Transcript population growth patterns

14.2 Measuring and Modeling
Population Change
• Read p.660 – 670
• Practice Questions!
– P.664 #1
– P.665 #2
– P.668 #3, 4
Carrying capacity
• The maximum number of organisms that
can be sustained by available resources over
a given period of time
"population dynamics," and the main
natural determinants.
-
changes in population characteristics
natality (birth rate)
mortality (death rate)
immigration
emigration
Biotic potential
• maximum reproductive rate under ideal
conditions (or, intrinsic rate of natural
increase)
• Example: Under ideal conditions, a population of
bacteria can grow to more than 10 in 24 h.
• Limiting Factor: the name applied to an essential
resource that is in short supply or unavailable, and
prevents an organism from achieving this potential
Fecundity: theoretical maximum number
of offspring that could be produced by a
species in one lifetime
– Example: Mice have the ability to produce over a dozen
offspring every 3 weeks.
Fertility: the number of offspring actually produced
by an individual during its lifetime, affected by food
supply, disease, mating success, etc.
Factors limiting reproductive
potential include:
•
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•
Migration
Disease
Food availability
Mating success
Population change
[(births + immigration) (deaths + emigration)] x100
initial population size
CLOSED POPULATION
• A population whose growth is influenced only by
natality and mortality
OPEN POPULATION
• A population whose growth is influenced by natality,
mortality and migrations
the equation used to calculate the
population change of an open
population.
the equation used to calculate the
population change of a closed
population.
SURVIVORSHIP CURVES
Type I Survivorship
• A population showing low
mortality rates until the
individuals are past their
reproductive years
• Example: Elephants are slow
to reach sexual maturity and
have few offspring.
Type II Survivorship
• These species show a uniform risk of
mortality during their lifetime.
• An example is birds, where predation is a
constant concern, but some level of parental
care is given for a time.
Type III survivorship pattern
• A population with very high
mortality rates among the young
and very low mortality rates
among sexually mature adults
• Sea turtles are an example: a
female lays hundred of eggs each
year, but less than 1% survive to
adulthood. Those that do can live
for hundreds of years.
POPULATION GROWTH
MODELS
Geometric growth
• A population that grows
rapidly during breeding
season, then declines through
the year until the next
breeding season
• Exponential growth occurs
under ideal conditions. Ex:
when a population is first
starting out and resources are
plentiful
Exponential growth
• reproduction is continuous throughout year
(i.e., no breeding season)
• constant growth rate
• examples: yeast, bacteria, humans
Logistic growth
• As population continues to grow, food,
water,light and space can limit population
growth.
• When the carrying capacity is reached,
reproduction slows and the death rate
increases.
• Equilibrium is reached.
• Logistic growth represents the effect of the
carrying capacity on the growth of a
population.
• Is the most common growth pattern in
nature.