L14. Extinction and Extirpation

Question 1

Extinction

Answer 1

death of the last individual of the species
- hard to prove

Question 2

Demonstrating extinction

Answer 2

successive searches throughout the native range and no individuals are found
- people disagree if search is thorough enough
- many times species is declared extinct and then we find it many years later

Question 3

Extinct in the Wild

Answer 3

• when a species is extinct in its habitat, but still found in captivity
• most species cannot be kept indefinitely in captivity: often to not breed well, prone to disease, very genetic diversity
• often the last stage before full extinction

Question 4

Functionally extinct

Answer 4

• a species which still has members present in the environment but population is greatly reduced compared to the ancestral population
• have decreased below their minimum viable population
• have obvious factors in the environment preventing populations from recovering
• are no longer preforming their role in the ecosystem

Question 5

Minimum viable population

Answer 5

• genetic diversity may be too low for healthy breeding over the long term
• greater likelihood that “chance events” could wipe out your entire population

Question 6

Why do species go extinct?

Answer 6

• global extinction arises in local extripations

Question 7

Extirpation

Answer 7

local extinction of a population from a geographical range
- other populations of the species survive elsewhere

Question 8

Why do populations get extirpated?

Answer 8

• people (harvesting, husbandry)
• extreme events
• pollution
• land use change
• reproduction
• Death rate
• immigration of other populations
• carrying capacity of resources

Question 9

Consequences of low populations

Answer 9

• allele effects
• loss of genetic diversity (greater susceptibility to disease, greater change of deleterious alleles becoming prominent in the population)
• less mating options
• genetic bottleneck may occur

Question 10

Gene flow

Answer 10

• the movement of alleles between two geographically separated populations
• a single individual moving between populations can cause gene flow

Question 11

Population viability analysis (PVA)

Answer 11

• use stochastic simulation models to integrate knowledge

Question 12

History of extinction

Answer 12

• extinction is the rule for species, not the exception
• estimated more than 5 billion species have evolved on earth with only 8.7 million species currently

Question 13

Human impacts on extinctions of species

Answer 13

• many extinctions occurred following human migration patterns
• ex. bird species going extinct after human populations landed in Hawaii

Question 14

How do humans cause extinctions

Answer 14

• direct predation
• land burning
• habitat change
• introduced species
• cascade effects

Question 15

Did humans cause extinctions?

Answer 15

• lines of evidence are unclear
• climate caused extinctions
• European colonial expansion may have caused extinctions

Question 16

Evidence of biodiversity loss

Answer 16

people are looking across systems and finding patterns
- ex. species richness, changes in abundance over time, fluctuations of turnover of species composition