The Theory of Evolution

What is the Theory of Evolution? Theory: well-supported testable explanation of phenomena that have occurred in the natural world Theory: well-supported testable explanation of phenomena that have occurred in the natural world Evolution: change over time; process by which modern organisms have descended from ancient organisms Evolution: change over time; process by which modern organisms have descended from ancient organisms

Who is Darwin? Charles Darwin is considered the father of modern evolutionary theory Charles Darwin is considered the father of modern evolutionary theory Darwin’s 5 year voyage as the naturalist on the HMS Beagle helped him develop the theory of how evolution occurs Darwin’s 5 year voyage as the naturalist on the HMS Beagle helped him develop the theory of how evolution occurs

Section 15-1 Figure 15–1 Darwin’s Voyage

Darwin Presents His Case Through his observations on the Galapagos Islands, he concluded that natural variation or differences occur among individuals of a population Through his observations on the Galapagos Islands, he concluded that natural variation or differences occur among individuals of a population Scientists later found out that these variations among individuals were caused by mutations Scientists later found out that these variations among individuals were caused by mutations

Natural Selection (Darwin’s main point) Organisms with more favorable traits or variations tend to survive and reproduce; organisms with less favorable traits are less likely to survive Organisms with more favorable traits or variations tend to survive and reproduce; organisms with less favorable traits are less likely to survive

2 Main Points of Natural Selection 1. Struggle for existence: competition for territory, food, water, and mates 2. Survival of the fittest: some organisms are better suited to survive in an environment as a result of adaptations (mimicry or camouflage)

Evidence for Evolution 1. Fossils: by using fossils, scientists can show the sequence of evolution in an organism 2. Geography: organisms that are similar but live in different parts of the world Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara

Evidence for Evolution 3. Homologous Structures: structures that are similar and seen in different species Ex: forelimbs of humans/batsEx: forelimbs of humans/bats

Evidence for Evolution 4. Embryology: by studying unborn organisms, we can see structures in common during development in different organisms

Embryology

5. Genetic Relationships: DNA comparisons help establish evolutionary relationships between different species