Evidence for Evolution

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

Whale Evolution

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

A lesson in Biogeography

The Wallace Line Read this interesting article by Jared Diamond (author of Guns, Germs, and Steel) about “Mr. Wallace’s Line”:

Wegener’s contributions to Biogeography Alfred Wegener found that the distributions of fossils of several organisms supported his theory that the continents were once joined together.

Galapagos Finches

Hawaiian Fruit Flies

Humerus Radius Ulna Carpals Metacarpals Phalanges HumanCatWhaleBat Comparative Anatomy Evidence: Homologous Structures

Comparative Anatomy Evidence: Vestigial Structures Boa pelvic region Human Coccyx (tailbone)

Comparative Embryology Evidence

Pharyngeal pouches Post-anal tail Chick embryo Human embryo Comparative Embryology Evidence

Fig Tetrapod limbs Amnion Lungfishes Feathers Amphibians Mammals Lizards and snakes 2 Hawks and other birds Ostriches Crocodiles Amniotes Tetrapods Birds

Biochemical Evidence: amino acid sequence of hemoglobin

Biochemical Evidence: amino acid sequence of cytochrome c

Biochemical Evidence: DNA sequence

Microevolution: a change in a population’s alleles over time How do we detect this change? Need to look at a population’s collection of alleles, or its gene pool. Darwin’s Finches video:

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)

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

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

Fig a-3 Original population Bottlenecking event Surviving population

“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…”

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

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

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.

Fig a

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

Fig Parents Offspring, with new combinations of alleles Gametes Meiosis  and A1A1 Random fertilization A1A1 A2A2 A3A3 A1A1 A2A2 A3A3 A3A3 A1A1 A2A2 A1A1

Fig. 13-9a Webbing No webbing

Fig. 13-9b Phenotypes 320 ––– 500 Genotypes Number of animals (total = 500) Genotype frequencies Number of alleles in gene pool (total = 1,000) Allele frequencies WW Ww ww = ––– 500 = ––– 500 = w160 W w 640 W 800 1,000 = 0.8 W 200 1,000 = 0.2 w

Fig. 13-9c Gametes reflect allele frequencies of parental gene pool W egg p = 0.8 Sperm w egg q = 0.2 W sperm p = 0.8 Eggs Allele frequencies Genotype frequencies Next generation: w sperm q = 0.8 WW p 2 = 0.64 ww q 2 = 0.04 wW qp = 0.16 Ww pq = WW0.32 Ww 0.04 ww 0.8 W0.2 w

Fig a-1 Original population

Fig a-2 Original population Bottlenecking event

Fig b

Fig b

Fig c

Fig “Right-mouthed” “Left-mouthed” ’82’83’84’85’86’87’88’89’90 Sample year Frequency of “left-mouthed” individuals

Fig. 13-UN1 Observations Heritable variations in individuals Overproduction of offspring Over time, favorable traits accumulate in the population Individuals well-suited to the environment tend to leave more offspring Inferences

Fig Original population Frequency of individuals Original population Evolved population Phenotypes (fur color) Stabilizing selectionDirectional selectionDisruptive selection

Fig. 13-UN3 Original population Pressure of natural selection Evolved population Stabilizing selection Directional selection Disruptive selection

Fig. 13-UN5