Name ______________________________________ Date _________

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TEKS Review 3.9A

TEKS 3.9A observe and describe the physical characteristics of environments and how they support populations and communities within an ecosystem

Environments and Ecosystems

Neighbors in Nature

What is around you right now? Look around. Are there desks and chairs? Are there walls and other students? Many of the things around you affect you every day. The same goes for all living things. Every living thing has an environment. An environment is made of all the living and nonliving things that surround and affect a living thing. An environment includes things you can touch as well as the conditions of an area, such as the weather.

Two organisms can live near each other and have very different environments. For example, a deer’s environment may include the forests and fields for several kilometers in any direction. The environment of an earthworm living in the soil just a few inches below the deer is very different. The deer and the earthworm may never see one another. They live in the same area, but their environments are very different.

You might think that earthworms and deer are not affected by one another. In reality, almost all organisms in an area are connected in some way. For example, earthworm tunnels and droppings make the soil more fertile. When there are more earthworms, more plants are able to grow, which provide food for more deer.

If you look at the connections among living things, you can outline areas that have a lot of connections. Very few connections go outside the area. These areas are called ecosystems. An ecosystem includes all the living things in a certain area as well as the nonliving aspects of the environment.

Ecosystems can be large or small. You could study the ecosystem in one small pond or the ecosystem of a large national forest. Some ecosystems may be temporary, such as watering holes during a rainy season. Others have remained mostly unchanged for thousands of years.

In a grassland ecosystem, all these living things interact with one another and with the nonliving elements of their environment.

Name ______________________________________ Date _________

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TEKS Review 3.9A

Populations and Communities

A scientist who studies interactions in ecosystems is an ecologist. Some ecologists study populations within an ecosystem. A population consists of all the individuals of one species in an ecosystem. You can count or estimate the number of individuals to find the population size. Many ecologists track how changes in an ecosystem affect the population size of different species.

Other ecologists specialize in studying communities. A community is composed of all the populations living and interacting in an ecosystem. For example, an ecologist may find that the community has fewer members—or fewer species—in ecosystems that have been altered by people.

Characteristics of Environments

A forest environment is very different than a pond environment. In fact, each environment on Earth has unique characteristics. These characteristics make different environments good homes for some plants and animals but not for others.

Many of the characteristics that affect living things in an ecosystem are nonliving, or abiotic, factors. These are part of the physical environment in an ecosystem. The sun, air, water, soil, and climate are all abiotic factors.

Each population interacts with the physical environment. Plants need the sunlight to grow, and they take water and nutrients from the soil. Fish and frogs live in water that birds and other animals drink.

A Closer Look: Forest Environments The characteristics of a forest

environment make it possible for many things to live there. The soil is deep and full of nutrients, and there is enough rainfall for trees to grow close together. The trees and other plants provide food and shelter for many animals. Woodpeckers find insects that live under tree bark. Owls nest in holes in trees. Salamanders, worms, and many insects live under the decaying layer of leaves on the forest floor.

A Closer Look: Desert Environments

When you observe a desert environment, you do not see many living things. That’s because there is not much precipitation in a desert. The things that live there must have body parts or behaviors to help them survive. Cacti store water in their thick stems. Many animals burrow underground or stay in the shade when it is hot. Flowering plants grow very fast after it rains so they can make seeds before the sandy soil dries out again.

A Closer Look: Pond Environments

Finding water in a pond environment is no problem most of the time. Water lilies, reeds, fish, frogs, turtles, and other aquatic organisms live in the water. Many insects live in or near the water, and they provide food for fish and birds. Some ducks eat vegetation that grows in the pond. Other ducks dive underwater and catch fish.

Name ______________________________________ Date _________

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TEKS Review 3.9A

Observe a Pond Ecosystem The physical characteristics of many ecosystems are constantly changing. Sometimes, these changes happen quickly. Other times, the changes take hundreds of years. In this activity, you will make a model of a pond ecosystem, and you will see how the ecosystem changes as the pond dries up. Procedure: 1. Make a model of a pond by spreading 5 cm of moist potting soil in the dishpan. Dig out a

low spot in the center, leaving 1 cm of soil. Pile up soil around the low spot to make gently sloping sides.

2. Slowly pour water into the low spot until the water is 4 cm deep. Put duckweed in the “pond.”

3. Sprinkle birdseed over the soil. Do not water it. Make a drawing in your notebook or take a photograph to record how your pond looked.

4. Every other day, use a watering can to add a small amount of water to the pan. Add water as if it were raining on the entire area, until the pond is ½ cm below the level it was the last time you added water. This will simulate a pond that is drying up.

5. Each time you add water, record your observations in a notebook. In addition to tracking the appearance of the living things, record changes in the physical environment.

6. When the pond has dried up, wait two days and make a final set of observations.

Discussion Questions: 1. What changes did you observe?

2. What can you infer caused the changes?

3. How can the physical environment help living things survive?

4. How can the physical environment harm living things?

Hands-On Activity

Materials • ruler • potting soil • plastic dishpan • water • duckweed • birdseed • notebook • camera (optional) • watering can

Name ______________________________________ Date _________

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TEKS Review 3.9A

Environments and Ecosystems

Look at the environment shown below. List 4 animal populations you would expect to find.

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Describe the physical characteristics of a desert environment.

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Choose an ecosystem to research. Draw the ecosystem and include as many parts as you can fit. Label all the parts that you include.

Name ______________________________________ Date _________

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TEKS Review 3.9A

TEKS Assessment 3.9A Fill in the letter of the best choice.

Which animal is able to meet its needs in a pond environment?

You see a raccoon in a city park. What can you conclude?

It is lost.

It is happy.

It is someone’s pet.

It has found food and shelter.

Which is the abiotic factor that limits the number of organisms in a desert?

air

water

light

predators

Look at the forest environment below.

Which statement BEST describes the

interactions that occur?

The squirrels do not interact with the other living things.

The mushrooms and other decomposers are abiotic parts of the environment.

The population size of all living things in the environment remains constant over time.

All living things in the environment are connected in some way.

What forms a biological community?

a city and its resources

several populations

an ecosystem

an environment

Name ______________________________________ Date _________

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TEKS Review 3.9A

Answer Key

Hands-On Activity (p. 3)

1. Answers will vary. Students should note that the duckweed grew well when there was plenty of water. As the pond dried up, the duckweed population decreased. The plants growing from seed grew well in the drier soil, but they were not able to grow in the deeper water of the pond.

2. The decrease in the amount of available water may have caused the changes.

3. The physical environment provides many of the basic needs for living things, including air and water. It also provides light to plants.

4. When the physical environment changes and it can no longer provide for the basic needs of certain living things, those things must find a new place to live or they may not survive.

Student Response Activity (p. 4)

1. Answers will vary. Sample answer: deer, squirrels, raccoons, and earthworms

2. A desert environment has very sandy soil. It receives only small amounts of precipitation each year. Because there are no tall trees to block it, the sun may be intense.

3. Check students’ drawings and labels for accuracy.

TEKS Assessment (p. 5)

1. A

2. D

3. B

4. D

5. B