Lecture 15: Extinction

Question 1

3 types of evolution:

Answer 1

1) local extinction
2) species extinction
3) mass extinction

Question 2

Local extinction :

Answer 2

loss of a species from a particular area. e.g. wolves & bears lost from Britain

Question 3

Species extinction :

Answer 3

loss of a species e.g. dodo & great auk

Question 4

mass extinction:

Answer 4

Period of geological time when extinction rate peaks. Characterised by brevity and breadth e.g. dinosaurs

Question 5

brevity =

Answer 5

geological e.g. 100,000 years

Question 6

breadth =

Answer 6

taxonomic breadth

Question 7

why do species go extinct?

Answer 7

• Racial Senescence
• competition from better adapted species
• environmental change

Question 8

racial senescene;

Answer 8

‘species undergo a life cycle like an individual organism’

- about Orthogenesis

Question 9

Orthogenesis;

Answer 9

evolution, once started, continues under its own momentum

Question 10

%? of all species have gone extinct

Answer 10

99%

Question 11

examples of racial senescence;

Answer 11

• irish elk; thought that antlers grew & grew, became negative to species so they died
• Gryphea; ‘devils toenails’ bump grows and traps animal in-side

Question 12

why is racial senescence NOT likely?

Answer 12

1) no mechanism known to produce orthogenesis
2) species don have an allotted life span e.g. lingula
3) On close inspection evidence crumbles

Question 13

examples of racial senescence REAL REASONS:

Answer 13

• irish elk; badly adapted to post ice age forests

- Gryphea; no evidence it evolved from Ostrea. No evidence that coiling increased. Mud caused locking of shells.

Question 14

Competition from better adapted species:

Answer 14

“species went extinct because of competition (or predate or disease) from better adapted species”

e.g. reptiles and mammals stance

Question 15

evolution is never

Answer 15

static

Question 16

Coevolution:

Answer 16

-parasites and hosts (/predators & prey) influence each others evolution

–>predators run faster –> selective pressure on prey to run faster –> prey runs faster –> selective pressure on predator to run faster –>

(RED QUEEN HYPOTHESIS)

Question 17

Environmental change - established idea..

Answer 17

panama land bridge formed, North american mammals moved down & outcompeted south american mammals

Question 18

Environmental change - possible that..

Answer 18

This was exacerbated by Andean rain shadow making south American mammals less well adapted that temperate north american mammals

Question 19

Mass extinctions:

Answer 19

• ORDOVICIAN 440mya marine inverts
• DEVONIAN 370mya marine inverts, fish
• PERMIAN 245mya marine inverts, trilobites,reptiles
• TRIASSIC 210mya marine inverts, reptiles,freshwater fish, insects
• CRETACEOUS 65mya marine inverts, ammonites, marsupials, belemnites, plesiosaurs, mosasaurs, pterosaurs, dinosaurs.

Question 20

Permian extinction:

Answer 20

• 50% of families, 95% of species
• MARINE SPECIES; late permian land masses join together.
• lost 50% of land coast, loss of shallow waters
• TERESTRIAL SPECIES;
• coastal areas have less extreme climate because temperature fluctuations are mediated by the sea.

Question 21

Cretaceous extinction:

Answer 21

• 25% of all families
• we know ASTEROID IMPACT
• an asteroid hit earth
• kicked dust out in to the atmosphere
• dust obscured the sun
• in sea-phyloplankton died
• on land -plants dies (though seeds survived)
• no food for dinosaurs
• mammals survived as nocturnal and were adapted

Question 22

Evidence for cretaceous extinction:

Answer 22

band of IRIDIUM around earth surface in rock records. found in space rocks, not to common on earth.

Question 23

Mass extinctions and evolution:

Answer 23

• mass extinction has a profound effect on evolution.
• even well adapted species may go extinct
• only one primate (Purgatorius) made it through cretaceous - IF IT HADNT WE WOULDNT BE HERE TODAY