Review vocabulary for last two lectures
Stochastic extinction
Mutational meltdown
Extinction debt
Mass extinction
Apes (clade)
Orrorin
Australopithecus
Homo erectus
Neanderthal
Denisovans

Note: Know all of the phylogenies that we have covered, and be prepared to construct a phylogeny for species from across the tree of life. Here is a summary of the phylogenies presented.

Some review questions for the last two lectures

1) What kinds of environmental changes, both biotic and abiotic, are most likely to cause extinction?

2) Explain how eliminating habitat patches that are not currently occupied can lead to species extinction.

3) What three properties characterize mass extinctions?

4) When did the 5 mass extinctions of the Phanerozoic occur?

The following questions concern material that will be covered on Tuesday.

5) Draw a phylogeny relating the following organisms: Homo sapiens, Australopithicus, Chimpanzees, Homo habilis, Homo erectus.

6) What type(s) of hominids could you have encountered: 1.8 million years ago? 100 thousand years ago?

Answers

1) Introduced species can drive local species extinct through either predation or competition. They have been responsible for many extinctions of island species. Habitat loss can lead to extinction even if no individuals are directly killed in the initial reduction of habitat.

2) Many populations inhabit environments with many small habitat patches. The local group in any particular patch will go extinct eventually, but before this, some individuals may colonize an empty patch elsewhere. The species can persist so long as empty patches are colonized at a high enough rate to balance local extinction. If empty patches are eliminated, this will reduce the rate of colonization without changing the rate of local extinction. This can create a situation in which the species is doomed to extinction even though there are, at the moment, some inhabited patches.

3) 1) They stand out, statistically, from background extinctions. 2) They are global and effect many different environments. 3) They kill off species in many, distantly related, groups.

4) End of:
Ordovician (~443 mya)
Devonian (~359 mya)
Permian (~252 mya)
Triassic (~201 mya)
Cretaceous (~66 mya)

5) Prune from this tree.

6) 1.8 million years ago: Australopithicines, Homo habilis, Homo erectus.
100 thousand years ago: Neanderthals, Denisovans, Homo sapiens, possibly Homo erectus, Homo floresiensis Jul 8, 2021