lesson18 - 18 The Monogamy Myth Key Terms and Concepts o o...

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18 The Monogamy Myth Key Terms and Concepts o Monogamy o Polygyny o Polyandry o Promiscuity o Polygynandry o Serial monogamy o Resource defense polygyny o Female defense polygyny o Male dominance polygyny o Biological markers o Body size ratio o Maturation rate ratio o Reproductive variance o Polygyny threshold Mating systems analysis is concerned with the distribution of mates within a population. Each individual has a finite reproductive capacity (number of offspring that can be produced in a lifetime), and this capacity is a resource that can be utilized by opposite-sex individuals. The study of mating systems is concerned with how this reproductive resource is distributed: with one other individual (monogamy) or with more than one (polygamy). The variations here are numerous, however, so we will begin with a classification of mating systems and a review of the ecological conditions that apparently contributed to their evolution. Lesson 18 209
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A Classification of Mating Systems Monogamy . Monogamy is the condition in which one male is mated with only one female. To the extent that there is mating with other individuals other than the mate, monogamy may grade into the other systems described below. Only about 3% of mammalian species are monogamous, but more than 90% of all bird species are monogamous. No single characteristic defines monogamy, but the following characteristics tend to occur together in monogamous species: First, male and female reside together in the same home range or territory. Second, there is exclusive or nearly exclusive mating between the paired male and female. Finally, both parents are involved in care of offspring. The other mating systems differ from monogamy in one or more of these characteristics. Monogamy seems to occur when two full-time parents are required to care for the offspring. In most birds, the mother and father bring food to the nestlings, share incubation duties, and so on. The chances of survival of the offspring are substantially reduced if either parent dies or fails to assist in offspring care. Monogamy is usually compared with a variety of mating systems in which individuals have more than one mate. Collectively, these other mating systems are referred to as polygamy . Let’s take a look at these other mating systems. Polygyny . Polygyny is the mating system in which a male is mated with two or more females. Polygyny occurs because some males are able to exclude other males from breeding. Thus, in polygynous populations there are usually more unmated males than unmated females (the latter are usually quite rare). Males can exclude other males in three basic ways, described below. (1) Resource defense polygyny . If the resources needed for reproduction are clumped in the habitat, the potential exists for some males to acquire and defend that resource against other males, while allowing access to females in exchange for mating privileges. An example of resource defense polygyny comes from the bee Anthidium maculosum
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lesson18 - 18 The Monogamy Myth Key Terms and Concepts o o...

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