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The sizes of reproductive cells in sexual reproduction.
Female gametes are larger than male gametes. This is not an empirical observation, but a definition: in a system with two markedly different gamete sizes, we define females to be the sex that produces the larger gametes and vice-versa for males (Parker et al. 1972), and the same definition applies to the female and male functions in hermaphrodites. Although asymmetry in gamete size rather than number is usually used as the defining characteristic, size dimorphism has the almost inevitable consequence that females produce fewer gametes than males due to a simple physical trade-off – larger things can be produced in smaller numbers, given a limited amount of resources. Therefore, in practice females differ from males in terms of both gamete size and numbers. This definition of the two sexes is a very simple one, yet it leads to some intricate, surprisingly...
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