Answers to Population Lesson Quiz

 

  1. What does deciduous tree mean?

    Deciduous is a broad-leaved tree that sheds all of its leaves once a year.

  2. How long does it take for a new oak tree to start producing acorns?
    (a) 5 years     (b) 10 years     (c) 20 years     (d) 40 years

    (c). It typically takes about 20 years.

  3. What is the life expectancy of oak trees?
    (a) 50 years     (b) 100 years     (c) 150 years     (d) 200 years     (e) 250 years

    (d). Oak trees typically live 200 years or more.

  4. What does defoliate mean?

    To remove most or all of the leaves of a tree.

  5. How many times a year does a squirrel have baby squirrels, and how many do they typically have?

    Even though some squirrels have kittens once a year, most species have kittens twice a year -- once in the spring and once at the end of the summer. Each time they have between two and five kittens.

  6. Are squirrels (a) carnivores, (b) herbivores, or (c) omnivores?

    (c). Squirrels are omnivores, which means that they eat both plants and animals.

  7. What does plumage mean?

    Plumage is the entire clothing of feathers of a bird.

  8. Do hawks like to live in cold weather in the snow?

    No. Hawks typically live in cold climates and migrate south during the winter.

  9. Match the terms on the right to the phrases on the left. Do the best match:
    (a) The maximum population size that an ecosystem can support (1) producers
    (b) A group of organisms of the same species living in the same area (2) life expectancy
    (c) The movement of organisms into an ecosystem (3) carrying capacity
    (d) The relationship between organisms of the same or different species going after the same resources (4) limiting factors
    (e) An estimate of how long an organism is expected to live (5) emigration
    (f) Conditions in the environment that limit a population size (6) population
    (g) The movement of organisms out of an ecosystem (7) competition
    (h) The organisms that live at the bottom of the ecological pyramid (8) immigration

    (a) -> (3) (b) -> (6) (c) -> (8) (d) -> (7)
    (e) -> (2) (f) -> (4) (g) -> (5) (h) -> (1)


  10. What data is needed to be able to predict the growth pattern of a population?

    The basic data needed is: the initial size of the population, the population growth rate, the limiting factors (such as prey and predator populations), and the carrying capacity.

  11. Under what conditions would a population growth curve follow exponential growth?

    When there are no limiting factors or when there are plenty of resources and the population reproduces at its maximum capacity.

  12. What limits the population growth to a certain level? In other words, why are there S-shaped or sigmoid curves of population growth?

    Limiting factors such as limitless resources at the lower trophic level and predators at the next trophic level up are what make population growth slow down and reach a somewhat stable level.

  13. Provide four different examples of population growth limiting factors.

    (1) Competition for food and water supplies, (2) Living space, (3) Predators, and (4) Contagious diseases.

  14. Assume a predator and prey populations live in a stable phase where their population sizes don't change much from year to year. Suddenly one year there are drastic changes in their sizes. Can you give three examples of factors or situations that can cause this?

    (1) A health problem that affects the prey population reducing their size, (2) A very good year for the producers that provide more food than normal for the prey population allowing them to increase their numbers, and (3) A new prey population immigrates to the area and the predator now has more choices, so the original prey population increases in numbers.

  15. If you run the model with a combination that produces a stable population balance for both squirrels and hawks, you might have noticed that the stable squirrels' population under that situation is smaller than the stable squirrel population when there are no hawks. Can you explain why?

    The reason is that when there are hawks, there are two limiting factors. One can see the effect of the predator on the prey.

  16. What formula would you use to determine population density?

    Population density can be calculated as the number of individuals in a population divided by the size of the specific area where they live. In case of a population living in water, one would divide the number of individuals by the volume of water where they live.

  17. What are the differences between density-dependent and density-independent factors?

    The impact of density-dependent factors depends on the number of organisms in the population whereas the impact of density-independent factors does not depend on the number of organisms in the population.

  18. Are predators a density-dependent or density-independent limiting factor for a population growth?

    It is a density-dependent factor. How much prey will be consumed by the predator is very dependent on both the number of prey and predators.

  19. How can one calculate the carrying capacity of a given species in an ecosystem?

    One way would be an empirical one; that is, one based on actual data collection. One could look at that species population growth curve and determine the number of individuals once the growth levels off and reaches a stable balance. That point of the curve is the carrying capacity and takes into account all the factors that help population growth as well as the ones that limit it.

    Another way is based on theoretical analysis where one would calculate and predict how many individuals could be supported by the environmental resources in the ecosystem. One would also have to take into account the limiting factors (such as predators) on the population.

  20. You may have noticed that in the population charts used by the program, the maximum value (or carrying capacity) for all the different organisms is known. How can this be?

    The program does the theoretical analysis predicting this maximum value based on all the conditions selected to run the model.

  21. Let's assume that there is a stable food chain and that suddenly the number of primary consumer individuals goes down to half. What would you expect would happen to the producer and to the secondary consumer?

    The number of producer organisms would increase as there would be less demand for them, and the number of consumers would decrease as competition among them for the same resource would increase.

  22. In a marsh ecosystem there are grasshoppers which are herbivores and frogs which feed on the grasshoppers. Which of the two populations do you expect to have more individuals and why?

    Based on the concept of the ecological pyramid, the bio-energy at the trophic level of the grasshoppers should be about 10 times larger than that at the level of the frogs and since the grasshoppers are smaller than the frogs, then the quantity of grasshoppers should be much larger than that of frogs.

  23. Based on the model used in this lesson, how many squirrels and how many hawks can a single oak tree sustain?

    A single oak tree can sustain somewhere between two and three squirrels. The model assumes that each hawk needs three squirrels per year. Therefore, one oak tree (in the model) can barely sustain one hawk. How does this compare with the 10% energy rule of the ecological pyramid?

  24. Describe what a food web is.

    A food web is a (sometimes complex) dependency between all the producers and consumers in an ecosystem which can be depicted in a diagram showing all the different species and their interdependencies.

  25. What makes the logistic equation so interesting?

    The fact that this simple non-linear equation has so many different behaviors based on minor changes of the r value. It goes all the way from normal decline to zero or growth to a stable value to complete chaotic behavior!

 

 


Back to Quiz

 

Last Updated: Monday, 13-Nov-2000 05:22:04 GMT


Arcytech
Java Home
Page
Provide
Feedback