Please enable JavaScript.
Coggle requires JavaScript to display documents.
Population Part 2 (ch 8/9 cont.) (Demographic characteristics (Sex ratios…
Population Part 2 (ch 8/9 cont.)
Demographic characteristics
Abundance
Age structure (old or young)
Can provide insight in the ecology and history of the population
recruitment (production of new individuals by birth)
Fecundity (Juvenile females vs breeding females)
Fertility (Number of live offspring produced during a life time)
Realized fertility vs. potential fertility
How many babies actually produced vs how many potential babies
Fecundity/Fertility is usually inversely related to amount of parental care given to young
Sex ratios (reflects is history of survival, reproduction, and growth potential)
Primary
Sex ration at fertilization
Secondary
Sex ratio at birth or hatching
Quaternary
Sex ration of the adult population
Tertiary
Sex ratio at sexual maturity
Reproduction variations
Mortality
Why they died and what age
Realized longevity (Actual lifespan living under real-life conditions)
potential longevity (maximum lifespan by an individual determined by physiology (what is dying of old age?))
Estimating survival
Summarizes pattern of survival in a population
Variations occur between populations of the same species and within the population themselves
Estimated through record books of survivorship and deaths
Methods
Cohort life table-identify individuals born at the same time (called a cohort) and keep track from birth until death
This is the most reliable
However
It is time consuming
animals are mobile
finding young may be difficult
Some species live forever
Static life table-record age at death
short time frame
however
Age of death is an estimate, from rings on horns and shells
Animals are tagged (think hunting)
Survivorship curves
Type 1
Low survival in young, high survival until old age -convex curve(think mammals)
Type 2
Constant across ages-diagaonal line (think birds)
Type 3
Mortality is high, but decreases in older age- concave curve (think plants)
Notes about survivorship curves
Habitat quality can affect the curve
Can differ between sexes
Definitions
Life expectancy- the expectation of life at a certain age, affected by the probability to die at different ages
Life span-the maximum number of years an individual can potentially live
Effective population size-the number of individuals that can actually breed
Smaller populations are more likely to go extinct
Stochastic events
demographic
environmental
catastrophe
genetic