Poorav Bawal- Carrying Capacity

Title: Carrying Capacity

Need to know

Principles Investigated: The pattern of population change over time, carrying capacity

Standards:

CA Content Standards for Science

Grade 9: Biology

6. Stability in an ecosystem is a balance between competing effects. As a basis for understanding this concept:

6a. Students know biodiversity is the sum total of different kinds of organisms and is affected by alterations of habitats.

6b. Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.

Materials:

Open Space

Procedure:

Begin the lesson by showing the students two pictures (one of overpopulation and one of deforestation), and have them think about how those two pictures are related. Then move right into the activity.

Activity:

1. Divide the class into two groups. One group will represent the animals (we will call them matadors) and the other will represent the resources. The animal group should be about 1/4^th of the students. The rest will be in the resources group.
2. Explain to the students that we will be using three resources (water, food, and shelter). The symbols for each will be finger on lips, hand on belly, and hands on top of head, respectively.
3. Create 2 lines far enough apart so that the students can interact in the space. All of the matadors go behind one line, and all of the resources will go behind the other line.
4. Have the students turn around so they cannot see each other. Tell them that they must decide on a resource. The matadors are deciding on what resource they need to survive. The resources are deciding simply which resource to be. Make sure they know the signs that portray each resource. Once they have decided, have them turn around to face each other.
5. Have the students interact in the middle space. The matadors are choosing which resource they want based on their sign. Once a matador has acquired the desired resource, they hold hands and go back across the matador line. The remaining matadors which did not find its resource will go back across the resource line(the organism in nature dies and provides nutrients to the environment). If two matadors are fighting for one resource, the first one to get to the resource gets to use it.
6. Repeat steps 4 and 5 as many times as you would like.
   1. Optional: If you have time, you can introduce other elements such as human interaction. You can assign one person to plow through as a truck with both arms extended out and whichever matadors that person touches becomes resources for the next interaction and whatever resources it touches are removed from the system entirely.
7. Either you or a student you appoint should be the recorder. This person will record the number of matadors at the beginning and end of each interaction. At the end, each student will plot the number of matadors at the beginning and end of each interaction. The x-axis of the graph will be the number of interactions, and the y-axis will be the number of matadors.

Once the activity is over, return to class and input the data into a spreadsheet (I am using google docs for convenience). The students will see the pattern of population size. It should look like a wave. Discuss the results with the students using the questions below. Feel free to use any of these questions or add your own. Go over the concept of Carrying Capacity. Once you have finished, go back to the two pictures displayed at the beginning of the lesson. Have the students relate those two pictures to the activity you just did.

Graph: I love Google

Student Prior Knowledge:

Students should already be familiar with the limiting factors that animals need to survive.

Explanation:

The purpose of this exercise is to demonstrate to the students how populations change over time as they interact with their environment. The students will be able to observe the continuous rise and fall of a population; the population is going above and below its carrying capacity and is constantly being balanced based on resource availability. Carrying capacity is defined as the maximum population size of a species to survive indefinitely given the resources available in the environment.

When the matadors are selecting their desired resource, what they are representing is the ecological niche of an organism. The ecological niche of an organism describes the relative position of that organism to other organisms in its ecosystem. The niche explains how an organism responds to the distribution of resources and predators. When the matadors could not find their ecological niche, they “died” off and became a part of the resources. This demonstrates the fall of a population when resources get scarce. During the first interaction, the matadors increased in population(most likely) since the starting number of matadors is low and the starting number of resources is high, showing that when the resources are plentiful a population will grow.

In the demonstration, there will only be time for a few interactions between matadors and resources. However, there are other factors that interact with organisms. One of those factors is humans. Humans have had such a huge impact on most of the ecosystems on earth. If there is enough time, the students will demonstrate the effects of human interaction when the demonstration runs interactions between matadors and resources with one student acting as a human interaction.

Teachers can use this demonstration to lead into discussion of current population trends and how that affects the human race.

Questions and Answers:

1. What did you notice when the number of people representing resources diminished? What happened in the subsequent interaction?

As the number of resources diminished, it was more difficult for the matadors to pair up with their corresponding resource. With limited resources, the matadors had a much more difficult time locating the resource they had chosen. These matadors subsequently “died” and became a part of the resources group(through processes such as decomposition).2. Describe the change you noticed in the population after many interactions. Explain why you observed this pattern.

The population number went up then down then up then down etc. over time. If graphed, the the pattern would appear as a wave. If there are abundant resources, then the population will increase over time. However, once the population increases, the resources will be consumed at a higher rate. The resources diminish, and thus the population stymies and begins to decline. The population is going above and below its carrying capacity.

3. What is unrealistic about the simulation?

Organisms need more than just one resource to survive. In this instance, the matador will require water, food, and shelter. If the habitat does not contain all of the essential resources, the organisms in a population will become weak and die as a result. When the organism dies, it does become recycled, but the process takes time and does not happen instantly.

Applications to Everyday Life:

All around the world, populations of organisms are on the decline due to the relative recent emergence of humans. Many species are becoming endangered or extinct due to unnatural involvement of humans around the world. We use the word unnatural in this case because humans have the capacity to force matter to do things it does not want to do. It is important for students to understand the implications of population declines throughout the world. Humans are dismantling habitats and reducing population size all while increasing its own population. Humans are therefore reaching or arguably passing its own carrying capacity. As we have seen in this activity, as resources diminish and population size goes up, there is a struggle for resources, which leads to decline in population size.

Photos:

Video:

References:

Colorado Division of Wildlife. (2010, November 19^th). Oh Deer! - Colorado Division of Wildlife. http://wildlife.state.co.us/Education/TeacherResources/ProjectWild/OhDeer.htm (2011, May 9^th)

Wikipedia. (2011, April 14^th). Carrying Capacity. http://en.wikipedia.org/wiki/Carrying_capacity (2011, May 9^th)

New Jersey Division of Fish and Wildlife. (2011, April 8th). NJDEP Division of Fish & Wildlife. http://www.state.nj.us/dep/fgw/pwinfo.htm (2011, May 12th).