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LIFE HISTORY EVOLUTION - viviparous species have 20-100...

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LIFE HISTORY EVOLUTION For each organism a story can be told about how it makes a living. Most of the traits that are part of this story have genetic bases and they contribute to fitness in some way. Usually in the context of life history strategies fitness is discussed in the context of different growth rates . New mutations that alter the growth rate-related traits of organisms should lead to the evolution of new life histories. A few stories: the agave plant lives for many/several years in the harsh desert environment and when sufficient rain occurs it sends up a tall reproductive structure, flowers, seets seed and dies. The codfish after reaching sexual maturity may produce a million eggs in a reproduction, and do so over several seasons; species of salmon forego reproduction until a late age, swim up current in certain rivers/streams, sink all of their digestive tract and much of their muscle mass into eggs in one reproductive effort, and die. Marine invertebrates:
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Unformatted text preview: viviparous species have 20-100 offspring, primitive brooders have 100-1000 eggs/offspring, species with no parental care have 1000-500,000,000 eggs (Aplesia, sea slug). How these different species achieve these feats is one question (a physiological one). Why they do it is a very different one and difficult to answer. We address this question by analyzing life history strategies. | Best done by considering components of life history 1) survivorship and 2) reproduction . Two further questions: 1) what is the best relative allocation of resources to each of these components, 2) what is the best timing of reproduction? G. C. Williams suggested that there is a trade-off between survival and reproduction: if one puts more resources into survival then there are fewer resources remaining for reproduction . Conversely, reproduction is costly and will reduce survivorship in subsequent years and reduce the future reproductive output....
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