8: Extinction

Question 1

In what geological periods were there mass extinctions (oldest to most recent)

Answer 1

Ordovician, Devonian, Permian, Triassic, Cretaceous, current

Question 2

If there are 10 million species on earth today, how many should go extinct naturally every year? %?

What is the actual rate?

Answer 2

1-10 species (0.000-0.00001%)

Actual rate is 0.01% (100-1000x higher)

Question 3

When is the sixth mass extinction expected to occur? What % of animal species?

Answer 3

2200
75% of animal species

Question 4

What species of birds tend to go extinct more often

Answer 4

Island birds (endemic species w small geographic range)

Question 5

Islands have had…

Answer 5

the highest rates of extinction and hold most of the endangered species in the world today

Question 6

Two reasons islands have the highest rate of extinction

Answer 6

1. Islands are small and thus have smaller (and fewer) populations
2. Species on islands have often evolved without predators, parasites & competitors

Question 7

What is enigmatic decline

Answer 7

Species in relatively pristine sites have disappeared (disease? climate change?)

Question 8

What is an estimate made based on a typical species-area curves

Answer 8

Species with broad geographic range have lower extinction rates

Question 9

Two alternatives to the SAR model

Answer 9

Matrix SAR: accounts for the quality of the matrix
Countryside SAR: accounts for landuse in human landscape by organisms

Question 10

Problem with the SAR model

Answer 10

over-predicts extinctions

Question 11

SAR model assumes…

Answer 11

Habitat is eliminated at random

Question 12

What is extinction debt

Answer 12

With habitat loss you may see increase in species richness in remnant habitats immediately after (over time the “extras” die)

Question 13

Why are large predators naturally rare

Answer 13

At the top of the trophic levels, less energy transfer

Question 14

What are the seven forms of rarity?

Answer 14

Geographic range: large or small
Population size: somewhere large, everywhere small
Habitat specificity: large broad, large restricted, small broad, small restricted

Question 15

What are endemics? Neoendemics? Paleoendemics?

Answer 15

Endemics = species found in single area and no other place (greatest risk)

Neoendemics = species that occupy small area but only recently evolved

Paleoendemics = species whose close relatives have all gone extinct

Question 16

What are other traits of species that tend to be vulnerable

Answer 16

• large home ranges
• intolerant of people
• carnivorous
• little behavioural flexibility
• limited dispersal ability
• distribution where human pop density is high