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BIOA02H3 (153)
Chapter 23

Chapter 23

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University of Toronto Scarborough
Biological Sciences

Chapter 23 Species and Their Formation Sex stimulates speciation (among other things) -Charles Darwin said sexual selection was the cause for evolution conspicuous trait in species -ex. larger antler of male deer -enlarged tail feathers of male peacock -traits are exaggerated in species in which individuals of one sex (usually male) compete to mate with opposite sex -exaggerated trait evolves in competition among males for access to female attracting discriminating females -sexual selection can also increase rate of new species form -comparison of the number of species found in sister clades (same ancestor) suggests development of new species from sexual selection -in promiscuous mating system, male bird evolved bright plumage and ornament (long tail feathers), female raises its child with no help from male -in monogamous species, members form pair bond and share responsibilities of raising the young -individuals of both sexes have dull plumage and look alike -sexual selection stimulates divergence of a lineage into many species -random mutation results in different physical characteristics 23.1 What Are Species? We can recognize and identify many species by their appearance -Linnaeus developed morphological species concept -classification of species on the basis of their appearance Species form over time -speciation is process by which one species splits into two or more daughter species, which evolve as distinct lineages -process is gradual -when the two populations at various stages become new species, it is impossible to decide whether individual belongs species 1 or 2 -reproductive isolation is when individuals of a population mate with one another, but not members of the other population -constitute distinct group in which genes recombine -become independent evolutionary unit, separate branches on the tree of life -Marys definition of species, biological species concept is: Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. -actually means individuals live in the same area and interbreed with one another -potentially means although individuals do not live in the same area (cannot interbreed), but they would interbreed if they get together -does not apply to organisms that reproduce asexually -reproductive isolation is one element to identify species www.notesolution.com
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