lectures 12 Flashcards
What is extinction?
Death of the last individual of the species.
What is being extinct in the wild?
A species can be extinct in its habitat, but still found in captivity.
- death of the last individual of the species in the wild.
- individuals persist in captivity.
Why is extinction in the wild often the last stage before full extinction?
Most species cannot be kept indefinitely in captivity.
- often do not breed well.
- prone to disease.
- very low genetic diversity.
What is being functionally extinct?
A species which still has members present in the environment. Population is greatly reduced compared to the ancestral population.
What are the characteristics of the species that are functionally extinct?
- have decreased below their minimum viable population.
- have obvious factors in the environment prevention group populations from recovering.
- are no longer performing their role in the ecosystem.
Explain the characteristic of minimum viable population of functionally extinct species.
- genetic diversity may be too low for healthy breeding over the long term.
- greater likelihood that “chance events” could wipe out the entire population (severe drought, hurricane, etc.).
What is extirpation?
Local extinction of a population from a geographical range.
Other populations of the species survive elsewhere.
Why do populations get extirpated?
Extirpation (n=0) is about population dynamics.
What determines the number of individuals (N) in a population over time?
A series of interlinked processes that together determine the numbers of individuals in the population over time.
What is the carrying capacity?
The number of individuals an environment can support before resources run out or the environment begins to degrade.
What are examples of factors that felt population numbers?
- Human impacts (harvesting, husbandry).
- Extreme events (diseases, natural catastrophes).
- Pollution (chemicals, changes in environment).
- Land-use change (changing environments, loss of habitat).
What are the stochastic simulation models?
- Computer programs that quantitatively describe all process that influence population size.
- Allo random variability in the parameters of the model (probability) from individual to individual year to year.
- Run the model many times, each time reassigning new random values to each parameter, and use he frequency across many simulations to estimate the probability of extinction in the population or species.
What are the consequences of a low population size on a stochasticity model?
Increased effect of stochasticity (random chance).
Population processes (allée effects) affects survival.
Explain mate limitations in terms of allee effects.
As populations become smaller, there are less chances to find a mate, especially in a big location.
Explain loss of genetic diversity in terms of allee effects.
Possible side effect of low genetic diversity:
- Greater susceptibility of low genetic diversity.
- Greater chance of deleterious alleles (i.e. detrimental to survival) becoming prominent in the population.
