Evolution Review Chapters 21, 22, & 23

Ch. 21 Genes within Populations

# 2 5 Mechanisms of evolutionary change 1. Natural selection traits that improve survival or reproduction will accumulate in the population adaptive change 2. Genetic drift frequency of traits can change in a population due to random chance events random change More pronounced in small populations

#2 and #9: Genetic Drift Chance events changing frequency of traits in a population not adaptation to environmental conditions not selection founder effect small group splinters off & starts a new colony it’s random who joins the group bottleneck a disaster reduces population to small number & then population recovers & expands again but from a limited gene pool who survives disaster may be random

Founder effect When a new population is started by only a small group of individuals just by chance some rare alleles may be at high frequency; others may be missing skew the gene pool of new population human populations that started from small group of colonists example: colonization of New World albino deer Seneca Army Depot Don’t fence me in!

Out of Africa Likely migration paths of humans out of Africa Many patterns of human traits reflect this migration

Bottleneck effect When large population is drastically reduced by a disaster famine, natural disaster, loss of habitat… loss of variation by chance event alleles lost from gene pool not due to fitness narrows the gene pool

Cheetahs All cheetahs share a small number of alleles less than 1% diversity as if all cheetahs are identical twins 2 bottlenecks 10,000 years ago Ice Age last 100 years poaching & loss of habitat

Conservation issues Bottlenecking is an important concept in conservation biology of endangered species loss of alleles from gene pool reduces variation reduces adaptability Breeding programs must consciously outcross Peregrine Falcon Golden Lion Tamarin

5 Agents of evolutionary change MutationGene Flow Genetic DriftSelection Non-random mating

#3: Variation & natural selection Variation is the raw material for natural selection there have to be differences within population some individuals must be more fit than others

Ch. 22 Evidence for Evolution

LaMarck ( ) Organisms adapted to their environments by acquiring traits change in their life time change in their life time Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat transmit acquired characteristics to next generation

Then along comes Darwin… Charles Darwin   British naturalist  Proposed the idea of evolution by natural selection  Collected clear evidence to support his ideas years old! Galapagos Islands

Darwin was amazed to find out: All 14 species of birds were finches… Finch?Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large Ground Finch Small Ground Finch Warbler FinchVeg. Tree Finch But there is only one species of finch on the mainland! How did one species of finches become so many different species now?

Correlation of species to food source Seed eaters Flower eaters Insect eaters Rapid speciation: new species filling new niches, because they inherited successful adaptations. Adaptive radiation

Differences in beaks allowed some finches to… successfully compete successfully feed successfully reproduce pass successful traits onto their offspring Darwin’s finches

Correlation of species to food source Whoa, Turtles, too! More observations…

Many islands also show distinct local variations in tortoise morphology… …perhaps these are the first steps in the splitting of one species into several?

Glyptodont fossils Modern armadillos Modern sloth Sloth fossils Why should extinct species & living species be found on the same continent? More observations…

Essence of Darwin’s ideas Evolution by Means of Natural Selection variation exists in populations over-production of offspring more offspring than the environment can support competition for food, mates, nesting sites, escape predators differential survival successful traits = adaptations differential reproduction adaptations become more common in population adaptations become more common in population

LaMarckian vs. Darwinian view LaMarck in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring Darwin giraffes born with longer necks survive better & leave more offspring who inherit their long necks

What are the 4 lines of evidence that support Darwin’s ideas?… LampreyFrogBird Dog MacaqueHuman

1. What are the lines of evidence that support Darwin’s ideas? Fossil record Millions of years ago Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg)

2. What are the lines of evidence that support Darwin’s ideas? Terminal bud Lateral buds Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Flower and stems BroccoliWild mustard Kohlrabi Stem Kale Artificial selection

Anatomical evidence 3. What are the lines of evidence that support Darwin’s ideas?

Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor

Analogous structures Solving a similar problem with a similar solution Does this mean they have a recent common ancestor? Don’t be fooled by their looks! Those fins & tails & sleek bodies are analogous structures! Convergent evolution

Vestigial organs Why would whales have pelvis & leg bones if they were always sea creatures? These are remnants of structures that were functional in ancestral species

Molecular record Millions of years ago Horse/ donkey Sheep/ goat Goat/cow Llama/ cow Pig/ cow Rabbit/ rodent Horse/cow Human/rodent Dog/ cow Human/ cow Human/kangaroo Nucleotide substitutions Comparing DNA & protein structure universal genetic code! DNA & RNA compare common genes cytochrome C (respiration) hemoglobin (gas exchange) Closely related species have sequences that are more similar than distantly related species  DNA & proteins are a molecular record of evolutionary relationships Closely related species have sequences that are more similar than distantly related species  DNA & proteins are a molecular record of evolutionary relationships 4. What are the lines of evidence that support Darwin’s ideas?

LampreyFrogBird Dog MacaqueHuman Why compare DNA & proteins across species? Why compare these genes? Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans  compare common genes  cytochrome C (respiration)  hemoglobin (gas exchange)  compare common genes  cytochrome C (respiration)  hemoglobin (gas exchange) The sequence in DNA & proteins is a molecular record of evolutionary relationships. Comparative hemoglobin structure

marsupial mammals marsupial mammals placental mammals placental mammals Convergent evolution These animals look very similar but does that mean they have a recent common ancestor? What is this evidence of?

Parallel/convergent evolution NichePlacental MammalsAustralian Marsupials Burrower Mole Anteater Mouse Lemur Flying squirrel Ocelot Wolf Tasmanian “wolf” Tasmanian cat Sugar glider Spotted cuscus Numbat Marsupial mole Marsupial mouse Anteater Nocturnal insectivore Climber Glider Stalking predator Chasing predator Convergent evolution of analogous burrowing characteristics

Coevolution Two or more species reciprocally affect each other’s evolution predator-prey disease & host competitive species mutualism pollinators & flowers

#7. Types of Natural Selection Selection acts on any trait that affects survival or reproduction predation selection physiological selection sexual selection

#8. Effects of Selection Changes in the average trait of a population DIRECTIONAL SELECTION STABILIZING SELECTION DISRUPTIVE SELECTION giraffe neck horse size human birth weightrock pocket mice speciation?