Chapter 5 Populations Section 5.1 How Populations Grow Section 5.2 Limits to Growth Section 5.3...

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