Chapter 15

1. Chapter 15 Fossils • Evidence of organisms that lived in past times. • Because there are many methods of formation, there are many types of fossils. See pg 382 & 418

2. Fossil types • Trace – marking left by animal; such as a footprint. • Casts – minerals fill a space left by a decayed organism. • Petrified – minerals penetrate and replace parts of an organism. • Imprint – thin object imprint preserved in hardened sediment. • Molds – organism buried in sediment decays, leaving empty space. • Amber – entire organism trapped in hardened tree sap. • Frozen – entire organism trapped and quickly frozen in ice.

3. Paleontology: the scientific study of ancient life using fossil evidence. Geologic Time Scale Formation of earth, estimated to be 4.6 billion years ago. EraPeriod# of years agoevents Precambrian 3.5 billion unicellular prok/euk Paleozoic cambrian 540 million invertebrates Ordovician 510 million vertebrates Silurian 439 million jawed fish/land plants Devonian 408 million amphibians Carboniferous 362 million seed plants/ reptile Permian 290 million conifers dominant Mesozoic Triassic 245 million dinosaurs/mammal Jurassic 208 million flowering plants/birds Cretaceous 146 million flowering plants dom Cenozoic Tertiary 66 million placental mammals Quaternary 1.6 million humans@200,000yrs

4. determining age of rocks • Relative dating • Geologic law: if rock layers have not been disturbed… • The layers at the surface are younger than the deeper layers. • Fossils in the top layers are younger than those fossils in deeper layers. • Relative dating cannot be used to determine actual age.

5. Radiometric dating • Utilizes radioactive isotopes to determine specific age. • Radioactive isotopes decay over time giving off radiation. • As radioactive decay continues, these isotopes form new elements. • Radioactive isotopes have decay rates, this rate can be used as a type of clock called half-life. • Rock/fossil age can be estimated by comparing the amount of radioactive isotope present to the amount of new element present in the sample item.

6. Examples of Radaiometeric dating • Radioactive half-life=1 million years If a rock contains equal amounts of the radioactive isotope and the new element to which it decays, the rock must be 1 million years old. • Fact: For very old rocks/fossils potassium 40 is used; it decays to argon 40. Half-life=1.3 billion years. • For rocks/fossils less than 50,000 years old carbon 14 is used; it decays to nitrogen 14. Half-life=5,730 years.

7. Evolution • Simply stated evolution is the change in living things, or populations, over time. • A change in the gene pool of a population.

8. Theories of evolution • In 1809 Jean Baptiste de Lamark was one of the first to present a theory of evolution. It was based on two principles : • The use and disuse of organs • Inheritance of acquired traits • His ideas are flawed and later his hypothesis is rejected

9. Others Who Influenced Evolutionary Thought Earth is ancient and changing • James Hutton – 1785, proposed that Earth is shaped by geological forces. • Charles Lyell – 1833, wrote principles of Geology and stressed that scientists must explain past events in terms of processes that they can actually observe, like geological forces. • Thomas Malthus – 1798, an economist who predicted that the human population will grow faster than the space and food supplies needed to sustain it. James Hutton Charles Lyell Thomas Malthus

10. Theories of Evolution • Charles Darwin (1809-1882) he published his book Origin of Species, on how species change over time…after 22 years of reading, study, specimen collection, observation and experimentation. • In it he presented his revolutionary new theory of evolution which remains the cornerstone of modern evolutionary thought today.

11. Darwin's travels on the HMS Beagle took him to the Galapagos Islands where he noted similar animals to those on the South American continent, but they were not exactly alike. One example were the finches he found on the different islands.

13. Darwin’s Principles • Variation exists within species, and some of this variation is heritable. • All organisms compete for limited resources. • Organisms produce more offspring than can survive, and many that do survive do not reproduce. • The environment selects organisms with beneficial traits Natural Selection ( survival of the fittest)

14. Evidence of Evolution 1. Fossils: • The fossil record gives us lots of evidence that species have changed over time Examples of extinct plants and animals comes in many forms such as imprints ,molds ,casts, petrified fossils and even insects trapped in amber .

15. 2. Geographic Distribution of Living Species. • The existence of similar but unrelated species. • Example: Darwin found entirely different species of animals on South America and Australia, yet when he looked at similar environments on those continents, he sometimes saw different animals that had similar anatomies and behaviors. This led to his theory of descent with modification. P 383

16. 3. Anatomical Evidence • Homologous structures are body parts found in different organisms with the same basic structure. Vary in form, or function not structure. These suggest a common ancestry • Vestigial structures organs that are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. Suggest evolution from organisms that used them. Ex: shortened legs, toes, appendixes in humans.

17. 4. Embryological Evidence • Embryonic cells develop in the same order and patterns to produce the tissues. • Similarities in development of embryos suggest a common evolutionary relationship

18. Analogous Structures • Wings of birds and wings of insects have the same function but not the same structure and are said to be analogous . They have no evolutionary relationship.

19. Ch. 16 Origins of Variation • Only genetic variations are passed from generation to generation • Genetic recombination during meiosis is one source of variation (gene shuffling can produce 8.4 million gene combinations) • Mutation is another important source • Artificial selection – breeding organisms with specific traits in order to produce offspring with identical traits, used to improve crops, livestock and pets. • Darwin hypothesized that if it happens artificially then it should be happening naturally.

20. Mechanisms of Evolution • Natural selection – occurs when organisms having particular positive variations survive, reproduce, and pass on the variations to the next generation. • These adaptations can be structural, anatomical, physiological processes and behavior. • Structural adaptation example: mimicry – enables one species to resemble another. • Physiological adaptations (can develop rapidly) Example: antibiotic resistance – bacteria • Members of a species that live in the same area are members of a population. • Evolution occurs when there is a change in the genetic makeup of a population.

22. Mechanisms of Evolution • A gene pool is all the alleles of all genes in all the individuals in a population. • The gene pool in a population will stay in equilibrium unless something happens to make it change. (Hardy-Weinberg Principle) • Relative frequency – of an allele is the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur. • For evolution to take place something must upset the genetic equilibrium of a population • These processes include : natural selection, migration, genetic drift, isolation, and mutation.

23. Before industrial revolution The classic example of Natural selection in action was the change in population densities of light colored moths during the industrial revolution in England. After industrial revolution

24. Darwin’s Hypotheses • Descent with Modification – Darwin proposed that over long periods of time natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. • Each generation is modified due to which individuals reproduce. • Darwin also suggests that all living organisms are related to one another called common descent. Looking back over time, one will find: • Tigers, panthers, and cheetahs share common ancestors • Felines, horses, dogs, and bats share common ancestors • Mammals, birds, reptiles, and fish share common ancestors • All species—living and extinct—share common ancestors.

25. Natural Selection on Polygenic trait Three types of natural selection occur • Directional selectionis gradual environmental pressure to change. • Stabilizing selection eliminates the extremes and reduces variation • Disruptive selection selects against the average and favors the extremes

26. Directional selection

27. Stabilizing selection

28. disruptive selection

29. Mechanism for Change:1. Migration • Migration is the movement of organisms into (immigration) and out of (emigration) a population. • This either increases or decreases the genes in a gene pool

30. 2. Genetic Drift • Genetic drift is the change in gene frequency of a very small population due to chance. • Individuals that carry a particular allele may leave more descendants than others, over time a series of chance occurrences of this type can cause an allele to become common in a population • Founder Affect – when the population that moved into a new environment have particular alleles that then start to present themselves due to the environment (chance not natural selection) The mutations seen in this Amish child occur at the rate of 1 in 14 as opposed to 1 in 1000 in the general population due to chance introduction in a small isolated population

31. 3. Isolation • Geographic isolation occurs when a physical barrier separates populations. Ex: Mountain, River,etc • Genetic isolation results when two populations are unable to interbreed. Ex: they reproduce at different times, have differences in courtship rituals or other reproductive stategies.

32. 4. Mutation • Many mutations are harmful (lethal) but when a mutation gives an organism an advantage it is retained (phenotype changed) in the gene pool and changes the frequency of alleles in the population.

33. Speciation • Speciation is the evolution of an organism into a new species. • A niche is the place and “profession” of a species (its job in its habitat) • It is difficult for two species to occupy the same niche, competition is bound to favor one over the other.

34. Speciation from Isolating Mechanisms Geographic isolation: occurs when a physical barrier separates populations Behavioral isolations: occurs when two population of organism have different courtship or mating rituals. Temporal isolation: occurs when two populations have two different mating seasons

36. Patterns of Evolution1. Divergent Evolution • Divergent evolution is the process by which organisms become less alike This can result in speciation. 1.5 It can also lead to adaptive radiation, where species adapt to a variety of habitats and evolve into diverse forms occupying different niches.

37. 2. Convergent Evolution • Convergent evolution occurs when distantly related organisms develop similar characteristics due to influence of similar environments and natural selection. • A good example of convergent evolution is marine mammals and fish

38. Convergent evolution can often lead to mimicry-when one organism evolves to resemble another. These animals have a selective advantage

39. 3. Coevolution • Two different species evolve in response to changes in each other over time. • Example: flowers that attract a specific type of pollinator.

40. Biochemical Evidence of Evolution • The more closely related organisms are, the more similar their biochemical makeup is. • Similar chemistry and structure of chromosomes in Eukaryotes

42. Cytochrome c is an example of a protein that can be used to check if an organism is closely related to another organism.

43. Ch.17 Models for Rate of Evolution • Gradualism – a slow gradual change in a species over a long period of time. (Think millions into billions of years) • Punctuated Equilibrium – patterns of long, stable periods interrupted by brief periods of more rapid change. (Think hundreds of thousands even millions of years)

44. Speciation rates Loxodonta africana Elephas maximus 0 1 2 Millions of Years Ago Mammuthus primigenius Elephas 3 Loxodonta 4 Mammuthus 5 Primelephas 6 Ancestral species about 55 million years ago

45. Related Topics • Extinction – disappearance of a species from all portions of its geographical range. Causes: natural selection, abiotic change and /or food web collapse. • Microevolution – change of allele frequency; genetic variation due to processes such as selection, mutation, genetic drift or migration. • Macroevolution – evolutionary change at or greater than the species level; formation of new species, new genera and so on.

46. Earth’s Early History (Hypothesis) • Early Earth’s atmosphere had hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water, very caustic environment. • 4 billion years ago first solid rocks and volcanic activity, no oceans still too hot. • 3.8 billion years ago cooled enough for water to remain liquid, this is when early life appeared. • First organic molecules – Miller, Urey –experiments produced organic compounds even cytosine and uracil.

47. e. Evolution of RNA and DNA – science is still working on this puzzle but have made surprising discoveries (viruses could be source of nucleus, choloroplasts and mitochondrion from bacteria – Margulis) RNA before DNA. f. Free Oxygen – photosynthetic bacteria became common in shallow seas of the Precambrian Era, they produced oxygen which combined with Iron causing the oceans to rust. This O2 accumulated and caused the formation of the ozone layer.

48. Origin of Eukaryotic Cells • Endosymbiotic theory- smaller prokaryotes began living inside larger cells causing a symbiotic relation such as the mitochondria and the chloroplast. (lynn Margulis)

49. Nucleic Acid comparisons (DNA fingerprinting) - the more closely related two organisms are, the more similar is their DNA, e.g. identical twins • Chlorophyll is the same basic molecule in all photosynthetic organisms