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Life History

Life History. Populations vary as a result of the life history features of their members. Life history refers to the schedule of certain important events that occur during the life of an organism. Life history traits are genetically controlled and are the result of natural selection .

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Life History

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  1. Life History Populations vary as a result of the life history features of their members. Life history refers to the schedule of certain important events that occur during the life of an organism. Life history traits are genetically controlled and are the result of natural selection.

  2. What are the important life history features for these organisms? • Daphnia and rice?

  3. Important features of an individual’s life history include: • the age of sexual maturity • frequency of reproduction • # of offspring produced during each reproductive period

  4. Two important factors include: • Survivorship - the percentage of individuals in a population that live to a given age. • Fecundity - the average number of young produced by a female in her lifetime. A male Abedus water bug carries hatched and hatching eggs on his back.Stebbins Reserve, California, USA http://www.alexanderwild.com/Insects/Bountiful-Bugs/4191931_FWpfRM#1060843628_Nr4EJ

  5. Three Main Survivorship Patterns • Type I • Low fecundity, few young are born • High juvenile survival rates due to good parental care • Most individuals reach sexual maturity • Most of a cohort or age group reach “old age” • Examples include humans and elephants

  6. Three Main Survivorship Patterns • Type III • High fecundity, many offspring are born • High juvenile mortality rate due to little or no parenting • Few individuals survive to reproductive age • Examples include oysters Ridley’s sea turtle hatching in Florida http://remaxinteractive.wordpress.com/2011/09/13/new-turtle-hatching-is-here-on-the-spacecoast/

  7. Three Main Survivorship Patterns • Type II • Survivorship pattern in between type I and type III • Percentage of individuals dying is constant over all ages • Examples include hydra, and flies

  8. Antelope herds in Sudan Leech eggs on adult Compare the survivorship patterns and life history for these two organisms.

  9. Opportunistic Life History • Also called r-selection because the population has a high r value (high growth rate) • Often found in unstable environments • Organisms typically produce many young in a single burst of reproduction • Type III survivorship pattern

  10. Equilibrial Life History • Also called K-selection because it is found in populations near their carrying capacity (K) • Populations living in relatively stable environments • High density populations where individuals are highly specialized for survival • Type I survivorship pattern

  11. Life Tables • Ecologists summarize information in a life table • Life tables are organized by cohorts or large groups of individuals all born at the same time (see text p 496 Table 14.2) • The table could include age class, number of individuals in the cohort, survivorship, fecundity or mortality (the probablity of dying) • The data can also be shown in an age pyramid

  12. Age Pyramid

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