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Biology Slide 1 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Slide 2 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Characteristics of Populations What characteristics are used to describe a population? Slide 3 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Characteristics of Populations Characteristics of Populations Three important characteristics of a population are its: • geographic distribution • population density • growth rate Slide 4 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Population Growth What factors affect population size? Slide 5 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Population Growth Population Growth Three factors can affect population size: • 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 6 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Population Growth Immigration, the movement of individuals into an area, is another factor that can cause a population to grow. Emigration, the movement of individuals out of an area, can cause a population to decrease in size. Slide 7 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Exponential Growth What are exponential growth and logistic growth? Slide 8 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Exponential Growth Exponential Growth Under ideal conditions with unlimited resources, a population will grow exponentially. 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 9 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Exponential Growth Exponential Growth Slide 10 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Logistic Growth Logistic Growth As resources become less available, the growth of a population slows or stops. Logistic growth occurs when a population's growth slows or stops following a period of exponential growth. Slide 11 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Logistic Growth Logistic growth is characterized by an Sshaped curve. Slide 12 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Limiting Factors What factors limit population growth? Slide 13 of 22 Copyright Pearson Prentice Hall End Show 5-1 How Populations Grow Density-Dependent Factors Wolf and Moose Populations on Isle Royale Moose Wolves Density-Dependent Activity Slide 14 of 22 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Limiting Factors Limiting Factors The primary productivity of an ecosystem can be reduced when there is an insufficient supply of a particular nutrient. Ecologists call such substances limiting nutrients. Slide 15 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Limiting Factors A limiting nutrient is an example of a more general ecological concept: a limiting factor. In the context of populations, a limiting factor is a factor that causes population growth to decrease. Slide 16 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Density-Dependent Factors A limiting factor that depends on population size is called a density-dependent limiting factor. Slide 17 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Density-dependent limiting factors include: • competition • predation • parasitism • disease Slide 18 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Density-dependent factors operate only when the population density reaches a certain level. These factors operate most strongly when a population is large and dense. They do not affect small, scattered populations as greatly. Slide 19 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Competition When populations become crowded, organisms compete for food, water space, sunlight and other essentials. Competition among members of the same species is a density-dependent limiting factor. Slide 20 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Competition can also occur between members of different species. This type of competition can lead to evolutionary change. Over time, the species may evolve to occupy different niches. Slide 21 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Predation Populations in nature are often controlled by predation. The regulation of a population by predation takes place within a predator-prey relationship, one of the best-known mechanisms of population control. Slide 22 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Wolf and Moose Populations on Isle Royale Moose Wolves Slide 23 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Dependent Factors Parasitism and Disease Parasites can limit the growth of a population. A parasite lives in or on another organism (the host) and consequently harms it. Slide 24 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Independent Factors Density-Independent Factors Density-independent limiting factors affect all populations in similar ways, regardless of the population size. Slide 25 of 21 Copyright Pearson Prentice Hall End Show 5-2 Limits to Growth Density-Independent Factors Examples of density-independent limiting factors include: • unusual weather • natural disasters • seasonal cycles • certain human activities—such as damming rivers and clear-cutting forests Slide 26 of 21 Copyright Pearson Prentice Hall End Show 5-2 Click to Launch: Continue to: - or - Slide 27 of 21 End Show Copyright Pearson Prentice Hall 5-1 Population density is the number of individuals a. that are born each year. b. per unit area. c. that immigrate. d. that emigrate. Slide 28 of 22 End Show Copyright Pearson Prentice Hall 5-1 When the birthrate of a population exceeds its death rate, the population a. decreases. b. increases. c. stays the same. d. increases then decreases. Slide 29 of 22 End Show Copyright Pearson Prentice Hall 5-1 An S-shaped curve on a graph of population growth is characteristic of a. exponential growth. b. logistic growth. c. carrying capacity. d. delayed growth. Slide 30 of 22 End Show Copyright Pearson Prentice Hall 5-1 Exponential growth in a population slows down or stops as a. resources become limited. b. rate of immigration increases. c. rate of emigration decreases. d. birth rate increases. Slide 31 of 22 End Show Copyright Pearson Prentice Hall 5-1 Exponential growth rate means that each new generation of a population a. adds the same number of new individuals as the previous generation did. b. increases at the same rate as the previous generation. c. is the same size as the generation before. d. increases by a varying amount. Slide 32 of 22 End Show Copyright Pearson Prentice Hall 5-2 A limiting factor that affects all populations in similar ways regardless of their size might be a. drought. b. disease. c. predation. d. crowding. Slide 33 of 21 End Show Copyright Pearson Prentice Hall 5-2 Which of the following would be a limiting factor affecting the panda population of China? a. programs that educate people about endangered species b. capture of some pandas for placement in zoos c. laws protecting habitat destruction d. a disease that kills bamboo plants Slide 34 of 21 End Show Copyright Pearson Prentice Hall 5-2 Density-dependent factors operate most strongly when a population is a. large and dense. b. large but sparse. c. small and sparse. d. small, but growing. Slide 35 of 21 End Show Copyright Pearson Prentice Hall 5-2 Within a limited area, if the population of a predator increases, the population of its prey is likely to a. increase. b. decrease. c. remain about the same. d. become extinct. Slide 36 of 21 End Show Copyright Pearson Prentice Hall 5-2 Which of the following is a density-independent factor affecting populations? a. predation b. disease c. a destructive hurricane d. parasites Slide 37 of 21 End Show Copyright Pearson Prentice Hall END OF SECTION