Darwin’s Theory of Evolution

1. Darwin’s Theory of Evolution Ch. 15 - 16

2. Evolutionary Theory • Collection of scientific facts, observations, and hypotheses • Evolution – change over time • Theory – well-supported testable explanation of phenomena that have occurred • I AM TEACHING YOU ABOUT A THEORY, JUST LIKE THE BIG BANG THEORY, OR HAVING A THEORY AS TO WHY SOME OF YOU LIKE PIZZA.

3. Darwin • 1831 – Darwin joined the Beagle and set sail around the world • He was interested in nature and organisms • He collected evidence, samples, notes, observations, etc. • He put this evidence together to come up with his theory of evolution.

4. Darwin and the Galapagos Islands • Darwin traveled to the islands • He noticed that each island had its own climate – some dry, some rainy, some humid, etc. • The plants and animals on each island were different • Each island had its own “version” of a tortoise, but they were different on each island… why?

5. Darwin’s Observations • Variation – he noticed that all species had variations of them • Tortoises – different shells • Finches – different beaks

6. Darwin’s Conclusion • Natural selection – “survival of the fittest” • All organisms struggle to survive – compete for food, mates,, space, etc. • Any adaptation that increases the chance of survival will stick around • Speed, camouflage, protection, etc.

7. Natural Selection • Example – mole rats • Some have big claws for digging, some have sharp claws for climbing, and some have no claws • All the mole rats live together with a predator • The predator has good sight and smell, can climb, but can’t dig • Which mole rats are more likely to survive?

8. Darwin’s Finches • The Galapagos islands also have varieties of finches • Each subspecies of finch has a different beak • Each subspecies of finch has a different diet

9. Natural Selection • Those organisms with favorable traits will survive and pass on their characteristics to their offspring • Another example: • 3 types of spiders • Big – easily seen by predators • Small – can’t find food • Medium - survive • after many generations which size spider is likely to be around?

10. Natural Selection • Survival of the biggest? • NO! • Survival of the fastest? • NO! • Survival of the lightest? • NO! • Survival of the fittest? • YES! • What does that mean? • Best adapted for their situation

11. Current Evidence for Evolution • 4 pieces of evidence currently support evolution • Fossils • Geographic distribution • Homologous body structures • Similarities in embryology

12. Fossil Evidence • Fossil – remains of ancient life • Fossils are found in layers • Older layers contain organisms that are not found in younger layers • This indicates they were present but did not survive

13. Geographic Distribution Evidence • There are organisms living on different continents with similar traits • Example – p. 383 • Each organism has very similar characteristics that helps it adapt to its environment, which are also similar

14. Homologous Body Structure Evidence • Structures that have different mature forms, but the same embryonic tissues • This supports that all 4-limbed organisms evolved from a common ancestor

15. Embryology Evidence • Supports homologous structures • Many organisms with backbones look very similar during early embryonic development

16. Summary of Darwin’s Theory • All species have variation • These variations are either favorable or not • The favorable variations help organisms survive – those traits will stick around • Unfavorable variations do not help organisms survive – those traits will eventually disappear • Organisms with similar traits evolved from a common ancestor