Ecology 2 Dec 5 2007 - Ecology 2 Life histories and Species...

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Unformatted text preview: Ecology 2: Life histories and Species interactions Lecture 12/05 Dr. Gurevitch I Life histories and strategies Fecundity curves, survivorship curves, life histories II Species Interactions Competition Predation/adaptations of predators and prey Parasitism and disease Mutualisms Different organisms have different life histories Def.: A life history describes the patterns of births, growth and survival over the course of life For example, fecundity (reproduction at each age) and survivorship (probability of death at each age) differ greatly among different organismsand even for the same species under different circumstances Fecundity curves Average births per female Age 10 4 5 45 cat human Survivorship curves: Type I, II and III Each species has a typical survivorship curvefor example, humans and elephants both have Type I curves, oysters have Type III curves Human survivorship curves have changed over time (light to darker green), and also differ between developed and developing countries most efforts of modern medicine infant mortality Life histories are shaped by evolution Life histories are acted upon by natural selection and are shaped by evolution Age of first reproduction, number of offspring per birth or clutch, number of times reproducing, lifespan all have to work together in a particular environment as a packageno one way works best Agaves reproduce once, then die Oaks reproduce every year for many years Tortoises reproduce late in life and live for many years Aphids reproduce early in life and live for a short time Characteristics of human life histories: Very long juvenile period, late age at first reproduction One offspring (rarely more) per birth Huge parental investment in offspring High rates of survival for offspring...
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Ecology 2 Dec 5 2007 - Ecology 2 Life histories and Species...

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