Chapter 14

Chapter 14 - Slide 1 Chapter 14: The Origin of Species...

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Unformatted text preview: Slide 1 Chapter 14: The Origin of Species Species Concept • What makes a species a species? • Most scientists use the reproduction concept: if two organisms can mate and produce fertile offspring, then they are considered the same species Slide 2 Slide 3 Culex “pipiens” vs. Culex pipiens molestus “London Mosquito” London Underground Slide 4 Mosquito Wars? • 1999: University of London • Concluded the two were separate species because they could not interbreed • Thought C. molestus living underground represented speciation • Concluded that C. molestus evolved from C. pipiens Slide 5 Mosquito Wars? (cont.) • 2004: The United States • Performed study to determine which type of mosquito transmitted West Nile Virus • Did genetic studies on 7 mosquito species from around the world • Determined that C. molestus and C. pipiens were so genetically different that one did not evolve from the other Slide 6 Mosquito Wars? (cont.) • 2004: The United States • Also determined that 40% of the mosquitoes in North America had genes from both species! • They are able to interbreed? • The carrier between birds and people? Slide 7 Mosquito Wars? (cont.) • The point? • “Species” is a difficult to define concept • Influenced by behavior, geography, and genetics Slide 8 Taxonomy • Taxonomy: The branch of biology concerned with classifying and naming life • Father of taxonomy: Carolus Linnaeus (1700s) • Developed “binomial nomenclature” (Genus species) for species names • Named over 11,000 species • Used Greek and Latin to describe physical characteristics • Homo sapiens = “wise, human being” Slide 9 Slide 10 Are physical characteristics sufficient? Eastern Meadowlark Western Meadowlark Sturnella magna Sturnella nelecta Slide 11 Are physical characteristics sufficient? Species Concepts 1. Biological species concept 2. Morphological species concept 3. Ecological species concept 4. Phylogenetic species concept Slide 12 Biological Species Concept • Species population(s) of organisms capable of interbreeding and producing fertile offspring Slide 13 Morphological Species Concept • Species based on observable and measureable phenotypic traits Slide 14 Ecological Species Concept • Species based on an organism’s ecological role Slide 15 Phylogenetic Species Concept • Phylogenetic (Tribe, Race, Birth) is the study of evolutionary relatedness among groups of organisms (e.g. species, populations), which is discovered through molecular sequencing data and morphological data matrices. The term phylogenetics derives from the Greek terms phyle (φυλή) and phylon (φῦλον), denoting “tribe” and “race”; and the term genetikos (γενετικός), denoting “relative to birth”, from genesis ( γένεσις) “birth”. • Species organisms with a unique genetic history Regardless, reproductive isolation is still going to be necessary to maintain separate species Slide 16 Reproductive Barriers • If two species cannot interbreed, what causes it? • Two main categories of reproductive barriers: 1. Prezygotic barriers 2. Postzygotic barriers Slide 17 Prezygotic Barriers 1. Temporal isolation 2. Habitat isolation 3. Behavioral isolation 4. Mechanical isolation 5. Gametic isolation Slide 18 Temporal Isolation • Breeding takes place at different times (not in the mood at the same time) Slide 19 Temporal Isolation (cont.) Slide 20 Eastern spotted skunk: breeds in late winter Western spotted skunk: breeds in fall Temporal Isolation (cont.) Monterey Pine: pollinates in February Bishop’s Pine: pollinates in April Slide 21 Habitat Isolation • Species live in the same general area, but not the same specific place Slide 22 Habitat Isolation (cont.) Garter snake living in water Slide 23 Garter snake living on land Behavioral Isolation • Little or no sexual attraction between the females and males Slide 24 Behavioral Isolation (cont.) Slide 25 Mechanical Isolation • Male and female sex organs are not compatible Slide 26 Mechanical Isolation (cont.) Slide 27 Mechanical Isolation (cont.) Slide 28 Gametic Isolation • The gametes won’t unite to form a zygote Slide 29 Postzygotic Barriers 1. Hybrid inviability – zygote does not survive 2. Hybrid sterility – offspring are sterile 3. Hybrid breakdown – hybrids can reproduce, but their offspring don’t survive Slide 30 Mechanisms of Speciation 1. Allopatric speciation 2. Sympatric speciation 3. Adaptive radiation Slide 31 Reproductive Barriers (summary) Slide 32 Zygote Gametes Prezygotic barriers Postzygotic barriers • Temporal isolation • Habitat isolation • Behavioral isolation • Mechanical isolation • Gametic isolation • Hybrid inviability • Hybrid sterility • Hybrid breakdown Viable, fertile offspring Allopatric Speciation • Allopatric speciation: occurs when gene flow between populations is blocked by geography Slide 33 Allopatric Speciation (cont.) Slide 34 Allopatric Speciation in the lab Initial sample of fruit flies Starch medium Maltose medium 22 9 8 20 Mating frequencies in experimental group Different Same Female Starch Maltose Male Maltose Starch Male Results of mating experiments Female Same Different population populations 18 15 12 15 Mating frequencies in control group Slide 35 Slide 36 Slide 37 A pupfish Sympatric Speciation • Sympatric speciation: occurs when reproductive isolation develops and a new species arises without geographic isolation • Common in plants • Often happens because of errors during meiosis Slide 38 Slide 39 Adaptive Radiation • Adaptive Radiation: evolution of many new species from a common ancestor that was introduced to a new and diverse environment Slide 40 Tempo of Speciation • Two views on how fast new species have appeared: 1. Gradualism 2. Punctuated equilibrium Slide 41 Slide 42 Gradualism Time Punctuated Equilibrium Time Slide 43 Slide 44 ...
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This document was uploaded on 02/08/2012.

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