19 Cycles in Nature SECTION 1 The Cycles of Matter

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Interactive Textbook 309 Cycles in Nature

SECTION

1 The Cycles of MatterCycles in Nature

Name Class Date

CHAPTER 19

After you read this section, you should be able to answer these questions:

• Why does matter need to be recycled?

• How are water, carbon, and nitrogen recycled?

Why Is Matter Recycled on Earth?The matter in your body has been on Earth since the

planet formed billions of years ago. Matter on Earth is limited, so it must be used over and over again. Each kind of matter has its own cycles. In these cycles, matter moves between the environment and living things.

What Is the Water Cycle?Without water there would be no life on Earth. All living

things are made mostly of water. Water carries other nutrients to cells and carries wastes away from them. It also helps living things regulate their temperatures. Like all matter, water is limited on Earth. The water cycle lets living things use water over and over.

In the environment, water moves between the oceans, atmosphere, land, and living things. Eventually, all the water taken in by organisms returns to the environment. The movement of water is known as the water cycle. The parts of the water cycle are explained in the figure below.

Precipitation is rain, snow, sleet, or hail that falls from clouds to Earth's surface. Most precipitation falls into the ocean. It never touches the land.

Condensation happens when water vapor cools and changes into drops of liquid water. The water drops form clouds in the atmosphere.

Evaporation happenswhen liquid water on Earth's surface changes into water vapor. Energy from the sun makes water evaporate.

Runoff is water that flows over the land into streams and rivers. Most of the water ends up in the oceans.

Transpiration happens when plants give off water vapor from tiny holes in their leaves.

Groundwater is water that flows under the ground. Gravity can make water that falls on the land move into rocks underground.

BEFORE YOU READ National Science Education StandardsLS 1c, 4b, 4c, 5a

STUDY TIPMnemonic As you read, create a mnemonic device, or memory trick, to help you remember the parts of the water cycle.

Say ItIdentify Describe to the class all the things you and your family do in a day that use water. Can you think of any ways you might be able to use less water?

TAKE A LOOK 1. Describe How do clouds form?



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The Cycles of Matter continued

What Is the Carbon Cycle?Besides water, the most common molecules in living

things are organic molecules. These are molecules that contain carbon, such as sugar. Carbon moves between the environment and living things in the carbon cycle.

PHOTOSYNTHESIS AND RESPIRATIONPlants are producers. This means they make their

own food. They use water, carbon dioxide, and sunlight to make sugar. This process is called photosynthesis.Photosynthesis is the basis of the carbon cycle.

Animals are consumers. This means they have to consume other organisms to get energy. Most animals get the carbon and energy they need by eating plants. How does this carbon return to the environment? It returns when cells break down sugar molecules to release energy. This process is called respiration.

DECOMPOSITION AND COMBUSTIONFungi and some bacteria get their energy by breaking

down wastes and dead organisms. This process is called decomposition. When organisms decompose organic matter, they return carbon dioxide and water to the environment.

When organic molecules, such as those in wood or fossil fuels, are burned, it is called combustion.Combustion releases the carbon stored in these organic molecules back into the atmosphere.

Respiration

Decomposition

Carbon infossil fuels

Carbon dioxide in the air Photosynthesis

Combustion

Carbon insoil and rock

Carbon in living things

The Carbon Cycle

STANDARDS CHECKLS 4c For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. That energy passes from organism to organism in food webs.

2. Analyze Explain the role of photosynthesis in the carbon cycle.

TAKE A LOOK 3. Complete Carbon dioxide in the air is used for

.

4. List What three processes release carbon dioxide into the environment?



SECTION 1

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The Cycles of Matter continued

What Is the Nitrogen Cycle? Nitrogen is also important to living things. Organisms

need nitrogen to build proteins and DNA for new cells. Like water and carbon, nitrogen cycles through living things and the environment. This is called the nitrogen cycle.

NITROGEN FIXATIONAbout 78% of Earth’s atmosphere is nitrogen gas. Most

organisms cannot use nitrogen gas directly. Bacteria in soil can change nitrogen gas into forms that plants can use. This is called nitrogen fixation. Other organisms can get the nitrogen they need by eating plants or by eat-ing organisms that eat plants.

Nitrogen in the air

Dead animals and plants

Bacteria in soil and plant roots perform most nitrogen fixation.

Decompositionreleases nitrogen into soil.

Bacteria in soil convert nitrogen back to gas.

Plant roots take up nitrogen from soil.

Animals get nitrogen from plants.Lightning causes some

nitrogen fixation.

The Nitrogen Cycle

How Are the Cycles of Matter Connected? Other forms of matter on Earth also cycle through the

environment. These include many minerals that living cells need, such as calcium and phosphorus. When an organism dies, every substance in its body will be recycled in the environment or reused by other organisms.

All of the cycles of matter are connected. For example, water carries some forms of carbon and nitrogen through the environment. Many nutrients pass from soil to plants to ani-mals and back. Living things play a part in each of the cycles.

Critical Thinking5. Apply Concepts How is nitrogen fi xation important to animals?

TAKE A LOOK 6. Identify What process releases nitrogen into the soil?

READING CHECK

7. Explain What happens to the substances in an organism’s body when the organism dies?



Name Class Date

Section 1 Review NSES LS 1c, 4b, 4c, 5a

SECTION VOCABULARY

combustion the burning of a substancecondensation the change of state from a gas to

a liquiddecomposition the breakdown of substances

into simpler molecular substances

evaporation the change of state from a liquid to a gas

precipitation any form of water that falls to Earth’s surface from the clouds

1. Identify In the water cycle, what makes water evaporate?

2. Summarize Draw arrows to show how carbon cycles through the environment and living things.

Plants Air

Animals

Decomposers

3. Explain Why does matter need to be recycled?

4. Explain Why is water so important to life on Earth?

5. Define What is nitrogen fixation?

6. Define What are organic molecules?


Interactive Textbook Answer Key 21 Life Science

Life Science Answer Key continued

4. No, only organisms of one species make up a population. There are usually more than one species of bird in an area.

SECTION 2 LIVING THINGS NEED ENERGY 1. Producers use energy from sunlight to make

their own food.

2. Tigers: carnivores

Deer: herbivores

Humans: omnivores

3. Decomposers break down dead matter into nutrients for other organisms to use.

4. Labels go on sun, grasses, prairie dog, coy-ote, vulture, and bacteria, in that order.

5. Most organisms eat more than one type of food.

6. Without producers, consumers would have no food. None of the animals would live.

7. about 90%

8. The middle level—deer are herbivores like the prairie dogs.

9. Wolves were at the top of the food chain and controlled the populations of herbivores.

Review 1. Producers use energy from the sun to make

their own food. Producers are the base of the food chain. All consumers depend on producers.

2. Grass (Producer) Mouse (Primary con-sumer) Snake (Secondary consumer)

3. Answers will vary but should include at least one of the organisms from question 2.

4. No, energy is lost as it moves through a food chain. After a few steps in the chain, there isn’t enough energy left to support more organisms.

SECTION 3 TYPES OF INTERACTIONS 1. a resource that keeps a population from

growing forever

2. if the amount of the limiting factor changes

3. in competition, as predator and prey, through symbiosis, and coevolution

4. elk and prairie dogs

5. speed, colors that let them blend with the environment

6. Possible answer: It may be difficult for the predator to see individual animals in the group.

7. Any combination of black and orange patches is acceptable.

8. mutualism, commensalism, parasitism

9. In mutualism, both species benefit. In com-mensalism, only one species benefits.

10. The host is hurt.

11. The wasps can use the caterpillar for food.

Review 1. Possible answers: food, water, sunlight,

shade, shelter

2. Individuals will die or will have to move to a new area. This will cause the population to decrease.

3. No, some species may use more resources than others. Some species may be more affected than others by a limiting factor.

4. First row, left to right: parasitism, parasite (flea)

Second row, left to right: both, none

Third row, left to right: commensalism

5. Commensalism; the pollinator is not harmed, but the plant still benefits.

Chapter 19 Cycles in NatureSECTION 1 THE CYCLES OF MATTER 1. Water vapor cools and changes into drops of

liquid water. The water drops form clouds.

2. Photosynthesis uses carbon dioxide from the air. When the sugars that a plant makes during photosynthesis are broken down, car-bon returns to the environment.

3. photosynthesis

4. respiration, combustion, decomposition

5. Animals need to get nitrogen from plants or other animals. Plants get their nitrogen from nitrogen fixation.

6. decomposition

7. They are recycled in the environment or reused by other organisms.

Review 1. energy from the sun

2. There should be arrows from air to plants to animals to decomposers to air, and from plants to decomposers.

3. Matter on Earth is limited, so it needs to be used over and over again.

4. Living things are made mostly of water. Water carries nutrients to cells and carries wastes away. Water also helps organisms regulate their body temperatures.


Interactive Textbook Answer Key 22 Life Science

Life Science Answer Key continued

5. Nitrogen fixation is the process in which bacteria in soil change nitrogen gas into a form that plants can use.

6. molecules that contain carbon

SECTION 2 ECOLOGICAL SUCCESSION 1. 34%

2. the first species to live or grow in an area

3. Lichens don’t have roots. They get their water from the air, so they do not need soil.

4. tall trees

5. in places where living things already exist

6. weeds

7. conifers

Review 1. Abiotic factors are the nonliving parts of the

environment. They include water, light, and space.

2. Primary succession is the change from bare rock to a community of organisms. Secondary succession is a change in a community where other living things already exist.

3. In secondary succession, there is already soil for new plants to use. In primary succession, soil has to develop before species other than lichens can grow.

4. There is little grass in a mature forest, because the tall trees prevent the light from reaching the ground. Nuts grow on many kinds of trees. Therefore, there would be more nut eaters than grass eaters.

5. Tall trees need deep soil. Pioneer species are the first species to live or grow in an area. There usually would not be soil in an area where no living things had been before.

6. the variety of species that live in an area

7. pieces of rock that have been broken down and remains of dead lichens

Chapter 20 The Earth’s EcosystemsSECTION 1 LAND BIOMES 1. Biomes are made of many related

ecosystems.

2. Africa, South America

3. plenty of rain, moderate temperatures

4. deciduous trees and shrubs

5. in cones

6. The evergreen conifers shade the forest floor, but the deciduous trees of the temper-ate forest allow light to reach the ground.

7. Coniferous forests get less rainfall than some other biomes.

8. Most of the animals are found in the trees.

9. The plants grow above the ground to get sunlight, which is lacking on the forest floor.

10. camouflage, hiding in burrows

11. The savanna gets about twice as much rain.

12. escaping the heat and hiding from predators

13. 25 cm � 2.54 cm/in. � about 10 in.

14. Growing close to the ground helps protect the plants from the cold and wind.

15. They are both large herbivores (consumers).

Review 1. Tundras, like deserts, receive little rainfall.

Tundra is not hot like most deserts, so it is a “frozen desert.”

2. Temperate grassland

Savanna

Abiotic factors warm summers and cold winters

constant warmth with seasonal rains

Types of producers

grass with a few trees

grass with a few trees

Types of consumers

herbivores such as prairie dogs and bison; predators such as coyotes

herbivores such as elephants, giraffes, zebras, and wildebeest; predators such as lions

3. Some plants have special spreading roots to gather rainfall before it evaporates. Many desert plants can store water in their stems or roots.

4. Alpine tundra is found at the tops of tall mountains; polar tundra is found at or near the poles.

SECTION 2 MARINE ECOSYSTEMS 1. near the equator

2. about 10°C

3. depth, sunlight, and temperature

4. The whale is the consumer, and the plankton is the producer.

5. The intertidal zone is regularly exposed to air.

6. phytoplankton and seaweed

7. They need sunlight for photosynthesis.

8. They eat each other and material that sinks from surface waters.

9. cold temperatures, no light, high pressure

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19 Cycles in Nature SECTION 1 The Cycles of Matter