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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
exponential and linearpopulation growth.
Relate
the reproductive patterns of different populations of organisms to models of population growth.
Predicteffects 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) Random2) Uniform3) Clumped
Population Growth• Growth Rate is effected
by several factors:1) Age Structure
number of males/females and
their ages2) Birthrate number of
babies born a year
3) Death rate number of deaths a year
4) Immigration members entering the range
5) Emigration members leaving the area
Types of Population Growth
J-shape growthExponential 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
Type of Population Growth
S-shape growthLogistic Growth:•After exponential growth slows down as resources become limited•Growth flattens out at maximum possible population size (carrying capacity)
Carrying capacity
Limits to Growth
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 GrowthLimiting 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 Factors1) Competition
• More members the more food/water that is required
• Kills off weaker members2) 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 Factors1) Weather Patterns• Ruin food supply• Run out of fresh
water• Limit time to
hunt/reproduce2) 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 TransitionDemography study of human populationsPeriods of Growth:1)High birth and death rates in unstable environments2)Lowering of death rates as environment becomes more stable3)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