Population Structure

population
a group of individuals of the same species living in the same place at the same time
-potentially interbreeding
-potentially immortal population
-unit of evolution
properties: individual vs population
-simply add
genotype —> gene pool
sex ——–> sex ratio
age ——–> age structure
location —-> distribution
emergent properties: individual vs population
size ———> population size
growth rate—>population growth
distribution
-area that individuals occupy
-affected by abiotic factors, biotic factors, and chance
dispersion
-spacing of individuals
1. even – uniform resources, – interactions, rare
2. random – uniform resources, indifferent, rare
3. clumped – not uniform resources, + interactions, most common
demography
study of age structure and growth of a population
cohort
a group of individuals who enter a population at the same time
age structure
-reproductive bell curve
-pre-reproductives, reproductives, post-reproductives
survivorship – lx
-probability of an individual surviving from age 0 to age X
-ie. life expectancy has increased in Sweden
X vs. log lx
Type I – land w/ steep cliff, western civ human populations
Type II – constant decline, ie. bird populations
Type III – sharp drop at first then leveling off, lots of young die but once you reach a certain age you’ll probably make it, ie. insects, marine invertebrates, plants
fecundity – bx
# of female offspring per adult female of age X
iteroparous
multiple offspring and continuous breeding
iteroparous
discrete breeding – only during breeding seasons
semelparous
only reproduces once
lifetable
X lx bx lxbx

-add all lxbx values together and you get Ro which is the net reproductive rate or the average # of offspring a female will have throughout her life