Ch. 5 Evolution

1. Ch. 5 Evolution APES Mrs. Sealy

2. I. Origins of Life • How do we know? • Chemical analysis: chemists have conducted lab experiments to show how simple organic compounds could have been created. • Radioactive dating: radiocarbon, radiometric dating with radioactive rocks and fossils

3. CH4 H2O Water vapor CO2 N2 Electrode H2 NH3 Electrical sparks simulating lighting provide energy to synthesize organic compounds Condenser Cold water Cooled water containing organic compounds H2O Sample for chemical analysis Fig. 5.3, p. 104

4. Life evolved in two phases over the course of 4.7-4.8 billion years Chemical evolution of organic molecules and polymers Biological evolution from single celled prokaryotic bacteria to multi-cellular eukaryotic organisms

5. Chemical Evolution • Formation of the Earth’s Crust: 4.6 to 4.7 billion years ago a cloud of cosmic dust condensed into planet earth which soon turned molten due to radioactive decay and meteorite impacts. As cooling took place a thin crust developed. • Formation of the earth’s seas: volcanic eruptions and comet impacts brought water vapor that rained down on earth to create the sea

6. Chemical Evolution (cont.) • Small organic molecules form in the seas: from eroded minerals from rocks • 4.4 billion years ago the first atmosphere was formed. The main components were believed to be: CO2, N2,H2O , CH4, NH3, H2S, HCL, no oxygen • This mixture is often to as: The primordial stew

7. Chemical Evolution (cont.) • Large organic molecules form in the seas: energy from lightening, heat from volcanoes, and UV light and the chemicals in the atmosphere combined to form the first large organic molecules such as amino acids and carbs. • Another theory is that these large molecules formed in hydrothermal vents. • First protocells form in the seas: these new compounds washed into the seas and sat for millions of years to form the first DNA and protocells

8. Chemical Evolution (1 billion years) Formation of the earth’s early crust and atmosphere Small organic molecules form in the seas Large organic molecules (biopolymers) form in the seas First protocells form in the seas Biological Evolution (3.7 billion years) Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Variety of multicellular organisms form, first in the seas and later on land Fig. 5.2, p. 103

9. Biological Evolution • 3.5 to 3.8 billion years ago, well below the surface of the sea away from harmful UV radiation the first prokaryotic cells formed: PROKARYOTIC • 2.3 to 2.5 billion years ago the first cyanobacteria appear and they: photosynthesize • 2.0-2.1 billion years ago oxygen: formed from cyanobacteria • 1.2 billion years ago we see the first eukaryotic cells arrive, which could reproduce sexually and produce a wide variety of organisms • 400-500 million years ago we see: the first land plants and animals • How do we know what organisms were around: • Fossil record • Radiometric dating of rocks near the fossils

10. Modern humans (Homo sapiens) appear about 2 seconds before midnight Age of mammals Recorded human history begins 1/4 second before midnight Age of reptiles Insects and amphibians invade the land Origin of life (3.6–3.8 billion years ago) Plants invade the land Fossils become abundant Fossils present but rare Evolution and expansion of life Fig. 5.4, p. 105

11. Evolution • Heritable changes in a population’s genetic make-up through successive generations • An overwhelming majority of biologists believe that this is the best explanation for the changes that have occurred over the last 3.7 billion years and also for why life on earth today is so diverse. • The theory of evolution is based on the idea that all species descended from other species http://www.hippocampus.org/Biology

12. 2nd Generation 1st generation GG, Gg = green beetle gg = brown beetle Evolution= shift in gene frequency in a population

13. Macroevolution • long term, large scale evolutionary changes among a group or species. One species leads to the appearance of many other species.

14. Genetic persistence: • The inheritance of DNA molecules from the origin of the first cells through all subsequent lines of descent which is the basis of the unity of life

15. Genetic divergence • Long term changes in lineage’s of species, which are the basis of the diversity of life

16. Genetic losses • The steady background extinction or relatively abrupt catastrophic loss of lineage

17. Microevolution: the small genetic changes that a population experiences • How does microevolution work?

18. It is the development of genetic variability in a population • A population’s gene pool is the sum total of all genes possessed by the individuals of the population’s species

19. Microevolution is a change in the species gene pool over time

20. Members of a population have different molecular forms of the same gene called alleles. Sexual reproduction leads to a shuffling of alleles. As a result each individual has a different combination of alleles. This is called genetic variability

21. Microevolution works through a combination of four processes: every • Mutation, natural selection, gene flow, genetic drift

22. Mutation: • The source for all new alleles (genes) is mutations, which are random changes in the structure of DNA molecules in a cell. • Adaptation: any genetically controlled trait that helps an organism survive and reproduce under a given set of environmental conditions • Every so often a mutation is beneficial and the result is a new genetic trait that will ensure the survival of offspring better • Mutations are rare

23. Natural Selection • Differential reproduction: because of random shuffling or recombination of genes, certain individuals may by chance have one or more beneficial adaptations that allow them to survive under various environmental conditions. As a result they are more likely to reproduce than individuals that do not have such adaptations.

24. Natural selection does not create favorable genes; instead it favors some individuals over others by acting on genes already in the gene pool. • Natural selection occurs when the combined effects of adaptation and differential reproduction result in a particular beneficial gene becoming more common in succeeding generations

25. Three types of Natural Selection: • Directional: it pays to be different: changing environmental conditions cause gene frequencies to shift so that individuals with traits at one end of the normal range become more common than midrange species

26. Natural selection Directional Natural Selection Average New average Previous average Snail coloration best adapted to conditions Number of individuals Number of individuals Average shifts Coloration of snails Coloration of snails Proportion of light-colored snails in population increases Fig. 5.6a, p. 110

27. Stabilizing: it pays to be average: in a stable environment species that have abnormal genes have no advantage and tend to be eliminated.

28. Natural selection Stabilizing Natural Selection Dark snails eliminated Light snails eliminated Snails with extreme coloration are eliminated Number of individuals Number of individuals Coloration of snails Coloration of snails Average remains the same, but the number of individuals with intermediate coloration increases Fig. 5.6b, p. 110

29. Diversifying: it doesn’t pay to be normal: when environmental conditions favor individuals at both extremes of the genetic spectrum and sharply reduce the number of mid-range individuals.

30. Natural selection Diversifying Natural Selection Intermediate-colored snails are selected against Snails with light and dark colors dominate Light coloration is favored Dark coloration is favored Number of individuals Number of individuals Coloration of snails Coloration of snails Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases Fig. 5.6c, p. 110

31. Gene Flow: Movement of genes between populations

32. Genetic drift: • involves change in a genetic composition of a population by chance and is important in small populations

33. Co evolution • When populations of two different species interact over a long time, changes in the gene pool of one species can lead to changes in the gene pool of the other species. For example:

34. An Example of evolution by natural selection: The peppered moths of England During the industrial revolution. http://www.echalk.co.uk/Science/Biology/PepperedMoth/Peppered_MothWEB.swf

35. Coevolution Coevolution can occur between animals that have a symbiotic relationship as well those who have a predator prey relationship Coevolution gone awry

36. Ecological Niches and Adaptation Ecological niche: the species way of life or the functional role of the species in an ecosystem. For example: • a. types of resources used • b. range of tolerance • c. how it interacts with components of the ecosystem • d. its role in flow of energy and matter cycling

37. Fundamental vs realized niche • Fundamental niche vs. realize niche: Your fundamental niche is all the possible conditions that you can live under. Your realized niche is how you are actually living. For example: you may be capable being a star, but competition keeps you from getting the job

38. Niche separation Generalistspecies with a broad niche Number of individuals Generalistspecies with a narrow niche Niche breadth Region of niche overlap Resource use Fig. 5.7, p. 111

39. Generalist species vs. Specialist species Generalist: have very broad niches and eat a variety of foods and can live in a variety of places under differing conditions. For example cockroach Specialist: narrow niche, may only be able to live in one type of habitat or eat only one type of food. For example: panda bear • Is it better to be a generalist or a specialist?

40. Speciation • Two species arise from one species in response to changes in environmental conditions. • The mechanism for speciation occurs in two phases • Geographic isolation: occurs when two populations of a species becomes physically separated for long periods • Reproductive isolation: occurs as mutation and natural selection occur independently in two separated populations of the same species. Eventually, the changes are so great that two groups will no longer interbreed.

41. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Northern population Arctic Fox Spreads northward and southward and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Early fox population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern population Gray Fox Fig. 5.8, p. 113

42. Convergent evolution: • Two separate species will evolve separately to create animals with similar characteristics. Species that have similar niches tend to evolve similar sets of traits in response similar environmental conditions. For example:

43. Divergent evolution: speciation creates separate species

44. Extinction • When environmental changes occur species either evolve or cease to exist and their genetic material is permanently lost. • Extinction patterns have been caused by large-scale movements of the continents and gradual climate changes like those from meteors and volcanoes. • All species inevitably disappear • Background extinction is the low rate that species constantly disappear. It is the normal level. Approx. 3 species per year • Mass extinction: an abrupt rise in extinction rates above the background rate. It is catastrophic, global and often results in 25% to 70% loss of species • There are have been five previous mass extinctions and we are currently in the six mass extinction, which is being caused by humans.

45. Speciation minus extinction equals biodiversity Although extinction is a natural process, humans have sped up the process and we have lost a lot of genetic material This mass extinction is different from previous extinctions in the following ways: 1. First time it has ever been caused by one species 2. This is the fastest it has every happened 3. Adaptive Radiation will be slow after because we are destroying habitats

46. Era Period Millions of years ago Bar width represents relative number of living species Species and families experiencing mass extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Extinction Today Quaternary Tertiary Cenozoic Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Jurassic Extinction Mesozoic 180 Triassic: 35% of animal families, including many reptiles and marine mollusks. Triassic Extinction 250 Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Permian Carboniferous Extinction Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. 345 Devonian Paleozoic Silurian Ordovician Extinction Ordovician: 50% of animal families, including many trilobites 500 Fig. 5.10, p. 115 Cambrian

47. Adaptive Radiation • Adaptive radiation: an extinction of one species is an opportunity for another species and after a mass extinction there is a period in which numerous new species can evolve • Speciation and extinction affects biodiversity:

48. Cenozoic Mesozoic Marsupials (kangaroos, etc.) Rabbits Rodents Primates Bats Insectivores Carnivores Whales Even-toed hoofed mammals Odd-toed hoofed mammals Elephants Monotremes (platypus, etc.) Fig. 5.11, p. 116

49. How does Macroevolution occur? A. Macroevolution is concerned with how evolution takes place above the level of species and over long periods of time and shows how small changes can lead to the eventual creation of many different species, genera and families. B. Gradualist model: theory that says macro evolutionary change occurs over many millions of years C. Punctuated Equilibrium: opposing theory that says there are long periods of relatively punctuated with brief periods of very rapid changes. • D. In reality it is probably a combination of both

50. Common Misconceptions about Evolution • “Survival of the fittest” is often misinterpreted as “survival of the strongest”. In biological terms fitness is a measure of reproductive success and the ones with the most descendants are the fittest. Natural selection is not "tooth and claw” competition. • “Humans evolved from apes”, this is not true. Apes and humans have a common ancestor from which both are descended. • Nature has a grand plan in which species become progressively more perfect, natural selection is random and there is no goal of perfection.