Population Growth, Limiting Factors & Natural Resources

KEY CONCEPT Populations grow in predictable patterns.

Changes in a population’s size are determined by immigration, births, emigration, and deaths. The size of a population is always changing. Four factors affect the size of a population. immigration births emigration deaths

Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources.

Logistic growth is due to a population facing limited resources.

Carrying capacity is the maximum number of individuals in a population that the environment can support. A population crash is a dramatic decline in the size of a population over a short period of time.

Ecological factors limit population growth. A limiting factor is something that keeps the size of a population down. Density-dependent limiting factors are affected by the number of individuals in a given area.

Density-dependent limiting factors are affected by the number of individuals in a given area. predation competition parasitism and disease Usually biotic factors

Density-independent limiting factors limit a population’s growth regardless of the density. unusual weather natural disasters human activities Usually abiotic factors

Human Population Growth Demography- the study of human population growth characteristics. Studies : Growth Rate – how fast the population is increasing (due to more births & immigration) A population’s growth rate is the difference between the birth rate and death rate. Birth rate higher than death rate = population growth Death rate higher than birth rate = decrease/decline in population Age Structure-proportions of a population that are at different age levels. Geographic Distribution – location of population, density in areas Fatality Rate – death rate

Mobility and Populations Immigration-movement into a population. Contributes to an INCREASE in the population (populations grow when: birth rate + immigration > death rate + emigration) Emigration-movement out of a population. Contributes to a DECREASE in a population (populations decline when: birth rate + immigration < death rate + emigration)

KEY CONCEPT As the human population grows, the demand for Earth’s resources increases.

Earth’s human population continues to grow. Earth’s human carrying capacity is unknown.

Technology has helped to increase Earth’s carrying capacity. gas-powered farm equipment medical advancements

The growing human population exerts pressure on Earth’s natural resources. Nonrenewable resources are used faster than they form. coal oil

Renewable resources cannot be used up or can replenish themselves over time. wind water sunlight Growing use of nonrenewable resources may lead to a crisis. Resources must be properly managed.

Effective management of Earth’s resources will help meet the needs of the future. Earth’s resources must be used responsibly. Careless use of resources makes them unavailable to future generations. Easter Island is an example of irresponsible resource use.

An ecological footprint is the amount of land needed to support a person. The land must produce and maintain enough food and water shelter energy waste

Several factors affect the size of the ecological footprint. amount and efficiency of resource use amount and toxicity of waste produced