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Concept 54 - in which an individual produces a large number...

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Concept 52.2 Life history traits are products of natural selection Natural selection favors traits that improve an organism’s chances of survival and  reproductive success. In every species, there are trade-offs between survival and traits such as frequency of  reproduction, number of offspring produced, and investment in parental care. The traits that affect an organism’s schedule of reproduction and survival make up its  life history. Life histories are highly diverse, but they exhibit patterns in their variability. Life histories entail three basic variables: when reproduction begins, how often the  organism reproduces, and how many offspring are produced during each reproductive  episode. Life history traits are evolutionary outcomes reflected in the development, physiology, and  behavior of an organism. Some organisms, such as the agave plant, exhibit what is known as  big-bang reproduction,
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Unformatted text preview: in which an individual produces a large number of offspring and then dies. This is known as semelparity. By contrast, some organisms produce only a few offspring during repeated reproductive episodes. This is known as iteroparity. What factors contribute to the evolution of semelparity versus iteroparity? In other words, how much does an individual gain in reproductive success through one pattern versus the other? The critical factor is survival rate of the offspring. When the survival of offspring is low, as in highly variable or unpredictable environments, big-bang reproduction (semelparity) is favored. Repeated reproduction (iteroparity) is favored in dependable environments where competition for resources is intense. In such environments, a few, well-provisioned offspring have a better chance of surviving to reproductive age....
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