Chapter 5 Populations

Biotic Potential: The size a population would reach if all offspring were to survive and reproduce

Conditions have to be ideal- enough food and living space

Population Density- Number of individuals in an area What Determines density and distribution?

Geographic Distribution- range- the area the population inhabits

Population Growth Affected by -Birth rate (natality) -Death rate (mortality) -Immigration- entering an area -Emigration- leaving an area

Populations increase if births exceed deaths and immigration exceeds emigration

Exponential Growth Exponential Growth occurs when the individuals in a population increase at a constant rate Look at graph on p.121

-under ideal conditions -population grows slowly at first -rises to an infinitely large size -J-shaped curve

Logistic Growth Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth. S-shaped curve-graph levels off

Carrying capacity- Usually population fluctuates around this point- s-shape Look at graph on p. 122

Carrying Capacity The number of individuals an area can support without ruining the area.

Limiting Factors Something that causes population growth to decrease Density dependent Density independent

Density- Dependent Factors Limit a population when the number of individuals reach a certain level Competition for food, water, space, sunlight, etc.

Predation Parasitism + disease

Wolf/Moose graph

Density -Independent Factors Affect all populations regardless of size Weather, natural disasters, seasonal change, human interventions (dams,logging, housing developments)

Populations usually decrease dramatically after such an event Can be permanent + cause extinction

Human Population Growth Slow growth historically Now, exponential growth- 6-7 billion Current World Population

Some countries have higher growth rates than others

Demographic Transition Dramatic change in birth and death rates Nutrition, medicine, clean water supplies increase survival rates

Some countries, population stabilizes, but for a while, births may exceed deaths

Age diagram

In some cases, populations may even decrease- U.S., Japan, Europe

Some countries are still growing exponentially Parts of Africa, Mexico, India

Many young people, of an age where they will still be having children

9 billion predicted by 2050 What will stop/slow the growth?