Ch. 22 Warm-Up1. Compare and contrast natural selection

vs. artificial selection.2. What are the key ideas of natural

selection?3. Define and give an example for the

following:Homologous structureVestigial structureAnalogous structure

Descent with Modification:

A Darwinian View of Life

Part B: Evidence for Evolution

Recap main ideas of natural selection:1. Evolution is change in species over time.2. There is overproduction of offspring, which

leads to competition for resources.3. Heritable variations exist within a population.4. These variations can result in differential

reproductive success.5. Over generations, this can result in changes in

the genetic composition of the population.

Remember:Individuals do NOT evolve! Populations

evolve.

Evidence for Evolution:1. Direct Observations2. Fossil Record3. Homology4. Biogeography

Evidence for Evolution1. Direct Observations

2. Fossil Record

3. Homology 4. Biogeography

Evidence for Evolution:1. Direct ObservationsExamples:Insect populations become resistant to pesticides (DDT)Antibiotic-resistant bacteria (MRSA)Peppered moth (pollution in city vs. country)

Evidence for Evolution:2. Fossil RecordFossils = remains or traces of organisms

from pastFound in sedimentary rockPaleontology: study of fossilsShow evolutionary changes that occur over

time and origin of major new groups of organisms

Prokaryotes (oldest fossils) eukaryotes (fish – amphibians – reptiles – birds – mammals)

Transitional forms = links to modern species

Evidence for Evolution:3. HomologyHomology: characteristics in related species can have

underlying similarity even though functions may differExamples:

Homologous structures: similar anatomy from common ancestors (eg. forelimbs of human/cat/whale/bat)

Embryonic homologies: similar early development (eg. vertebrate embryos with tail & pharyngeal pouches)

Vestigial organs: structures w/little or no use (eg. flightless bird wings)

Molecular homologies: similar DNA and amino acid sequences

Molecular HomologiesCompare DNA and

amino acid sequences

Convergent EvolutionDistantly related species can resemble one

anotherSimilar problem, similar solutions!Analogous structures: similar structures,

function in similar environmentsEg. Torpedo shape of shark, penguin, &

dolphin

Evidence for Evolution:4. BiogeographyBiogeography = geographic distribution

of a speciesSpecies in nearby geographic areas

resemble each otherContinental drift and Pangaea explains

similarities on different continentsEndemic species: found at a certain

geographic location and nowhere elseEg. Marine iguanas in the Galapagos