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Lecture 9

Biology 2483A Lecture Notes - Lecture 9: Exponential Growth, Life Table, Fecundity

Course Code
BIOL 2483A
Hugh Henry

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Unit 3: Populations Lesson 9: Population Growth and Regulation (Oct. 5th 2017)
Life Tables Show How Survival and Reproductive Rates Vary with Age, Size, or Life Cycle Stage:
Use life table to see how populations change.
Can vary with size, age or life cycle stage.
Life yle stage is’t eessarily orrelated ith size ad age.
Age is appropriate for most organisms.
Demography study of the vital statistics of populations and how they change over time:
o Fecundity (Fx): average number of offspring produced by females aged x.
o Survival rate (Sx) chance that an individual aged x will live to age x+1.
X ould e easured i ay tie, represetatie of the orgais you’re
o Survivorship (Ix): proportion of individuals that survive form birth to age x.
o Nx: number alive at age x.
o Cohort: group of individuals born during the same time period.
o Cohort life table: follow a cohort from birth until the last one has died:
Short lived and non moving animals.
Followed form birth, know the age.
o Static life table: collect demographic information from individuals of different ages:
Long lived and moving animals.
Not followed from birth, have to estimate age.
Survivorship curves:
o Type 1 most individuals survive until old age (K-selected).
o Type 2 individuals have a constant change of dying throughout their lives (K-selected).
o Type 3 most individuals die young (r-selected).
o Can vary:
Among cohorts, populations and between sexes.
Life Table Data Can Be Used to Predict Future Characteristics of a Population:
Can use the life tables to predict the future of the population.
Use the age structure:
o Age structure proportion of individuals in each age class.
Juvenile pre-reproductive
Adult reproductive
Adult post-reproductive
If young populations are high, then there will be an increase in population.
0 growth if the number of young equals the number of adults.
Age structure diagrams are not perfect predictors of future population size; birth and death
rates can change if the environment changes.
o Temperature and weather are able to change the rates of organisms
o The amount of water available is less than the amount of water it needs.
Mortality goes up.
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