Chapter 24 outline - Chapter 24 The Origin Of Chapter...

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Unformatted text preview: Chapter 24 - The Origin Of Chapter Species Species 12/03/09 12/03/09 1 Introduction Macroevolution is the origin of new taxonomic groups. (i.e. new species, genera, families, kingdoms) (i.e. Speciation (2 types), or the origin of new species, explains this because all taxonomic groups are created from a new species that cannot be categorized by a higher taxon. higher Anagenesis (phyletic evolution) – accumulation of heritable changes in a population that leads to a new species. species. Cladogenesis (branching evolution) - a new species arise from a population that buds from a parent species. arise 2 12/03/09 12/03/09 What is a species? Species – A class of individuals that share common characteristics and are grouped according to morphology (body form/appearance), body functions, biochemistry, behavior, and genetic makeup. behavior, Biological Species Concept – A species is a population or group of populations whose members have potential to interbreed to produce viable offspring, but not with other species. (Relies on the concept of reproductive isolation by factors or barriers) 12/03/09 12/03/09 3 Prezygotic Barriers Prezygotic barriers impede species or hinder fertilization of ova if members of different species attempt to mate (5 types) species 1. Habitat Isolation – Two species that are 1. Habitat located in the same area live in different habitats and do not meet and 2. Behavioral Isolation – Special signals and 2. Behavioral unique behavior that attract mates prevent different species from courting 12/03/09 12/03/09 4 Prezygotic Barriers Cont. 3. 3. Temporal Isolation – Two species that breed Temporal during different times of the day, season, or year, cannot mix their gametes year, 4. Mechanical Isolation – Anatomical 4. Mechanical incompatibility of sexual organs prevent different species from reproducing species 5. Gametic Isolation – Gametes of different 5. Gametic species will rarely fuse to form a zygote species 12/03/09 12/03/09 5 Postzygotic Barriers Postzygotic barriers – prevent the hybrid zygote of different species from fully developing (3 types) types) 1. Reduced Hybrid Viability – Genetic 1. Reduced incompatibility may abort development during some embryonic stage and fail to reach sexual maturity maturity 2. Reduced Hybrid Fertility – If hybrids are 2. Reduced sterile, genes cannot flow back to parent species sterile, 3. Hybrid Breakdown – Offspring of first3. Hybrid generation hybrids are feeble or sterile 12/03/09 12/03/09 6 Alternate Concepts Ecological Species Concept – view a species in terms of its ecological niche terms Pluralistic Species Concept - uses reproductive isolation or adaptation to an ecological niche, or both Morphological Species Concept - defines a species by a unique set of anatomical features (mainly used) by Genealogical Species Concept - defines a species as a set of organisms with a unique genetic makeup 12/03/09 12/03/09 7 Modes of Speciation Two Two modes of speciation based on how gene flow among populations is initially interrupted flow 1. Allopatric Speciation – A population forms a 1. Allopatric new species while geographically isolated from parent population 2. Sympatric Speciation – A small population 2. Sympatric becomes a new species without geographical isolation from parent population (biological factors such, i.e. chromosomal changes and nonrandom mating that reduce gene flow) nonrandom 12/03/09 12/03/09 8 Polyploidy Polyploidy Polyploidy – mutant condition in which extra sets of chromosomes result during cell division cell Autopolyploid – individual that has more than 2 chromosome sets, all derived from a single species single Allopolyploid – species with multiple sets of chromosomes derived from different species species 12/03/09 12/03/09 9 Tempo of Speciation Fossil Fossil record shows many episodes when species suddenly appear, persist through several strata, and apparently disappear several Punctuated Equilibrium – species diverge in spurts of relatively rapid change instead of a steady pace of Long Long periods of stasis punctuated with rapid speciation speciation 10 12/03/09 12/03/09 Speciation to Macroevolution Speciation Speciation is the boundary between micro and macroevolution macroevolution Microevolution – change over generations in a population’s allele frequencies population’s Macroevolution – change over millions of speciation episodes speciation Speciation occurs when a population’s genetic Speciation divergence from its parent population results in reproductive isolation. This accumulation of changes leads to macroevolution changes 12/03/09 12/03/09 11 Speciation to Macroevolution Cont. Charles Charles Darwin: “descent with modification” – most complex structures gradually evolved from simpler versions of the same function the Exaptions – Structures that evolve in one context but become co-opted for another function function 12/03/09 12/03/09 12 Evolution of the Genes That Evolution Control Development Control Genes that program development control the rate, Genes timing, and spatial pattern of changes in organisms timing, Allometric Growth – Proportioning of the body through different growth rates for different parts of the body the Heterochrony – Evolutionary change in the rate of timing of development timing Paedomorphosis – Condition in which the organism Paedomorphosis retains juvenile structures at sexual maturity due to a change in timing of reproductive development relative to somatic development (caused by heterochrony) 12/03/09 12/03/09 13 Changes in Spatial Pattern Evolutionary Evolutionary change can also result from alteration of in genes that control placement alteration Homoetic genes determine where structures are Homoetic located on an organism located Hox genes provide positional information in an Hox animal embryo (product of homoetic genes) animal Changes in temporal and spatial development Changes have played big roles in macroevolution have 12/03/09 12/03/09 14 ...
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This note was uploaded on 12/02/2009 for the course SCI 90210 taught by Professor Durkka during the Spring '09 term at École Normale Supérieure.

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