| A | B |
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| Population: | a group of organisms belonging to a single species that lives in a given area |
| Characteristics of Populations: | 1. Geographic distribution: area inhabited by the population; 2. Density: number of individuals per unit area; 3. Growth rate; 4. Age structure |
| 3 factors that effect population growth: | 1. Number of births; 2. Number of deaths; 3. Number that enter and leave the population |
| Immigration: | movement of individuals into an area |
| Emigration: | movement of individuals out of an area |
| Types of population growth: | 1. Exponential growth; 2. Logistic Growth |
| Exponential growth: | occurs when individuals in a population reproduce at a constant rate; * under ideal conditions with unlimited resources, a population will grow exponentially |
| Logistic Growth: | occurs when a population’s growth slows or stops following a period of exponential growth; * as resources become less available, the growth of a population slows or stops |
| Carrying Capacity: | the largest number of organism that a given environment can support for a particular species |
| Limiting factors: | a factor that causes population growth to decrease |
| Examples of Limiting Factors: | Competion; Predation; Parasitism and Disease; Drought and other climate extremes; Human disturbances |
| Density-dependent limiting factor: | Depends on population size; Become limiting only when the population density reaches a certain level; Includes things such as: competition, predation, disease |
| Density-Independent Factors: | Affect all populations in similar ways, regardless of the population size; Includes things such as: weather, natural disasters, seasons, human activities such as cutting down a forest |
| Human Population | as advances in medicine, agriculture, and technology occurred, the human population began growing very rapidly. Today, the world’s human population is greater than 6 billion people |
| Human population is increasing | by about 1.4 percent each year |
| Demography: | scientific study of human populations |
| Factors predicting population growth rates: | * Birthrates, death rates, and the age structure of a population help predict why some countries have high growth rates and others grow more slowly |
| Demographic transition: | a dramatic change in birth and death rates |
| Future Population Growth: | Projections say that the population will reach more than 9 billion by 2050 |
