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BIOL 4120: Principles of Ecology Lecture 8: Life History Patterns

Life History . Life history is species lifetime pattern of growth, development and reproduction.Measure of organism's reproductive success is fitness: Those individuals who leave the largest number of mature offspring are the most fit the environments.Trade-off between growth and reproduction: mod

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BIOL 4120: Principles of Ecology Lecture 8: Life History Patterns

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    1. BIOL 4120: Principles of Ecology Lecture 8: Life History Patterns Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

    2. Life History Life history is species lifetime pattern of growth, development and reproduction. Measure of organism’s reproductive success is fitness: Those individuals who leave the largest number of mature offspring are the most fit the environments. Trade-off between growth and reproduction: mode of reproduction, age at rep., allocation to rep. number and size of eggs, young or seeds, parental care.

    3. Life History Patterns 8.1 Reproduction may be sexual or asexual 8.2 Sexual reproduction takes a variety of forms 8.3 Mating systems 8.4 Mate selection 8.5 Females may acquire mates based on resources 8.6 Organisms budget time and energy to reproduction 8.7 Species differ in the timing of reproduction 8.8 Parental investment 8.9 Fecundity depends on age and size 8.10 Food supply affects the production of young 8.11 Reproductive effort may vary with latitude 8.12 Habitat selection influences reproduction success 8.13 Environmental conditions influence the evolution of life history characteristics

    4. 8.1 Sexual or Asexual Reproduction Asexual reproduction (produce offspring without involving of egg and sperm) New individuals are the same as the parent Many plants (underground stem) such as strawberry; some animals (hydra, some aphids, parthenogenesis) If fitness is high, matches organism to environment If fitness is low, possible extinction (less variation) Stress can result in use of sexual cycle to give new gene combinations (hydra, aphid) Sexual Reproduction More common form. Can produce new gene combinations able to cope with a changing environment. Greater energy commitment Specific organelles Production of gametes, courtship activities, and mating are energetically expensive. Feeding offspring The expense of reproduction is not shared equally by both sexes

    5. 8.2 Types of sexual reproduction Dioecious Sexes are separate individuals Greatest diversity of offspring Hermaphroditic Perfect Male and females organs in same flower Can result in significant inbreeding Monoecious Separate male and female flowers Reduces but does not eliminate inbreeding

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