Lecture 15 - extinction

Question 1

What are the 2 types of extinction?

Answer 1

• contemporary
• geological

Question 2

What are the 2 contemporary types of extinction?

Answer 2

• local extinction
• species extinction

Question 3

What are the 3 geological types of extinction?

Answer 3

• background extinction
• extinction events
• mass extinction events

Question 4

What % of species are threatened with extinction?

Answer 4

25%

Question 5

Give an example of local extinction

Answer 5

loss of population from a particular area - e.g. wolves from Britain

Question 6

Describe extinction in the fossil record

Answer 6

• extinction is a feature of life on Earth
• because of current concerns we tend to focus on species/local extinctions & forget extinction has been happening since life on Earth began
• 99% of all species that ever existed have give extinct

Question 7

What is background extinction?

Answer 7

the sum of all normal species terminations during a defined time interval

Question 8

What are extinction events?

Answer 8

times where many species go extinct for a shared reason, typically regional rather than global in scale, but pertaining to selective extinction of clades

Question 9

What are mass extinction events?

Answer 9

times of geologically rapid global disappearance of much of life, when many species of wide ecological range died out worldwide

Question 10

Describe the mass extinction events

Answer 10

• End-Ordovician (444 mya) - glaciation
• Late Devonian (372 mya) - Large Igneous Province (LIP), ocean anoxia
• End Permian (252 mya) - LIP
• End - Triassic (201 mya) - LIP
  End-Cretaceous (66 mya) - Meteorite impact

Question 11

Describe after mass extinctions

Answer 11

• survivors of mass extinctions are not random
• often share ‘generalist’ characteristics
• sometimes referred to as ‘disaster laxa’

Question 12

What is species senescence?

Answer 12

suggestion that species undergo a lifecycle like individuals:
- birth
- development
- reproduction
- death

Question 13

What is orthogenesis?

Answer 13

change in organisms was due not to natural selection, but to unchecked directional trends within a lineage

Question 14

Why did Irish Elk (giant deer) go extinct? (SUPPOSEDLY - ACCORDING TO ORTHOGENESIS)

Answer 14

• evolved on an irreversible trajectory towards larger & larger antlers
• Irish elk went extinct when antlers became too large
• could no longer hold up their heads
• got entangled in the trees

Question 15

Why is evidence for species senescence weak?

Answer 15

• no mechanism for Orthogenesis
• completely at odds with natural selection
• species don’t have ‘allotted’ lifespans

Question 15

How did Irish Elk actually go extinct?

Answer 15

• sexual selection favoured large antlers and large body size
• natural selection favoured smaller size in response to rapid changing towards warmer, more temperature climates at the end of the last ice age

Question 16

What causes only some species to go extinct?

Answer 16

• competition & the Red Queen (biotic factors)
• environment - the Court Jester (abiotic factors)

Question 17

What are factors explaining the probability of speciation?

Answer 17

1. species age
2. species diversity
3. climate
4. ecology

Question 18

What drives speciation in Planktonic foraminifera?

Answer 18

diversity (competition)

Question 19

What drives extinction in Planktonic foraminifera?

Answer 19

climate

Question 20

What drives the probability of speciation?

Answer 20

biotic factors (the red queen)

Question 21

What drives the probability of extinction?

Answer 21

abiotic factors (environmental factors - the court jester)

Question 22

What is species selection?

Answer 22

the idea that some lineages (or species) have characteristics that make them more likely to speciate or less likely to go extinct

• e.g. species that are large might be just as likely to go extinct, but more likely to speciate