Biology - Chapter 14 Evolution: How Change Occurs

1. Biology - Chapter 14Evolution: How Change Occurs Charles Page High School Stephen L. Cotton

2. Section 14-1: Developing a Theory of Evolution • OBJECTIVES: • Discuss the importance of evolutionary theory.

3. Section 14-1: Developing a Theory of Evolution • OBJECTIVES: • Identify the basic assumptions of Lamarck’s theory of evolution.

4. Section 14-1: Developing a Theory of Evolution • OBJECTIVES: • Explain some of the major ideas that helped shape Darwin’s theory of evolution.

5. Section 14-1: Developing a Theory of Evolution • Evolutionary theory is the foundation on which the rest of biological science is built • Theodor Dobzhansky wrote that nothing in biology makes sense, except in the light of evolution

6. Section 14-1: Developing a Theory of Evolution • Observing that evolution has occurred is relatively simple, because we can see changes • Explaininghow and why evolution occurs is more difficult

7. Section 14-1: Developing a Theory of Evolution • Certain parts of Darwin’s original theory have been revised in the years since he proposed it • Evolutionary change is undeniable – it does happen. • it is a collection of carefully reasoned and tried hypothesis

8. Section 14-1: Developing a Theory of Evolution • Consider the fact that we have no doubt that gravity exists, but we do not completely understand how it works • Jean Baptiste de Larmarck (1744-1829) was among the first to recognize change over time

9. Section 14-1: Developing a Theory of Evolution • Lamarck also called this change to the attention of other scientists • He realized that organisms adapted to their environments • Lamarck relied on three assumptions (which we now know are incorrect)

10. Section 14-1: Developing a Theory of Evolution • #1. A desire to change. Lamarck thought that organisms change because they have an inborn urge to better themselves • -birds had an urge to fly, and their constant efforts led to the development of wings

11. Section 14-1: Developing a Theory of Evolution • #2. Use and Disuse. He said that organisms could alter their shape by using their bodies in new ways • -also that if a body part was not used, that body part would decrease

12. Section 14-1: Developing a Theory of Evolution • #3. Passing on Acquired Traits. The belief of Lamarck, and many other scientists at that time, was that acquired characteristics could be inherited • -Figure 14-2, page 292 about cropped ears in dogs

13. Section 14-1: Developing a Theory of Evolution • Even though many of Lamarck’s ideas were incorrect, he did pave the way for Darwin’s theory of evolution • Darwin (1809-1882) came after Lamarck (1744-1829)

14. Section 14-1: Developing a Theory of Evolution • Lamarck’s ideas may seem strange to us now, but was consistent with knowledge of that time • a later understanding of genetics and heredity showed his ideas to be false

15. Section 14-1: Developing a Theory of Evolution • Darwin was greatly influenced by his personal experiences on the Beagle, books he read, and people he talked with • Charles Lyell, a geologist, affected Darwin’s thinking by presenting information about the age of the earth

16. Section 14-1: Developing a Theory of Evolution • The long periods of time it would have taken for millions of species to evolve from a common ancestor- can only be explained if the Earth was very old • Darwin also observed changes in the earth- such as volcanoes

17. Section 14-1: Developing a Theory of Evolution • And if the Earth itself could change over time, so too could life on Earth! • Darwin talked with many plant and animal breeders • they could not cause variation; it happened naturally or not

18. Section 14-1: Developing a Theory of Evolution • Once the variations did occur, they could use it to their advantage- selective breeding • Darwin called this artificial selection- only the best organisms were allowed to produce offspring

19. Section 14-1: Developing a Theory of Evolution • Darwin was convinced that a process similar to artificial selection must be at work in nature • Another important influence on Darwin was the economist Thomas Malthus (1766-1834)

20. Section 14-1: Developing a Theory of Evolution • Malthus observed that babies were being born at a faster rate than people were dying • sooner or later there wouldn’t be enough food or space • to prevent human growth: famine, disease, and war

21. Section 14-1: Developing a Theory of Evolution • In time, these unpleasant observations were called the Malthusian Doctrine • Darwin realized this applied even more to plants and animals than humans, because most other species produce more offspring

22. Section 14-1: Developing a Theory of Evolution • Marine animals, such as the common mussel, produce millions of eggs • if they all survived, the oceans would be overrun with them • but, only a few survive: Why?

23. Section 14-2: Evolution by Natural Selection • OBJECTIVES: • Describe the process of natural selection.

24. Section 14-2: Evolution by Natural Selection • OBJECTIVES: • Provide an example of natural selection in action.

25. Section 14-2: Evolution by Natural Selection • Finally, Darwin recognized a process similar to artificial selection- but this happened in nature • he called it “natural selection” • this was based on many observations he made

26. Section 14-2: Evolution by Natural Selection • Those individuals with characteristics best suited to their environment survive the struggle for existence • “survival of the fittest” • the fact that many do not survive keeps numbers down

27. Section 14-2: Evolution by Natural Selection • An example of natural selection in action is the peppered moth • Fig. 14-8, page 297 • spend time resting on tree bark • some light in color, some dark • which ones seen easier?

28. Section 14-2: Evolution by Natural Selection • When the Industrial Revolution began in England, the soot stained the trees • which was easier to see now? • Birds are the major predators • However, more testing is needed to reach any conclusions

29. Section 14-2: Evolution by Natural Selection • Kettlewell, a British ecologist, did such a test for this hypothesis • showed that in each environment the moths that were better camouflaged had the higher survival rate

30. Section 14-3: Genetics and Evolutionary Theory • OBJECTIVES: • Explain how genes affect natural selection.

31. Section 14-3: Genetics and Evolutionary Theory • OBJECTIVES: • Define evolution in genetic terms.

32. Section 14-3: Genetics and Evolutionary Theory • OBJECTIVES: • Relate genes to fitness and adaptation.

33. Section 14-3 Genetics and Evolutionary Theory • Darwin worked under a serious handicap- • he had no idea how the inheritable traits were passed from one generation to the next • Mendel made his ideas in Darwin’s lifetime- went unknown

34. Section 14-3 Genetics and Evolutionary Theory • Genetics and evolutionary theory are inseparable! • Today we define fitness, adaptation, species, and the process of evolutionary change in genetic terms

35. Section 14-3 Genetics and Evolutionary Theory • Genes, the carriers of inheritable characteristics, are also the source of random variation and genetic interaction • mutations cause variation • variation occurs as chromosomes are shuffled

36. Section 14-3 Genetics and Evolutionary Theory • Variation does not occur because an animal needs to or wants to evolve • no way for an organism to cause a particular change • no way for them to prevent the variations that do occur

37. Section 14-3 Genetics and Evolutionary Theory • Entire organisms, NOT individual genes, either survive and reproduce or do not • Natural selection can operate only on the phenotypic variation among individuals that is already present

38. Section 14-3 Genetics and Evolutionary Theory • Today, evolutionary biologists study populations- a collection of individuals of the same species in a given area, whose members can breed with one another • since they can interbreed, they share a common group of genes, called a gene pool

39. Section 14-3 Genetics and Evolutionary Theory • The number of times an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur is called the relative frequency of the allele • sexual reprod. alone doesn’t change the relative frequency

40. Section 14-3 Genetics and Evolutionary Theory • Cards? Shuffling produces an enormous variety of different hands, but does not change the relative number of aces, kings, fours, etc. • Evolution is any change in the relative frequencies of alleles in the gene pool of a population

41. Section 14-3 Genetics and Evolutionary Theory • Each time an organism reproduces, it passes copies of its genes to its offspring • Thus, evolutionary fitness is the success an organism has in passing these genes on • adaptation: increases fitness

42. Section 14-3 Genetics and Evolutionary Theory • In the past, biologists defined a species as a group of organisms that looked alike • but there are exceptions

43. Section 14-3 Genetics and Evolutionary Theory • Now, a species is a group of similar-looking (though not identical) organisms that breed with one another and produce fertile offspring in the natural environment

44. Section 14-3 Genetics and Evolutionary Theory • Thus, they share a common gene pool • Horse + donkey = mule, which is usually sterile; males

45. Section 14-4 The Development of New Species • OBJECTIVES: • Define niche.

46. Section 14-4 The Development of New Species • OBJECTIVES: • Relate the availability of niches to speciation.

47. Section 14-4 The Development of New Species • OBJECTIVES: • Describe the process of speciation.

48. Section 14-4 The Development of New Species • We are now nearly ready to explain HOW new species evolve from old ones- a process biologists call speciation • A niche is the combination of an organism’s “profession” and the place in which it lives

49. Section 14-4 The Development of New Species • If two species try to occupy the same niche, they will compete for food and space • one species will not survive • No two species can occupy the same niche in the same location for a long period of time

50. Section 14-4 The Development of New Species • If the two species occupy different niches, however, they will not compete with each other as much • With less competition, there is less chance that one species will cause the other to become extinct