PDS AP Environmental Science 8th Period 2010-11

On our chapter 2 test I missed the question, “During succession, biodiversity is greatest in the…” I thought it was “late stage” because the longer some environment has been around, the more species will have had the chance to come live it in. It also takes a long time for some tress to grow so I thought the tree diversity would be greater during this stage too. Can someone please explain why it is not the late stage?

My other question is something that Mr. Willard suggested I do for advice today at help session and I think it is a really good idea. For those of you who have done well on your exp.-design questions or you just feel like you really get it, what’s your secret? I.e. what do you do when you read the question? Do you have a certain order of steps or any insight into how to be successful on them?

Can someone please explain the difference between commensalism and mutualism? I understand mutualism for the most part, but I wrote down lichen and tree as an example of commensalism, but i’m not really sure what that means….

This 18-minute video was made by me a few years ago. While it is a bit grainy, it covers the major field research techniques I try to show students at Davidson each year. It’s mandatory viewing if you did not go, and a good review if you did:

You can also check out Miriam’s post that details our day.

*Note: The Internet filter at school will not let you view YouTube videos, so you have to watch it at home.

Here is the slide deck from today’s class on succession. Remember:

1.  Succession involves more than just a change in producers.
2.  A climax community is not necessarily the outcome of a linear progression.
3.  A little disturbance ain’t so bad, it just “resets” succession (and might increase biodiversity).

Note: You can ignore the last few slides on ecotones and edge effects for testing purposes.

On October 1st, our APES Class took a field trip to Davidson College to participate in an experimental design lab in the field. The day went as follows: we arrived at Davidson College, and attended a lecture by Dr. Mike Dorcas, a leading herpetologist. The lecture was interesting, and frightening, because it was about….giant Burmese pythons! Dr. Dorcas showed us a powerpoint concerning the history of how Burmese pythons were introduced to the Florida Everglades, how the python populations have grown, and what is being done to try and curtail the rapid growth of the python populations. For those of us in AP Stat, many of the statistical tools we learn in class were presented in Dr. Dorcas’ data, and the overall presentation was an excellent example of how precise field work can really make a difference. We also heard a presentation about Barn Swallow nesting habits, another example of a lab designed for the field.

Here is a link to a website talking all about Burmese pythons, and a video in which Dr. Dorcas is interviewed. (it’s the first one) http://www.nps.gov/ever/photosmultimedia/invasives.htm

Second, we actually went out into the ecological preserve. We split into groups, and walked around the forest area, looking for organisms (mainly frogs, snakes, and the occasional spider) in the drift fences on the ground. Drift fences are small tarps that are put up and 5 gallon buckets line the edge of the fence. The aim is to get organisms who walk towards the fence, and can’t get passed it, to walk along the edge of the tarp until they fall into a bucket and can be examined. We found small bullfrogs, spiders, and a dead mouse, but our group found no snakes. Along the drift fence were several traps for larger animals, such as larger snakes, that were lined with bait. Next, we went to a more clear area, and checked under coverboards (large boards made of wood or tin that can serve as resting places for ectothermic animals who need external temperature to regulate their own temperature). Snakes and small critters such as insects use these coverboards, and can be a useful place to look for organisms.

Checking Coverboards

We then went back to the buildings themselves to eat lunch and attend student presentations. (and hold a black snake!) The presentations were helpful in learning how to set up an experimental design. Some things we learned: 1) funding and man power can make a lab tricky. The result is to adapt to get the results you need. One of the students designed a lab to count types of frogs, yet didn’t have the funding to go out and search for hours for frogs. Instead, she listened to frog calls at dusk with other students (cost-friendly) and gathered her research that way. 2) labs that are done outside can take a lot longer than those done inside. We are accustomed to labs that can occur in one class period, or at most over the weekend, whereas some experimental design labs outdoors can last years. One of the student presentations was of a lab that lasted all summer, and will continue next summer. 3) It is important to get good and accurate data for many reasons; to prove your model (or disprove your model), make yourself understood, get published, and get more funding for research.

Finally, we headed back out to the field to start our detritivore lab. We split into boys and girls, and the boys went to the oak dominated forest, girls to the pine dominated forest. We learned how to use transects (measuring tape that is extended a certain number of feet, depending on the size of the area under study), a random number generator (numbers that are chosen off of a piece of paper to decided how far (in ft.) to travel to the left or the right of the transect) and a quadrat (a piece of tubing, square shaped, that can be any size. A quadrat is used to keep a constant amount of ground under research. We used our quadrat to collect the same amount of leaf litter from each area). Transects and quadrats are ways to take control of a situation when doing experiments outdoors: the transect and random number generator ensure that you take samples from all different areas of the space you are examining, and the quadrat helps to ensure you take the same amount of samples from the different areas.

After collecting our samples, and bagging and labeling them, we went to an open field with what looked like corn plants. (I have no idea if that is actually true, probably not.). The purpose of this exercise was to use a transect-like set up, where we used two measuring tapes stretched up and down and side to side. We then used larger quadrats, 1m by 1m I believe, and counted the number of stalks to each side of the transect like device. Our group leader, a spider lover and expert, then used sweep nets (they look like big butterfly nets made of canvas) to swish over the plants 20 times (10 to each side) and collected insects from off of the plants. We put the insects he caught in pharmacy bottles and examined them, looking at the biodiversity in the area of insects (note* they were not all insects, there were some spiders in there as well)

From our Davidson field trip, we learned some techniques of how to take samples in the field for experimental design labs. It was very helpful, and Mr. Willard recommends we discuss actual METHODS of how to collect data in our AP essays, as that is a more clear idea of what you are trying to convey.

Today I elaborated on some good examples of keystone species (population control and engineer type) as well as introducing the term foundation species…this short slide show goes with the handout you can download from “the box.”

The basis of our discussion today…hope it clears up “relationship issues” in ecological communities:

Today we began an introduction to ecology. Where as our previous biology courses focused on the biological makeup and functions of organisms, environmental science has a huge focus on ecology, which focuses on the relationships that exist between organisms and their physical surroundings.

We began by looking at the levels of organization of life:

Biosphere
Biome (ex. SW U.S.=temperate desert)
Ecosystem* (location)
Community (“a group of groups”)
Population
Organism (species)
Organ systems
Organ
Tissues
Cell

It is important to be wary of the counter intuitiveness of these various terms. For example, we often look at the term “community” and think of a community in which people live, i.e. community as a location. However, in this context, a community refers to the collection of several different populations (or species) of organisms as one big group—a “group of groups of organisms.”

Ecosystems* are the center of ecology. Ecosystems have 2 components: biotic and abiotic. The biotic component represents the community of organisms that exists in the ecosystem, while the abiotic component (abiotic meaning, without, no-living) represents the limiting factors on the particular ecosystem.

The limiting factors of an ecosystem are: pH, temperature, water, nutrients (especially N, P, S) and light, and they limit what can survive in the ecosystem, thus controlling the range or law of tolerance for survival. An example of this is the necessary pH of 6-8 in bodies of water needed to sustain the life of the fish that live there. If the pH is changed and, for example, drops to a pH of 3-4, the fish will die and the entire ecosystem will be affected.

The last thing that we discussed was the idea that in an ecosystem, nothing exists alone. Each organism has both a habitat, or an “address,” and a niche, which is basically their understood “occupation” or “job.”

Primary producers, or autotrophs, are at the bottom of the pyramid as they create biomass (dry mass) simply by the process of photosynthesis. The second level consists of primary consumers, or herbivores that consume the producers, which are generally plants. The next levels consist of secondary and tertiary consumers, or heterotrophs, that are carnivorous and consume the primary consumers. As far as habitat and job go, Mr. Willard’s analogy may help. You could say, “Banking is my job, and my habitat is the bank and my house.” while a rabbit could say, “Eating plants and then feeding snakes, owls, and other predatory animals is my job, and the forest and my burrow is my habitat.”