Lecture 18 - Extinctions & Adaptive Radiations Flashcards

1
Q

What does the history of life reveal?

A

the rise and fall of major groups of organisms

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2
Q

What are the 3 factors that major changes can be attributed to?

A
  1. plate tectonics/continental drift
  2. mass extinctions
  3. adaptive radiations
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3
Q

What was the formation of countries originally called?

A

Pangea

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4
Q

How many times has Pangea formed?

A

come together and shifted apart 3 times

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5
Q

How many mass extinction events occurred?

A

5

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6
Q

How many of earth’s species became extinct during these mass extinctions?

A

More than 50%

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7
Q

What was the Permian extinction?

A
  • loss of 95% of marine species
  • largest extinction ever
  • caused by volcanoes
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8
Q

What was the Cretaceous extinction?

A
  • loss of mammals
  • probably caused by meteor (65 mya)
  • loss of dinosaurs
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9
Q

What is evidence of a meteorite?

A

The Chicxulub crater off the coast of Mexico

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10
Q

Why could we be in the midst of the 6th mass extinction?

A
  • more species than ever

- extinction rates are extremely high

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11
Q

What are 3 taxonomic issues why current species estimates are bad?

A
  1. lumpers vs. splitters
  2. different species definitions
  3. hard to distinguish hybrids from distinct species
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12
Q

What are 5 types of reasons that explain why current species estimates are bad?

A
  1. taxonomic issues
  2. geographic biases
  3. taxonomic biases
  4. taxonomists are going extinct
  5. difficulty of documenting extinction
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13
Q

What are 3 reasons why past species estimates are bad?

A
  1. fossilization is rare
  2. fossils are nearly impossible to ID to species
  3. fossil record is biased
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14
Q

What is the fossil record bias toward?

A
  • large, widespread organisms
  • higher taxa
  • North America/Europe
  • economic importance
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15
Q

When can adaptive radiations occur? (3)

A
  1. when organisms colonize a new habitat
  2. when groups go extinct
  3. when key innovations evolve
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16
Q

What is adaptive radiations?

A

diversification of group of organisms into forms filling different ecological niches