Evidence for Evolution. Types of Evidence for Evolution 1.Fossil Record (ex: horses and whales) 2.Biogeography 3.Comparative Anatomy –Homologous Structures.
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Slide 1 Evidence for Evolution Slide 2 Types of Evidence for Evolution 1.Fossil Record (ex: horses and whales) 2.Biogeography 3.Comparative Anatomy Homologous Structures Vestigial Structures 4.Comparative Embryology 5.Molecular Biology / Biochemical evidence Protein (aa sequence) comparisons DNA sequence comparisons Slide 3 Fossil Record Evidence: Horse evolution four toes on ground (#2-5), short teeth good for eating soft leaves on shrubs & trees one toe on ground (#3), long teeth good for eating tough blades of grass Slide 4 Look at how the bones in horse feet have changed over time. They became longer and more streamlined, enabling horses to run faster to avoid predators. mya = million years ago Slide 5 Whale Evolution Slide 6 Fossil Record of Whale Evolution Pelvis and hind limb Rhodocetus (predominantly aquatic) Pakicetus (terrestrial) Dorudon (fully aquatic) Balaena (recent whale ancestor) Pelvis and hind limb Slide 7 Slide 8 A lesson in Biogeography Slide 9 The Wallace Line http://evolution.berkeley.edu/evolibrary/article/history_16 http://theglyptodon.wordpress.com/2011/05/25/the-wallace-line/ Read this interesting article by Jared Diamond (author of Guns, Germs, and Steel) about Mr. Wallaces Line: http://discovermagazine.com/1997/aug/mrwallacesline1198 Slide 10 An Example of Biogeographical Evidence: Galapagos Finches and Adaptive Radiation Slide 11 Humerus Radius Ulna Carpals Metacarpals Phalanges HumanCatWhaleBat Comparative Anatomy Evidence: Homologous Structures Slide 12 Comparative Anatomy Evidence: Vestigial Structures Boa pelvic region Human Coccyx (tailbone) Slide 13 Comparative Embryology Evidence Slide 14 Pharyngeal pouches Post-anal tail Chick embryo Human embryo Comparative Embryology Evidence Slide 15 Fig. 13-6 Tetrapod limbs Amnion Lungfishes Feathers Amphibians Mammals Lizards and snakes 2 Hawks and other birds Ostriches Crocodiles 1 3 4 5 6 Amniotes Tetrapods Birds Slide 16 Biochemical Evidence: amino acid sequence of hemoglobin Slide 17 Biochemical Evidence: amino acid sequence of cytochrome c Note: These sequences use 1-letter amino acid codes. The alignment lines show where the amino acids are the same or different (+ or a blank). The + indicates a different amino acid but with the SAME R-group properties (nonpolar, polar or charged). Slide 18 Amino Acids by R-group Properties with 3-letter and 1-letter abbreviations http://www.bio.miami.edu/dana/pix/aminoacids.gif (neg. charged) (pos. charged) Slide 19 Biochemical Evidence: DNA sequence Slide 20 Microevolution: a change in a populations alleles over time How do we detect this change? Need to look at a populations collection of alleles, or its gene pool. Darwins Finches video: http://www.hhmi.org/biointeractive/origin-species-beak-finch http://www.hhmi.org/biointeractive/origin-species-beak-finch Rock Pocket Mouse video: http://www.hhmi.org/biointeractive/making-fittest-natural- selection-and-adaptation Slide 21 Hardy-Weinberg Theorem H-W allows you to predict allele frequencies for a non-evolving population. For a population to be in H-W equilibrium, the following must be true: Population must be very large in size Population must be isolated from other pops (no gene flow: no immigration or emigration) No mutations Mating must be random No natural selection (equal chance of survival & reproductive success) Slide 22 Any changes to expected allele frequencies over time may indicate that micro-evolution is occurring in the population. Allele frequencies Genotype frequencies Dominant homozygotes Heterozygotes Recessive homozygotes p + q = 1 p 2 +2pq + q 2 = 1 Hardy-Weinberg Theorem Slide 23 Fig. 13-13 Original population Frequency of individuals Original population Evolved population Phenotypes (fur color) Stabilizing selectionDirectional selectionDisruptive selection Slide 24 Causes of Microevolution 1.Genetic Drift Produces random changes to the gene pool of small breeding populations An allele may be eliminated from pop by chance A.Bottleneck Effect : dramatic decr in pop size due to environmental fluctuation (depletion of food supply, disease outbreak) Examples: Cheetahs, Florida Panthers B.Founder Effect : when one or a few individuals from a large pop establish a colony (new pop), and bring with them only a small fraction of genetic variation from orig pop Example: Marine Iguanas in Galapagos Slide 25 Fig. 13-11a-3 Original population Bottlenecking event Surviving population Slide 26 By 1990s, the endangered Florida panther a flagship species and one of the last remaining symbols of wilderness in Florida - was in serious trouble. There were fewer than 30 panthers remaining in the wild. The population suffered from several biomedical and morphological abnormalities, including low genetic diversity, heart defects, reproductive dysfunctions and kinked tails. Many of these problems were thought to be indicative of inbreeding, and conservation biologists recommended genetic restoration. This recommendation was controversial but was ultimately implemented after careful planning http://research.ifas.ufl.edu/featured-discoveries/genetic-restoration-saves-endangered-florida-panther# Slide 27 Causes of Microevolution 2. Gene Flow movement of alleles by migration of individuals to a new population Generally increases variation within a population 3. Mutation Unpredictable change in DNA, a source of new alleles Introduces variation in pop Only inheritable if occurs in gametes Can be harmful, beneficial, or neutral 4. Natural Selection Leads to adaptive evol change, as fittest indiv survive to reproduce Slide 28 Fig. 13-3b Chromosome with allele conferring resistance to pesticide Additional applications will be less effective, and the frequency of resistant insects in the population will grow Survivors Pesticide application Slide 29 Causes of Microevolution 5. Non-random Mating A.Inbreeding : Individuals mate more freq with closely related individuals Common in plants in the form of self-fertilization Not always harmful but sometimes leads to inbreeding depression (lower fitness: sterility, higher juvenile mortality) Examples: Cheetahs, Florida Panthers B.Sexual selection (mate selection) : individuals select mates by their phenotype Can change genotype frequencies Examples: Peacocks, Mallards, Humans, etc. Slide 30 Fig. 13-14a Slide 31 Fig. 13-UN4 Microevolution (a) may result from change in allele frequencies in a population is the (g) (c) (b) (d) (e) (f) individuals or gametes best adapted to environment adaptive evolution random fluctuations more likely in a due to movement of may be result of leads to due to of individuals
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