1. Populations
Chapter 21, lesson 1

2. 1
Populations
What do you think?

3. 1 Populations Do you agree or disagree?
Some life exists in the ice caps of the North Pole and the South Pole.
A community includes all organisms of one species that live in the same area.

4. 1 Populations What defines a population?
What factors affect the size of a population?

5. 1 Populations biosphere limiting factor community population density
biotic potential
competition
carrying capacity

6. Vocabulary Build a Class Definition
1. Write the word competition on chart paper or the board.
2. Explain that competition is an inescapable fact of life for all organisms, including human beings. Plants compete for water, sunlight, soil nutrients, and space in which to grow. Animals compete for mates, habitats, and food. People compete for grades in school, entrance into good colleges, desirable jobs, boyfriends and girlfriends, and victory in sporting events.
3. While developing a class definition for competition, have class groups compete to see who can come up with the best definition.

7. About the Photo
If the meerkats sense danger, they make a warning sound to alert other members of the group. They can make a variety of warning sounds, including barks and whistles. Each sound is specific to a particular predator.

8. Guiding Questions In what other ways might meerkats interact?
*Meerkats might interact with each other in their group, with other groups of meerkats, or with other animals who invade their territory.
What do you think meerkats might do to extend their range of sight when watching for predators?
They stand upright or stand on something, such as an anthill or a rock.
What does meerkat group lifestyle and sentry behavior tell us about the maintenance of populations?
They tell us that the survival of a population is often easier if the members of the population live together and look out for one another.

9. Teacher Demo What is a census?
Basically, a census is a count of all of the individuals in a country, an area, a state, or a county. Explain that, in the United Sates, a census is taken of the human population once every ten years (1990, 2000, 2010). Discuss what kinds of information a census count might provide for a country or a city. A census might tell a local government how many people have moved into or out of an area. Ask how increased population might affect resources.

10. Bellringer Transparency
A lone wolf is a good hunter,
but a pack of wolves is fierce.
By cooperating with one
another, pack members can
hunt deer, moose, and other
large prey. Often they kill the
older, weaker members of the
prey population.
Wolves were hunted nearly to
extinction in the United States.
Today, laws protect wolves.
Their populations are rising
in many places.
1 What do wolves need to survive?
2 How do wolves change the populations of the animals they hunt?
3 Why did people hunt wolves in the past?

11. Lesson 1: Populations A. The Biosphere and Ecological Systems
1. The biosphere is the parts of Earth and the surrounding atmosphere where there is life.
2. The biosphere includes all the land, water, and ice on Earth.

12. Lesson 1: Populations B. What is a population?
1. A(n) species is a group of organisms that have similar traits and are able to produce fertile offspring.
2. A(n) population is all the organisms of the same species that live in the same area at the same time.

13. Lesson 1: Populations
3. A(n) community is all the populations of different species that live in the same area at the same time.
4. A(n) ecosystem is a group of organisms that live in an area at one time, as well as the climate, soil, water, and other nonliving parts of the environment.
5. The study of all ecosystems on Earth is called ecology.

14. Lesson 1: Populations C. Competition
1. Competition is the struggle in a community for the same resources, such as food, water, and shelter.
2. When few resources are available, there is more competition to survive in a community.

15. Lesson 1: Populations D. Population Sizes
1. Changes in environmental factors, such as temperature, food availability, water,and shelter, can change the size of a population.
2. A(n) limiting factor is anything that restricts the size of a population.
3. Limiting factors can include water, food, shelter, sunlight, temperature, disease, predators, and natural disasters.

16. Lesson 1: Populations
4. One method that is used to count and monitor animal populations is the capture mark-and-release method.
5. Population density is the size of a population compared to the amount of space available.
6. A population’s biotic potential is the potential growth of a population if it could grow in perfect conditions with no limiting factors.

17. Lesson 1: Populations
7. No populations on Earth ever reach their biotic potential because no ecosystems have a(n) unlimited supply of natural resources.

18. Lesson 1: Populations
8. The largest number of individuals of one species that an environment can support is the carrying capacity.
a. The carrying capacity of an ecosystem increases and decreases as the amount of available resources increases and decreases.
b. Overpopulation occurs when the size of a population becomes larger than the carrying capacity of its ecosystem.
c. Overpopulation of one species can cause problems for other organisms in the community.

19. Discussion Question What is the biosphere, and what is included in it?
The biosphere is the parts of Earth and the surrounding atmosphere where there is life. The
biosphere includes all the land, water, and ice on Earth.

20. The Biosphere and Ecological Systems Guiding Questions
Why might the North Pole have very little green?
There is no vegetation at the North Pole.

21. Guiding questions What is an ecosystem? What defines a population?
An ecosystem is all the living and nonliving things that make up an environment.
What defines a population?
A population is all the organisms of the same species that live in the same area at the same time.

22. Using a visual How does a population relate to a community?
Communities are made up of populations.
How does a community relate to an ecosystem?
Ecosystems are made up of communities.
How does an ecosystem relate to a biosphere?
Biospheres are made up of ecosystems.

23. Competition and Population Sizes
in any community, resources are limited. As a result, the members of that community must compete with one another for those resources. If resources become even more limited, competition increases.
population level an environment can support may vary. As a result, the population may increase in some periods and decrease in others as the environment changes.

24. Guiding questions
What will happen to a population if food in the area becomes less plentiful?
The population will decrease.
Name two ways that the population in an area can decrease.
A population can decrease if not as many members of the species survive to adulthood. It can also decrease if part of the population moves to a different area.

25. Limiting Factors
the availability of food is just one of the limiting factors determining population size.
What is a limiting factor?
It is anything that restricts the size of a population.
What factors affect the size of a population?
Limiting factors include available water, food, shelter, sunlight, and thermal energy. They also include natural disasters, disease, and predation.

26. Measuring Population Size
Describe two ways you can estimate population size.
You can estimate an animal population in an area by using the capture-mark-and- release method. For plants, you can make an estimate with a sample count. With that method, you count all the members of a plant species in a representative area, and then multiply by whatever factor will translate that number to the larger area in question.
Why is it difficult to establish the exact number of animals in an area?
It is difficult because animals are always moving about. You might not find all of them or you might count some twice.

27. biotic potential
biotic potential describes how limiting factors affect the biotic potential of a population.
Why is it almost always impossible for a population to reach its biotic potential?
It is almost always impossible for a population to reach its biotic potential because no ecosystem has an unlimited supply of natural resources.

28. Carrying Capacity What is carrying capacity?
Carrying capacity is the greatest number of one species that an environment can support.
How can the carrying capacity of an environment change?
It can either increase or decrease if available resources increase or decrease.

29. Overpopulation How can overpopulation affect a community?
Overpopulation can lead to food shortages and environmental damage.

30. What factors affect population size in the graph above?
disease, space, predators, food supply

31. 1
Populations
Do you agree or disagree?
Some life exists in the ice caps of the North Pole and the South Pole.
Agree. The North and South Poles are parts of Earth’s biosphere.

32. 1
Populations
Do you agree or disagree?
A community includes all organisms of one species that live in the same area.
Disagree. A community is all the populations of different species that live together in the same area at the same time.

33. 1
Populations
What defines a population?
A population is all the organisms of the same species that live in the same area at the same time.

34. 1
Populations
What factors affect the size of a population?
Population sizes vary due to limiting factors such as environmental factors and available resources.