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Week 7 Study Questions
Terms in this set (10)
What are the two major kinds of stochasticity that influence population growth rates? Which is important only at small population sizes? Write a sentence that describes what each kind of stochasticity is and what creates it.
Environmental: erratic changes in environmental conditions and all size populations. (unpredictable changes in environment)
Demographic stochasticity: Variability in population growth rates arising from random differences among individuals in survival and reproduction within a season. Important at small populations.
What is a one sentence definition of genetic stochasticity?
Changes in the frequency of genotypes over generations at low density through a reproduction event.
What 4 numbers influence the risk of population extinction?
1. Quasi-extinction (if population reaches this level, there will be problems) Risk of becoming extinct in the future.
2. Population size: How it is expanding and changing (N/lambda)
Look at one of the example extinction risk figures shown in class - be able to explain what these mean and how to find, for example, the time in the future when there is a 50% risk of extinction [or quasi-extinction].
Cumulative probability of extinction vs. time .
Small populations have a greater risk of going extinct than large populations.
Graph: multiple exponentially growing upwards layered on top of each other
How are habitat degradation and habitat fragmentation different?
Habitat Degradation: habitat is being lost, species can live there, but not as many.
Habitat fragmentation: One continuous patch has been modified so there are numerous patches that are separate & next to each other
Meta-population dynamics explain how a species that exists as only very small populations can avoid complete extinction. Explain how this process works to allow the long term persistence of a species or set of populations.
Fragmentation and Dispersal. Extinction events are saved by immigration events. Populations of population. For a meta-population to work, there has to be more colonization than extinction. Populations that are spatially distinct from one another.
What are trophic interactions? what are non-trophic interactions?
Trophic interactions: higher up on the food chain. Vertical.
Non-trophic interactions: Mutualism, not effecting cycle. Horizontal.
(Trophic level: separation from autotroph)
What is a 'community'?
A group of different species living in the same habitat.
exploitative and interference competition
Exploitative: Using up all resources and are competing indirectly through mutual effects on the availability of a shared resource. Examples: Elk and Cow. Vine Kiduzu completely grow over SC trees. Graph intersects at point of coexisting.
Interference: competing over who is using resources. Interference competition is less likely to lead to coexistence. Example: pitcher plants soil not good in area so they eat insects, frogs, etc.
The 'ghost of competition past' is a phrase that implies that competition can be difficult to see in nature, precisely because it has strong effects. in your own words, describe this idea.
Competition is so strong between species that it is not visible because the prey had to completely change habitat. However, if there had been coexisting, they would have been able to survive without a problem
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