1. Ch 5- Population Why do populations change?
There are 3 important characteristics of a population- Geographic distribution, density and growth rate
Geographic distribution- the area inhabited by a population
Population density- number of individuals per unit area
Depends on species and its ecosystem

2. Population Growth What factors affect population size?
# of births, # of deaths, and # of individuals that enter and leave the population
Immigration- the movement of individuals into an area
Emigration- the movement of individuals out of an area
What causes these movements?
Young animals reach maturity search for mates, shortage of food

3. Exponential Growth
Individuals in a population reproduce at a constant rate
Under ideal conditions with unlimited resources, and in the absence of predation and disease, a population will grow exponentially

4. Logistic Growth
A population’s growth slows or stops following a period of exponential growth
Why might this happen?
Resources become less available
Carrying capacity- the largest number of individuals that a given environment can support
Many natural populations follow the logistic growth curve

5. Sec 2- Limits to Growth
Limiting factors- factor that causes population growth to decrease
A resource can also affect long term survival of a species
Pandas
Density-dependent factors- limiting factor that depends on population size
Factors greatly affect large and dense populations
Factors include; competition, predation, parasitism, and disease

6. Competition may occur between individuals of same species or of different species
The more individuals the faster the resources are used up
Competition between different species leads to evolutionary change
Predation- often controls populations in nature
Moose populations rise, wolves population soon rises. Moose populations soon decrease, later followed by the decline in wolves
Parasitism and disease- range in size, similar to predators, take nourishment from host, weakening or causing death to them

7. Density-Independent Factors- affect all populations in similar ways, regardless of population size
Unusual weather
Natural disasters
Seasonal cycles
Certain human activities- clearing forests, damming rivers
Environments are always changing, most populations can adapt to certain amount of change

8. Sec 3- Human Population Growth
Like populations of many other living organisms, the size of the human population tends to increase with time
Think back to early human existence, how has human populations increase?
Can the human population keep growing exponentially forever?
Are birthrates, death-rates, and age structure the same in every country?

9. Demography- scientific study of human populations
Demographic transition- dramatic change in birth and death rates
Change from high birthrates and high death rates to low birthrates and low death rates
What causes changes?
Birth rates exceed death rates, advances in nutrition, sanitation, and medicine. Population increases rapidly. Societies modernize, people have less kids, population growth slows
Age Structure diagrams- shows the population of a country by gender and age
Can predict future growth
Future Population growth- world population will continue to rise but at a slower rate