218

How AreCotton & Cookies

Connected?

How AreCotton & Cookies

Connected?

In the 1800s, the economy of the South depended heavily on cotton andtobaccotwo crops that rob the soil of nutrients, especially nitrogen. By thelate 1800s, the soil was in poor shape. A scientist named George WashingtonCarver set out to change that. He promoted the technique of crop rotationalternating soil-depleting crops such as cotton with soil-enriching crops such aspeanuts. Many farmers listened to Carver and began planting peanuts. However,there was little market for the crop. So Carver poured his energy into developinguses for peanuts. Ultimately, he came up with more than 300 products madefrom peanutseverything from soap to axle grease. He also created the firstrecipe for peanut butter cookies, which have become an American favorite.

Visit unit projects at to find project ideas and resources.Projects include: History Investigate land use in the U.S. during the past 200 years. Design flip

charts to compare, and then predict, the land use of the future. Technology Research how legumes fix nitrogen and why crop rotation

keeps farm land more productive. Model Explore peanut inventions. Design your own creative use for peanuts,

write directions, and build a prototype for a class peanut invention fair.Recycling Plastics explores the seven classes of plastics and theiruses, as well as the chemistry of plastic. Discover what it takes torecycle plastic, glass, paper, and aluminum.

glencoe.com

http://www.glencoe.com

220220

sections

1 Living Things

2 How are living things classified?

3 Cell StructureLab Comparing Cells

4 VirusesLab Comparing Light Microscopes

Virtual Lab How are living thingsclassified into groups?

Surrounded by Life!This scientist is getting a chance to seemany different living things and to studyhow they interact. Living things have somecommon characteristics. These characteris-tics are what scientists use to classify life. Byclassifying life, scientists can determine howall living things, including humans, relate toeach other.

Make a list of the living things yousee in this photo.Science Journal

Lifes Structureand Classification

LE 1.1a: Living things are composed of cells. Cells provide structure and carry on major functions tosustain life. Cells are usually microscopic in size. 1.1b: The way in which cells function is similar in allliving things. Cells grow and divide, producing more cells. Cells take in nutrients. Also covered: 1.1c,1.1d, 1.1e, 1.1f, 1.1g, 1.1h, 1.2a, 1.2j, 1.3d, 5.1a, 5.1c.

Lifes Structure and Classifica-tion Make the following Fold-able to help you understand the

vocabulary terms in this chapter. Use this Foldableto review for the chapter test.

Fold a sheet of notebook paper inhalf lengthwise.

Cut along every third line of only thetop layer to form tabs.

Turn vertically and label each tab asdescribed below.

Build Vocabulary As you read the chapter, listthe vocabulary words about the classificationand structure of life on the tabs. As you learn thedefinitions, write them under the tab for eachvocabulary word.

STEP 3

STEP 2

STEP 1

Classifying LifeLife scientists discover, describe, and namehundreds of organisms every year. Whatmethods do they use to decide if an insect ismore like a grasshopper or a beetle?

1. Observe an insectcollection or a collection of other organisms.

2. Decide which feature could be used to separate

the organisms into two groups, then sort the organisms into the two groups.

3. Continue to make new groups using dif-ferent features until each organism is in acategory by itself.

4. Think Critically List the features youwould use to classify the living thing inthe photo above. How do you think scien-tists classify living things?

Start-Up Activities

221221

Preview this chapters contentand activities at glencoe.com

http://www.glencoe.com

222 CHAPTER 8 Lifes Structure and Classification

What are living things like?What does it mean to be alive? If you walked down your

street after a thunderstorm, youd probably see birds flying andclouds moving across the sky. Youd see living and nonlivingthings that are alike in some ways. For example, birds and cloudsmove. Yet clouds are nonliving things, and birds are livingthings. Any living thing is called an organism.

Organisms vary in sizefrom the microscopic bacteria inmud puddles to gigantic oak treesand are found just abouteverywhere. They have different behaviors and food require-ments. In spite of these differences, all organisms have similartraits. These traits determine what it means to be alive.

Living Things Are Organized Imagine looking at almost anypart of an organism, such as a plant leaf or your skin, under amicroscope. You would see that it is made up of small units calledcells, such as the ones pictured in Figure 1. A cell is the smallestunit of an organism that carries on the functions of life. Cellstake in materials from their surroundings and use them in com-plex ways. Some organisms are composed of just one cell whileothers are composed of many cells. Each cell has an orderlystructure and contains the instructions for cellular organizationand function in its hereditary material. All the things an organ-ism can do are possible because of what their cells can do.

How are living things organized?

Distinguish between living andnonliving things.

Identify what living things needto survive.

All living things, including you, havemany of the same traits.

Review Vocabularytrait: a feature of a living thing

New Vocabulary

organism cell homeostasis

Living Things

Figure 1 The human body isorganized into many differenttypes of cells. Two types areshown to the right.

Muscle cells

Nerve cells

Color-enhanced SEM Magnification: 2500

Color-enhanced LM Magnification: 106

LE 1.1a: Living things are composed of cells. Cells provide structure and carry on major functions to sustainlife. Cells are usually microscopic in size. Also covered: 4.3d, 5.1a, 5.1c.

Living Environment

1.1a: Define cell. Include adescription of its structure andfunction.

Living Things Grow and Develop When a puppy is born,it might be small enough to hold in one hand. After the samedog is fully grown, you might not be able to hold it at all. Howdoes this happen? Growth of a many-celled organism, such asa puppy, is mostly due to an increase in the number of cells. Inone-celled organisms, growth is due to an increase in the sizeof the cell.

Organisms change as they grow. Puppies cant see or walkwhen they are born. In eight or nine days, their eyes open, andtheir legs become strong enough to hold them up. All of thechanges that take place during the life of an organism are calleddevelopment. Figure 2 shows how four different organismschanged as they grew.

The length of time an organism is expected to live is its lifespan. Some dogs can live for 20 years. Other organisms have ashort life span. For example, mayflies live only one day. Yet,others have a much longer life span. A land tortoise can livefor more than 180 years, and some bristlecone pine trees havebeen alive for more than 4,600 years! A humans life span isabout 80 years.

SECTION 1 Living Things 223

Figure 2 Complete develop-ment of an organism can take afew days or several years.

A human

A butterflyA peaplant

A dog

Human Stages ofDevelopment Humaninfants cant take care ofthemselves at birth.Research to find out whathuman infants can do atdifferent stages of develop-ment. Make a chart thatshows changes from birthto one year of age.

Topic: Homeostasis Visit for Web links to information about homeostasis.

Activity Choose two livingthings and describe a method eachuses to maintain homeostasis.

glencoe.com

Living Things Respond Living things must interact withtheir surroundings. Anything that causes some change in anorganism is a stimulus (plural, stimuli). The reaction to a stim-ulus is a response. Often, that response results in movement. Anorganism must respond to stimuli to carry on its daily activityand to survive.

Living Things Maintain Homeostasis Living things alsomust respond to stimuli that occur inside them. For example,water or food levels in an organisms cells can increase ordecrease. The organism then makes internal changes to main-tain the right amounts of water and food in its cells. The regu-lation of an organisms internal, life-maintaining conditiondespite changes in its environment is called homeostasis.Homeostasis is a trait of all living things.

What is homeostasis?

Living Things Use Energy Staying organized and carryingon activities like finding food requires energy. The energy usedby most organisms comes either directly or indirectly from theSun. Plants and some other organisms can use the energy insunlight, carbon dioxide, and water to make food. You and manyother organisms cant use the energy in sunlight directly.Instead, you take in and use food as a source of energy. In orderto release the energy in food, you and many other organismsmust take in oxygen.

Some bacteria live at the bottom of the oceans and in otherareas where sunlight cannot reach. They cant use the Sunsenergy to produce food; instead, the bacteria use energy storedin some chemical compounds and carbon dioxide to make food.Unlike many other organisms, most of these bacteria do notneed oxygen to release the energy that is found in their food.

Living Things Reproduce All livingthings eventually reproduce, to make more oftheir own kind. Some bacteria reproduceevery 20 minutes, while it might