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Download Chapter 24 Origin of Species and Speciation
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Species The Origin of Species and Speciation Characteristics used to distinguish species Appearance, biochemistry, genetic makemake-up, behavior Speciation Figure 24.1 Two patterns of speciation The Biological Species Concept Different species can look a lot alike There can be a lot of variation within the species Figure 24.4 Reproductive Barriers Prezygotic barriers impede mating or hinder fertilization if mating does occur Habitat isolation Behavioral isolation Temporal isolation Individuals of different species Gametic isolation Mechanical isolation BEHAVIORAL ISOLATION Viable fertile offspring REDUCED HYBRID VIABILITY GAMETIC ISOLATION TEMPORAL ISOLATION (b) Hybrid breakdown Fertilization Mating attempt HABITAT ISOLATION Reduce hybrid fertility Reduce hybrid viability MECHANICAL ISOLATION (g) REDUCED HYBRID FERTILITY HYBRID BREAKDOWN (k) (j) (d) (m) (e) (l) (f) (a) (c) (h) (i) 1 Figure 24.3 Courtship ritual as a behavioral barrier between species species Morphological species Other species concepts Coral Snake Yellowjacket Scarlet King Snake Paleontological Ecological Phylogenetic Clearwing moth Figure 24.7 Allopatric speciation of squirrels in the Grand Canyon Figure 24.5 Two main modes of speciation (a) (b) Allopatric speciation Sympatric speciation. 2 Figure 24.8 Has speciation occurred during geographic isolation? isolation? Autopolyploidy Figure 24.14b The new primrose species of botanist Hugo de Vries Allopolyploidy Habitat and Mate choice in two species of Lake Victoria cichlids cichlids Adaptive Radiation 3 In Lake Victoria alone there are 300 species of cichlids that differ in color, size, shape, behavior and parental care. Figure 24.13 Two models for the tempo of speciation Today more than 100 of these are extinct due to various pressures such as the introduction of the Nile Perch a highly predatory animal and high levels of water pollution Time (a) Gradualism model. Species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations. (b) Punctuated equilibrium model. A new species changes most as it buds from a parent species and then changes little for the rest of its existence. 4
