Ecology Chapter 10 ECU
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Concept 10.1: Populations exhibit a wide range of growth patterns, including (4)
exponential growth, logistic growth, fluctuations, and regular cycles.
Concept 10.2: Delayed density dependence can cause
populations to fluctuate in size.
Concept 10.3: The risk of extinction increases greatly in -----------
in small populations.
Concept 10.4: Many species have a metapopulation structure in which
sets of spatially isolated populations are linked by dispersal.
Logistic growth curves incorporate a
carrying capacity (K)
Exponential growth only occurs over
short time periods and some conditions
Few populations exhibit -----------, noise remains
Many populations exhibit fluctuations in population growth because of
density dependent and independent factors
Regular cycles most often result from
density dependent factors
Delayed density dependence results from mismatches between -------------- and ------------------.
prey growth rates and predator growth rates.
Many factors can drive populations to extinction:
- Predictable (deterministic) factors, as well as fluctuation in population growth rate, population size, and chance events = Genetic Drift
- Demographic Stochasticity
- Environmental Stochasticity
Why are small populations more prone to extinction?
Random events kill a larger portion of the population
chance events influence which alleles are passed on to the next generation.
Drift reduces the genetic variation of small populations, but has little effect on
Genetic drift can cause allele frequencies to
change at random from one generation to the next in small populations.
Small populations are vulnerable to the effects of genetic drift for three reasons:
- 1. Loss of genetic variability reduces the ability of a population to respond to future environmental change.
- 2. Genetic drift can cause harmful alleles to occur at high frequencies.
- 3. Small populations show a high frequency of inbreeding (mating between related individuals
Inbreeding tends to increase the frequency of ------------- which can lead to reduced reproductive success.
homozygotes, including those that have two copies of a harmful allele,
Inbreeding: three results
- 1)Increases expression of deleterious alleles
- 2)Decreases reproductive success
- 3)Can lead to lower population growth rates
changes in the average birth or death rates that occur from year to year because of random changes in environmental conditions.
population-level birth and death rates are constant within a given year, but the actual fates of individuals differ.
spatially isolated populations that are linked by the dispersal of individuals or gametes
Metapopulations are characterized by
epeated extinctions and colonizations.
species persists because the metapopulation includes populations that are
going extinct and new populations established by colonization.
Populations of some species are prone to extinction for two reasons:
- 1. The landscapes they live in are patchy (making dispersal between populations difficult).
- 2. Environmental conditions often change in a rapid and unpredictable manner.
If the -------------- is greater than the ---------------- then the population will go extinct.
- probability of extinction
- probability of colonization
large tracts of habitat are converted to spatially isolated habitat fragments by human activities, resulting in a metapopulation structure.
Some patches are better than others and they produce more propagules that disperse
increased nutrient inputs caused eutrophication and increased phytoplankton biomass, decreased oxygen, fish die-offs, etc.
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