Predator vs. Prey • prey impacts predator population more
hunters kill 500,000 deer/year
predators switch prey instead of starve
Act. 1 – lynx and hareAct. 2 – pike and perch
Population density/distribution (14.3, pgs. 436-439)
population density – how many organisms live in a defined area
clumpeddispersion
uniformdispersion
randomdispersion
population dispersion –
how the population is spread out
Population density/distribution (14.3, pgs. 436-439)
clumped – for mating, protection, or food spotuniform – territory and food competition
Population density/distribution (14.3, pgs. 436-439)
clumped
uniform
Population density/distribution (14.3, pgs. 436-439)
Type I – big mammals (black bear)• few young (1-3), lots of care
Type II – small mammals, birds, rabbits• more young (4-12), less care
Type III – insects, parasites• thousands of young, no care
Population density/distribution (14.3, pgs. 436-439)
Population growth patterns (14.4, pgs. 440-444)
Factors that affect populations:1. immigration – species moving in
2. emigration – species moving out
3. birth rate – goes up when habitat is good
4. death rate – goes down when habitat is good
Population growth patterns (14.4, pgs. 440-444)
exponential growth – rapid population growth due to abundant resources (pennies)
J-curve
Australia: 24 were brought in 1859 for sport hunting, but enough food, and no good predators = 200-300 million today
Population growth patterns (14.4, pgs. 440-444)
logistic growth – slow growth, then exponential growth, then level off due to resource limits
S - curve
Population growth patterns (14.4, pgs. 440-444)
carrying capacity - average # supported by an ecosystem; environment quality can change capacity
population crash - dramatic decline• when above carrying capacity• weather related possibly• fire• new species that messes things up
Population growth patterns (14.4, pgs. 440-444)
limiting factors – factors that keep population down
1. density-dependent factors: are affected by the population of individuals; when above capacity• competition, predation, parasitism and disease,
starvation
2. density-independent factors: not related to population; can happen anytime
• unusual weather, natural disasters, human activity