Extinction Rates

Question 1

How can we differentiate the “normal” extinction rate (background extinction) from a mass extinction?

Answer 1

Background extinctions occur at normal rates. Mass extinctions occur at rapid rates on a global scale that affects a range of organisms

Question 2

The 5 Extinction Events

Answer 2

Ordovician
Devonian
Permian
Triassic
Cretaceous

Question 3

Ordovician

Answer 3

443 mya

Question 4

Devonian

Answer 4

359 mya

Question 5

Permian

Answer 5

251 mya

Question 6

Triassic

Answer 6

200 mya

Question 7

Cretaceous

Answer 7

65 mya

Question 8

The proportion of an original sample that survives for a particular amount of time

Answer 8

Lineage Survivorship Curve

Question 9

What does a straight line in the lineage survivorship curve represent?

Answer 9

The probability of subgroups becoming extinct was constant over the life span of the larger clade.

Question 10

What’s the typical probability of extinction for a group over time?

Answer 10

Within the same group, the probability of extinction of a group stays the same.

Within different groups, the probability of extinction of a group differs.

Question 11

What is the evidence for and against the 6th mass extinction event?

Answer 11

Scientists believe we are in the midst of a 6th mass extinction event due to high extinction rates and significant habitat loss. Scientists disagree that we are in the midst of a 6th mass extinction event because of the things that fossilize well not many of gone extinct during our history.

Question 12

Predict which clade might be more prone to extinction if provided information about their geographical range or life history

Answer 12

Benthic and Pelagic. Benthic are more likely to go extinct.

Question 13

What are some possible reasons for the decline in origination & extinction rates for Phanerozoic marine invertebrates?

Answer 13

Optimization of fitness
Decrease in solar input over time
Decrease in the amount of exposed sedimentary rock

Question 14

Looking at fossils in sedimentary rock can tell us when an organism lived on earth – how can we observe extinction and origination over time using both fossils and phylogenetic trees?

Answer 14

We can observe extinction with fossils by dating the fossils. We can observe extinction with phylogenetic trees because we can use the information the fossil tells us to place it in the correct lineage and see its common ancestor and descendants.

Question 15

How do we figure out how habitat destruction is affecting the extinction rate?

Answer 15

1. Multiply the number of species found per hectare in different environments by rates of habitat loss measured from satellite photos.
2. Quantify the rate at that well-known species are moving from threatened to endangered to extinct status in the lists maintained by conservation groups.
3. Estimate the probability that all species currently listed as threatened or endangered will actually go extinct over the next 100 or 200 years.

Question 16

True or false: Is it possible to determine extinction rates for phylogeny if you have no fossil data? (Louca & Pennell 2020)

Answer 16

False