Chapter 53 - KEY
1. Contrast and compare population density and dispersion.
Density is the number of organisms per area
Dispersion is how the organisms are distributed though out the area.
2. Identify and explain the dispersion patterns seen in organisms.
Clumped – patches of resources or strong attractions to stay together to avoid predators
Uniform – antagonistic interactions between the individuals
Random – no strong attractions or repulsions
3. One species of fish is highly territorial, while another lives in large schools. Predict and explain
each species’ likely pattern of dispersion.
– the territorial fish will likely have regular distribution
- because of the antagonistic interactions between the individuals.
– the fish that live in schools will have clumped distribution
- because they are found together in clumps.
4. Describe what produces a Type I, Type II and Type III survivorship curve and give an example
organism for each.
Type I – low death rate when young, high death rate when old – humans, other mammals, other
Type II – even death rate over all ages – annual plants, hydra, squirrels, other
Type III – high death rate when young, steady rates afterwards – oysters, fish, other
5. Contrast and compare FIVE characteristics of "r" and "k" life history strategies. 5 pts total
- r strategists – many offspring, small parental investment in each offspring,
early reproduction age, many reproduction events, short life span, unstable
environments, Type III curve, J- growth other
- k strategists – few offspring, large parental investment in each offspring,
later reproduction age, fewer reproduction events, longer life span, stable
environments, Type I curve, S-growth curve, other
6. Identify and discuss THREE factors that regulate population size.
Density Dependent factors such as disease, nesting space, predation, parasites, waste,
other and Density Independent such as weather, other
7. Animals that cannot find enough food or that experience other forms of stress may abandon
their young to die. Explain the adaptive value (if any) of this behavior.
– this behavior allows the parents to survive to reproduce another day when conditions are
more favorable. Continuing to try to raise the young while stressed may result in the
death of both the parents and the young.
8. In some species of fish, females disperse some of their eggs widely and lay other eggs in a nest.
Only the latter receive parental care. Explain the trade-offs in reproduction that this behavior
illustrates.
– eggs that are dispersed are an “r” behavior. Little resources are expended by the parent by
few offspring will survive.
½ pt – eggs in nests are a “K” behavior. More resources are expended by the parent but more
offspring should survive.
9. Endangered organisms usually have which life history strategy? Discuss why their life history
strategy may contribute to their being endangered. 1 pt total
½ pt - Most endangered species are k strategists.
½ pt They can’t reproduce as rapidly and recover losses to their populations. They also require
stable environments which are often threatened by humans.
10. Most pests have which life history strategy? Discuss why their life history strategy contributes
to their success as pests.
- Pests have r strategy.
- They can reproduce rapidly and survive in unstable environments.
11. When a crop field is abandoned in Indiana, it is quickly colonized by fast-growing weeds.
Discuss if these species more likely to be k-species or r-species and justify your answer.
– r species
- they have the ability to colonize in opportunistic situations.
12. An age-structure diagram for Indiana shows that 20-28 age group is larger in size than the
birth – 8 age group. Predict what this pattern might mean for the future population of
Indiana?
- The population is shrinking or is becoming zero population growth.
13. As an ecologist that manages a wildlife preserve, you want to increase the preserve’s carrying
capacity for a particular endangered species. Discuss how you might go about accomplishing
this plan.
– they may increase the habitat for the species, food sources, nesting spaces etc.
14. Discuss how humans differ from other species in their ability to “choose” a carrying capacity
for their environment.
– humans can modify the environment thus changing its carrying capacity, few other
species have that ability (or similar answer).