Natural Selection and Evolution

Hi

Charles Darwin

• Was a naturalist and on Dec. 27, 1831 sailed on the HMS Beagle

• Nov. 1859 Darwin Published “The Origin of Species By Natural Selection” where he discussed his theory of Natural Selection and Evolution

Natural Selection: “Survival of the Fittest”

• Natural Selection means that in any population of individuals with better variations for a particular environment will survive, reproduce, and pass these variations on to the next generation

Adaptations

• Are the changes made by a species caused by genetic variation

Mimicry

• Is a natural adaptation that provides protection for an organism by copying the appearance of another species

Camouflage

• Is a natural adaptation that enables an organism to blend in with its surroundings

Evidence for Evolution

• Date of the Earth: 4.6 Billion Years old

• The fossil record supports evolution by comparing fossils from the past with modern day organisms

Biological Molecules Contain Evidence

• Comparing amino acid and DNA sequences- closer related have more similarities

Phylogenetic Tree

Anatomy and Development Suggests a Common Ancestry

• Vestigial structures are structures that are reduced in size and function (example: appendix and wings on flightless birds)

Homologous Structures

• Are structures that show a common ancestry (limbs of humans, wings of bats, and fins of whales)

Analogous Structures

• Are structures that are similar in function but different in structure (example: wings of birds and insects)

Similarities among vertebrate embryos…

• Suggest evolution from a common ancestry

Evolution of Species

• Speciation is the evolution of new species and occurs only with the production of fertile offspring.

3 WAYS SPECIATION OCCURS

Geographic Isolation

• Barrier separates a population into groups

Reproductive Isolation

• Occurs when formerly interbreeding organisms no longer produce fertile offspring!

Polyploid

• Occurs when any species has any difference of the normal set of chromosomes. This occurs because of mistakes during meiosis.

Rates At Which Speciation Occurs

Gradualism

• Is the idea that new species originate through the slow buildup of new adaptations over long time period

Punctuated Equilibrium

• States that speciation occurs in quick bursts then long time periods in between

2 Types of Evolution

Divergent Evolution

• The pattern of evolution in which species once all related to a common ancestor become more and more distinct.

• Example: Darwin’s Finches

Convergent Evolution

• NON- related organisms evolve similar traits; occurs when two organisms occupy similar environments and face similar selection pressures

• EXAMPLE: Fish and whale