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Bio finals study notes on Coyne.doc

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Spencer Barret

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Bio finals study notes on Coyne Chapter 1: What is Evolution? Darwin was first to use data from nature to convince people that evolution was true and started idea of natural selection. However, he was not the first to think of evolution. Life on Earth evolved gradually beginning with one primitive species, perhaps a self- replicating molecule 3.5 billion years ago. It then branched out over time, throwing off many new and diverse species and the mechanism for most evolutionary change is natural selection. 6 components of Darwinism: 1. Gradualism: many generations to produce evolutionary change 2. Evolution: species undergoes genetic change over time 3. Common ancestry: flip side of speciation. Can find descendant lineages fuse at ancestors/nodes. 4. Speciation: evolution of different groups that can’t interbreed/exchange genes 5. Natural selection: if individuals within species differ genetically, these differences affect ability to survive and reproduce in environment. Good genes leading to high fitness will make it to the next generation, while unfit genes will not get passed. 6. Nonselective mechanisms of evolutionary change: genetic drift/random changes in proportion of genes. GECS NN Horseshoe crabs and gingko trees haven’t changed over millions of years. Evolution doesn’t predict how often species evolve or how they will change when they do. Coelacanth = living fossil, looks almost identical to ancestors millions of years ago. Different plant species use different pollintators or flower at different times, preventing cross-fertilization. Darwin didn’t really explain how new species arose (no knowledge of genetics). Never knew about barriers to gene exchange. Evolution is not like cardboard books of matches. Doesn’t fall into a natural classification in the same way as living species. Can sort matchbooks by size, country within size, color within country. Or by advertising. No sorting system all collectors agree on. Matchbooks = creatures under creationist explanation of life. We wouldn’t expect to see species falling into a nested hierarchy of forms that is recognized by all biologists. Rather than evolving so that each matchbook gives rise to another that is only slightly different, each design was created from scratch by human whim. Natural selection is not a master engineer, it’s a tinkerer. It doesn’t produce the absolute perfection by scratch, but does the best it can with what it has to work with. Not intelligent to design millions of species that went extinct and replace them with similar species that will also vanish. Mutations are changes in traits that already exist, rarely builds brand new features. Evolution = architect that cannot design building from scratch, but build upon preexisting buildings. Natural selection leads to the fitter, not the fittest. Theories must be testable and make verifiable predictions. Alfred Wegener – continential drift. Chapter 4: The Geography of Life pg 113. Island has not a single native species of fresh water fish, amphibian, reptile or mammal. In NA and SA, succulents are in cactus family. Succulents in deserts of Asia, Australia and Africa are in euphorb family. Sap is clear/watery in cacti, but milky/bitter in euphorbs. Cacti introduced to old world deserts still do very well. Share convergent traits = demonstrates common ancestry, speciation, natural selection. Prickly pear of NA introduced to Australia to extract red dye from cochineal beetle that eats the plant. Prickly pear became pest, destroyed farmland. Introduced cactoblastis moth to control prickly pear. Two types of islands: 1) continental islands (islands once connected to continent, but separated by rising sea levels or by moving continential plates e.g. Britain, Japan, Sr Lanka etc) and 2) oceanic islands are bereft of life and arose from sea floor e.g. Hawaii, Galapagos). Cane toad, poisonous amphibian from Central America was introduced to Hawaii to control beetles on sugarcane are now a pest. They kill cats and dogs that eat them. Mammals, amphibians, reptiles and freshwater fish do well when introduced to oceanic islands. Oceanic islands have high radiation of species e.g. wild variety of finches, no other birds. Hawaii has wide variety of drosophila. Life is unbalanced. The missing groups from these islands cannot easily disperse far away, can’t fly, swim via ocean etc. Plant seeds can float. Coconut palm = large, buoyant seeds. Continential islands also have somewhat unbalanced flora and fauna, even more so if they are very old. The older they are, the more like oceanic islands. E.g. Madagascar before primates evolved. It has unique lemurs that radiated despite being continental island. New Zeland has Moasm kiwi, kakapo flightless birds. Time and chance alone determine who gets marooned = Robinson Crusoe effect. Many animals/plants in unoccupied habitats will thrive and form new species, filling ecological niches. Will usually find relatives on nearest island or mainland. Island ecosystems = fragile, easily ravaged by invaders. Worst is humans + we bring invasive species. Chapter 5: The Engine of Evolution Asian giant hornet from Japan – long as thumb, orange/black stripes, lethal stinger. Hornet scout places drop of pheromone near entrance of bee colony. 20-30 hornets go up against 30,000 honeybees. In one week, eat honey, bring dead bees back to nests to feed offspring. Honeybees in Japan have resistance. Hornet scout is mobbed, raising temperature by vibrating abdomens and cooks hornet to death. Larvae rap heads constantly against nest to show hunger. European honeybees = defenseless. Roundworm parasitizes Central American ant. Ant’s black abdomen turns bright red, turns sluggish, raises abdomen in air, doesn’t alarm with pheromones when attacked so don’t alert nestmates. Birds thinks it’s a berry and eats ant. Birds pass eggs in droppings and ants take back via scavenging to feed larvae. Worms hatch in ant larva. When ant larva becomes a pupa, worms migrate to abdomen and mate, producing more eggs. Katydids look like leafs with leaf patterns. Orchids have flowers that look like bees and wasps. Males try to mate with it getting pollen on insect’s head. Some orchids produce chemicals that smell like sex pheromones of bees. 3 things involved in creating adaptation by natural selection VHS): 1) Starting population must have variable genes. E.g. different coat color of mice. 2) Proportion of that variation must come from changes in the form of genes. Genes must be heritable. Agouti gene produces black color in rats + cats. Mc1r gene produces light color coat in rats and in mutant form in humans produces freckles and red hair in Irish populations. Mutations occur randomly+regardless of whether they’d be useful to the individual. Can be neutral, harmful or helpful. 3) Genetic variation must affect individual’s probability of leaving offspring. Kaufman showed, most camouflaged mice leave more copies of genes. Evolution by selection has random/indifferent process of mutations occurring and a lawful process of natural selection. = “The nonrandom survival of random variants” by Richard Dawkins. A gene that kills after reproductive age has no evolutionary disadvantage. Accumulation of these genes by natural selection = why we age. Genes that allow for reproduction when young gives wrinkles and enlarged prostate gland later in life. Natural selection wouldn’t help individual survive after menopause. When males displace head lion male of a pride = slaughter of cubs. Reduces total number of lions = higher chance of extinction, but good for invading lions since they can fertilize females and replace dead cubs with own/better genes, instead of babysitting unrelated cubs. Evolution = change in proportion of alleles in a population. Genetic drift = type of evolution, changing allele frequency over time. E.g. ABO blood system. In Old Order Amish, few immigrants on an island or new area. No B blood type in Native American populations. Drift is random. Can’t ever cause evolution of adaptations. Can’t build wing or an eye. That needs nonrandom natural selection. It can cause evolution of useful/harmful features to the organism. It can overpower natural selection in small populations, esp small pop. Sampling effect is so large that harmful gene frequency is very high even though selection is working in opposite direction. Genetic drift must occur because any population of finite size always has sampling effects during reproduction. Every single dog came from single species Eurasian gray wolf – breeded by humans. Sculpted dogs to their liking. Fulfils 2/3 reqs for evolution by selection 1. Variation in color, size, shape, behavior of ancient dogs to create all these breeds 2) variations of genetic mutations could be inherited. Very fast selection within 10,000 yrs. Artificial selection is very quick. Turkeys now bread with breasts so large, must artificially inseminate females since males can’t mount females anymore. Ancestor of corn = grass. Wild cabbage given rise to broccoli, kohlrabi, Brussels, sprouts, cauliflower etc. Studying bacteria = can see all 3 components of selection – variation, heritability, different survival/reproduction of variants. When delete gene in microbe needed to break down lactose, E.coli used another enzyme that previously couldn’t break down lactose, but now could weakly. Got better in generations, mutations increasing amount of enzyme produced etc. Found that 1. Natural selection can lead to evolution of complex, interconnected biochemical systems and 2) selection doesn’t create new traits from thin air, builds new adaptations by modifying old ones. Can show adaptive radiation via bacteria too. New species formed. Some viruses don’t evolve e.g. polio and measles. Unlike influenza. Macroevolution – one ‘type’ of animal into another vs microevolutionary change (small changes). Stabilizing selection – human birth weight is all around same average. Soapberry bug Jadera of the New World lives on two native plants. The bug uses long needle-like beak to penetrate fruit, eat seeds inside, liquefy contents. Now 3 new plant species introduced into range. Two are very large, one very small in comparison to original native plants. Beak size changed. Large fruit = larger beaks and vice versa. 25% change in a few decades. Very fast. Under drought, plants flower earlier than ancestors since soils dry out quickly after rains. Mustard plant Brassica rapa in California. Flowering time did change during drought. More examples e.g. guppies less colorful to escape notice of predators. Evolution of complex biochemical features + pathways not easy since no trace in fossil record. Key protein in clotting = fibrinogen dissolved in blood plasma. In last step of blood clotting, protein gets cut by enzyme and shorter proteins fibrins stick together forming clot. Found in sea cucumber protein that’s related to blood clotting but not used to clot blood. Ken Miller and Doolittle worked out plausible + adaptive sequence of evolution of entire blood-clotting cascade from pts. Of precursor proteins in invertebrates with nonclotting functions. Possible way eyes formed: 1. Start with light-sensitive pigment in flatworms 2. Skin folds into cup protecting eyespot allowing it to better localize light source like limpets. 3. Narrowing of cup’s opening to produce improved image and capped by protective transparent cover to protect opening like in ragworms. 4. Fluid of eye coagulated to form a lens like in abalones to focus light. Nearby muscles in mammls move lens and vary focus. 5. Retina, optic nerve etc. follow similar processes of natural selection. Each step is feasible. At the end is camera eye. Small adaptive steps. 400,000 yrs estimated to make camera eye via mathematical models. 550 million years ago, animals with eyes. More than enough time. Eyes evolved independently in over 40 groups of animals. However breeders haven’t turned a cat into a dog. No bacterium has been turned into a new amoeba, but new species of bacteria have been formed in lab. Big transformations take time. Can’t see Grand Canyon getting deeper, but know it does. Page 177 Chapter 6 – how sex drives evolution Why peacocks have bright feathers – can’t fly, attracts predators esp in monsoons when tail gets heavy. Also energy put into making tail. Irish elk – neither Irish nor an elk is the largest deer that disappeared 10,000 years ago with huge antlers. Sexual dimorphisms – traits that differ between males and females of species. These traits don’t increase survival, but increases chances of having offspring = sexual selection. Selection that increases individual’s chance of getting a mate. Red-winged blackbird defends their territories. It’s polygynous. Males that are ‘floaters’ go unmated. They try to invade established territories to sneak copulations with females. Protect territories with songs + threat displays. Postmating competition – snakes and rodents have substances that plug up female’s reproductive tract after mating, barricading other males. With fruit files, males inject females with anti-aphrodisiac, making her unwilling to remate for several days. Can also inactivate stored sperm of males who mated previously. Female choice has driven evolution of many sexual dimorphisms. Those who produce sexually lose half its genes in comparison to those who reproduce asexually/pathenogenesis. Bringing together favourable genes in one individual, sex might promote faster evolution to deal with changing environments. Or sex could purge bad genes into one disadvantaged individual – genetic scapegoat. Why 2, not 3 or 4 sexes that mate and combine genes? Why do sexes have different numbers/sizes of gametes. 2 is most stable strategy. Evolved from two sexes where gametes were equal size. Natural selection will favor when male makes lots of small gametes and females make fewer but larger gametes. This asymmetry sets stage for all of sexual selection. Males have little to lose by mating with a sick/weak female since they can mate repeatedly. Selection then favors genes that make a male promiscuous. For females, high investment in eggs and offspring, so picky with mate. Almost all females will eventually find mates. Good males will find mates, substandard males will go unmated. However, evolution can favor monogamy if males have more offspring by helping with child care than if they abandon offspring to seek more matings. In some birds, both parents needed. Females may simply be larger because they need to produce large and costly eggs. Or males and females may be better predators if they specialize in different food. Reduced competition for two sexes could lead them to evolve different body sizes. So dimorphism doesn’t have to involve sexual selection. Sexual dimorphisms in socially monogamous species – adultery. No adultery if no difference between sexes. Males have beautiful colors in fairy wren. Sometimes it’s t
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