Mating Systems

Mating Systems - The Biology of Mating Systems and Parental...

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The Biology of Mating Systems and Parental Care
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Why Have Sex?
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Some Species Get By Without It Some very successful groups do not reproduce sexually every generation, these include aphids, parasitic wasps, mites, certain crustaceans, the majority of vascular plants, etc. A diverse collection of species never reproduce sexually; the whiptail lizards Cnemidophorus sp. , certain gekos, the stream fish Pocelliopsis sp. , the common dandelion Taxacum oficiale , At Least One Entire Phylum Never Reproduces Sexually, the bellidoid rotifers (small freshwater invertebrates) never reproduce sexually.
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Why Pass on Half Your Genes, When You COULD Pass on ALL of THEM? Like all human and animal behaviors, sexual reproduction evolved by natural selection. Natural selection favors individuals that pass on their genes to the next generation. In most species, however, males contribute nothing but sperm to reproduction. A parthenogenic female should have a distinct advantage, she passes on twice as many of her genes with each offspring.
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The asexual route, pictured to the left, propogates twice as many of the female’s alleles.
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Sex is Expensive Sexual displays and rituals can be enormously expensive in terms of energy, time, and resources. Example: male bower birds in Australia spend weeks constructing enormous “bowers”, which they decorate with found objects, solely for the purpose of attracting mates. Female water striders are “ridden” by the males after copulation, sometimes for many hours. This process interferes with the foraging of females and places them at increased risk of some forms of predation.
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Sex is Dangerous Seeking mates is dangerous for many species: Example; tree frogs in Central America call to attract mates. Females are strongly attracted to the calls, it is much easier to get a mate if a frog invests a lot of time calling. Carnivorous bats are also attracted to the calls. They come in on the calling male and pluck them right off of the tree. Calling crickets suffer a similar situation. Calling males are much more attractive, but parasitic flies home in on the sound and deposit their eggs into singing males.
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Reasons a SPECIES benefits from Sex Recombination provides the genetic diversity necessary for the survival of the species “The “Red Queen Hypothesis” Without recombination, mutation can drive an asexual species extinct-”Muller’s Rachet”.
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The “Red Queen” hypothesis Even species that do not seem to be changing are undergoing rapid evolution. This is because the natural world is so challenging that, without constant evolution, species go extinct. Sex and recombination provide the necessary variation that keeps evolution going…without constant evolution, pathogens, competitors, and environmental change would lead to the extinction of all species.
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Muller’s Ratchet Without occasional recombination, mutation alone can drive an asexual species
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Mating Systems - The Biology of Mating Systems and Parental...

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