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5/16/14 5-1 How Populations Grow Biology Slide 1 of 22 End Show Copyright Pearson Prentice Hall 5-1 How Populations Grow Characteristics of Populations Slide 2 of 22 End Show Copyright Pearson Prentice Hall 5-1 How Populations Grow Characteristics of Populations I. Characteristics of Populations What characteristics are used to describe a population? Three important characteristics of a population are its: • geographic distribution • density • growth rate Copyright Pearson Prentice Hall 5-1 How Populations Grow Slide 3 of 22 Slide 4 of 22 End Show End Show Characteristics of Populations Copyright Pearson Prentice Hall 5-1 How Populations Grow Population Growth Geographic distribution, or range, describes the area inhabited by a population. Population density is the number of individuals per unit area. What factors affect population size? Growth rate is the increase or decrease of the number of individuals in a population over time. Slide 5 of 22 Copyright Pearson Prentice Hall End Show Slide 6 of 22 Copyright Pearson Prentice Hall End Show 1 5/16/14 5-1 How Populations Grow Population Growth 5-1 How Populations Grow II. Population Growth Population Growth Immigration, the movement of individuals into an area, is another factor that can cause a population to grow. Three factors can affect population size: Populations can increase by immigration as animals in search of mates or food arrive from outside. • the number of births • the number of deaths • the number of individuals that enter or leave the population A population can grow when its birthrate is greater than its death rate. Slide 7 of 22 End Show Copyright Pearson Prentice Hall 5-1 How Populations Grow Population Growth Slide 8 of 22 End Show Copyright Pearson Prentice Hall 5-1 How Populations Grow Exponential Growth Emigration, the movement of individuals out of an area, can cause a population to decrease in size. Emigration can occur when animals leave to find mates and establish new territories. What are exponential growth and logistic growth? A shortage of food in one area may also lead to emigration. Copyright Pearson Prentice Hall 5-1 How Populations Grow Slide 9 of 22 Slide 10 of 22 End Show End Show Exponential Growth Copyright Pearson Prentice Hall 5-1 How Populations Grow Exponential Growth III. Exponential Growth Under ideal conditions with unlimited resources, a population will grow exponentially. Exponential Growth Exponential growth occurs when the individuals in a population reproduce at a constant rate. The population becomes larger and larger until it approaches an infinitely large size. Slide 11 of 22 Copyright Pearson Prentice Hall End Show Slide 12 of 22 Copyright Pearson Prentice Hall End Show 2 5/16/14 5-1 How Populations Grow Logistic Growth 5-1 How Populations Grow IV. Logistic Growth Logistic Growth As resources become less available, the growth of a population slows or stops. In nature, exponential growth does not continue in a population for very long. Logistic growth occurs when a population's growth slows or stops following a period of exponential growth. Slide 13 of 22 5-1 How Populations Grow Slide 14 of 22 End Show Copyright Pearson Prentice Hall End Show Copyright Pearson Prentice Hall Logistic Growth 5-1 How Populations Grow Logistic Growth Carrying Capacity Logistic growth is characterized by an S-shaped curve. The largest number of individuals of a population that a given environment can support is called its carrying capacity. When a population reaches the carrying capacity of its environment, its growth levels off. The average growth rate is zero. Copyright Pearson Prentice Hall Slide 15 of 22 Slide 16 of 22 End Show End Show 5-1 Copyright Pearson Prentice Hall 5-1 Population density is the number of individuals a. that are born each year. Click to Launch: Continue to: b. per unit area. - or - c. that immigrate. d. that emigrate. Slide 17 of 22 Slide 18 of 22 End Show Copyright Pearson Prentice Hall End Show Copyright Pearson Prentice Hall 3 5/16/14 5-1 5-1 When the birthrate of a population exceeds its death rate, the population An S-shaped curve on a graph of population growth is characteristic of a. decreases. a. exponential growth. b. increases. b. logistic growth. c. stays the same. c. carrying capacity. d. increases then decreases. d. delayed growth. Slide 19 of 22 Slide 20 of 22 End Show End Show Copyright Pearson Prentice Hall Copyright Pearson Prentice Hall 5-1 5-1 Exponential growth rate means that each new generation of a population Exponential growth in a population slows down or stops as a. adds the same number of new individuals as the previous generation did. a. resources become limited. b. rate of immigration increases. c. rate of emigration decreases. b. increases at the same rate as the previous generation. d. birth rate increases. c. is the same size as the generation before. d. increases by a varying amount. Copyright Pearson Prentice Hall Slide 21 of 22 Slide 22 of 22 End Show End Show Copyright Pearson Prentice Hall END OF SECTION 4