The Theory of The Theory of EvolutionEvolution

What is the Theory of What is the Theory of Evolution?Evolution?

TheoryTheory: well-supported testable : well-supported testable explanation of phenomena that have explanation of phenomena that have occurred in the natural worldoccurred in the natural world

EvolutionEvolution: change over time; : change over time; process by which modern organisms process by which modern organisms have descended from ancient have descended from ancient organisms organisms

Who is Darwin?Who is Darwin?

Charles Darwin is Charles Darwin is considered the father of considered the father of modern evolutionary modern evolutionary theorytheory

Darwin’s 5 year voyage Darwin’s 5 year voyage as the naturalist on the as the naturalist on the HMS BeagleHMS Beagle helped him helped him develop the theory of develop the theory of how evolution occurshow evolution occurs

Section 15-1

Figure 15–1 Darwin’s Voyage

DarwinDarwin PresentsPresents HisHis CaseCase

Through his observations on the Through his observations on the Galapagos Islands, he concluded that Galapagos Islands, he concluded that naturalnatural variationvariation or differences occur or differences occur among individuals of a populationamong individuals of a population

Scientists later found out that these Scientists later found out that these variations among individuals were variations among individuals were caused by mutationscaused by mutations

Natural SelectionNatural Selection(Darwin’s main point)(Darwin’s main point)

Organisms with more favorable traits Organisms with more favorable traits or variations tend to survive and or variations tend to survive and reproduce; organisms with less reproduce; organisms with less favorable traits are less likely to favorable traits are less likely to survivesurvive

2 Main Points of Natural 2 Main Points of Natural SelectionSelection

1.1. Struggle for existenceStruggle for existence: competition : competition for territory, food, water, and matesfor territory, food, water, and mates

2.2. Survival of the fittestSurvival of the fittest: some : some organisms are better suited to organisms are better suited to survive in an environment as a survive in an environment as a result of adaptations (mimicry or result of adaptations (mimicry or camouflage)camouflage)

Evidence for EvolutionEvidence for Evolution

1.1. FossilsFossils: by using : by using fossils, scientists can fossils, scientists can show the sequence of show the sequence of evolution in an evolution in an organismorganism

2.2. GeographyGeography: organisms : organisms that are similar but live that are similar but live in different parts of the in different parts of the worldworld

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Evidence for EvolutionEvidence for Evolution

3.3. Homologous Homologous StructuresStructures: : structures that structures that are similar and are similar and seen in different seen in different speciesspecies

• Ex: forelimbs of Ex: forelimbs of humans/batshumans/bats

Evidence for EvolutionEvidence for Evolution

4.4. EmbryologyEmbryology: by studying unborn : by studying unborn organisms, we can see structures in organisms, we can see structures in common during development in common during development in different organismsdifferent organisms

EmbryologyEmbryology

5.5. Genetic RelationshipsGenetic Relationships: DNA : DNA comparisons help establish comparisons help establish evolutionary relationships between evolutionary relationships between different speciesdifferent species