Life HistoryPopulations 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.

Daphnia and rice?

What are the important life history features for these organisms?

the age of sexual maturity frequency of reproduction # of offspring produced during each reproductive period

Important features of an individual’s life history 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.

Two important factors include:

A male Abedus water bug carries hatched and hatching eggs on his back.

Stebbins Reserve, California, USAhttp://www.alexanderwild.com/Insects/Bountiful-Bugs/4191931_FWpfRM#1060843628_Nr4EJ

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

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

Three Main Survivorship Patterns

Ridley’s sea turtle hatching in Florida

http://remaxinteractive.wordpress.com/2011/09/13/new-turtle-hatching-is-here-on-the-spacecoast/

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

Three Main Survivorship Patterns

Antelope herds in Sudan

Leech eggs on adult

Compare the survivorship patterns and life history for these two organisms.

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

Opportunistic 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

Equilibrial Life History

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

Life Tables

Age Pyramid