Population Dynamics and Extinction

population loss is approximately equal to

habitat loss

a population is defined as

multiple individuals of the same species in the same general geographic location

population size is determined by

• birth rate

• death rate

• immigration

• emigration

open populations are influenced by

all 4

closed populations are influenced by

only birth and death rate

metapopulation

a group of separate local populations of the same species that live in different habitat patches and interact when individuals move between them

intrinsic risk(s) of red ruffed lemur

small range

intrinsic risk(s) of devil’ s hold pupfish

small range

intrinsic risk(s) of sonoran pronghorn

few and small populations

intrinsic risk(s) of iberian lynx

few and small populations

intrinsic risk(s) of monterey pine

low migration

intrinsic risk(s) of bighorn sheep

low genetic diversity

intrinsic risk(s) of florida panther

low genetic diversity, restricted range,

intrinsic risk(s) of koala and panda bears

specialized niche

three main causes of extinction for small populations

1. loss of genetic diversity

2. demographic fluctuations

3. environmental fluctuations

3 ways loss of genetic diversity contributes to extinction

1. loss of evolutional flexibility

2. genetic drift

3. inbreeding depression

loss of evolutionary flexibility

reduces ability for a population to adapt to enviormental change

genetic drift

can cause harmful alleles to occur more frequently

inbreeding depression

reduced reproductive success

demographic stochasticity has a bigger/smaller impact on smaller populations

bigger

demographic stochasticity has influence on

• species with variable death rates

• low birthrates

• uneven sex ratio

when a population drops below _____ individuals the population will fluctuate randomly

50

why does population fluctuate randomly when below the minimum number of individuals

hard to maintain consistent birth/death rates

allee effects will lead to diminished survival and reproduction due to things such as

• individuals unable to find or acquire mates

• critical group behaviors lost

• inadequate social ques for key behaviors

environmental stochasticity relates to changes in

predators, pathogens, food supply, climate cycles

an extinction vortex starts with

small effective population