Principles of Evolution Chapter 18 section 1

Transcription

1 Principles of Evolution Chapter 18 section 1

2 Announcements: Quiz 5 (last quiz!!!) is on Wednesday Topics: biotechnology (chapter 17.1) and principles of evolution (chapter 18.1)

3 Learning Goals for Today: Discuss the theory of evolution List some of the evidence that Darwin used to formulate the theory of evolution List some of the data used to support the theory of evolution Predict how a population may change over time

4 Evolution: what is it? Book definition of evolution: the change over time in the characteristics of a population A population consists of all the individuals of one species in one location Micro- : An increase in the frequency of the gene for dark wings in beetles from one generation to the next Macro- : The extinction of all dinosaurs

5 Pre-Darwin and Wallace: All organisms were created simultaneously (by a creator) They did not change

6 Greek philosophers: Plato ( B.C.) each object on Earth is just a temporary reflection of its divinely inspired ideal form Aristotle ( B.C.) increasing complexity of organisms indicates their perfection in the Ladder of Nature 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

7 What got people thinking that organisms could change 18 th century: world exploration revealed more species than anticipated Naturalists including Georges-Louis Leclerc noticed that each geographical location had its own group of species, even when environments were similar Some species in the same location were similar but different in some aspects Having different sets of species in the same location was inconsistent with the idea of fixed and unchanging forms

8 How could this change (evolution) happen? Jean Baptiste Lamarck ( ) proposed inheritance of acquired characteristics Due to use or disuse of different parts use it or lose it These modifications are passed to offspring Theory unsupported for genetic inheritance Is supported for cultural/behavioral characteristics

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10 Dude, step off!!

11 According to Lamarck

12 Modern Perspectives Mid 1800s Explanations for the concept of evolution Both did expeditions in the tropics Charles Darwin (1831 to 1836, S. America, Australia, and Africa) Alfred Wallace (Brazil, 1848 to 1852; Malay Archipelago, 1854 to 1862)

13 Published 28 years after the expedition in The Beagle began

14 Voyage of the H.M.S. Beagle and Darwin

15 Voyages of Wallace and Darwin

16 Australia America Darwin (and Wallace) noticed: Similar organisms on different continents Found in similar environments Appear to have similar roles

17 Darwin s Finches, Residents of the Galápagos Islands Beak size corresponds with food preference Idea: changes in food supply leads to selection for or against specific beak shapes For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey. Darwin noticed that different, yet related, animal species often occupied different habitats within a local area.

18 Darwin notices fossil organisms that resembled modern organisms Armadillo Glyptodon

19 Darwin noticed that species were changing Darwin wanted to explain the biological diversity he observed in a scientific way As he traveled, Darwin noticed three distinctive patterns of biological diversity: (1) Species vary globally, (2) species vary locally, and (3) species vary over time.

20 Idea of natural selection Exploration of new lands revealed a staggering diversity of life Discovered vast numbers of new species Early explorers often took naturalists along to catalogue the plant and animal life they found Darwin: naturalist on the Beagle Wallace was a naturalist too but he worked independently Idea of survival of the fittest explains changes in populations

21 Natural selection Successful reproduction of individuals with favorable traits that survive environmental change because of those traits Leads to evolutionary change Fit = has more babies that survive

22 How Does Natural Selection Work? Darwin (and Wallace) proposed that life s diverse forms arose through the process of descent with modification (evolution) Individuals in each generation differ slightly from the members of the preceding generation Over long time periods, small differences accumulate to produce major transformations

23 LaMarckian and Darwinian views

24 Four postulates of evolution Variation in phenotype Postulate 1: Individual members of a population differ from one another Fig. 14-6

25 Phenotypes must be heritable Postulate 2: phenotypic differences can be passed on from parents to offspring must be heritable

26 More offspring are produced than are Postulate 3: In each generation, some individuals in a population survive and reproduce successfully but others do not able to survive

27 Survival of the fittest because of natural selection Postulate 4: Individuals with advantageous traits (phenotypes) survive and leave the most offspring, process known as natural selection

28 What is natural selection? Unequal survival and reproduction of organisms with different phenotypes, caused by environmental forces

29 Natural selection modifies populations over time Natural selection acts on individuals within a population; however, it is the population that changes over time Over generations, the population changes, as the percentage of individuals inheriting favorable traits increases

30 Adaptation A heritable trait that helps the survival and reproduction of an organism in its present environment The webbed feet of platypuses are an adaptation for swimming The snow leopards thick fur is an adaptation for living in the cold The cheetahs fast speed is an adaptation for catching prey

31 How does natural selection happen: step by step? A population with genetic/phenotypic variation 1. A change occurs in the environment 2. Well-adapted individuals leave more offspring than do poorly-adapted individuals 3. Genetic frequencies within the population change

32 How Natural Selection Works

33 How Natural Selection Does Not Work Adaptation has nothing to do with effort Natural selection does not give organisms what they need An advantage must be heritable in order for it to be passed on to offspring

34 Worksheet on natural selection

35 Support for the Process of Evolution Fossils provide evidence of evolutionary change over time Comparative anatomy gives evidence of descent with modification Embryological similarity suggests common ancestry Modern biochemical and genetic analyses reveal relatedness among diverse organisms

36 Millions of years ago Fossils Provide Evidence for Whale Evolution from Land Mammals 0 Modern whales 40 Basilosaurus Dorudon Rhodocetus Ambulocetus Pakicetus Fig. 14-7

37 The Evidence for Natural Selection Fossil record Transitional fossils Archaeopteryx 145 mya Caudipteryx 125 mya Reptiles birds

38 The Evidence for Natural Selection Fossil record Transitional fossils Tiktaalik 375 mya Lobed-finned fish Water land animals salamander

39 The Evidence for Natural Selection Fossil record Transitional fossils Modern toothed whales Land back to sea Rodhocetus swam with an up-and-down motion. 47 mya Ambulocetus probably walked on land. 49 mya Pakicetus attocki lived on land. 55 mya

40 Divergent evolution Sometimes, evolution gives rise to groups of organisms that become tremendously different from each other When two species evolve in diverse directions from a common point, it is called divergent evolution

41 Comparative anatomy (homologous structures) is a result of divergent evolution and provides support for common ancestry humerus ulna Pterodactyl Dolphin Dog radius carpals metacarpals phalanges Human Bird Bat Seal Sheep Shrew FLYING SWIMMING RUNNING GRASPING Bones in the appendages share the same overall construction

42 Vestigial Structures: evidence of loss of once important structures (divergent evolution), evolutionary baggage The bones of a salamander s hindlimb function in support and locomotion (a) Salamander (b) Baleen whale These vestigial bones are similar in structure to those of the salamander but serve no function; all three animals inherited the bones from a common ancestor (c) Boa constrictor Shrunken to the point that they no longer constitute a survival-reducing burden.

43 The Evidence for Natural Selection Comparative anatomy Vestigial structures relics of the past

44 The Evidence for Natural Selection Pseudogenes Dead genes Products of divergent evolution Example: Ascorbic acid (vitamin C) synthesis

45 Convergent Evolution gives rise to analogous structures Similar traits ( analogous structures ) evolve separately, but in similar environments Similar selection pressures Example: Placental mammals vs marsupials Niche Burrower Nocturnal Anteater Climber Glider Insectivore Stalking Predator Chasing Predator Placental Mammals Mole Grasshopper mouse Flying squirrel Wolf Lesser anteater Ring-tailed lemur Ocelot Australian Marsupials Numbat Spotted cuscus Thylacine Marsupial mole Marsupial mouse Flying phalanger Tasmanian quoll

46 Convergent Evolution North America Asia & Australia Cactus Euphorbia

47 Analogous Structures: similar function but unrelated, product of convergent evolution Fig

48 All vertebrate embryos look similar homologous traits in embryos provide evidence of a common ancestor Lemur pig human At one point all possess gill slits and a tail Which is the lemur, pig, human?

49 Homologous biochemical and cellular features - Evidence for common ancestry Shared features of all cells DNA as a genetic blueprint RNA, ribosomes, and approximately the same genetic code for translation same set of 20 amino acids to build proteins ATP to transfer energy

50 Cytochrome c gene is highly conserved human mouse human mouse human mouse human mouse human mouse human mouse human mouse human mouse between species

51 Natural Selection - conclusions Natural selection is not random Traits are produced by chance mutations The traits that persist in a population are those that work best in the organism s environment