Populations

Populations Population growth Definition of population: All the individuals of: The same species Living in the same area Breeding with one another Factors that affect the rate of population growth: Food supply Predation Disease Populations size will continue to rythmically increase and decrease as a result of these factors. Food supply An increase in the number of organisms competing for limited supplies of food will lead to the weaker species dying off and the strongest surviving. Unlimited supply Increase in population Limited supply Decrease in population Predation When there is an abundance of prey, predators will thrive and increase in numbers. When the abundance of prey diminishes, the predators will start to decrease due to competition. Disease When there is an increase in population, disease will spread more rapidly. The population will then decrease and disease will spread less rapidly. Sigmoid curve – three phases 212725210820Time Population LAG LOG STATIONARY LAG – Slow growth due to adjustment to environment. LOG – Rapid increase due to availability of food STATIONARY – Populations remains constant due to limiting factors 00Time Population LAG LOG STATIONARY LAG – Slow growth due to adjustment to environment. LOG – Rapid increase due to availability of food STATIONARY – Populations remains constant due to limiting factors Human population growth Reasons for recent rapid increase in population size: Reduction of disease Prevention of typhoid and cholera through provision of clean drinking water and sewage removal. Mass immunizations have prevented multitudes of child deaths from measles, mumps and small pox. Use of antibiotics has made treatment of bacterial infections more successful. Increase in food supply Agricultural methods have become more efficient and therefore a higher yield is produced from crops. More land is being cultivated. Factors effecting human population growth Birth rate higher than death rate Increase. Vice versa. Birth rate equals death rate ZPG (Zero Population Growth) Emigration (Leaving area) Immigration (Entering area) Natural disasters War Education regarding heal care and contraception Disease and food supply Social implications of human population growth Most barriers to human population growth have been eliminated. Population of the world now increases rapidly (population explosion). Birth control in developed areas has reduced the birth rate. People may be prevented from using birth control due to: Religious beliefs Expense It being unaccesible (Rural areas) Preference for larger families (cultural) Increase in human population results in: Less water and food Less agricultural space More waste materials More pollution More overcrowding Increased spreading of disease Less money per person for educaton and medicine Increase in birth rate Interpreting graphs Increasing population Stable population Many young at reproductive age Low mortality rate Many more to come High mortality rate The larger the difference in the widths of the consecutive rows, the higher the motality rate.