1. Ch. 15 Darwin’s Theory of Evolution You can acquire new pants, but you can’t change your GENES!

2. Ch. 15 Outline 15-1: The Puzzle of Life’s Diversity –The Voyage of the Beagle –Darwin’s Observations –The Journey Home

3. Ch. 15 Outline 15-2: Ideas that Shaped Darwin’s Thinking –An Ancient, Changing Earth –Lamarck’s Evolution Hypotheses –Population Growth 15-3: Darwin Presents His Case –Publication of On the Origin of Species –Inherited Variation and Artificial Selection –Evolution by Natural Selection –Evidence of Evolution –Summary of Darwin’s Theory –Strengths and Weaknesses of Evolutionary Theory

4. The Puzzle of Life’s Diversity The variety of living things is called biological diversity Evolution: The process by which species change over time Scientific Theory: Well-supported testable explanation. It explains a phenomena.

5. Voyage of the Beagle Darwin’s Hypothesis, supported by a large body of evidence has become the theory of evolution. Charles Darwin –From England –Joined the crew of the H.M.S. Beagle as the ship’s naturalist –5 year trip around the world –Darwin collected specimens at each stop

6. Voyage of the Beagle

7. Argentina and Australia have similar grassland ecosystems. Grassland ecosystems were inhabited by very different animals. Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. –This hypothesis is now called the theory of evolution.

8. Darwin’s Observation Patterns of diversity –Many plants and animals seemed well suited to their environment –Organisms survived and reproduced in many different ways –Not all organisms lived everywhere

9. Darwin’s Observation Living Organisms and Fossils Darwin collected fossils –Fossil: Preserved Remains of ancient organisms Some fossils didn’t resemble any living organisms

10. Darwin’s Observation Some fossils didn’t resemble any living organisms Why had so many species disappeared? How were they related to living species?

11. Darwin’s Observations The Galapagos Islands –Off the west coast of South America –The Location that most influenced Darwin –Each Island had a different climate and different organisms –Noticed the birds had different shaped beaks on each island and tortoises had different shaped shells

12. Darwin’s Finches

13. The Journey Home After returning back to England, Darwin wondered if the birds he collected all belonged to the same species at some time Darwin’s wrens, warblers, and blackbirds were ALL really finches!

14. The Journey Home Darwin’s Question Were the animals on different islands he visited once been members of the same species?

15. An Ancient, Changing Earth James Hutton and Charles Lyell –Developed the theory that the earth is very old. This idea was contrary to what people thought at the time. Hutton and Geological Change: –Hutton was a geologist. He proposed that layers of rock form very slowly and others are pushed up from the sea floor to form mountains. (This takes a long time)

16. Lyell’s Principles of Geology Lyell believed that the same processes that changed the Earth in the past still operate in the present. Darwin was influenced by Hutton and Lyell’s work. He reasoned, if the Earth can change over time (earthquakes, volcanoes) maybe life can change too!

17. Lamarck’s Evolution Hypotheses Before Darwin’s work, Jean- Baptiste Lamarck observed that life changes and the species descend from other species.

18. Lamarck’s Evolution Hypotheses Lamarck had two ideas: 1.Organisms can alter their bodies by “use and disuse” Use: Use a structure and it will change Disuse: Structures not used will disappear 2.Acquired characteristics can be inherited. If you increase your muscle mass your children will inherit your big muscles

19. Lamarck’s Evolution Hypotheses Although Lamarck’s ideas were incorrect, he was one of the first ones to realize that organisms are adapted to their environments and propose a theory of evolution.

20. Use and Disuse

21. Population Growth Another influence of Darwin was Thomas Malthus. This scientist published a book in which he stated that babies were being born faster than people were dying. –Sooner or later food and living space will run out.

22. Population Growth Thomas Malthus’ Reasoning if the human population continued to grow unchecked, sooner or later their would be insufficient living space and food for everyone

23. Population Growth Darwin thought this applied to plants and other animals even more because humans usually only have one offspring at a time. –So why wasn’t the Earth completely covered in maple trees (for example)? Why were some surviving and others not?

24. Darwin Presents His Case After Darwin returned to England in 1836, he continued to study his specimens. He discovered that the birds from the Galapagos were all finches, not wrens, warblers or blackbirds like he thought (these finches were found nowhere else in the world).

25. Darwin Presents His Case The same was true for the tortoises –All the species resembled ones on the South America mainland, but they were a different species.

26. Darwin Presents his Case Over 20 years later, Darwin published all his findings in a book called, On the Origin of Species. He didn’t publish it earlier because it went against the common beliefs about organisms.

27. Darwin Presents his Case Not only did Darwin propose the theory of evolution, he also proposed a mechanism by which it happens: –Natural Selection

28. Evolution by Natural Selection Darwin realized members of each species competed for resources (struggle for existence). He noted that organisms better suited to their environment (ex. Run faster, hide from predators) survived to reproduce and pass on their genes.

29. Evolution by Natural Selection Natural Selection –Genetic variation is found in wild species as well as in domesticated plants and animals

30. Evolution by Natural Selection Artificial Selection –In artificial selection, nature provided the variation, and humans selected those variations that they found useful.

31. Evolution by Natural Selection Struggle for Existence –Members of each species compete regularly to obtain food, living space, and other necessities of life.

32. Evolution by Natural Selection Fitness: The ability of an animal to survive and reproduce Adaptation: an inherited characteristic that increases an organism’s chance of survival

33. Evolution by Natural Selection Successful adaptations, Darwin concluded, enable organisms to survive and reproduce. –Types of adaptations Anatomical (Structural) Physiological processes Behavior

34. Evolution by Natural Selection –Types of adaptations Anatomical –Porcupine’s quills Physiological processes –Photosynthesis in plants Behavior –Animals living and hunting in small groups

35. Evolution by Natural Selection Survival of the fittest: individuals that are better suited for their environment survive and reproduce most successfully. (Natural Selection) How is artificial selection compared to (or like) natural selection? How is it different?

36. Evolution by Natural Selection How is artificial selection compared to (or like) natural selection? How is it different? –Like: Only certain individuals of a population produce new individuals –Different: Natural Selection— Traits being selected contribute to an organism’s fitness to the environment Takes place without human control or direction

37. Evolution by Natural Selection Over time, natural selection results in changes in the inherited characteristics of a population. These changes increases a species’ fitness in its environment.

38. Evolution by Natural Selection Darwin proposed that over long periods of time: natural selection produces organisms that have different structures. These species establish different niches, or occupy different habitats Species today look different than their ancestors

39. Evolution by Natural Selection Descent with Modification: Each living species has descended, with changes from other species over time. –Implies that all living organisms are related to each other –All species – living and dead were derived from common ancestors

42. Evidence of Evolution Fossil Record Geographic Distribution of Living Species Homologous Body Structures Embryology

43. Evidence of Evolution Fossil Record Darwin saw fossils as a record of the history of life on earth Earth is very old Species lived then died out over course of time Transitional fossils document various intermediate stages in the evolution of modern species from organisms that are now extinct

44. Evidence of Evolution Geographic Distribution of Living Species –All of Darwin little brown birds that he collected from the Galapagos were finches. –They all were slightly different –Darwin decided that they all could have descended with modification from a common ancestor, but changed over time, adapting to their environment

45. Evidence of Evolution Geographic Distribution of Living Species –Different species lived in South America or Australia even though the environments were similar. –These species descended from different ancestors. –They were exposed to similar pressures of natural selection, so different animals ended up evolving certain features in common.

46. Evidence of Evolution Homologous Body Structures –Even though arms, wings, legs and flippers vary greatly in form and function, they are all constructed from the same basic bones –All limb bones develop from the same clump of cells in embryos –Structures which have different forms but mature forms but develop from the same embryonic tissue are called homologous structures

47. Evidence of Evolution Homologous Body Structures –Bat wings are more similar to the front wings of humans, whales and other mammals

48. Evidence of Evolution Homologous Body Structures –Organs that are reduced in size and traces of homologous organs in other species are called vestigial organs –In humans, the appendix is a vestigial organ

49. Evidence of Evolution Embryology –Embryos of many animals with backbones are very similar –Look especially similar during early stages of development – Same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues of all and organs of all vertebrates.

50. Homologous Structures TurtleAlligatorBirdMammal Ancient lobe-finned fish