Download Ecosystems – Unit 2 - Reeths

Predator vs. Prey
• prey impacts predator population more
hunters kill 500,000
deer/year
predators switch prey
instead of starve
Act. 1 – lynx and hare
Act. 2 – pike and perch
Population density/distribution
(14.3, pgs. 436-439)
population density – how many
organisms live in a defined area
Population density/distribution
(14.3, pgs. 436-439)
population dispersion –
how the population is
spread out
clumped – for mating,
protection, or food spot
uniform – territory and
food competition
clumped
dispersion
uniform
dispersion
random
dispersion
Population density/distribution
(14.3, pgs. 436-439)
uniform
clumped
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)
S - curve
logistic growth –
slow growth, then
exponential growth,
then level off due to
resource limits
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