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Date Created: 08/04/14
EVOLUTION SUMMARY TABLE 264 Evolutionary Processes DefinitionDescription Effect on Genetic Variation Effect on Average Fitness Natural selection Certain alleles are favored Can maintain increase or reduce genetic variation Can produce adaptation increasing f ness Genetic drift Random changes in allele Tends to reduce genetic variation Random with respect to fitness frequencies most important via loss or fixation of alleles usually reduces average fitness in small populations Gene flow Movement of alleles between May increase genetic variation Random with respect to fitness populations reduces differences by introducing new alleles may may increase or decrease average between populations decrease it by removing alleles fitness by introducing high or low fitness alleles Mutation Production of new alleles Increases genetic variation by Random with respect to fitness introducing new alleles most mutations in coding sequences lower fitness SUMMARY TABLE 263 Modes of Selection 1 NATURAL SECTION produces adaptation Effect on Genetic Mode of Selection Effect on Phenotype Variation II GENETIC DRIFT Directional selection Favors one extreme Genetic F d ff t phenotype causing variation is 0un er ec the average reduced Imm1grat1ng and starting a new population phenotype in the population to change in one direction Bottleneck effect only small part of population survive a Favors phenotypes Genetic h near the middle variation is p enomena of the range of reduced e t quotYP Vaquota v III NONRANDOM MATING mam amm avera e phenotype 9 only changes genotype frequencies but not allele frequencies Favors extreme Genetic phenotypes at both variation is 93 lnbreedlng ends of the range of increased increase homozygozity 39 he tV39 i Va a 39 accelerate natural selection causes inbreeding depression decrease in average fitness Balancing selection No single phenotype Genetic is favored in all variation is populations of a maintained IV MUTATION species at all times constantly creates heritable variation in all traits in all populations in every generation 1 Habitat FOSSIL RECORDS BIASES 2 Taxonomic and Tissue 3 Temporal 4 Abundance ADAPTIVE RADIATION A Ecological Opportunity new niches or resources 1 Competitors wiped out 2 Colonized a new region B Morphological Innovation allow a descendants to live in new niches SPECIATION 1 Genetic isolation lack of gene ow 2 Genetic divergence mutation drift selection SUMMARY TABLE 272 Three Most Common Species Concepts Criterion for Identifying Populations as Species Advantages Disadvantages Biological species Reproductive isolation between populations they don t breed and don t produce viable fertile offspring Reproductive isolation evolutionary independence Not applicable to asexual or fossil species difficult to assess if populations do not overlap geographically Morphospecies Morphologically distinct populations Widely applicable Subjective researchers often disagree about how much or what kinds of morphological distinction indicate speciation misidentifies polymorphic species misses cryptic species Phylogenetic species Smallest monophyletic group on phylogenetic tree Widely applicable based on testable criteria Relatively few wellestimated phylogenies are currently available if individuals from different populations do not have unique traits or genes then there are no synapomorphies and the populations represent the same species TABLE 271 Mechanisms of Reproductive Isolation PTOCBSS Example Prezygotic Isolation Temporal Habitat Behavioral Gametic barrier Mechanical Populations are isolated because they breed at different times Populations are isolated because they breed in different habitats Populations do not interbreed because their courtship displays differ Matings fail because eggs and sperm are incompatible Matings fail because male and female reproductive structures are incompatible Bishop pines and Monterey pines release their pollen at different times of the year Parasites that begin to exploit new host species are isolated from their original population To attract male fireflies female fireflies give a speciesspecific sequence of flashes In sea urchins a protein called bindin allows sperm to penetrate eggs Differences in the amino acid sequence of bindin cause matings to fail between closely related populations In alpine skypilots a flowering plant the length of the floral tube varies Bees can pollinate in populations with short tubes but only hummingbirds can pollinate in populations with long tubes Postzygotic Isolation Hybrid viability Hybrid sterility Hybrid offspring do not develop normally and die as embryos Hybrid offspring mature but are sterile as adults When ringnecked doves mate with rock doves less than 6 percent of eggs hatch Eastern meadowlarks and western meadowlarks are almost identical morphologically but their hybrid offspring are usually infertile a Allopatric speciation different location 1 Vicariance splitting of an existing range into fragments 2 Dispersal founder effect drift and selection b sympatric speciation Same land 1 external disruptive section adapting to different ecological niches 2 internal meiosis mistake reproductive isolation Red algae GREEN ALGAE Ulvophytes spores or I Coleochaetes zygotes encased in tough coat of Stoneworts sporopollenin NONVASCULAR PLANTS T Liverworts H Mosses Cuticle pores Homwons 4 M03 key Sl quot ala SEEDLESS VASCULAR PLANTS innovations Early vascular plants for living on f0SSquotS 0nlY land evolved T l YC0PhT93 only once True leaves 1 Vessel elements Wood evolved more than once Vessel elements 39 Vessel elements FIGURE 319 A Series of Evolutionary Innovations Allowed Plants to Adapt to Life on Land ADAPTATIONS of land plants Cuticle and stomata Vascular tissue S7 S rl S tquot Flowers 39 Whisk ferns Vascular tissue I Ferns Iili Roots tracheids Horsetails GYMNOSPERMS Ginkgo Cycads Redwoods et al Pines et al Gnetophytes ANGIOSPERMS Angiosperms Embryophyte condition gametangia Pollen protect sperm cell Seeds protect embryo SN139d N139 4 Red algae GREEN ALGAE Ulvophytes Coleochaetes Simple Stoneworts gametangia egg retention on parent NONVASCULAR PLANTS Livenivorts Mosses I I I I Thickwalled spores complex gametangia embryo retention alternation of generations T Hornworts SEEDLESS VASCULAR PLANTS Lycophytes Heterospory Whisk ferns Ferns I Sporophytedominated life cycle Horsetails GYMNOSPERMS Ginkgo Cycads Redwoods et al I Pines et al Heterospory pollen seeds Gnetophytes ANGIOSPERMS SLNV39d GEIEIS Ii Angiosperms Flowers and fruit FIGURE 3123 Evolutionary Innovations Allowed Plants to Reproduce Efficiently on Land SJNV39d I139l39IOS1A SLNVd NV39 Choanoflagellates Fungi ANIMAL Choanoflagellates Poriferal V E 2 T ANlMALlA A sponges I Multicellularity Ctenophora 1 comb jellies Cnidaria f iellyfish corals Fiquot I sea anemones we 7quot Diploblasty Acoela acoels 4q LOPHOTROCHOZOA T T Rotifera A rotifers Loss of 1 coelom Platyhelminthes flatworms Segmentation 39 Annelida gti TFD0baStV segmented worms 1 3 Protolstome Monusca gt 2 w deve opment snails clams Cggt i ylogeny of Major Animal tn g FIGURE 33 2 A Ph 39 39 sq 39 39quot E Phyla Based on DNA Sequence Data This 3 ECDYSOZOA phylogenetic tree IS based on similarities and Nematoda differences in the DNA sequences of several roundworms genes from various animal phyla The black bars along the branches indicate when certain IIIIII A h d Cephalization CNS coelom rt ropo a morphological traits originated Segmentation insects spiders J EXERCISE Recent work suggests that crustaceans segmentation may have arisen independently T within mollusks Add a Segmentation bar and DEUTEROSTOMES quot label to the tree to indicate this possibility Other Radial symmetry Echinodermata E research suggests that some of the basic toolkit in adults sea stars a genes for segmentation may have existed in the I sand dollars common ancestor to bilaterians only to be lost DeUter0St0me development I 3 in some lineages and elaborated upon in others Se mentation Chordata 33 Add a Tookit genes for segmentation bar 9 Ve391ebrates tunicates 4 and label to the tree to indicate this possibility ADAPTATIONS of animals 1 multicellularity cell binds and communications division of labor 2 tissue allows more complexity and aids in muscle movements a diploblasty b triploblasty i ectoderm skin and nervous system ii endoderm lining of digestive tract iii mesoderm tissues circulatory system internal structures 3 bilateral symmetry and cephalization able to respond more quickly and specialization 4 coelom hydrostatic skeleton movement 5 segmentation important for specialization
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