Mass extinctions

Question 1

Background rate of extinction

Answer 1

average number of FAMILIES (easier to tell apart) going extinct, figure it out by examining the fossil record (limits in the fossil record)

Question 2

Chronospecies

Answer 2

single species changing morphologically, genetically, or ecologically over a long time scale- identify them as a separate species

Question 3

Psuedoextinction

Answer 3

when a species is presumed extinct but has actually just become a different species

Question 4

Rates of extinction

Answer 4

historically, 0.1/ million/ year

Question 5

Biotic mechanisms of extinction

Answer 5

competitive exclusion by a closely related species, prey species develops unbeatable defense, new predator, disease

Question 6

evolutionary causes for extinction vulnerability

Answer 6

poor disperser, at or near the top of the food chain, small range, rare, low genetic variability, specialized requirements, large body size

Question 7

abiotic mechanisms of extinction

Answer 7

niche/habitat no longer supports species, climate fluctuations, sea level change, meteorites, volcanism

Question 8

Mass extinction

Answer 8

extinction of a large number of unrelated species over a short period of geological time- global distribution

Question 9

similarities of background and mass extinction

Answer 9

can both have multiple causes, both change evolutionary history

Question 10

difference of background and mass extinction

Answer 10

different outcomes, mass extinctions= whole communities removed, previously minor species become dominant- fundamental changes

Question 11

1. End Ordovician mass extinction

Answer 11

49% animal genera lost- marine organisms suffered most, caused by: volcanic activity depositing silicate materials- CO2 in air deposited in sea, less CO2 in atmosphere and less greenhouse effect- colder, & land moves to the south pole- glacier formation- less water in oceans

Question 12

2. Late Devonian

Answer 12

20% of families, 70-80% of animal species lost, shallow water species impacted- dominant reef builders lost, unusually long, no single cause, combination of silicate weathering cooling globe and phosphorus erosion

Question 13

Devonian plant hypothesis

Answer 13

large number of plants led to global cooling and lack of oxygen in oceans, CO2 in atmosphere combines with water to form carbonic acid- falls as acid rain and weathers silicates- bicarbonate erodes and ends up in ocean- CO2 in atmosphere sequestered as limestone in ocean- sped up by plants- break apart rocks and also secrete own acids

Question 14

Formation of dead zones

Answer 14

chemical weathering of rocks by plants releases phosphorus- erodes to ocean, leads to algal blooms- algae dies and drifts down- bacteria uses oxygen to break down algae- low oxygen levels in that area

Question 15

3. End Permian

Answer 15

“the great dying”- 70% terrestrial vertebrates 96% marine species lost- all life today descendants of the few survivors here; causes- series of massive volcanic eruptions- release CO2, methane, SO2 and burned coal deposits- global warming; lost half of oxygen content; ocean salinity increased- deep water circulation more difficult; buildup of dead matter and dead zones

Question 16

4. End Triassic

Answer 16

76% species extinct- left empty niches on land led to rapid diversification of dinosaurs; no clear cause: gradual climate change; more minor asteroid impact; massive volcanic eruption

Question 17

5. End Cretaceous

Answer 17

75% plant and animals species extinct- only smaller tetrapods survived, end of dinosaurs, followed by rise of mammals - rapid adaptive radiation; causes: impact hypothesis massive bolide impact, threw cloud of particles into atmosphere- global winter- interfered with photosynthesis by blocking sunlight; proof of impact in crater and iridium sediment buildup in rock layers; Deccan Traps (india)- massive basalt floods produced similar effect as previously with volcanic activity; both contributed

Question 18

Press-pulse hypothesis

Answer 18

first even stresses environment, second even then occurs and causes a greater-than-expected impact

Question 19

Sixth Mass Extinction

Answer 19

human impact, high rate of extinction- fast

Question 20

Planned extinction

Answer 20

directed human efforts to drive species to extinction- “pest” species