Unit 3 Evidence of Evolution and Biodiversity Part 3 Evolution and Natural Selection

Who was Charles Darwin Studied medicine Received a BA in Theology Hated the sight of blood Received a BA in Theology Had 10 children Darwin was a Naturalist on the HMS Beagle

While traveling Darwin noticed slight differences within species and developed his Theory of Evolution

In The Galapagos Islands, Darwin collected species of finches (13) Each had a specialized diet and beak structure These finches all closely resembled a South American finch ancestral species On the trip Darwin saw things he could only attribute to a process called: “Natural Selection”

Darwin called this process by which populations change in response to their environment: Natural Selection

Darwin’s Finches

Natural Selection is based on these inferences: There is variation within populations Some variations are favorable Not all young produced in each generation can survive Individuals that survive and reproduce are those with favorable variations Favorable traits will increase in future generations. Survival of the Fittest

Types of Evolution Adaptive Radiation Divergent Evolution Co-Evolution Convergent Evolution

Adaptive Radiation Evolution of many diverse species from one common ancestor Ex: famous Galapagos finches discovered by Darwin

Divergent Evolution (spread apart) -Isolated populations evolve independently Ex: polar & grizzly bears changed independently due to different habitats

Coevolution (together) -Species that interact closely adapt to one another Ex: Flowers & Pollinators (Birds, Bees and Butterflies too)

Convergent Evolution (come together) -Unrelated species become more alike because they live in similar environments Ex: shark & dolphin

Speed of Evolution? 2 thoughts

Gradualism the slow appearance of new characters in interbreeding subspecies that, over time, lead to the evolution of a new species from ancestral forms. this is not supported in much of fossil data, where new species seem to appear suddenly. 

Punctuated Equilibrium evolution occurs primarily through short bursts of intense speciation, followed by lengthy periods of stasis or equilibrium. We see this in fossil data.