod Biodiversity Lab” (On-line), Enviroliteracy.org. Accessed October 8, 2015 at http://www.enviroliteracy.org/pdf/materials/1243.pdf.
Myers, P. 2001. "Arthropoda" (On-line), Animal Diversity Web. Accessed October 8, 2015 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Arthropoda.html.
Life In The Leaf Litter. (n.d.). Retrieved October 8, 2015, from http://www.amnh.org/our-research/center-for-biodiversity-conservation/publications/general-interest/life-in-the-leaf-litter
Myers, P. 2001. "Arthropoda" (On-line), Animal Diversity Web. Accessed October 8, 2015 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Arthropoda.html.
Life In The Leaf Litter. (n.d.). Retrieved October 8, 2015, from http://www.amnh.org/our-research/center-for-biodiversity-conservation/publications/general-interest/life-in-the-leaf-litter