BIOL 1442: Lecture 5 Chapter 24: The Origin of Species
BIOL 1442: Lecture 5 Chapter 24: The Origin of Species Biol 1442
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This 4 page Class Notes was uploaded by Jasmine Rodriguez on Thursday September 8, 2016. The Class Notes belongs to Biol 1442 at University of Texas at Arlington taught by Jill Devito in Fall 2016. Since its upload, it has received 3 views. For similar materials see Ecology and Evolution in Biology at University of Texas at Arlington.
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BIOL 1442 Lecture 5 Ch. 24 The Origin of Species ________________________________________________________________________________ Chapter 24: The Origin of Species Learn how to read a phylogenetic tree 1) All of them have a common ancestor 2) Three exist today 3) Loxodonta Africana (Africa) and Loxodonta cyclotis (Africa) 4) Elephas maximus (Asia) 5) 6 million years ago Clade – a branch on the tree of life, including all descendants of a common ancestor (but not including anyone else) 6) B, C, E Species a group (of organisms) whose members possess similar anatomical characteristics and have the ability to interbreed A composite definition Biological Species Concept population whose members can interbreed in nature to produce viable, fertile offspring with each other, but not with members of other populations Morphological Species Concept defining species by measurable anatomical criteria The old way of distinguishing species Still used, but in conjunction with other methods Just based on appearance Paleontological Species Concept based on morphological differences known only from the fossil record Neanderthals were considered a diff. species from humans b/c of anatomy We now know that humans are mostly hybrids of human and Neanderthals Ecological Species Concept defining species in terms of ecological roles (niches) Phylogenetic Species Concept – a species as a branch on the tree of life with an ancestor Macroevolution sometimes leads to speciation favors intermediate variants by acting against both extremes Anagenesis accumulation of heritable changes alters the typical phenotype for the species over generations “ana” = up “genesis” = origin, birth Cladogenesis branching evolution leads to new species (this requires reproductive isolation) When one species evolves into many different species over time Happens when diff. populations of the same species are isolated and therefore adapt differently to diff. environmental pressures “Clado” = branch “Genesis” = origin, birth Allopatric Speciation ancestral population segregated by geographic barrier (divided into two or more geographically isolated populations) “Allo” = different “Patric” = lands Galapagos Finches Adaptive Radiation Galapagos finches have evolved in many different directions (and some of these are not very “finchy”) Video resulting adaptations Galapagos finches Robust beak for larvae Needle like bill for insects Longer pointed beak for cactus Different beaks for “different jobs” One single common ancestor that traveled to the Archipelago led to the 13 species of finches that each adapted to diff lifestyles Different finches sound different Sound and appearance (only mating with finches that look the same) affect whether two finches mate Prezygotic Barriers – are evolutionary adaptations that prevent hybridization before fertilization Habitat isolation – live in different areas so they don’t meet and therefore don’t mate Temporal Isolation – active at different times of day, year, or breeding season Behavioral Isolation – distinct color and courtship display can prevent hybridization (many birds, frogs, insects) Mechanical Isolation – structural differences in genitalia may prevent accidental sperm transfer (many plants, insects, spiders) Gametic Isolation – inability of sperm to fuse with ovum of other species (e.g. chemical barrier as in sea urchins) Postzygotic are biological accidents that can result in decreased or zero fitness Not an adaptation Consequence of hybridization Reduced Hybrid Viability – hybrid offspring does not develop properly (most organisms) Reduced Hybrid Fertility – hybrid F1 offspring may be healthy but cannon reproduce as easily as their parents Hybrid Breakdown – future generations are less viable (some ornamental garden flowers, crops: cotton, rice Mules are unsuccessful because of the diff. number of chromosomes so gametes are not produced correctly Hybrid of these two mallards was not fit because no female of either species would mate with him Adaptive Radiation emergence of numerous species from a common ancestor (in an environment that presents a diversity of new opportunities and problems) Ecological Niche the unique environmental role of a species (every resource that it uses, and all aspects of its habitat that allow it to thrive) Video – “Empty” niches provide the potential for diversification; where (or when) would such opportunities arise? B/c if it already is occupied by a species, it would be hard to compete with an already adapted species. Islands emptied by natural disaster or if a species was wiped out of an environment Four different lizards (anoles) in puerto rico Separated vertically The different layers have diff. environments that require diff. adaptations Ground lizards have longer legs so they can run faster in order to catch prey Twig lizards have shorter legs in order Each species has a different dewlap – probably changed because of the different conditions of their environments On nearby islands, lizards evolved with similar body types independently Ecological Forces can shape diversification