Ch 24 - The Origin of Species (1 slide per page)-1

G evolution of increased brain size in ancestral

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Unformatted text preview: r, ancestral spp is extinct • e.g. Evolution of increased brain size in ancestral human spp • But, how different is different? Both processes important in speciation • Parental spp does not immediately go extinct • Only via branching evolution can species increase in number • e.g. Adaptive radiations • e.g. birds’ ancestors split off from other reptiles 49 49 51 51 General process of speciation via Cladogenesis 3 pops of 1 spp connected via gene flow Barrier to gene flow separates 1 population (i.e. no interbreeding) Populations diverge genetically (i.e. Evolution) Reproductive barrier (incompatability) develops between pops i.e. A new species Figure 24.14 (Campbell et al 9th ed) 52 52 Cladogenesis Speciation Mechanisms 1. Allopatric speciation – (very common) geographic separation restricts gene flow between two populations 2. Sympatric speciation – (very rare) biological factor creates two populations in the same area with reduced gene...
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