BIOEE 1780 Prelim 2 Study Guide
BIOEE 1780 Prelim 2 Study Guide BIOEE1780: Evolutionary Biology
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BIOEE1780: Evolutionary Biology
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This 1 page Study Guide was uploaded by Carly Siege on Monday April 4, 2016. The Study Guide belongs to BIOEE1780: Evolutionary Biology at Cornell University taught by Dr.Sarvary in Spring 2016. Since its upload, it has received 28 views. For similar materials see Biology: Evolution and Biodiversity in Biological Sciences at Cornell University.
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Date Created: 04/04/16
Grant’s Finch Study on Daphne Major Island (8.1) Daphne Major was the perfect environment to conduct this study pristine no agriculture no invasive species/domesticated animals no species had gone extinct since the arrival humans Drought of 1977 barren landscape only birds with big deep beaks could crack the hard woody caltrop seeds average beak size increased from an average depth os 9.2 mm to 9.7 mm shift was because ﬁnches with bigger beaks have a better change of serving the drought and could therefor produce a bigger fraction of the next generation Rains of 1985 (El Nino Event) El Nino: weakening or reversal or normal trade winds results in a band of warm water in the equatorial paciﬁc ocean evaporation oﬀ this warm water results in elevated rainfall over the region occurs every 2-7 years and may last 9-20 months rains came and the spurge bloomed producing lots of small seeds small beaked birds had the advantage bc they could eat small seeds more eﬃciently average beak size decreased by 2.5% shift was bc small beaked birds had more food so they could grow faster and have more energy for producing oﬀspring z lessons natural selection can vary in intensity evolution can happy surprisingly fast pattern of election can change over time Natural Selection Fact 1: all species have such great potential fertility that their population size would increase exponentially if all reproduction was successful Fact 2: populations normally display stability in size except for minor annual and occasional major ﬂuctuations Fact 3: Natural resources are limited. In a stable environment, they remain relatively constant. Inference 1: since more individuals are produced than can be supported by the available resource but population size remains stable, it means that there must be a ﬁerce struggle for existence among the individuals of a population, resulting in the survival of only a part, often a small part, of the progeny of each generation there is always going to be a check on your population growth Fact 4: no two individuals are exactly the same; rather, every population displays enormous variability (variation can be obvious or at the genetic level) Fact 5: much of this variation is heritable Inference 2: survival in the struggle for existence is not random but depends in part on the hereditary constitution of the surviving individuals. This unequal survival constitutes the process of natural selection Inference 3: over the generations, this process of natural selection will lead to a continuing gradual change of populations, that is to evolution and to the production of new species Four Good Rules to Remember about Natural Selection 1. Natural selection acts on individuals. Individuals survive and reproduce. Natural selection does NOT act “for the good of the species” 2. Natural selection acts on traits (phenotypes), but evolution occurs only when there is a genetic change in the population. Thus, natural selection results in evolutionary change when it acts on traits that are heritable. 3. Natural selection acts according to the ecological context of the moment 4. Natural selection is not forward-looking. It does not strive for or result in perfection Natural selection is short sighted and operates according to immediate environmental conditions. traits are not inherently adaptive or maladaptive, their adaptive value depends on the environmental condition Biological Examples of Natural Selection Analogous Example: Oldﬁeld Mice with coloring that matches the soil where they live predators on light colored sand are likely to capture dark mice, and vice versa blending in reduced predation strong selection for coat color to match the soil with each population of mice convergent evolution: light coloration evolving through a diﬀerence set of mutations in diﬀerent locations King snakes and coral snakes coral snake are venomous and use their coloration to warn predators king snakes are not venomous but mimic the coloration of coral snakes to avoid predation kind snakes that look like coral snakes are less likely to be eaten selection for mimicry is only seen when both species are present Lactose Intolerance and milk drinking in human populations allele for milk tolerance is most common where cattle were common as less common in populations where milk consumption is less prevalent Adaptation: any variation that can help an organism survive in its environment Artiﬁcial Selection: selection resulting form human activity, like when breeders non randomly choose individuals with economically favorable traits to use as breeding stock Evolution: genetic change in a population natural selection and genetic drifts are mechanisms for evolution Darwin malthus gave darwin the idea that species have the potential to increase their population exponentially malthus was an english clergyman —> professor Darwin’s Three Postulates: natural selection will occur when individuals are variable in some traits at least some of this variation is heritable the variation causes diﬀerences in survival and reproduction Kinds of Selection Directional Selection selection favors phenotypes at one end of the distribution darwin ﬁnch response to drought Stabilizing Selection selection favors values towards the middle of the distribution while ﬁtness at either end is low body weight in newborn babies (not over weight or underweight) Disruptive Selection selection favorites individuals who are towards the two are ends, further from the mean origin of new species (hybrids) Senescence: a decline with age in per capita reproductive performance, physiological function, or the probability of survival Fitness Darwinian Fitness: The ability of an individual to survive and reproduce in a certain environment, compared to other individuals of that population Fitness: an individual’s proportional representation in the gene pool of subsequent generations ﬁtness depends on reproduction, positive selection on post reproductive traits is absent or weak Direct ﬁtness: is the individual’s own reproductive success their genetic contribution to future generations via their own direct oﬀspring determined by number of oﬀspring (and that survive to maturity) involves tradeoﬀs among present and future reproduction Indirect Fitness: is the component of ﬁtness gained through aiding the survival and reproduction of non-descendant relatives Inclusive Fitness: an individuals total ﬁtness direct ﬁtness (own success at genetic contribution) + indirect ﬁtness (success of other individuals that share alleles) Antagonistic Pleiotropy: when a genetic variant with beneﬁcial eﬀect on one trait also has a detrimental eﬀect on another trait an allele may be favored bc it leads to a beneﬁcial trait early in life enhancing reproductive output, or ensuring early surveil, even though the same allele may lead to other traits that are very detrimental later in life Virginia Opossum Experiment Sepelo Island separated from mainland and from danger (bobcats, cars, humans) longer lifespan on island than on mainland test to see if the diﬀerence in survival has any adaptive aﬀects relating to senescence test tail collagen breaking points found that collagen aging is a good general measure of the physiological aging found that island longevity is greater litter size is larger on mainland allocation tradeoﬀs mainland females should invest now bc they won’t survive to give birth another year Life History Evolution: the timing and duration of key events during a life time age and duration of reproduction number and size of oﬀspring lifespan Tradeoﬀs tradeoﬀs arise when investment in one trait result in lower investment in another trait investment in reproduction is often at the expense of investment in growth or maintenance selection may favor alleles that are beneﬁcial early in life, even if they’re deleterious late in life in tradeoﬀs, individuals are allocating resources in other rather than other strategy bc resources are ﬁnite and cannot have both can’t have high reproduction AND high survival these conﬂicts relate to the allocation of resources but not between stages but between individuals in a family siblicide (oﬀspring-oﬀspring conﬂict) blue footed boobies: only the slightly older chick will survive and kick the younger away from the nest under favorable conditions, direct ﬁtness of the parents and the indirect ﬁtness of the senior chick are both increased by survival to reporictun of the subordinate in unfavorable conditions, siblicide is triggered with a 20-25% weight deﬁciency of the senior sibling Blue Footed Boobies: siblicide depending on ﬁtness Nazca Boobies: Obligate Siblicide parent-oﬀspring conﬂict Male sand Gobies will eat some of their eggs when there are stressful conditions (low oxygen and high egg density) in order to ensure the survival of the clutch as a whole parent-parent conﬂict eurasian penduline tits mothers and fathers compete to leave the nest and mate with other Extrinsic Mortality the rate at which external events (predation, starvation) lead to death Intrinsic Mortality the rate at which internal events (aging, disease, mutations) lead to death Kin selection: predicts that individuals should help relatives more than non-realtives, selection arising from the indirect ﬁtness beneﬁts of helping relatives Altruism: behaviors that decrease the ﬁtness of the individual performing the behavior and increase the ﬁtness of one or more other individuals (Self sacriﬁcing behaviors) true altruism is rare and evolutionary disadvantageous most apparent altruism is better explained as Kin Selection Belding’s Ground Squirrels give an alarm call when a predator is approaching increases the risk to the individuals who actually calls,, but gives the other members of the colony time to escape. females are more likely to give alarm calls females are willing to take the risk of calling bc its their own relatives that they are protecting life history of these squirrels is that mature males disperse to unrelated colonies (to prevent inbreeding) and the colony retains a female based family structure r = coeﬃcient of relatedness the probability that the altruist shares identical copies of a particular allele In diploid species, r=0.5 n=number of ‘generational links’ WD (Bill) Hamilton idea of kin selection an inclusive ﬁtness Hamilton’s Rule rB>C r= relatedness B= beneﬁt to recipient C= cost to donor A ‘helping’ behavior can spread in a population if the cost to the donor is smaller than the beneﬁt to the recipient weighted by relatedness. Connect to the Ground Squirrel example behaviors can evolve where the ground squirrel is more likely to make an alarm call when in a family group. If such behaviors arise in a population, they are quickly favored by natural selection. Heritable variation: contributes to phenotypic diﬀerences and causes variations in ﬁtness Individual Selection: diﬀerential performance (ﬁtness) of individuals causes some genotypes to replace other genotypes Group Selection: diﬀerential performance of groups in individuals causes some groups to compete and replace other groups (very rare) for groups to outcompete other groups, they need cooperation, self-sacriﬁce, “living for the group” or “living through the good of the species” thinking population or cooperating individuals are not stable individuals with selﬁsh traits will be favored by natural selection selﬁshness will increase in a population yet, society and cooperation are common in nature Beneﬁts: increased vigilance, dilution eﬀect, enhanced defense capability, cooperative foraging/hunting, improved defense of critical resources Costs: increased conspicuousness to predators, increased competition for good, increase competitions for mates, decreased certainty of paternity/maternity, increased transmission of disease/parasites Examples of Group Selection African Wild Dogs In a pack of wild dogs, there are only one or two reproductive females. The rest of the pack helps to take care of the pups. african wild dogs hunt more eﬀectively as a pack and can take down bigger prey together White Fronted Bee Eaters in Africa Cornell research found out that they help each other more depending on how closely related they are Eusociality: non reproductive organisms help with rearing the young SEXUAL SELECTION Asexual Reproduction: oﬀspring derive from a single parent Recombination: the formation of new allelic combinations in oﬀspring; occurs during meiosis vie the crossing over btw homologous chromosomes in eukaryotes Other kinds of genetic exchange can function like sexual recombination (e.g. conjugation in bacteria) Sexual Reproduction: two parents contribute generic information Two Fold Cost of Sex: asexual organisms can multiply caster than sexual organisms Additional Costs of Sex: Requires ﬁnding an appropriate mate Parents are less related to their own oﬀspring Risk of contracting sexually-transmitted disease Sex is Common bc Helps purge deleterious mutations (Muller's Ratchet) in truly asexual lineages the entire genome is passed along as a unit btw generations and deleterious mutations accumulate This accumulation of deleterious mutations results in ever-increasing Genetic Load In sexual lineages, recombination allows unfavorable mutations to be purged by natural selection Sex combines of favorable mutations With sex: independent mutations can be brought together in recombinant oﬀspring Without sex: mutations must arise sequentially in the same lineage Promotes faster evolution (Red Queen Eﬀect) evolutionary arms race btw parasites and their hosts Sex allows for faster adaptation through reshuﬄing of genetic diversity (alleles) Anisogamy: the fusion of two dissimilar gametes leads to diﬀerent female and male investment females usually invest more sperm are cheap (small) and eggs are costly (large) males and females ﬁgger in certainty of parentage females usually have higher certainty sometimes females have specialized physiology for care of their oﬀspring Variance in reproductive success is generally higher among males than among females male’s have more variable reproductive success than females in most species there are more males than females available to mate results in a skewed Operational Sex Ratio competition btw males Females Males limited by their own energy and ability limited by access to females to produce eggs males that mate with more females often beneﬁt it they invest extra will generally sire more oﬀspring parental care Common strategies: mate with as more eggs = higher ﬁtness many females as possible, invest in common strategies: put energy into achieving more matings rather than in egg, wait to mate with sexiest male, oﬀspring care put time/care/energy into raising oﬀspring Sexual selection is a form of natural selection involving diﬀerential reproductive success among individuals, intrasexual: via competition with members of the same sex prediction: members of the sex under higher sexual selection will compete Intrasexual: male-male competition ﬁghting post mating: Sperm Competition females often mate with more than one male such that sperm from multiple males are competing for the same eggs best to produce as much sperm as possible or impregnate as many females as possible will see larger tested in species who partake in sperm competition bighorn sheep female-female competition wattled jacana bird intersexual: via attraction of member of the opposite sex prediction: member of the sex under weaker sexual selection will be choosy Intersexual female choice Occurs when individuals of one sex mate nonrandomly with members of the opposite sex bright colors elaborate morphologies particular courtship behaviors Females often choose males based on the beneﬁts they provide. Direct Beneﬁts (Table 11.2) Food Shelter Protection help Indirect Beneﬁts (Table 11.3) ‘Good Genes’ Arbitrary Choice (‘Runaway’) ‘Sexier sons’ General Patterns of Sexual Selection Usually stronger for males than females most NOT ALL of the time Stronger in more polygamous systems polygyny, promiscuous mating systems rather than monogamous Leads to traits that are costly to other ﬁtness components sexual dimorphism: both male-male competition and female choice a phenotypic diﬀerence in the male and females of a population morphology size ornamentation behavior Sexual conﬂict: when the interests of the two sex are opposed - the male bee that injects poison into the female while mating so she can’t mate with anyone else SPECIATION Speciation: the splitting of one group of interbreeding lineages into two metapopulation: a group of population that are connected by gene ﬂow phylogenetic species concept: focuses on the phylogenetic history of organisms biological species concept: deﬁnes species as a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups the biological species model particularly helps us focus on the process of speciation by an isolating barrier general lineage species concept: species are metapopulations of organisms that exchange alleles frequently enough that they comprise the same gene pool and the same evolutionary lineage Barriers to Gene ﬂow geographical barriers (extrinsic) mountains rivers, oceans, deserts physical separation that prevents gene ﬂow Allopatry - occurs when populations are in separate, nonoverlapping geographic area Physical isolation by vicariance Dispersal and Colonization reproductive barriers (intrinsic) mating preferences, hybrid incompatibilities evolutionary divergence prevents gene ﬂow Prezygotic isolating barriers that impeded gene transfer before sperm or pollen can be transferred to other species behavioral isolation: diﬀerences in behaviors that prevent members of diﬀerent species formatting, such s lack of attraction ecological isolation: isolating barriers that are by products of the ecology of diﬀerent species Mechanical Isolation: reproductive structures (genitalia, pollination structures) do not ﬁt together mechanically making it diﬃcult for fertilization to occur post mating: gametic isolation: Post-zygotic isolating barriers that impeded gene transfer after spermor pollen has been transferred to other species hybrid availability: hybrids die before or shortly after birth hybrid sterility physiological sterility: hybrids suﬀer problems in the reproductive system or gametes behavioral sterility: hybrid suﬀer neurological or physiological defects that prevent them from ﬁnding mates Ecological speciation - the evolution of reproductive barriers between population by adaptation to diﬀerent environment or ecological niches AKA Sympatric speciation Post-zygotic SELECTION ——————> Pre-zygotic forms can reproduce, but natural selection leads from forms don’t reproduce hybrid oﬀspring are inferior post zygotic to pre zygotic (don’t court or mate, (sterile or inviable) isolation, and formation of diﬀerent ﬂowering times) new species Hybrid Zones A hybrid zone exists where the ranges of two forms meet, interbreed, and create hybrid oﬀspring. These forms are populations that are genetically diﬀerentiated to some degree. Types of hybrid zones Secondary hybrid zone: Arises from secondary contact between two previously allopatric populations Primary hybrid zone: A primary hybrid zone is formed by selection on a previously homogeneous species across an environmental gradient Hybrid zones will create a cline in allele frequencies There will be a transition in the frequency of alleles, genotypes, or phenotypes along a geographical transect Clines can distinguish primary and secondary hybrid zones Clines for diﬀerent traits will not be concordant Clines will reﬂect diﬀerent types of ecological gradients, which are unlikely to overlap exactly Neutral traits will not show a cline Hybrid zones can form through two distinct processes (1) through secondary contact following a period of allopatry (secondary) (2) in situ during parapatric speciation (primary) Reinforcement - the increase of reproductive isolation between hybridizing forms through selection against hybrid oﬀspring Ecomorph: species with the same structural habitat/niche, similar in morphology and behavior - do not cluster together, meaning that they are not closely related - species on the same island generally cluster together, meaning they are closely related For a species to arise, something has to prevent or strongly limit between populations (extrinsic or intrinsic) speciation 2 Adaptive Radiation: when an ancestral species diversiﬁes into many descendant spaces that occupy diﬀerent environment habitats can be triggered by: - evolution of a new adaptation - vacated niches - specialization absorptive heterotrophy: a process that involves secreting digestive enzymes into the environment Convergent evolution: Diﬀerent groups of organisms can independently evolve similar traits by adapting to similar environments Opisthokonts: Fungi Paraphyletic: Eukarya that aren’t animals, fungi, or plants. Saprobic Fungi take up nutrients from non living organic matter important decomposer enzymes digest cellulose, lignin, keratin Parasitic Fungi take up nutrients by parasitic interactions obligate facultative plants are hosts of choice cordyceps create zombie ants Predatory Fungi fungi can be active predators by secreting digestive enzymes from their hyphae adhesive constricting ring Mutualistic Fungi symbiotic mutualism: when two species are in close association and both parties beneﬁt fungi (and photobiont) and lichen Microsporidia unicellular, tiniest eukaryotes aquatic Highly reduced fungi No functional mitochondria called mitosomes Intracellular parasites of animals Insects, crustaceans, ﬁshes responsible for amphibian population crashes chytrids paraphyletic group aquatic single or multicellular chytrids funges: responsible for amphibian population crashes Dikarya sac fungi (Ascomycota) morels, most yeasts, lichen synapomorphy: the ascus (cell where meiosis occurs) contains several fungal rock stars morel mushrooms Saccharomyces cerevisiae: baking and brewing industries (not to men7on molecular developmental biology) Penicillium chrysogenum, producer of penicillin Candida albicans, cause of thrush, diaper rash Cryphonectria parasitica, chestnut blight Club fungi (Basidiomycota) true fungi: mushrooms … edible and poisonous synapomorphy: the basidium (cell in which meiosis occurs) Arbuscular mycorrhizal fungi crucial economically for plants world wide Arbuscules: site of nutrient exchange have infected 90% of plants penetrate cell wall but not plasma membrane fungus gets the products of photosynthesis plant gets increased surface area for soil nutrients/moisutre Blastula bilaterians diploblastic 2 cell layers radial triploblastic 3 cell layers bilateral Collar cells also found in basal Animals; never in other Protists, Plants or Fungi! Sponges multicellular, composed of an aggregation of specialized cells body with pores, atria, and an osculum that serve for passage of water aquatic no symmetry no organs, true tissue, or nervous system spicule skeleton made from CaCO3, protein spongin or silica Eumetazoans: Diploblasts true tissue symmetrical body plan gastrodermis (endoderm) Epidermis (ectoderm) Comb Jellies ciliated ctenes- cilia bearing plates complete digestive tract simple life cycle Cnidarians jellies, anemones, corals aquatic polyp stage and medusa stage able to reverse back to polyp stage—> immortal jelly most life spent in diploid stage incomplete gut synapomorphy: cnidocytes (explosive stinging/adhesive cells) use a muscular bell that surrounds the blind gastrovascular cavity to move tradeoﬀs polyps: promote survival and maintenance of local populations bc they can reproduce without a mate but they limit the ability to disperse Medusae: may enhance dispersal probability and population Animals - Lophotrochozoans lophophore: ring of ciliated tentacles around the mouth use to ﬁlter food particles out from the water trochophore: band of cilia used for movement in larvae ancestral features lost in many lineages bryozoans, brachiopod, pharonoid Bilateral Protostomes Flatworms incomplete digestive tract bilateral triploblasts aceolomate no specialized circulatory/respiratory organs hermaphroditic parasitic ﬂatworm no central body cavity — assimilate bilateral symmetry one opening for mouth and anus depends entirely on host so devotes most energy to reproduction hermaphroditic penis fencing free-living ﬂatworm (planaria) no internal body cavity nervous tissue clusters eye spots lacks circulatory system mouth on the under belly also used for waste tapeworms no digestive system head with hooks and suckers body composed of proglottids parasitic longest human tapeworm is over 100 feet Annelids earthworm ﬂuid ﬁlled coelom allows for increase in size and activity in organism rigidity and movement synapomorphy: segmented animals, each separated by a septum chitinous setae closed circulatory system transport nutrients, blood cells and gases around the body blood is enclosed at all times within vessels (closed system) ventral nerve chord digestive tube with 2 openings, mouth and anus Setae: bristles used for locomotion hermaphroditic clitellum: used for the transfer of sperm coelomates Mollusks foot: large muscle used for locomotion bivalves use it for digging instead bilateral coelomates synapomorphy radula: tongue mantle: cloaks visceral mass that houses important organs open circulatory system: tissue is bathed in ﬂuid called hemolymph cephalopods have closed mostly free living hermaphroditic and separate sexes gastropods one shell (snails) gastropod torsion: twisting of the mantle cavity adaptations to avoid fouling incurrent and excurrent siphon and left gill variation in shell shape nudibranchs: sea slugs who go through torsion and detorsion Bivalves two shells: include clams, oysters, mussels, scallops two siphons Cephalopods agile predators squids and octopuses siphon, tentacles, vertebrate like eyes intelligence Animals: Ecdysozoans Arthropods segmented bodies some fused together to form more specialized segments like with ants synapomorphy: jointed appendages (foot) antennae: sensing mouthparts: tasting claws: grabbing food walking legs Abdominal appendages – swim, holding eggs, mating Reduced coelom/open circulatory system Hemocoel/hemolymph Developed ventral nervous system brain, ventral nerve cord, segmental ganglia Exoskeleton of chitin secreted by the underlying epidermis Costs: non expandable molting of cuticle required for growth heavy with increasing size vulnerable after molting Beneﬁts structural suport water loss protection Ecdysis (molting): the shedding of an old cuticle Insects coleoptera (beetle) Lepidoptera (butterﬂy) diptera (ﬂy) Hymenoptera (bee/wasp) 3-part body: head, thorax, abdomen Antennae Reduced number of walking lets to 6 3 pairs of legs acached to thorax wings Tracheae extend from spiracles Metamorphosis Early development starts with an egg and post-embryonic development involves dramatic changes in form. Each stage between molts is called an instar. Complete metamorphosis 88% of insects Growth stage (larva) Diﬀerentiation (pupa) Adult Incomplete metamorphosis No pupa stage good bc you can have a specialized niche for each body form giant insects? lower oxygen levels the larger and animal grows the greater the distance required for oxygen to be transported to the internal tissue Nematodes have a complete digesBve tract (THIS IS TRUE!) D. Nematodes are pseudocoelomates (ALSO TRUE!)
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