Interactions and Changes in Populations and Communities

1. Chapter Introduction Lesson 1 Populations Lesson 2 Changing Populations Lesson 3Communities Chapter Wrap-Up Chapter Menu

2. How do populations and communities interact and change? Chapter Introduction

3. What do you think? Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements. Chapter Introduction

4. 1. Some life exists in the ice caps of the North Pole and South Pole. 2. A community includes all organisms of one species that live in the same area. 3. Some populations decrease in numbers because of low birthrates. Do you agree or disagree? Chapter Introduction

5. 4. An extinct species has only a few surviving individuals. 5. No more than two species can live in the same habitat. 6. A cow is a producer because it produces food for other organisms. Do you agree or disagree? Chapter Introduction

6. Populations • What defines a population? • What factors affect the size of a population? Lesson 1 Reading Guide

7. Populations • biosphere • population • community • competition • limiting factor • population density • biotic potential • carrying capacity Lesson 1 Reading Guide

8. The Biosphere and Ecological Systems The parts of Earth and the surrounding atmosphere where there is life is called the Earth’s biosphere. Lesson 1

9. The Biosphere and Ecological Systems (cont.) • The biosphere includes all the land of the continents and islands, all of the earth’s oceans, lakes, and streams, as well as the ice caps at the North Pole and the South Pole. • Parts of the biosphere with large amounts of plants or algae often contain many other organisms as well. Lesson 1

10. What is a population? • An ecosystem is a group of organisms that lives in an area at one time, as well as the climate, soil, water, and other nonliving parts of the environment. • The study of all ecosystems on Earth is ecology. Lesson 1

11. What is a population? (cont.) A communityis all the populations of different species that live together in the same area at the same time. Lesson 1

12. What is a population? (cont.) A populationis all the organisms of the same species that live in the same area at the same time. Lesson 1

13. What is a population? (cont.) A species is a group of organisms that have similar traits and are able to produce fertile offspring. What defines a population? Lesson 1

14. Competition • Competitionis the demand for resources, such as food, water, and shelter, in short supply in a community. • When there are not enough resources available to survive, there is more competition in a community. Lesson 1

15. Population Sizes • Changes in environmental factors can result in population size changes. • A limiting factoris anything that restricts the size of a population. • Available sunlight is a limiting factor for most organisms. • Without sunlight, green plants cannot make food, which effects animals that eat plants. Lesson 1

16. Population Sizes (cont.) • Temperature is a limiting factor for some organisms. • When the temperature drops below freezing, many organisms die because it is too cold to carry out their life functions. • Disease, predators, and natural disasters such as fires or floods are also limiting factors. Lesson 1

17. Population Sizes (cont.) What factors affect the size of a population? Lesson 1

18. Population Sizes (cont.) • Population densityis the size of a population compared to the amount of space available. • One way of estimating population density is by sample count. Lesson 1

19. Population Sizes (cont.) population from Latin populus, means “inhabitants” density from Latin densus, means “thick, crowded” Lesson 1

20. Population Sizes (cont.) • A population’s biotic potentialis the largest number of offspring that can be produced when there are no limiting factors present. • No population on Earth ever reaches its biotic potential because no ecosystem has an unlimited supply of natural resources. Lesson 1

21. Population Sizes (cont.) • The largest number of individuals of one species that an environment can support is the carrying capacity. • A population grows until it reaches the carrying capacity of an environment. Lesson 1

22. Carrying capacity is determined in part by limiting factors. Lesson 1

23. Population Sizes (cont.) • Disease, space, predators, and food are some of the factors that limit the carrying capacity of an ecosystem. • The carrying capacity of an environment is not constant because it increases and decreases as the amount of available resources increases and decreases. • When the size of a population becomes larger than the carrying capacity of its ecosystem, overpopulation occurs. Lesson 1

24. The population density of organisms, including green plants and algae, varies throughout the world. • A community is all the populations of different species that live together in the same area at the same time. Lesson 1

25. The number of individuals in a population varies as the amount of available resources varies. Lesson 1

26. Which term refers to all the populations of different species that live together in the same area at the same time? A. a population B. a biosphere C. a community D. an ecosystem Lesson 1

27. Which of these refers to anything that restricts the size of a population? A. population density B. limiting factor C. carrying capacity D. biosphere Lesson 1

28. Which of these increases when there are not enough resources available in a community for all its organisms to survive? A. competition C. organisms B. population D. food Lesson 1

29. 1. The biosphere includes all parts of Earth and the surrounding atmosphere that support life. 2. A community includes all organisms of one species that live in the same area. Do you agree or disagree? Lesson 1

30. Changing Populations • How do populations change? • Why do human populations change? Lesson 2 Reading Guide

31. Changing Populations • birthrate • death rate • extinct species • endangered species • threatened species • migration Lesson 2 Reading Guide

32. How Populations Change • A population change can be measured by the population’s birthrate and death rate. • A population’s birthrateis the number of offspring produced over a given period of time. • The death rate is the number of individuals that die over the same period of time. Lesson 2

33. How Populations Change (cont.) • If the birthrate is higher than the death rate, the population increases. • If the death rate is higher than the birthrate, the population decreases. • When a population is in ideal conditions with unlimited resources, it grows in a pattern called exponential growth. Lesson 2

34. How Populations Change (cont.) exponential Science Use a mathematical expression that contains a constant raised to a power, such as 23 or x2. Common Use in great amounts Lesson 2

35. How Populations Change (cont.) • During exponential growth, the larger a population gets, the faster it grows. • E coli bacteria are microscopic organisms that undergo exponential growth; the population doubles in size every half hour. Lesson 2

36. How Populations Change (cont.) • Disease and natural disasters such as floods, fires, or volcanic eruptions can decrease populations. • Predation—the hunting of organisms for food—also reduces population size. Lesson 2

37. How Populations Change (cont.) • If populations continue to decrease in numbers, they disappear. • An extinct speciesis a species that has died out and no individuals are left. • Extinctions can be caused by predation, natural disasters, or damage to the environment. Lesson 2

38. How Populations Change (cont.) extinct from Latin extinctus, means “extinguish” Lesson 2

39. How Populations Change (cont.) • An endangered speciesis a species whose population is at risk of extinction. • A threatened speciesis a species at risk, but not yet endangered. Tom Brakefield/Getty Images Lesson 2

40. How Populations Change (cont.) • Populations also change when organisms move from place to place. • Migrationis the instinctive seasonal movement of a population of organisms from one place to another. • Ducks, geese, and monarch butterflies are examples of organisms that migrate annually. Lesson 2

41. How Populations Change (cont.) List three ways populations change. Lesson 2

42. Human Population Changes • Human population, like all other populations, are affected by birthrate, death rate, and movement. • Unlike other species, humans have developed ways to increase the carrying capacity of their environment. • Scientists estimate that there were about 300 million humans on Earth a thousand years ago. Lesson 2

43. Human Population Changes (cont.) • Today there are more than 6 billion humans on earth. • As human population grows, people need to build more houses and roads and clear more land for crops, which means there is less living space, food, and other resources for other species. • Human energy use contributes to pollution that affects other populations. Lesson 2

44. Lesson 2

45. Human Population Changes (cont.) • Factors that keep the human birthrate higher than its death rate include food, resources, sanitation, and medical care. • Advances in agriculture have made it possible to produce food for billions of people. • Today people have access to more resources because of better transportation methods. Lesson 2

46. Human Population Changes (cont.) • Modern water treatment and more effective cleaning products help prevent the spread of disease-causing organisms that can lead to death. • Human populations in some parts of the world are decreasing in size because of factors like disease, drought, and natural disasters. Lesson 2

47. Human Population Changes (cont.) Like other organisms, populations of humans might move when more resources become available in a different place. Lesson 2

48. Human Population Changes (cont.) What makes human populations increase or decrease in size? Lesson 2

49. The birthrate and the death rate of any population affects its population size. • The giant moa is classified as an extinct species because there are no surviving members. • A population that is at risk but not yet endangered is a threatened species. Tom Brakefield/Getty Images Lesson 2

50. Which term refers to a species that is at risk, but not yet endangered? A. an extinct species B. a threatened species C. an endangered species D. a migrating species Lesson 2