Transcript Populations

Chapter 5
Populations
Section 5.1 How Populations Grow
Section 5.2 Limits to Growth
Section 5.3 Human Population Growth
Section 4.1 Population Dynamics
Compare
&
contrast
Relate
Predict
exponential and linear
population growth.
the reproductive patterns of
different populations of
organisms to models of
population growth.
effects of environmental
factors on population growth
What is a Population?
• One species
spread over it
geographic range
(all areas it lives)
• Density # in
population within
the geographic
range
• 3 types:
1) Random
2) Uniform
3) Clumped
Population Growth
•
1)
2)
3)
4)
5)
Growth Rate is effected
by several factors:
Age Structure
number of
males/females and
their ages
Birthrate number of
babies born a year
Death rate number
of deaths a year
Immigration
members entering
the range
Emigration members
leaving the area
Types of Population Growth
Exponential Growth:
• As a population
gets larger, it also
grows at a faster
rate
• Always the
growth rate after
a succession or a
new species is
introduced
J-shape growth
Type of Population Growth
Logistic Growth:
• After exponential
growth slows down
as resources
become limited
• Growth flattens out
at maximum
possible population
size (carrying
capacity)
S-shape growth
Limits to Growth
Carrying capacity
The number of organisms of one
species that an environment can
support indefinitely is its carrying
capacity
When a population overshoots the
carrying capacity, then limiting
factors may come into effect
Limits to Growth
Limiting Factor any
factor that limits a
populations size
• Food, predators,
space, water, etc..
2 Types:
• Density-Dependent
• Increase/decrease
with population’s
size
• Density-Independent
• Size of population
has no affect
Density-Dependent Limiting Factors
1) Competition
• More members the more
food/water that is
required
• Kills off weaker members
2) Predation
• Prey and Predator
numbers are effected by
each other
3) Overcrowding
• Stress of crowds weakens
immune systems and
increases fighting
4) Parasitism and Disease
• Overcrowding spreads
disease faster
Density-Independent Limiting Factors
1) Weather Patterns
• Ruin food supply
• Run out of fresh
water
• Limit time to
hunt/reproduce
2) Natural Disasters
• Massive lowering of
population numbers
• Change the
ecosystem
• Remove important
food supply
Human Population Growth
• Human’s used to have a very
high birthrate but also a very
high death rate
• Today the birthrate is 4
babies a second but the
death rate is much lower
• What factors lowered our
death rate?
• Food supply, medicine,
civilization, etc…
Demographic Transition
Demography study of
human populations
Periods of Growth:
1) High birth and death
rates in unstable
environments
2) Lowering of death
rates as environment
becomes more stable
3) Birthrates fall to meet
death rates as
resources become
limited
Age Structure’s Effects on Growth
• Populations with
high numbers teens
and young adults will
lead to fast massive
growth
• Large number in the
older generation will
have slower growth
• Most stable growth is
having near even
numbers in all age
groups
• Read Ch. 6; You have another
presentation coming up
• Ch. 6 vocabulary
• Ch. 5 “Apply Vocab” and
questions #1-16 on p. 123-124