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ISBN 978-0-15-362053-9ISBN 0-15-362053-6

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VOCABULARYcellorganismmicroscopiccell membranenucleuscytoplasmprotist

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A cell is the basic unit of structure for living things. All living things, or organisms, are made up of cells.

Things that can only be seen with a microscope are called microscopic.

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The nucleus directs all the cells activities. Most cells have a nucleus.

Every cell has a thin covering called a cell membrane. It protects the cell and holds it together.

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A protist is a single-celled organism. Some protists are plantlike and some are animal-like.

Cytoplasm is the jellylike material between the cell membrane and the nucleus.

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4READING FOCUS SKILLB6>C>9:66C99:I6>AH

The main idea is what the text is mostly about. Details are pieces of information about the main idea.

Look for examples of different kinds of cells and details about how they are alike and different.

8ZaahEach of the living things you see every day is made of cells.

A cell is the basic unit of structure and function of all living things. Most animals and plants are made up of huge numbers of cells. Almost all cells are microscopic. They can be seen only with a microscope.

Tell what the basic unit of structure and function of all living things is called.

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56c^bVa8ZaahEvery cell has tiny parts called organelles. These keep the

cell alive and working. For example, every cell is covered by a cell membrane. This organelle protects the cell and keeps its contents together.

Most cells have a nucleus that controls the cells activities. Other organelles are suspended in the cells cytoplasm.

Name one organelle found in an animal cell. Tell what the organelle does.

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EaVci8ZaahPlant cells have two organelles that animal cells do not have.

A plant cell has a cell wall that helps support the cell. Plant cells also have chloroplasts that help the plant make food.

Tell one detail that makes a plant cell different from an animal cell.

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Cell Structures Organelle Function Kind of CellNucleus directs a cells activities plant and animalChromosome inside nucleus; contains plant and animal information about cellCell membrane holds a cell together and plant and animal separates it from its surroundingsCell wall supports and protects a plant plant cellCytoplasm a jellylike substance plant and animal containing chemicals that help the cell stay healthyChloroplast makes food for the cell plantVacuole stores food, water, or wastes plant and animalMitochondria release energy from nutrients plant and animal

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1. A ______ is the basic structure of all living things.

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2. Most cells have a ______ that controls the cells activities.

3. Plant cells have ______ and ______ that animal cells do not have.

4. A protist is one kind of ______ organism.

Review Review

H^c\aZ"8ZaaZYDg\Vc^hbhA protist is one kind of single-celled organism. A protist has

a nucleus and organelles. Some protists are plantlike. They have cell walls and chloroplasts. Other protists have no cell walls or chloroplasts. They are more animal-like.

Tell one detail that makes a protist more plantlike than animal-like.

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VOCABULARYtissueorganorgan systemdigestive system

A tissue is a group of cells that work together for a certain function. Muscle is a kind of tissue.

An organ is several kinds of tissue working together for the same function. The lungs are organs.

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An organ system is a group of organs that work together to do a job for the body. Your digestive system is an organ system. It helps the body get nutrients from food. This diagram shows the digestive system.

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READING FOCUS SKILL8DBE6G:6C98DCIG6HI

To compare and contrast is to show how things are alike and different.

Look for ways that tissues, organs, and organ systems are alike and different.

I^hhjZEach cell in your body is able to carry out its own function.

But your bodys cells also work together. Cells that work together to perform a certain function form a tissue. There are four kinds of tissue in your body.

Your skin is made of epithelial (espuhsTHEEsleesuhl) tissue.

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11

Most of your bodys mass is made of muscle tissue. Muscle tissue contracts and relaxes to move the skeleton.

Tendons and ligaments are connective tissue. Tendons connect bones to muscles. Ligaments connect bones to bones. The bones and cartilage of your skeleton are connective tissue, too.

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Nervous tissue is found in the brain, in the spinal cord, and in nerves. Nervous tissue carries signals to all parts of the body. This helps it function smoothly.

Compare muscle tissue and connective tissue.

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Dg\VcCells work together to form tissue, and tissues work together

to form organs. An organ is several kinds of tissue working together for the same function.

Your heart is an organ. It pumps blood to all parts of your body. The heart is made mostly of muscle and connective tissue. Nervous tissue carries signals from the brain to the heart to keep it beating.

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The lungs are organs, too. They are made of several tissues. The tissues work together to take oxygen from the air and move it into the blood.

Tell how a tissue and an organ are alike and different.

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Dg\VcHnhiZbOrgans that work together to do a job for the body are

called an organ system. There are ten major organ systems in your body. Systems work together to keep your body alive and healthy.

Tell the difference between an organ and an organ system.

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Cells to Systems

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9^\Zhi^kZHnhiZbThe digestive system takes nutrients from the food that you

eat. The cells of the body use the nutrients for energy, growth, and repair.

Digestion starts in the mouth. Food is broken down into smaller pieces as you chew. Glands in your mouth produce saliva. Chemicals in the saliva begin breaking down some food.

From the mouth, the food travels into the stomach. Acid and other chemicals in the stomach break down food.

How does saliva compare to stomach acid?

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1. All tissue is made up of ______.

2. Tendons and ligaments are both ______ tissue.

3. Tendons connect ______ to ______.

4. The heart and the lungs are both ______.

5. The heart ______ blood throughout the body. The lungs take ______ out of the air.

Review Review

From the stomach, partly digested food moves into the small intestine. There digestion is completed. The small intestine is lined with tiny tubes called villi. The villi have many blood vessels. Nutrients move into the blood vessels of the villi. Then the nutrients are carried throughout the body.

How has food been changed from the stomach to the small intestine?

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VOCABULARYcirculatory systemrespiratory systemskeletal systemmuscular systemnervous systemexcretory system

The circulatory system transports oxygen, nutrients, and wastes throughout your body.

The respiratory system exchanges oxygen and carbon dioxide with the air.

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The muscular system includes muscles and tendons that move bones.

The skeletal system gives your body structure. It protects your organs.

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The excretory system removes liquid wastes from your body.

The nervous system enables you to sense and react to your environment.

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18

READING FOCUS SKILLH:FJ:C8:

To sequence is to put things in the order in which they happen.

Look for ways to sequence the processes that occur in the systems of the body.

gZYWaddYXZaa8^gXjaVidgnHnhiZbThe circulatory system is

made up of the heart, blood, arteries, capillaries, and veins. The heart gets blood from the lungs. It pumps it to the body. At the same time, it gets blood from the body. It pumps it to the lungs.

Blood leaves the heart through arteries. Arteries lead to small blood vessels called capillaries. Capillaries connect to veins. Veins return the blood to the heart.

Red blood cells carry oxygen to all of the bodys cells.

What happens when blood leaves the heart?

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In the alveoli, oxygen in the lungs is exchanged for carbon dioxide in the blood. The blood carries the oxygen to all the cells of the body. Carbon dioxide is exhaled.

Tell what happens to the air you breathe after it enters the lungs.

GZhe^gVidgnHnhiZbThe respiratory system exchanges oxygen and carbon

dioxide between your body and the air. The body gets the oxygen it needs when you breathe.

The air travels down the trachea, or windpipe. In your chest, the trachea branches into two large tubes. These lead to the lungs.

In the lungs, the tubes branch into smaller tubes. At the ends of these tubes are tiny air sacs called alveoli. These are surrounded by capillaries.

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20

H`ZaZiVaHnhiZbYour skeletal system gives your body structure. It also

protects many of your organs.The skeletal system includes bones, cartilage, and ligaments.

Cartilage is spongy connective tissue. It cushions the ends of many bones.

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An adults skeleton is made up of 206 bones. Ligaments are bands of connective tissue that hold the bones together.

Blood cells are made inside the largest bones. The blood cells pass from these bones into the circulatory system.

Explain where blood cells are made and how they move throughout the body.

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BjhXjaVgHnhiZbYour muscular system is made up of three kinds of muscles.

The muscles that work with your skeleton to move your body are called skeletal muscles.

Skeletal muscles work in pairs. One muscle contracts to bend a joint. The other muscle contracts to straighten it.

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Smooth muscle lines some organs, including blood vessels and digestive organs.

Cardiac muscle makes up the wall of the heart. It contracts to pump blood to all parts of the body.

Tell why the skeletal muscles work in pairs.

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CZgkdjhHnhiZbYour nervous system helps you sense your environment

and react to it. It directs the activities of other body systems. It also connects all organs to your brain.

The nervous system has two parts. The central nervous system is made up of the spinal cord and brain. It receives and interprets signals from nerves throughout the body.

The peripheral nervous system is made up of your sense organs. Sensory organs contain special nerves called receptors. Receptors send signals to the central nervous system about your surroundings.

Explain how receptors would work if you were to cut your hand.

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1. Blood leaves the heart through ______ , which lead to small blood vessels called ______.

2. Air you breathe travels down the ______ , which branches into two ______ , which each lead to a ______.

3. Urine flows from the ______ , through the ______ , and into the ______.

Review Review

:mXgZidgnHnhiZbThe excretory system removes

liquid wastes from your body. The kidneys filter wastes out of

the blood, forming urine. The urine flows into the bladder. When the bladder is full, urine is eliminated from the body.

What happens after urine leaves the kidneys?

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GLOSSARYcell (SEL) the basic unit of structure and function of living things.cell membrane (SEL MEMsbrayn) the thin covering that surrounds

every cell.circulatory system (SERskyoosluhstawrsee SISstuhm) the organ

system that transports oxygen, nutrients, and wastes throughout your body.

cytoplasm (SYTsohsplazsuhm) the jellylike material inside a cell between the cell membrane and the nucleus.

digestive system (dihsJESstiv SISstuhm) the organ system that takes nutrients from food.

excretory system (EKSskruhstawrsee SISstuhm) the organ system that removes liquid waste from the body.

microscopic (myskruhsSKAHPsik) too small to be seen without using a microscope.

muscular system (MUHSskyoosler SISstuhm) the organ system that includes muscles and tendons that move bones.

nervous system (NERsvuhs SISstuhm) the organ system that senses your surroundings and controls other organs.

nucleus (NOOskleesuhs) the cell part that directs a cells activities.organ (AWRsguhn) a group of tissues that work together to perform

a certain function.organ system (AWRsguhn SISstuhm) a group of organs that work

together to do a job for the body.organism (AWRsguhnsizm) any living thing.protist (PROHTsist) a type of organism with a nucleus and organelles.respiratory system (RESspersuhstawrsee SISstuhm) the organ

system that exchanges oxygen and carbon dioxide between the body and the air.

skeletal system (SKELsuhstuhl SISstuhm) the organ system that protects the body and gives it structure.

tissue (TISHsoo) a group of cells that work together to perform a certain function.

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School-Home ConnectionExplain to a family member how the body is organized from single cells to organ systems. Choose one of the bodys systems as an example.

Hands-On Activity 1. Use different colors of clay to make a model of a plant

or animal cell. 2. Use strips of construction paper to label each of the

cells parts. 3. Use the model to explain how a cell functions.

Think About the Reading 1. What can you do to help you remember what you have

learned in this book? 2. What questions do you have after reading this book?

How can you find the answers to your questions?

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Harcourt LeveledReaders Online Database www.eharcourtschool.com

j]Y+6.%3'Z[W>

ISBN-13: 978-0-15-362053-9ISBN-10: 0-15-362053-6

GRADE 5

Book 1

WORD COUNT

1228

GENRE

Expository Nonction

LEVEL

See TG or go Online