Topic 10 Flashcards
Age structure
number of different age classes + the number of individuals in each age class
Age class
discrete group of individuals for at the same time
Cohort
individuals that make up an age class
Important because different age classes have ..
different birth and death rates. age classes contribute different numbers of offspring to the population
Birth rate
number of female offspring produced per female in particular age class
Number of offspring produced will differ ..
among age classes (sexual maturity)
Primarily concerned w females because..
- birth rate is limited by number of females
- difficult to quantify contribution of each male
Death rate
number of females that die per age class in the population
Number of individuals dying will ..
differ among age class
Survivorship curves
number of individuals alive (log scale) versus age. 3 hypothetical curves, few populations fit one precisely
Birth (b) and death (d) differ amount..
age classes so each age class contributes to population size differently
Population 1
same number of individuals in all age classes. pop. size increase if birth > death
Population 2
only pre reproductive adolescents and adults to old to breed. pop size decrease if death> birth
Life table
tabulation of b and d rates of each age class in a population. allows us to quantify whether the size of a population is increasing, stableor decreasing
Cohort life tables (dynamic)
follow one cohort (indivs. w an age class) from birth to death determine d and b in each age class,
Example cohort life tables
plants, sessile animals, mobile animals where dispersal is limit.
Difficult to use cohort life table because
you cannot track high mobile animals, can take a long time to collect the data.
Static life tables (time specific)
snapshot of the population at one point in time. estimate d by terming the age specific survival independently for each age class at a specific time.
Example of static life tables
high mobile animals.
Difficult to use static life tables because
hard to determine the ages of all individuals. can use stage or size classes if age cannot be determined.
Underlying assumption of static life tables is stable age structure which =
number of individuals in each age class remains the same though time
Ignore the variation of..
b and d amount individuals in an age class (ex size, competitive ability, social status)
To construct a cohort life table we need to..
collect all the data
