Lec 12: Diversification - Extinction and Extirpation Flashcards
What is extinction?
the death of the last individual of a species
- can be extinct in the WILD
what is the last stage before full extinction?
extinct in the wild, because most species cannot be kept in captivity indefinitely
what does it mean to be FUNCTIONALLY extinct?
- species no longer performs its role in the ecosystem
- specie has decreased below its minimum viable population
Why can’t functionally extinct populations recover
- genetic diversity too low for healthy breeding
- chance events can wipe out entire pop
what is extirpation?
extinction of a population of a species in one place
what are the variables in a population size model?
1) population size in last time period
2) rate of population increase
3) carrying capacity K
4) variation
What are factors affecting population size?
- humans
- extreme evetns
- pollution
- land-use change
What are the consequences of having a low population size, in terms of the probability of extirpation?
- increased effect of stochasticity
- population processes (Allee effects)
What are some Allee effects?
- mate limitations
- loss of genetic diversity (more susceptible to spread of genes that decrease fitness and more susceptible to disease)
What is a metapopulation?
a network of populations connected by SOME exchange of individuals
What is gene flow?
movement of alleles between 2 populations
Where is chance a factor in population viability?
- in the probability of natural catastrophes
- in the population demography
- in metapopulation dynamics
in the effects of small population size
is extinction a rule or an exception for species
a rule
what are mechanisms by which humans have made species go extinct on islands?
- direct predation
- secondary effects (habitat change, introduced species, cascade effects)
What are lines of evidence for human caused extinction on continents?
the overkill hypothesis:
- larger mammals were disproportionately affected
- there is evidence that mammoths were hunted
