Populations How Populations Grow Characteristics of Populations Population

Populations

How Populations Grow �Characteristics of Populations Population Density-The number of individuals per unit of area. Geographic Distribution- The area inhabited by a population. Growth Rate- How fast a population of a given species grows or increases in number.

Population Growth �Factors that influence population rate. growth Number of births Number of deaths Number of individuals that enter or leave the population ▪ Immigration- The movement of individuals into an area. ▪ Emigration- The movement of individuals out of an area.

Growth Cont…. . �Exponential Growth: A growth pattern on which the individuals in a population reproduce at a constant rate. Under ideal conditions with unlimited resources a population can grow this way �Logistic Growth: A growth pattern in which a population’s growth rate slows or stops following a period of exponential growth. When a resource becomes less available and begins to slow or stop a population from growing Carrying Capacity: Largest number of individuals of a population that a given environment can support

Limits to Growth �Limiting growth factors are factors that cause population growth to decrease. 1. )Density Dependent Factors: Depend on population size. ▪ Competition ( resources) ▪ Predation (predator vs. prey) ▪ Parasitism/Disease 2. )Density-Independent Factors: Affects all populations regardless of size. Organism population will “crash”. ▪ Climate Extremes (Drought, Flood) ▪ Human Disturbance

Human Population Growth � Like the population of other living things the size of the human population tends to increase with time. � Demography- The scientific study of the human population. � Like other population; Births, deaths, etc. affect the human population. � Historical Overview: Life was different years ago, medicine and technology not as advanced. Only half of the human population made it to adulthood. The Industrial Revolution changed that and humans began to grow exponentially.

Human Population Growth �Demographic Transition- Change in population from high birth and death rates to low birth and death rates. Societies modernize: Education, Medicine, Tech. Demographic transition is complete when birth rate fails to meet death rate, population growth stops. Hasn’t happen yet in most countries.

Human Population Growth �Age structure(diagram)- The numbers of males and females of different ages groups of a population. Use a diagram to study the age structure of a population. �Future Population Growth? ? Populations keep growing If growth doesn’t slow down serious damage to the global environment is inevitable.