Transcript Honors Population Notes

III. Populations
A. Population
1. Members of a species that live in the same area at
the same time
2. Population Growth
a. Immigration – when organisms move in
b. Emigration – when organisms leave a
population (exit)
c. Migration – seasonal movements into and out
of an area (ex: Turkey Vultures)
B. Carrying Capacity
1. Definition - the largest population size a given
environment can support
2. Enough food, water & shelter for all (Happy #)
3. Depends on size of ecosystem & amount of
resources
C. Limiting Factors of populations –
1. Definition – any environmental factor
that causes a population to decrease
2. Density Dependent Factors - factors
that depend on population size
a. Food supply, predation, disease
b. Show a “S shaped” growth curve
3. Density - Independent factors - factors that
affect the same amount of a population
regardless of size
a. natural disasters (flood, fire, etc.),
climate change, human disturbance
(habitat damage)
b. Show a Rise and Crash (Boom & Bust)
growth curve
D. Population growth patterns
1. Exponential Population Growth – growth
where each generation is much greater than
the last
a. Any population can grow very quickly
in the “perfect environment”
b. Perfect environment is rarely there,
resources are limited
example – this classroom
c. J shaped curve on graph (Lily Pads!)
(pg. 115)
2. Logistic Growth – a population’s initial
exponential increase is slowed and finally
stopped by limiting factors
a. eventually reaches a point where birth
and death rates are almost equal
*at this point there is little
population growth – numbers stay
right around carrying capacity
b. Show a “S shaped” growth curve
*start growing VERY fast then slow
as numbers reach carrying capacity
(pg. 115)
E. Determining Population Size (pg. 105)
1. Direct observation – count every member of
a population
Example – crabs in tide pool
– students in class
2. Indirect observation – count signs of organisms
Example – nests of cliff swallows
– Count lockers of students
3. Sampling - count the number of organisms
(sample) in a small area then multiply
to estimate the total population
Example – students in HMS by classroom
4. Mark & Recapture –
a. Take a sample, “tag” & release
b. Re-sample at a later date.
c. Keep separate count of marked &
unmarked organisms.
d. Use a formula to estimate total
population.
Example –turtles in a bay