Population Ecology – 53.4-53.5
Part I: Life History Patterns
Natural selection shapes different life history traits under different environmental conditions. Some populations exhibit r-selection, and others K-selection.
On what is the life history of an organism based?
Name three variables that help to form the life history of a species.
Compare the contrasting life histories by completing this chart.
Characteristic r-Selection K-Selection
Life history emphasis
Relative body size
Number of offspring per reproduction
Stability near carrying capacity
Age at first reproduction Younger
Emphasis on ____ of offspring Quality and care
Part II: Limiting Factors
It is not realistic for any population to grow exponentially for an extended period of time. Environmental factors prevent this from occurring and keep populations at or near carrying capacity. These factors can be classified as density
dependent, where death rate rises as a population density rises, or density independent, where birth or death rate does not change with population density.
Fill in the following table.
Factor affecting population size Explanation Example
Competition for resources
Identify each of the following limiting factors as density dependent (DD) or density independent (DI). a.
_____ have more effect when the population is larger b.
_____ have more effect when the population is smaller c.
_____ effect does not depend on density of population d.
_____ competition for food e.
_____ fire f.
_____ predation g.
_____ stress produced by crowding h.
_____ competition for nesting sites i.
_____ storms j.
_____ drought k.
_____ disease l.
_____ heat and cold m.
_____ habitat disruption by humans n.
_____ cause populations to stabilize in size, presumably near carrying capacity o.
_____ cause rapid population growth followed by unpredictable crashes p.
_____ seem to cause boom and bust cycles among predators and prey q.
_____ number of lynx limit the snowshoe hare population r.
_____ number of snowshoe hare limit the lynx population s.
_____ effects of the non-living environment t.
_____ effects of other organisms u.
_____ reduce clutch size as song sparrow population grows v.
_____ responsible for lemming boom or bust population cycles