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Extinction Flashcards

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1
Q

Extinction in the Holocene era (10,000 years ago)

A

Largest ground sloth was the size of an elephant.
Claws could reach 50cm in length.
Ground sloth was nothing like other animals, tiny head, slim shoulders and massive hind quarters.
Herbivores like their modern day tree sloth predecessors.

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2
Q

What is there a long term balance between

A

Rates of speciation and extinction

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3
Q

How can an equilibrium species richness be predicted

A

Based on rates of extinction and speciation among existing species

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4
Q

How many species have evolved on earth over the last 3.5 billion years

A

4 billion

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5
Q

What percentage of the 4 billion species have gone

A

99%

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6
Q

What does the species we have today represent

A

A very small proportion of what has been living in the planet

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7
Q

How many mass extinctions has there been

A

5 so far

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8
Q

What are mass extinctions

A

Times when the earth loses more than three quarters of its species in a geologically short interval

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9
Q

What are the names of the extinction events

A 
Ordovician 
Devonian 
Permian
Triassic
Cretaceous
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10
Q

How much did the Ordovician event lose

A

86%

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11
Q

How much did the Devonian event lose

A

75%

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12
Q

How much did the Permian event lose

A

96%

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13
Q

How much did the Triassic event lose

A

80%

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14
Q

How much did the Cretaceous event lose

A

76%

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15
Q

The main causes of the Ordovician event

A

Onset of alternating glacial and interglacial episodes

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16
Q

The main causes of the Devonian event

A

Global cooling followed by warming, tied to diversification of plants

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17
Q

The main causes of the Permian event

A

Siberian volcanism and global warming

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18
Q

The main causes of the Triassic event

A

Elevated co2 levels increasing temperature and ocean acidification

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19
Q

The main causes of the Cretaceous event

A

A meteor causing a global cataclysm and caused cooling . May have also been climate change before

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20
Q

What do mass extinctions account for

A

4% of total extinctions (background rate is high)

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21
Q

What do mass extinctions do

A

Disrupt overall development of diversity

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22
Q

What do survivors of mass extinctions tend to be

A

Generalists and opportunists

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23
Q

How long does it take after a mass extinction to recover biodiversity

A

10 million years

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24
Q

What is the lifespan of all species

A

1 million

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25
What does the IUCN red list data say about extinction
27,000 species are threatened. 14% birds 25% mammals 40% amphibians
26
Why is speciation not a relevant time frame to ya
Because time frame for speciation isolation is longer than extinction
27
What are traits promoting survival
``` R-selected traits Large populations. Widespread. High genetic variability. Rapid dispersal. Human commensalism. ```
28
Traits promoting extinction
``` K-selected traits. Small populations. Rare. Low genetic variability. Slow dispersal. Exploited by humans. ```
29
What are r species
Opportunistic pioneers. They have been selected for their ability to reproduce rapidly
30
What are k species
Specialists. Have features that favour populations remaining close to the habitats carrying capacity
31
Example of an r selected species
Brown rat | 6 rats per pregnancy and 6 generations a year
32
Example of a k selected species
African elephant | 1 calf per female every 5 years
33
What is the potential growth of the female population of rats vs elephants
Over 2 trillion female rats but only 2.4 female elephants
34
What are the features to look at for r and k species
``` Habitat Populations Body size Growth Time to mature Reproductive period Offspring Parental care Adult mortality Dispersal ability ```
35
What is the habitat like for r species
Unstable, unpredictable
36
What is the population like for r species
Fluctuate widely
37
What is the body size like for r species
Small
38
What is the growth like for r species
Rapid
39
What is the time to mature like for r species
Short
40
What is the habitat like for k species
Stable and predictable
41
What is the populations like for k species
Close to carrying capacity
42
What is the body size like for k species
Large
43
What is the growth like for k species
Slow
44
What is the time to mature like for k species
Long
45
What is the offspring like for k species
Many, small
46
What is the parental care like for k species
Little or none
47
What is the adult mortality like for k species
High
48
What is the dispersal ability like for k species
High
49
What is the offspring like for r species
Few, large
50
What is the reproductive period like for k species
Longer
51
What is the parental care like for k species
High
52
What is the adult mortality like for k species
Low
53
What is the dispersal ability like for k species
Low
54
How does population size affect extinction
Initial population size defines likelihood of extinction for both animals and birds e.f small is more likely
55
How does range size affect extinction
Small geographic ranges (species endemic to islands) means more extinction
56
What are the demographic reasons about why small and isolated population so vulnerable
Unequal sex ratio. Low change of locating a reproductive partner. Low fecundity due to age, illness. Low cooperative interaction in food acquisition, predator detection.
57
Example of a skewed sex ratio
Selecting hunting of males in elephants seals leads to skewed sex ratio. Males:females. 10:90 means only 36 are the effective population
58
How does genetic variation affect extinction
Small populations means low genetic diversity and low genetic diversity limits the ability to respond to new conditions and causes inbreeding depression - leads to higher offspring mortality.
59
How does dispersal ability affect extinction
High dispersal ability you have lowest rate of extinction to proportion going extinct. Being able to disperse reduces vulnerability to extinction.
60
How does relationship with humans affect extinction
Some species benefit from humans (commensal species derive food or other benefits from another organism without hurting or helping it) but others have antagonistic relationships with humans.
61
What is the most likely explanation for global extinction of megafauna in pleistocene
Humans or maybe climate change - depends where and and the species. Synergetic effect. In Africa it’s mainly climate change but in the America it’s mainly humans
62
What are the parts of the extinction vortex
A mix of directional factors, genetic problems and stochastic factors all affecting each other.
63
What are directional factors
Habitat loss Pollution Over exploitation Exotic species
64
What are the stochastic factors
Demographic stochasticity Environmental variations. Catastrophes.
65
What is the extinction vortex
Small fragmented isolated populations -> inbreeding loss of genetic diversity -> reduces adaptability, survival and reproduction -> reduced N -> back to the beginning
66
What are the predispositions to extinction
``` Rarity (small range, small populations) Large, slow growing and long lived. Large area requirements. Top of food web/conflict with humans. Specialised needs. Adapted to core habitats. Poor dispersal/insular. ```
67
How do forest edge effects on populations
Some species use corridors between rainforest patches e.g generalist ants but others can’t live in the disturbed environment e.g forest specialised ants.
68
What animals has a large area requirements and conflict with humans
Eurasian wolf

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