History of Life on Earth

1. History of Life on Earth Chapter 12

2. The Age of the Earth • 4.5 billion years old • Radiometric dating • Radioactive isotopes break down over time • Half-life – time it takes for half of amount to decay • Using this can estimate age of earth • Non-living chemicals reacted and produced organic molecules • Combination of chemicals and energy from lightning/heat/Sun’s UV created organic molecules • 2 Theories about how

3. Primordial Soup • Oceans filled with organic molecules • Sparks simulate lightning • Amino acids, fatty acids. And other hydrocarbons formed • 1 problem: no ozone to protect from UV, certain compounds couldn’t have existed

4. Bubble Model • Gases from undersea volcanoes trapped in bubbles that protect them from UV and concentrate them • Reactions happen faster • Bubbles rise, burst, release compounds • Energy from UV and lightning creates more reactions • Complex organic molecules fall into ocean and start again

5. Precursor of 1st Cells • Molecules of life can arise from simple chemistry • RNA can be made in lab • RNA believed to be 1st self-copying information storing molecule • Makes proteins and changes from generation to generation; acts as an enzyme

6. Microspheres • Amino acid chains form droplets in water • Coacervate • Droplet made of different kinds of molecules like amino acids and sugars • These are steps toward cellular organization • Microspheres last longer and longer and bring other molecules in

7. Origin of Heredity • DNA came after RNA • RNA catalyzed early proteins • Many believe RNA was brought into microsphere and could pass traits on • But how DNA, RNA, and hereditary mechanisms first developed is still not known

8. 12.2 The Evolution of Cellular Life:Prokaryotes • Fossil preserved or mineralized remains or imprints of an organism that lived long ago • Oldest (2.5 billion years old) photosynthetic prokaryotes - cyanobacteria • Created oxygen but took millions of years to build up to current amount

9. Eubacteria Peptidoglycan in cell walls Many cause disease and decay Archaebacteria No peptidoglycan Unique lipids in cell membrane Believed to resemble ancient archaebacteria Two Groups of Bacteria Split Very Early

10. Evolution of Eukaryotes • 1.5 bya first eukaryotes showed up • Larger; internal membranes; DNA in nucleus • Mitochondria in almost all • Chloroplasts in plants and protists

11. Endosymbiosis • Theory states bacteria entered large cells as parasites or undigested prey • Begin to live inside host and performed cellular respiration or photosynthesis • Mitochondria – descendents of symbiotic, aerobic eubacteria • Chloroplasts – descendents of symbiotic, photosynthetic eubacteria

12. Support for Endosymbiosis • Size and Structure • Mitochondria like eubacteria • Chloroplasts like cyanobacteria • Genetic Material • Circular DNA similar to bacteria is different than hosts DNA • Ribosomes • Similar in size to those of bacteria • Reproduction • Simple fission independent of host

13. Multicellularity • All living things are broken into 6 kingdoms • Eubacteria, Archaebacteria, Protista, Fungi, Plants, Animals • Eubacteria and Archaebacteria oldest; single celled prokaryotes • Protista – first eukaryotic kingdom, multicellular and unicellular • All other eukaryotes, fungi, plants, and animals, came later and all came from protists

14. Unicellular is very successful • Almost every cell you can see is multicellular

16. Origins of Modern Organisms • Cambrian Explosion • Most animal phyla originated during late Precambrian and early Cambrian periods • Great evolutionary expansion • Many unusual marine organisms appear that have no living relatives

17. Burgess Shale • 1909 geological formation in Canada found • Ordovician Period – 505 mya – 438 mya • Trilobites – extinct 250 mya

18. Burgess Shale

19. Mass Extinctions • Large number of species become extinct • 5 Major extinctions • 440 mya • 360 mya • 245 mya – 96% of all species • 210 mya • 65 mya – 2/3 of all land species • Today? Human activity might be causing another • ½ of rainforests destroyed • Keep up our current rate • 22% to 47% of plants gone • 2,000 of the 9,000 birds

21. 12.3 Life Invaded Land • Ozone Layer • Life evolved protected in oceans from dangerous UV rays from Sun • No life on land during Cambrian period • 2.5 bya photosynthesis puts O2 into air which reacts and forms Ozone, O3 • Blocks UV • Eventually enough to make it safe to live on land

22. Plants and Fungi on Land • 1st organisms on land were probably a combination of plants and fungi; 430 mya • Plants can make nutrients by photosynthesis • Fungi can absorb minerals from rock • Together called mycorrhizae, these exist today • Mutualism – 2 species live together and both benefit

23. Theory of Evolution Chapter 13

24. 13.1 The Theory of Evolution by Natural Selection • Before Darwin most people believed each species was a divine creation existing as it was when it was created • But why were there fossils of unknown organisms?

25. Jean Baptiste Lamarck 1809 • Features of organisms change during life and are passed on to offspring • Giraffe stretches neck to reach leaves, offspring have longer necks • WRONG!!

26. And now for Darwin • Charles Darwin was from a wealthy family • Studied medicine but became a minister (though he never became ordained) • In 1831 Darwin went on a voyage on the HMS Beagle as a naturalist • Galapagos Islands – plants and animals resembled those of the coast of South America

27. Darwin believed the organisms arrived from the coast and changed once they were there • Called this “descent with modification” which would become known as evolution • Most famous were the finches and the tortoises • He studied the data he collected for many years

28. Thomas Malthus essay 1798 Human population was increasing faster than its food source Unchecked populations will grow geometrically Humans are checked by disease, war, & famine Charles Lyell book Principles of Geology Surface of Earth changed over time Things That Affected Darwin

29. Populations are all of the individuals of a species that live in a specific geographical area and can interbreed • Darwin believed Malthus’s idea of unchecked population growth applied to all species • “Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits”

30. Evolution By Natural Selection • Natural Selection – Number of individuals with favorable characteristics that are inherited will increase • Adaptations are inherited traits that become common because it produces a selective advantage

31. Publication of Darwin’s Work • 1831 – Beagle voyage • 1844 – very low public opinion of evolution • 1859 – Another scientist, Alfred Russel Wallace, writes Darwin asking for help to publish his work that describes natural selection!! • Darwin publishes his work and people aren’t happy to hear they are “related to apes”

32. Major Points of Theory • Inherited variation exists within the genes of every population or species • In environments, some individuals are better suited and have more offspring • Beneficial traits spread • Evidence that living species evolved from extinct organisms

33. UPDATE • Now know genes are responsible for inherited traits • Natural selection causes the frequency of certain alleles in a population to increase or decrease over time

34. Species Formation • Reproductive Isolation • 2 populations of the same species do not breed with each other due to geographic separation, difference in mating periods, or other barriers • Eventually they may not be able to breed with each other • Kaibab squirrel and Abert squirrel

35. Tempo of Evolution • Gradualism • Slow/gradual process of changing that occurs continuously • Punctuated Equilibrium • Large changes that occur quickly

36. 13.2 Evidence of Evolution • Fossils • Many intermediate life forms have been found in fossils • Not complete • Certain environments are better for forming fossils • Animals that live in areas that are not good for fossils are missing • Studied by paleontologists

37. Anatomy and development • Comparisons can show similarities • Vestigial structures • Structures that have no use or have a less important function than they do in other related organisms • Whale’s hind limbs • Humans appendix

38. Vestigial Structures

39. Homologous Structures • Share a common ancestry • Similar structure in different organisms • Development of Embryos • Believe you can see evolutionary history • At some point all vertebrates have a tail, buds that become limbs, and pharyngeal pouches

40. Embryology

41. Biological Molecules • Proteins • Smaller differences between closely related and larger between more distantly related • DNA sequences • Similar to relationships predicted by biologists

42. 13.3 Examples of Evolution • Factors in Natural Selection • All populations have genetic variation • The environment presents challenges to successful reproduction • Individuals tend to produce more offspring than the environment can support • Better suited individuals leave more offspring

43. Example of Natural Selection • Tuberculosis (TB) kills more adults than any other infectious disease • Antibiotics introduced in 50s now don’t work because bacteria are resistant • Mutation in some bacteria made it resistant so it survived and passed on genes and becomes more common in population

44. Evolution in Darwin’s Finches • Darwin collected 31 specimens from 3 islands • 9 distinct species all similar except for bills • Large bills fed on seeds • Small bills ate insects

45. Formation of New Species • Divergence – accumulation of differences between groups • Speciation – process by which a new species forms • Subspecies – populations of the same species that differ genetically because of adaptations to different living conditions • First step of speciation

46. Subspecies

47. Maintaining New Species • When subspecies become different enough a reproductive barrier may form • Geographic isolation • Different reproduction times • Physical differences • Offspring not fertile