Reading Questions 6A

Reading Questions 6A

• New England Forests Come Full Circle
• Nature exists at several levels of complexity.
• Population ecologists study the factors that regulate population abundance and distribution.
• Growth models help ecologists understand population changes.

1. Fill in 5 key events in the re-establishment of the New England forest in the Opening Story:

2. Distinguish between each level of analysis:

3. Which level of analysis would be most appropriate for a scientist to use in each scenario?
   1. Monitoring the Grey Wolves of Yosemite

Individual

1. Investigating the connections among organisms in a soil sample

Community

• Determining whether or not natural selection favors light or dark coloration in mice

Individual

1. Evaluating the status of the Florida Everglades

Ecosystem

4. How does the Opening Story demonstrate the importance of community-level analysis and interactions between species?

Different plants have different needs, for example, plants like goldenrods are very sunlight reliant. When they do not get the sunlight they need and they die off, so do the insects and animals that eat them and eventually the cycle is messed up. Each organism is connected to each other in some way in a community.

5. When considering a population as a system, what 2 processes are inputs that increase population size and what 2 processes are outputs that decrease population size?

Input 1 (+): birth                                                                              Output 1 (-): emigration

Input 2 (+): immigration                                                                Output 2 (-): death

6. Key Idea: Five major characteristics help us understand how populations change over time:

7. Key Idea: Density-dependent factors & density-independent factors can affect population sizes and growth rates:
   1. True/false: Wildfires occurring in the Southern California chaparral (shrubland biome) influence populations of local species in a density-dependent way.

True

1. What variable served as the limiting resource in Gause’s paramecium experiment?

food

1. Explain how the carrying capacity (k) of an environment is determined:

Population growth slowed as population size increased because there was a limit to how many individuals the food supply could sustain. This tells us about  the limit to the number of individuals that can exist in a population.

1. What are common limiting resources for terrestrial plants?

Water and nutrients

1. What are common limiting resources for animal populations?

Food, water, shelter

1. True or false: Density-independent factors deal with limiting resources

True

8. Predict what would happen to the population sizes of aurelia and P. caudatum if Gause had continued his experiment by alternating between high-food and low-food conditions each day:
9. Aurelia and P. caudatum populations are going to continue to increase over time. Alternating between high food and low food conditions is normal in an environment.
10. The Exponential Growth Model
    1. What does the intrinsic growth rate (r) for a species measure?

A populations maximum potential for growth.

1. Chart the growth of the following population of mice at a growth rate of 10% per year:

10. The Logistic Growth Model
    1. Why is the exponential growth model usually insufficient to describe real populations?

Formula that allows us to estimate future population.

1. How does the population growth rate CHANGE as it approaches the carrying capacity of its environment, and why?

The population growth rate changes because it is reaching its max population potential with the same amount of resources so a population is trying to surviving

1. What factors prevent the continued growth of populations beyond the carrying capacity?

They are struggling to survive.

11. Variations on Logistic Growth
    1. Why is population overshoot always followed by a die-off?

There is a population die-off because because it has reached its capacity and is no longer thriving as a population.

1. True/false: during population overshoot, the environment’s carrying capacity increases.

False.

12. Reproductive Strategies and Survivorship Curves
    1. Characteristics of k-selected and r-selected species:

1. Which type of species can evolve faster? Explain why.

r-selected species because they produce more frequently and have more offspring at a time than k-selected species.

1. True/false: Most organisms show strict k-selected or r-selected reproduction strategies

True

1. Which type of species is at greater risk for extinction? Explain why.

K-selected species because these populations have slow growth rates and cannot respond quickly to trauma.

13. What is a metapopulation, and why is it important to study them?

A group of spatially distinct populations that are connected by occasional movements of individuals between them. This is an important part of each populations overall persistence. Small populations are more likely to go extinct than large ones and metapopulation provides protection from diseases and other threats for these populations.