topic 12 extinction

Question 1

define speciation

Answer 1

○ Birth of a species

○ Evolution of reproductive isolation within an ancestral species, resulting in two or more descendant species

Question 2

define extinction - when is it certain?

Answer 2

○ Death of a species
○ When the last existing member of a given species dies
○ In other words…there aren’t any more left!
○ – It is a scientific certainty when there are no surviving individuals
left to reproduce

Question 3

• Background Extinction- define

Answer 3

– A long-lasting rate at which taxa become extinct

– Constant within clades but vary greatly between clades

Question 4

define functional extinction

Answer 4

– Only a handful of individuals are left

– Odds of reproduction are extremely slim

Question 5

define mass extinction

Answer 5

– A highly elevated rate of extinction of taxa; extends over a
relatively short geological interval
– Must eliminate >60% of species in a relatively short period of
geological time with wide-spread geographic and taxonomic
impacts
– May occur periodically

Question 6

causes of extinction

Answer 6

• Genetics and demographics
	• Small npop = increased risk 
	• Mutations 
		○ Cause flux in natural selection 
		○ Beneficial traits are overruled 
	• Loss of genetic diversity 
		○ Shallow gene pools promote massive in breeding

Question 7

describe habitat degradation - toxicity

Answer 7

• Toxicity
Kills off specimens directly through food/water
– Indirectly via sterilization
– Can occur in short spans (single generation)
– Can also occur over several generations

Question 8

describe habitat destruction

Answer 8

• Habitat destruction 
		Can be caused by natural processes
		Ø Volcanoes, floods, droughts, etc.
		– Elimination of living space
		– Change in habitat
		Ø Rainforest à to range lands for cattle
		– Other anthropogenic causes

Question 9

directr and indirect effects of invasive species

Answer 9

• Direct effects
	– Competition
	– Predation
	– Pathogens & parasites
	• Indirect effects
	– Habitat alteration

Question 10

invasive sp exs.

Answer 10

– Rosy Wolfsnail in Hawaii à eight native snail species
– Red Fox in Australia à several species including lesser bilby
– Brown Tree Snake in the Island of Guam after WWII à more than
half of Guam’s bird & lizard species
– Feral cats in New Zealand à flightless Stephen Island Wren as
early as 1900

Question 11

describe planned extinction

Answer 11

Human controlled
	v Thought to help humans
	v Deadly viruses
	– Smallpox
	Ø Extinct in the wild
	– Polio
	Ø Near extinct (only in small parts of the world –
	Afghanistan & Pakistan)

Question 12

how long was phanerozoic

Answer 12

• 
	An Eon of over 540 million years
	Ø Jack Sepkoski (1984)
	studied the marine record
	based on 30,000 marine
	genera in more than 4,000
	families with hard
	skeletons

Question 13

diversity in cabrian + ordovician vs rest of paleozoic? after paleozoic?

Answer 13

Ø Rapid increase of diversity
	in Cambrian & Ordovician
	Ø Plateau during rest of
	Paleozoic
	Ø Post-Paleozoic increase
	Ø Some major extinction
	events throughout the eon
	are also evident

Question 14

mass extinction?

Answer 14

• A sharp decrease in number of species on
Earth in a short period of time
• Coincides with a sharp drop in speciation
• Statistically distinct from background
extinction levels

Question 15

5 mass extinctions?

Answer 15

5 Mass extinctions at the end of:
	– Ordovician (~443 mya)
	– Devonian (~359 mya)
	– Permian (~251 mya)
	– Triassic (~200 mya)
	– Cretaceous (~65 mya)

Question 16

• Does extinction probability of
species in a group increase,
decrease, or remain constant the
longer the group survives?

Answer 16

• Van Valen found evidence that
	the extinction probability remains
	constant as a group ages
	•  He proposed the Red Queen
	Hypothesis, which holds that as a
	group ages, its environment
	continually deteriorates. It must
	evolve continually, just to survive
	v Like the Red Queen in Lewis
	Carroll’s Through the Looking-
	Glass, a species must ‘run’
	(evolve, adapt) just to stay in the
	same place (survive, avoid
	extinction)

Question 17

causes of mass extinction

Answer 17

• Possible causes include
	-Impact of extra-
	terrestrial objects
	-Worldwide cooling
	(including glaciation) or
	warming
	-Massive volcanic
	eruptions
	-Changes in ocean
	chemistry
	-Release of toxic gases
	from the oceans