LS Chapter 5-3

Evolution of Species

• Which is the closer relative?

The Role of Genes in Evolution

• Mutations – in genes cause variation

• Only traits controlled or inherited by genes can be passed on to offspring.

Evolution in Action

• Drought on the Galapagos affected the population of finches.

• Peppered moths in England

How Do New Species Form?

• When a group of individuals remains separated from the rest of its species long enough to evolve different traits.

• Kaibab squirrel and Abert squirrel

More Allopatric Speciation• Geographical barriers: mountains,

oceans, rivers. A few members of a species manage to cross by a rare chance event.

• This is the mechanism by which Darwin’s finches evolved into separate species in the Galapagos islands. Only very rarely can birds cross the ocean to get to other islands.

• Or, the barrier develops slowly as conditions change: the gradual formation of the Grand Canyon split a population into 2 isolated groups, that have diverged into separate species, the Kaibab and Albert squirrels.

Continental Drift

• Species become isolated when the continent began drifting.

• Ex. Australia – most mammals are marsupials. Very few marsupials in other continents.