Chapter 15 – Darwin’s Theory of Evolution

1. Chapter 15 – Darwin’s Theory of Evolution

2. Charles Darwin • Made observations and collected evidence that led him to propose a theory on evolution • Theory – a well supported testable explanation • Evolution – genetic changes in a population over time

3. Darwin’s 5 year voyage on the Beagle…

4. Darwin’s Observations • An enormous number of species live on Earth • Species: interbreeding groups of organisms that can produce healthy, fertile offspring. • Galapagos Islands – The tortoises on the Galapagos island were similar in form except for variations in their shells and necks.

5. Pinta Tower Marchena Pinta IslandIntermediate neck and shell James Fernandina Santa Cruz Isabela Santa Fe Hood Island Long neck and open shell around legs Floreana Hood Isabela Island Short neck and dome-shaped shell On the Galapagos Islands… Intermediate vegetation Sparse Vegetation Abundant Vegetation

7. Section 15-3 Darwin Presents His Case

8. Darwin’s Variation • Variation – members of each species vary from one another • Ex: some plants in a species bear larger fruit; some cows give more milk • Artificial selection - Pick and choose traits that we like/want • Example: • Humans select what we want in a mate – looks, personality, character…..

9. Adaptation – • Adaptations help populations fit in their niche and increase fitness • Niche: place and role of each organism in the environment • where organisms live, what they eat, their predators, and biotic conditions

10. Adaptation • Mimicry enables an organism to copy the appearance of another species.

11. MIMICRY

12. Viceroy – mimics the monarch to avoid being eaten Monarch – tastes bad to birds

13. Milk Snake Coral Snake

14. Camouflageis a structural adaptation that enables an organism to blend in with its surroundings.

15. CAMOUFLAGE

17. Darwin’s Conclusions: • Struggle for Existence: organisms compete for limited resources

19. Darwin’s Conclusions: 2. Natural Selection: individuals that are genetically suited to survive and reproduce in that environment ***The ones that survive have the DNA for that environment and transfer that DNA to their offspring for better survival of their population.

21. Figure 22.9 A few of the color variations in a population of Asian lady beetles

22. Darwin’s Conclusions: 3. Descent with modification – All species evolved from ancestors with changes, but look similar to ancestors • implies species have a common descent

23. Evidence of Evolution

24. Fossil Record • Found in different layers, which represents life forms at different times • Show when organisms became extinct and how organisms have changed over time • Certain fossils are only found in certain layers

25. Look at V and III. More modern forms of life have evolved from earlier life forms. Complexity

26. Biogeography: Geographic Distribution • Populations of the same species adapt to different geographic environments and change over time (descent with modification)

27. Geographic Distribution of Living Species Beaver Beaver Muskrat Beaver andMuskrat Coypu Capybara Coypu andCapybara NORTH AMERICA Muskrat SOUTH AMERICA Capybara Coypu

28. Molecular Homologies • Similar base pair sequences in DNA can link similar organisms in evolutionary descent • Therefore, we can also determine amino acid sequences, too

29. More than anything else, an organism DNA is the most accurate at determining how close species are. Which species is the unknown most closely related to?

31. Anatomical Homologies • Different mature body parts develop from the same embryonic tissues • ***Four limbs of all vertebrates suggests they descended from common ancestors

36. The fact that all these animals have the same bones suggests that at one time, they arose from the same common ancestor, and then, over time, adapted to their different environments.

37. Homologous Body Structures Turtle Alligator Bird Mammal Ancient lobe-finned fish **The color coordination of the bones indicate that they came from the same embryonic tissue; therefore, they are homologous.

38. Vestigial Organs • Structures that are useless or reduced in size of one organism but are homologous and useful to another organism • Examples: • Tailbone in humans • Femur bone in whales and snakes

39. Vestigial Organs Femurs are used to walk—it is the largest leg bone in humans. Whales have femurs, yet they cannot walk. This is an example of a vestigial structure.

40. Embryological Homologies • Vertebrates go through similar early stages of development • Embryonic cells develop in similar patterns to produce common tissues and organs of all vertebrates • Similar embryology also suggests similar genes

42. Which organism is most closely related to the salamander? Fish Salamander Turtle Chick Rabbit Human

43. Reproductive Homologies • Sexual vs. Asexual Reproduction • How do organisms do these? • What types of organisms? • Reproductive strategies • R vs. K strategists • Seed bearers • Amniotic Egg

45. Analogous Structures • Have same function, but NOT similar structure (develop from different embryonic tissues) • Example: • Bird wing vs. Insect wing—Both are used for flying. Birds’ wings have bones, insects’ wings do not; therefore, they have developed from different tissues

46. Analogous Structures Top: Bird’s wing Bottom: Insect’s wing Both used for flying, but they come from different embryonic tissues.