Evolutionary Thought Through Centuries: Roots, Theories, and Discoveries

1. Chapter 13 Principles of Evolution

2. 13.1 How Did Evolutionary Thought Evolve? • A timeline of the roots of evolutionary thought Buffon (species created, then evolve) Hutton (gradual geologic change) Lamarck (mechanism of species change) Cuvier (catastrophism) Smith (sequence of fossils) Lyell (very old Earth) Darwin (evolution, natural selection) Wallace (evolution, natural selection) 1800 1700 1750 1850 1900 Fig. 13-1

3. 13.1 How Did Evolutionary Thought Evolve? • Early biological thought did not include the concept of evolution. • One of the earliest scientific beliefs was called “______________,” which suggested that all organisms were created by God simultaneously, and that each organism remained fixed and unchanging from the moment of its creation. • Both Plato and Aristotle (427–347 B.C.) proposed these ideas to students of the day. • Aristotle categorized all organisms into a linear hierarchy that he called the “______________________.” • These ideas remained unchallenged for 2,000 years.

4. Humans Mammals Birds Reptiles and amphibians Whales and porpoises Fish Squids and octopuses Lobsters, crabs, etc. Snails, clams, etc. Insects, spiders, etc. Jellyfishes, sponges, etc. Higher plants Lower plants Inanimate matter Fig. 13-2

5. 13.1 How Did Evolutionary Thought Evolve? • Exploration of new lands revealed a staggering diversity of life. • Discoveries of the wide diversity of life forms and how similar to one another many were suggested that organisms were capable of change, and that some could have been ancestral to others. • Early naturalists noticed that the species found in one place were different than those found in other places. • Others saw that in a given location, species closely resembled one another, yet differed in some characteristics. • These observations were inconsistent with the idea that species were fixed and unchanging.

6. 13.1 How Did Evolutionary Thought Evolve? • A few eighteenth century scientists speculated that species had changed over time. • The French naturalist George Louis LeClere (1707–1788) suggested that the original creation provided a small number of founding species, and that some modern species had been produced by time; that is, they evolved through natural processes.

7. 13.1 How Did Evolutionary Thought Evolve? • Fossil discoveries showed that life has changed over time • Developments in geology cast doubt on the idea of permanently fixed species that remained unchanged through time. • Fossils—the preserved remains or traces of organisms that had died long ago—and the layers of rock in which they were found suggested that animals lived a long time ago, and they were different than those of today. • Fossils can be bones, wood, shells, tracks, burrows, pollen grains, eggs, and feces.

8. 13.1 How Did Evolutionary Thought Evolve? • Types of fossils eggs in nest fossilized feces(coprolites) bones footprint skin impression Fig. 13-3

9. 13.1 How Did Evolutionary Thought Evolve? • Fossil discoveries showed that life has changed over time. • Scientists discovered that fossil remains showed a remarkable progression. • Fossils from the oldest rock layers were very different from modern organisms. • Fossil resemblance to modern organisms gradually increased in progressively younger rocks. • Conclusion: different types of organisms had lived at different times in the past

10. 13.1 How Did Evolutionary Thought Evolve? • Fossils of extinct organisms (a) Trilobite (b) Seed ferns (c) Allosaurus youngestrocks oldestrocks Fig. 13-4

11. 13.1 How Did Evolutionary Thought Evolve? • Some scientists devised nonevolutionary explanations for fossils. • Despite the growing fossil evidence, many scientists of the eighteenth century still did not accept the idea that species changed and new ones had arisen over time. • Georges Cuvier (1769–1832) advanced the idea of catastrophism. • Catastrophism states that a vast supply of species was created initially, and that successive catastrophes—like the Great Flood described in the Bible—destroyed some species. • He theorized that organisms of the modern world are those that survived the catastrophes.

12. 13.1 How Did Evolutionary Thought Evolve? • Geology provided evidence that Earth is exceedingly old. • The concept of _________________, proposed by geologist Charles Lyell (1797–1875), was proposed to show that geological processes have occurred over a long period of time and gradually changed the landscape, implying that the Earth is very old. • Modern geologists estimate that Earth is about ____ __________ years old. • Lyell showed that this was enough time for evolution to occur, but he was uncertain how evolution took place.

13. 13.1 How Did Evolutionary Thought Evolve? • Some pre-Darwin biologists proposed mechanisms for evolution. • Baptiste Lamark (1744–1829) hypothesized that organisms evolved through the inheritance of acquired characteristics. • This idea states that the bodies of living organisms are modified through the use or disuse of parts, and these modifications are inherited by offspring. • According to this concept, if giraffes tried to improve their lot by stretching upward to feed on leaves that grew high up in trees, their necks became longer as a result.

14. 13.1 How Did Evolutionary Thought Evolve? • Their offspring would inherit these longer necks; eventually, this process would produce modern giraffes with very long necks. • Today, we know that acquired characteristics are not inherited. • The fact that a prospective father pumps iron does not mean that his child will look like a champion body-builder.

15. 13.1 How Did Evolutionary Thought Evolve? • Darwin and Wallace proposed a mechanism of evolution. • By the mid-1800s, many biologists had concluded that present-day species had evolved from earlier ones; but how? • In 1858, Charles Darwin and Alfred Russel Wallace, working separately, provided convincing evidence that evolution was driven by a simple yet powerful process. • Darwin and Wallace observed that among all the diversity of life there were some species that differed in only a few features.

16. 13.1 How Did Evolutionary Thought Evolve? • Darwin’s finches (a)Large ground finch, beak suited tolarge seeds (b) Small ground finch, beak suited tosmall seeds (c) Warbler finch, beak suited to insects (d) Vegetarian tree finch, beak suited to leaves Fig. 13-5

17. 13.1 How Did Evolutionary Thought Evolve? • Both researchers found that some species differed in only a few features. • Both were familiar with the fossil record showing an increase in complexity with time. • Both knew that the Earth was extremely old. • These facts suggested that species change over time. • In separate but similar papers that were presented to the Linnaean Society in London in 1858, Darwin and Wallace each described the same mechanism for evolution. • The next year, Darwin published his monumental book, On the Origin of Species by Means of Natural Selectionwhich outlined how species evolve, and its concepts form the basis for the modern understanding of evolution.

18. 13.2 How Does Natural Selection Work? • Darwin and Wallace proposed that life’s huge variety of excellent designs arose by a process of descent with modification, in which individuals in each generation differ slightly from the members of the preceding generation. • Over long stretches of time, these small differences accumulate to produce major transformations. • Darwin and Wallace’s theory rests on four postulates.

19. 13.2 How Does Natural Selection Work? • Postulate 1: Individual members of a population differ from one another in many respects. • People differ in size, eye color, skin color, and many other physical features; similar variability occur in other organisms. • These variations occur as a result of random mutations in DNA; differences among individuals extends to the molecular level.

20. 13.2 How Does Natural Selection Work? • Postulate 2: At least some of the differences among members of a population are due to characteristics that may be passed from parent to offspring. • Although observations of people, pets, and farm animals seemed to show that offspring generally resemble their parents, Darwin and Wallace did not have scientific evidence to support this postulate. • Mendel’s work on the principles of genetics was not published until far later, but confirmed postulate 2 through experimentation.

21. 13.2 How Does Natural Selection Work? • Postulate 3: In each generation, some individuals in a population survive and reproduce successfully but others do not. • Darwin knew that organisms produce far more offspring than are required to replace the parents. • However, the numbers of individuals in a population tend to remain constant; more individuals are born than survive long enough to reproduce. • It is clear that in a population, some individuals have more offspring than others.

22. 13.2 How Does Natural Selection Work? • Postulate 4: The fate of individuals is not determined entirely by chance or luck; an individual’s likelihood of survival and reproduction depends upon its characteristics; individuals with advantageous traits survive the longest and leave more offspring, a process known as ___________ _____________. • Reproductive success depends upon an individual’s characteristics. • For example, larger male elephant seals in a California population have more offspring than smaller males. • These results show that in the competition to survive and reproduce, winners are determined not by chance but by the traits they possess.

23. 13.2 How Does Natural Selection Work? • Natural selection modifies populations over time. • Observation and experimentation suggest that the four postulates of Darwin and Wallace are sound. • Natural selection acts on individuals within a population; over generations, the population changes as the percentage of individuals inheriting favorable traits increases; an individual cannot evolve, but a population can. • Although it is easier to understand how natural selection would cause changes within a species, under the right circumstances, the same principles might produce entirely new species.

24. 13.3 How Do We Know That Evolution Has Occurred? • Fossils provide evidence of evolutionary change over time. • If it is true that many fossils are the remains of species ancestral to modern species, we ought to find a series of fossils that start with ancient, primitive organisms and culminate with modern species. • Such series has been found for ancestors of modern whales, fossil giraffes, elephants, horses, and mollusks. • These fossil series suggest that new species evolved from, and replaced, previous species.

25. 13.3 How Do We Know That Evolution Has Occurred? • The evolution of the whale 0 Modern whales millions of years ago 40 Basilosaurus 45 Dorudon Rhodocetus Ambulocetus 50 Pakicetus Fig. 13-7

26. 13.3 How Do We Know That Evolution Has Occurred? • ______________ anatomy gives evidence of descent with modification. • Comparing the bodies of organisms of different species can reveal similarities that can be explained only by shared ancestry,and differences that could result only from evolutionary change during descent from a common ancestor. • The study of comparative anatomy has supplied strong evidence that different species are linked by a common evolutionary heritage.

27. 13.3 How Do We Know That Evolution Has Occurred? • Homologous structures provide evidence of common ancestry. • The forelimbs of birds and mammals are variously used for flying, swimming, running, and grasping objects. • Despite this diversity of function, the internal anatomy of all bird and mammal forelimbs is remarkably similar. • This similarity is what would be expected if the forelimbs were derived from a common ancestor; each forelimb has been modified to perform a particular function. • Such internally similar structures are called _______________ structures and have the same evolutionary origin.

28. 13.3 How Do We Know That Evolution Has Occurred? • Homologous structures humerus ulna radius Pterodactyl carpals Dolphin metacarpals Dog phalanges Human Bird Sheep Shrew Bat Seal FLYING SWIMMING RUNNING GRASPING Fig. 13-8

29. 13.3 How Do We Know That Evolution Has Occurred? • Functionless structures are inherited from ancestors. • Evolution by natural selection helps explain ______________ structures that serve no apparent purpose. • Examples: molar teeth in vampire bats (which live on blood and thus don’t chew their food) and pelvic bones in whales and some snakes • These are homologous structures to those found in, and used by, other vertebrates; ancestors of whales had four legs with well-developed pelvic bones. • During whale evolution, losing the hind legs provided a streamlining advantage; therefore, modern whales only have small, useless pelvic bones.

30. 13.3 How Do We Know That Evolution Has Occurred? • Vestigial structures The bones of asalamander’shindlimb functionin support andlocomotion (a) Salamander These vestigial bones aresimilar in structure tothose of the salamanderbut serve no function; allthree animals inheritedthe bones from acommon ancestor (b) Baleen whale (c) Boa constrictor Fig. 13-9

31. 13.3 How Do We Know That Evolution Has Occurred? • Some anatomical similarities result from evolution in similar environments. • There are many anatomical similarities that do not stem from common ancestry. • Such similarities stem from ___________ evolution, in which natural selection causes non-homologous structures that serve similar functions to resemble one another. • Both birds and insects have wings, but this similarity did not arise from evolutionary modification of a structure that both birds and insects inherited from a common ancestor. • Such outwardly similar, but non-homologous, structures are called ______________ structures, and have very different internal anatomy.

32. 13.3 How Do We Know That Evolution Has Occurred? • Analogous structures Fig. 13-10

33. 13.3 How Do We Know That Evolution Has Occurred? • Embryological similarity suggests common ancestry. • All vertebrate embryos look quite similar to one another early in their development. Fig. 13-11

34. 13.3 How Do We Know That Evolution Has Occurred? • In early embryonic development, fish, turtles, chickens, mice, and humans all develop tails and gill slits. • Only fish retain gills as adults, and only fish, turtles, and mice retain tails. • Ancestral vertebrates possessed genes that directed the development of gills and tails; all their descendents still have these genes. • In fish, these genes are active throughout development; in humans, these genes are active only during early development, and the structures are lost as adults.

35. 13.3 How Do We Know That Evolution Has Occurred? • Modern biochemical and genetic analyses reveal relatedness among diverse organisms. • Biochemical similarities among organisms provide perhaps the most striking evidence of their evolutionary relatedness. • The protein _______________ c is present in all plants and animals, and performs the same function in all of them. • The DNA sequence of nucleotides is similar in all these diverse species; this provides evidence that a common ancestor of plants and animals had cytochrome c in its cells.

36. 13.3 How Do We Know That Evolution Has Occurred? • Molecular similarity shows evolutionary relationships. human A T G G G T G A T G T T G A G A A A G G C A A G A A G A T T T T T A T T A T G A A G mouse A T G G G T G A T G T T G A A A A A G G C A A G A A G A T T T T T G T T C A G A A G human T G T T C C C A G T G C C A C A C C G T T G A A A A G G G A G G C A A G C A C A A G mouse T G T G C C C A G T G C C A C A C T G T G G A A A A G G G A G G C A A G C A T A A G human A C T G G G C C A A A T C T C C A T G G T C T C T T T G G G C G G A A G A C A G G T mouse A C T G G A C C A A A T C T C C A C G G T C T G T T C G G G C G G A A G A C A G G C human C A G G C C C C T G G A T A C T C T T A C A C A G C C G C C A A T A A G A A C A A A mouse C A G G C T G C T G G A T T C T C T T A C A C A G A T G C C A A C A A G A A C A A A human G G C A T C A T C T G G G G A G A G G A T A C A C T G A T G G A G T A T T T G G A G mouse G G C A T C A C C T G G G G A G A G G A T A C C C T G A T G G A G T A T T T G G A G human A A T C C C A A G A A G T A C A T C C C T G G A A C A A A A A T G A T C T T T G T C A A T C C C A A A A A G T A C A T C C C T G G A A C A A A A A T G A T C T T C G C T mouse human G G C A T T A A G A A G A A G G A A G A A A G G G C A G A C T T A A T A G C T T A T mouse G G A A T T A A G A A G A A G G G A G A A A G G G C A G A C C T A A T A G C T T A T human C T C A A A A A A G T A C T A A T G A G mouse C T T A A A A A G G T A C T A A T G A G Fig. 13-12

37. 13.3 How Do We Know That Evolution Has Occurred? • Other biochemical similarities also extend to all living cells. • All cells have _______. • All cells use RNA, ribosomes, and the same ________ code. • All cells use the same 20 __________ ________ in proteins. • All cells use ______ as a cellular energy carrier. • The explanation for such widespread sharing of these complex and specific biochemical traits is that they are homologous, arising from a common ancestor.

38. 13.4 What Is The Evidence That Populations Evolve By Natural Selection? • Controlled breeding modifies organisms. • ____________ ____________ is the breeding of domestic plants and animals to produce specific desirable features. • Humans produced radically different dogs in a few thousand years by repeatedly selecting individuals with desirable traits. • Therefore, it is plausible that natural selection by an analogous process acting over hundreds of millions of years produce the spectrum of living organisms.

39. 13.4 What Is The Evidence That Populations Evolve By Natural Selection? • Dogs descended from wolves, and today, the two will readily cross-breed; modern dogs do not resemble wolves. Fig. 13-13

40. 13.4 What Is The Evidence That Populations Evolve By Natural Selection? • Evolution by natural selection occurs today. • Brighter coloration can evolve when fewer predators are present. • In Trinidad, guppies live in streams with larger predators that eat them. • In the shallow upstream waters, the guppies are free of predators and are more brightly colored than the downstream guppies. • Thus, where predators are common, they act as agents of natural selection by eliminating the bright-colored guppies.

41. 13.4 What Is The Evidence That Populations Evolve By Natural Selection? • Natural selection can lead to pesticide resistance. • Insect pests can evolve resistance to pesticides through natural selection. • In Florida, a pesticide called Combat was used to control the number of roaches; roaches that liked it were killed. • Those that survived inherited a rare mutation that caused them to dislike the sugar that was used in the Combat bait. • Soon, all the roaches had this mutation and were immune to Combat.

42. 13.4 What Is The Evidence That Populations Evolve By Natural Selection? • Experiments can demonstrate natural selection. • Anolis sagrei lizards were released in small groups onto 14 small Bahamian islands that previously did not have the lizards. • The original lizards came from an island with tall vegetation and many trees; the island where they were transplanted had few or no trees, and were covered with small shrubs and other low-growing plants.

43. 13.4 What Is the Evidence That Populations Evolve by Natural Selection? • After 14 years, the released lizards were examined and displayed shorter and thinner legs than the original population. • Lizards grew shorter legs to allow for more agility on narrow surfaces; long legs were at a disadvantage on thin-branched bushes. Fig. 13-15

44. 13.4 What Is the Evidence That Populations Evolve by Natural Selection? • Selection acts on random variation to favor the phenotypes that work best in particular environments. • The variations on which natural selection works are produced by chance mutations. • The mutations that produced bright or dark colored Trinidadian guppies, a distaste for Combat poison in cockroaches, and shorter legs in Bahamian lizards were beneficial traits that arose spontaneously in each case.

45. 13.4 What Is the Evidence That Populations Evolve by Natural Selection? • Natural selection favors organisms that are best adapted to a particular environment. • Natural selection does not select the “best” in any absolute sense, but only for what is best in the context of a particular environment. • A trait that is advantageous under one set of conditions may become disadvantageous if conditions change.