User:Jordan Lenkin/Notebook/Biology 210 at AU
July 14, 2015 Invertebrates and Vertebrates
In continuing the study of levels of biodiversity present in the transect, the next organisms that were observed were invertebrates, followed by a brief examination of the vertebrates present in and around the transect. Despite their size, invertebrates are a highly diverse and complex phyla of organisms. It is believed that the more simplistic systems present in invertebrates eventually evolved into the complex organs systems of vertebrates today. Using the Berlese Funnel system set up during the previous lab, a number of invertebrates were identified and examined in detail.
The Berlese Funnel was broken down by pouring 10-15 mL of liquid and organisms each into two petri dishes. Invertebrates were separated from the debris present using a combination of observations under the microscope and with the naked eye. Each organism found was identified using a dichotomous key. Upon completing the study of invertebrates, a final trip to the transect was made to observe and identify larger animals in order to complete a food web.
The table below details the specifics of the four invertebrates that were observed once the Berlese Funnel was broken down.
- It should be noted that many bees were observed in the transect during the various visits, however there were none in the sample collected for the Berlese Funnel.
As Table 1 demonstrates, the invertebrates collected ranged in size from about seven millimeters to approximately 15 with the bees being the largest and the beetle and pill bugs being the smallest. Because no bees were collected, there is no count for the number present in the sample. There were two pill bugs and one of each of the other invertebrates (see images below). Additionally, it should be noted that while instructions called for identification of five invertebrates, only three were present in the Berlese Funnel.
Image 1: Pill Bug
Image 2: Cedar Beetle
Image 3: Earwig
Table 2 includes a list of five vertebrates that might inhabit the transect.
Of the five vertebrates listed above, three are species that have been observed with frequency on American University’s campus and that are likely to inhabit an area akin to the transect chosen for this study. Two of the species (the house sparrow and the grey squirrel) were actually present in the transect during observations.
Before considering how each of the observed species present in the transect are interconnected, it is important to consider how the general abiotic and biotic characteristics may benefit each of these organisms. As previously listed, the abiotic features present in the transect include soil, rocks, sprinklers, but also rainfall, sunlight, and dead organisms. Each of these provides a benefit in some way or another. For example, the soil provides a habitat for many of the microorganisms as well at some of the invertebrates. The water, whether it is coming from the sprinklers or from rainfall, promotes vegetative growth, which in turn promotes habitation by a range of the organisms observed. And the sunlight promotes photosynthesis in the plant life present, which is a food source for many, if not most, of the other organisms present in the transect. Diagram 1 below is a food web based on all of the organisms observed in the transect. As noted in the Results section, only four invertebrates were identified from the transect and included in the food web. This may be an indication that the transect is lacking in high levels of diversity.
Diagram 1: Transect Food Web
As the diagram demonstrates, although not especially diverse, there is a functioning community of organisms present within the transect. Beginning at the microbiotic level and following through to the vertebral level, the organisms present interact with each other in this common location. For example, the sparrows feed on the pill bugs that feed on the dead plant matter. If there were no plants to produce the dead plant matter, the pill bugs would not have a food source. Although the sparrows feed on a variety of other invertebrates, pill bugs seemed to be the invertebrates with the greatest population, so the sparrows may go elsewhere to find a more abundant food source if the population of pill bugs came into rapid decline. Additionally, the sparrows represent a good example of the carrying capacity within the transect. Of all the vertebrates observed, the sparrows appeared to have the largest population. This would suggest that the transect provides a proper habitat, reliable food sources, and enough water to sustain the population. However, in order to determine if the sparrow population is actually at it’s carrying capacity or if it is simply in equilibrium, further tests and observations would have to be carried out. JL