POPULATION GROWTH NOTES

Module 2 Ecology

Growing rapidlyTripled in size in about 70 yearsEst. size to day 6 billion+ (approx. 2 billion in 1930)

Human Population

Problems cause by humans

Thinning ozone layer – ozone layer protects living things from ultraviolet radiation form the sun

Climatic changes Greenhouse effect: insulates earth from the deep

freeze of space; keep Earth warm Caused extinction of other species – extinction rate

higher today than at any other time Increased pop. requires increasing amts. of food,

energy, space – greater share of Earth’s resources will be required

Burning Fossil Fuels for energy – releases carbon dioxide; excess CO2 traps too much heat in Earth’s atmosphere

Human Population Growth

Improved by agricultural development, hygiene, diet, and economic conditions improved

Today, population growth is faster in less-developed countries and slower in more developed countries

Population Dynamics

Changes in size and composition over time

Measure include: birth rate - number of births over time (in US

it is 4 million per year) death or mortality rate – number of deaths

in a period of time (in US it is 2.4 million per year)

life expectancy – how long an individual is expected to live (1996: in US it was 72 yrs. for a man and 79 for a woman)

Population Growth Rates

Amount of change within a population’s size in a given time

Four factors that affect growth rates: Birth Death Emigration – movement out of a population Immigrations – movement into a population

Demographers – scientists who study populations dynamics

Birth rate – death rate = growth rate

Carrying capacity of a population is the number if individuals the environment can support for an indefinite period of time.

Populations fluctuate over time do to environmental changes.

Small populations are less able to rebound from environmental changes. They are more likely to experience inbreeding and their genetic diversity is low.

Population Growth Curves

Linear – growth occurs along a straight lineNOT what we see w/ populations of organisms

Population Growth Curves

Exponential – as population gets larger, it grows faster (population explosion)“J shaped”

Predator-Prey

Predator-Prey – (predation is density dependent limiting factor)

When population grows beyond carrying capacity of environment, density-dependent Limiting Factors reduce population population grows/shrinks cycles

Carrying Capacity

What is seen in most populations of organisms. Population growth is limited by factors in the environment such as food supply or habitat.