Natural Causes of Population Decline and Extinciton Flashcards
What is the Theory of Island Biogeography?
The number of species of a given taxon represents a dynamic equilibrium between the rate of immigration of new colonizing species and the rate of extinction of previously established ones.
What is an Island characterized by?
- Various Sizes
- Various Distances
What is the Species-Area curve?
A tool used to estimate biodiversity in a habitat, where number of species on an island or patch increases as area increases.
What is the equation for the species-area curve?
S = cA (z-superscript)
What are the two factors of Island Biogeography?
Island Size & Island Isolation
Larger islands have greater range of ________.
Microhabitats
Near islands are more likely to be ___________.
Colonized
_______ island populations are more likely to go extinct.
Small
True or False: As the number of resident species increases the number of new immigrants decreases because there are fewer new potential immigrants from the source pool.
True.
Given a finite resource base, as number of species increases, population size of individual species must _________.
decline
What theory does the Turnover Rate apply to?
Theory of Island Biogeography
What is the Turnover Rate?
The rate at which species are lost and new ones gained.
Define the Rescue Effect:
Extinction of a dwindling population may be slowed or halted through immigration of new individuals.
What is turnover rate influenced by?
- Island Size (Patchy)
- Nearness to other sources immigrants
What are some types of islands?
- Mountaintops
- Bogs
- Ponds
- Dunes
- Insects and their parasites
What is the rule of thumb in the Theory of Island Biogeography?
A tenfold increase in area leads to a doubling of the number of species.
Define a Metapopulation:
If they are far enough apart to exist as distinct, partially isolated sub-populations each possessing its own population dynamics, linked only through dispersal (emigration/immigration).
_____ Effect: The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.
Founder Effect
Define the Genetic Bottleneck:
A sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as specicide, widespread violence or intentional culling.
What is an example of a genetic bottleneck?
Elephant Seals
Define Random Genetic Drift:
The changes that occur in the frequency of alleles in a population due to random chance.
Define Inbreeding:
The breeding between close relatives.
What are the 4 genetic aspects of Metapopulations?
- Founder Effect
- Genetic Bottleneck
- Random Genetic Drift
- Inbreeding
Define the Minimum Viable Population:
The minimum number of individuals that will ensure the persistence of a metapopulation for some set period of time (100 years commonly used).
What is the 50 / 500 rule for an effective population size?
An effective population sizeof 500 is required to offset the effects of genetic drift while a minimum of 50 is needed to avoid inbreeding depression.
What is an effective population size?
the number of breeding adults that pass gametes on to the next generation, not just those capable of breeding.
What are some limitations of a minimum viable population?
smaller population sizes are at risk for extinction in a shorter period of time.
PRACTICE THE EXTINCTION VORTEX
Week 1: Slide 26
Define a Niche:
A multidimensional space occupied by a species, defined by position along physical, environmental and temporal gradients.
What is an example of a niche?
Crayfish in MB, its like having a McDonalds in a mall, you won’t often see two in the same place, one will outperform the other.
Explain competition in terms of a niche:
If two species occupy the same niche, one will eventually eliminate the other through competition.
What is Resource Portioning?
Similar species usually differ in some habit or feeding requirement that allows them to co-exist.
True or False: Disease and Parasitism often work in concert with other factors.
True, it either weakens a population so other factors (pollution, climate change, etc.) have a greater impact
What type of case is the Chestnut Blight?
Disease / Parasitism, a fungus introduced accidentally to NY around 1900 from Asia.
What are the Wood Bison an example of?
Hybridization
