Two opposite-sex animals can produce {mating}| offspring by uniting sperm and egg. Sexual reproduction allows more variation and more sexual selection.
polygamy
Animals can have more than one mate. Polygamy is typical, because parental investment in children is typically unequal. Abundant food at least once a year, heavy predation, precocious young, greater longevity, different gender maturation ages, and different gender niches favor polygamy. High competition for mates leads to polygamy and mate monopolization. Polygamous species tend to have high sexual dimorphism.
monogamy
Animals can have one mate. Monogamy is rare. Monogamy happens in territories with scarce resources that require two animals to maintain or defend. Monogamy happens in difficult environments. Monogamy happens in species with early breeding. Monogamous species tend to have low sexual dimorphism.
Mating {breeding}| related individuals {inbreeding, alleles} tends to pair recessive alleles. Mating unrelated individuals {outbreeding} mixes alleles more.
Species can choose mates for good survival characteristics {selective breeding}|. High competition for mates leads to polygamy and mate monopolization.
Organisms select mates {sexual selection}|. Sexual behaviors tend to resist social evolution.
males
Sexual behaviors can be strategies to ensure that parent has conceived cared-for offspring. For males, sexual selection can involve keeping other males away from females, to prevent reproduction. Males can transmit more genes if they produce more females, rather than males.
males: displays
In many species, male pattern and behavioral displays lure females. Displays are fewer if food is scarcer or predators are more numerous.
females
For females, sexual selection involves selecting mates. Species with more receptive females have less fighting among males. Females can transmit more genes if they produce one male.
4-Biology-Evolution-Reproduction
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Date Modified: 2022.0225