Biological Diversity BSCI 10110 1 MWRF 1 10 2 00 Dr Mark Kershner Week 4 9 21 Speciation 1 Populations of a single species become different due to reproductive isolation ecological temporal and or geographical change over time of gene frequencies traits genetic differences genetic drift Fig 22 5 leopard frogs geographical isolation behavioral isolation mating calls different hybridization experiments in lab no successful embryos Speciation by Genetic Drift Hawaiian fruit flies Drosophila species 1000s species Hawaiian Islands Fig 22 13 fixed become part of the genome by non random natural selection OR random courtship rituals that separate them temporal isolation among species different time of year different times of day habitat isolation only mate on particular plants founder effect as new islands form they re colonized by taxa from other islands Speciation by Natural Selection populations diverge during process of adaptation Anoles Fig 22 7 dewlaps are colorful do push ups have served as forms of behavioral isolation used primarily for courtship territoriality 2 Other isolation mechanisms evolve maintaining those differences natural selection to avoid hybridizing costs to these events young are not as fit reinforcement Fig 22 6 because individuals who consistently do not hybridize offspring increased fitness How long does speciation take speciation is more likely when they are geographically isolation allopatric founder effect geographical barrier arises some population may go extinct leaves remaining populations further apart probably takes a long time natural selection and or genetic drift Papuan kingfishers Fig 22 9 New Guinea 9 23 Speciation allopatric geographic isolation separation between among populations random genetic drift non random natural selection sympatric no geographical isolation species populations occur together other forms of reproductive isolation kick in much less common because gene flow occurs high likelihood of mating reduces divergence snails shell population of snails and find a few left handed snails vast majority are right handed coiling is driven by a single gene mutation left can mate with left right can mate with right unlikely that left can mate with right mechanical isolation divergence of gene pool result in speciation event genetically incompatible takes a long time true fruit flies Tephritidae Rhagoletis species exceedingly host plant specific relative to breeding Hawthorn female lays eggs on a specific species of Hawthorn eggs maggots adult flies mate strictly on Hawthorn trees colonization of North America apple trees at some point some flies mated strictly on apple trees speciation due to behavioral isolation and ecological isolation now distinct species cannot produce viable offspring instantaneous sympatric speciation mutation dead end sometimes survive and reproduce polyploidy offspring have more than two sets of chromosomes meiosis problem they can mate sometimes tetraploids very common in plants Adaptive radiation extremely rapid production of many new species common in systems with few species present and plenty of resources food habitat diversity generally newly formed systems Hawaiian Islands fruit flies younger islands because of resource diversity competition for food is not critical because they can switch food types African cichlids Great Rift Lakes evolved into many foraging niches How does speciation proceed Gradualism Fig 22 17 Punctuated Equilibrium change occurs gradually intermediate forms present short bursts of change associated with speciation Fig 22 17 9 24 Fig 22 17 Fig 22 18 5 mass extinctions most recent 65 million years ago Chicxulub crater Yucatan dust cloud circled earth for 6 months to 6 years blocked sunlight iridium plants will die reduced forage increased detritivores temperature decreases decrease ectotherms cold blooded increased endotherms mammals Systematics and Phylogenetics Chapter 23 Fields of biology process of speciation order of speciation historical evidence of natural selection how did traits change over time classification use common ancestry to group organisms What is systematics What is phylogenetics method of classifying living extinct organisms within an evolutionary framework system of naming based on evolutionarily important similarities and differences technique for reconstructing evolutionary history based on direct evidence of common ancestry based on shared trait can t study this diversity without some systematic ways of grouping classifying and naming Goals 1 inventory catalog of all living things 2 develop universal system for classifying naming things taxonomy 3 determine evolutionary relationships among organisms phylogenetics Fig 23 2 Vertebrates phylogenetic tree vertebrae jaws lungs amniotic membrane in eggs mammals hair lactation tail loss bipedal 9 25 important assumptions 1 Closely related species are more similar to each other than to unrelated species descendant species are similar to ancestral species 2 similarities differences are heritable organisms near each other on the tree are more closely related to each other Phylogeny tree depicting a hypothesis regarding how organisms are related to each other convergent evolution such as wing presence can invalidate assumptions Fig 23 11 while moving through the tree time is increasing traits early in the phylogeny are ancestral characteristics later in the phylogeny are derived characteristic after this it is a shared derived characteristic all traits are derived from common ancestor in order to understand bird evolution we need to understand ancestors characteristics order Tree of Life Chapter 26 Naming Binomial nomenclature Two name genus species Homo sapiens Domain kingdom phylum class Capitalize genus never species Always written in italics or underlined order family genus species Linnean Hierarchy idea of domain developed by Carl Woese Domain Common Ancestor Bacteria Archaea Eukarya Bacteria and Archaea prokaryotes lack membrane bound nucleus organelles Eukarya eukaryotes possess membrane bound organelles Archaea more closely related to Eukarya than Bacteria Domain Eukarya membrane bound organelles Kingdom Animalia nervous systems Phylum Chordata vertebral column backbone Class Mammalia hair lactation Order Primata five fingers toes thumb Family Hominidae bipedalism no tail Genus Homo Species sapiens Domain Bacteria Kingdom Bacteria no membrane bound organelles single celled disease infections Kingdoms Humans
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