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  • Sunshine State STANDARDS SC.F.1.3.2: The student knows that the struc- tural basis of most organisms is the cell and most organisms are single cells, while some, including humans, are multicellular. SC.H.1.3.6: The student recognizes the scientific contributions that are made by individuals of diverse backgrounds, interests, talents, and motivations.

    Chapter 16: Systems, Support, and Movement 571

    BEFORE, you learned

    • All living things are made of cells

    • All living things need energy • Living things meet their needs

    through interactions with the environment

    NOW, you will learn

    • About the organization of the human body

    • About different types of tissues • About the functions of organ

    systems

    KEY CONCEPT

    The human body is complex.

    The body has cells, tissues, and organs. Your body is made of many parts that work together as a system to help you grow and stay healthy. The basic level of organization in your body is the cell. Next come tissues, then individual organs, and then systems that are made up of organs. The highest level of organization is the organism itself. You can think of the body as having five levels of organization: cells, tissues, organs, organ systems, and the organism. Although these levels seem separate from one another, they all work together.

    Check Your Reading What are five levels of organization in your body?

    MAIN IDEA WEB As you read this section, complete the main idea web begun on page 570.

    THINK ABOUT

    How is the human body like a city?

    A city is made up of many parts that perform different functions. Buildings provide places to live and work. Transportation systems move people around. Electrical energy provides light and heat. Similarly, the human body is made of several sys- tems. The skeletal system, like the framework of a build- ing, provides support. The digestive system works with the respiratory system to provide energy and materials. What other systems in your body can you compare to a system in the city?

    FCAT VOCABULARY tissue p. 572 organ p. 573

    VOCABULARY organ system p. 574 homeostasis p. 574

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  • 572 Unit 5: Human Biology

    Cells The cell is the basic unit of life. Cells make up all living things. Some organisms, such as bacteria, are made of only a single cell. In these organisms the single cell performs all of the tasks necessary for sur- vival. That individual cell captures and releases energy, uses materials, and grows. In more complex organisms, such as humans and many other animals and plants, cells are specialized. Specialized cells per- form specific jobs. A red blood cell, for example, carries oxygen from the lungs throughout the body.

    Tissues A is a group of similar cells that work together to perform a par- ticular function. Think of a tissue as a brick wall and the cells within it as the individual bricks. Taken together, the bricks form something larger and more functional. But just as the bricks need to be placed in a certain way to form the wall, cells must be organized in a tissue.

    Check Your Reading How are cells related to tissues?

    The human body contains several types of tissues. These tissues are classified into four main groups according to their function: epithelial tissue, nerve tissue, muscle tissue, and connective tissue.

    tissue

    SystemsSystems

    SKILL FOCUS Predicting

    MATERIALS large sheet of

    paper

    TIME 20 minutes

    How do the systems in your body interact? PROCEDURE

    Work with other classmates to make a list of everyday activities.

    Discuss how your body responds to each task. Record your ideas.

    Identify and count the systems in your body that you think are used to perform the task.

    Have someone from your group make a chart of the different activities.

    WHAT DO YOU THINK? • Which systems did you name, and how did they work together

    to perform each activity?

    • When you are asleep, what activities does your body perform?

    CHALLENGE How could you make an experiment that would test your predictions?

    4

    3

    2

    1

    reminder

    Notice that humans have cells, tissues, organs, and organ systems like those of multicellular organisms that you studied in grade 6.

    Content Review FLORIDA

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  • • Epithelial (ehp-uh-THEE-lee-uhl) tissue functions as a boundary. It covers all of the inner and outer surfaces of your body. Each of your internal organs is covered with a layer of epithelial tissue.

    • Nerve tissue functions as a messaging system. Cells in nerve tissue carry electrical impulses between your brain and the various parts of your body in response to changing conditions.

    • Muscle tissue functions in movement. Movement results when muscle cells contract, or shorten, and then relax. In some cases, such as throwing a ball, you control the movement. In other cases, such as the beating of your heart, the movement occurs without conscious control.

    • Connective tissue functions to hold parts of the body together, providing support, protection, strength, padding, and insulation. Tendons and ligaments are connective tissues that hold bones and muscles together. Bone itself is another connective tissue. It supports and protects the soft parts of your body.

    Organs Groups of different tissues make up organs. An is a structure that is made up of two or more types of tissue that work together to carry out a function in the body. For example, the heart that pumps blood around your body contains all four types of tissues. As in cells and tissues, the structure of an organ relates to its function. The stom- ach’s bag-shaped structure and strong muscular walls make it suited for breaking down food. The walls of the heart are also muscular, allowing it to function as a pump.

    organ

    Chapter 16: Systems, Support, and Movement 573

    The human body can be studied at different levels of organization.

    Levels of Organization

    Tissue (cardiac muscle)

    Organ (heart)

    Organ system (circulatory system)

    Cells (muscle cells)

    Organism (human)

    250 �

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  • Organ Systems An is a group of organs that together perform a func- tion that helps the body meet its needs for energy and materials. For example, your stomach, mouth, throat, large and small intestines, liver, and pancreas are all part of the organ system called the digestive system. The body is made up of many organ systems. In this unit, you will read about these systems. They include the skeletal, muscular, res- piratory, digestive, urinary, circulatory, immune, nervous, and reproductive systems. Together, these systems allow the human organ- ism to grow, reproduce, and maintain life.

    The body’s systems interact with one another.

    The ability of your body to maintain internal conditions is called (HOH-mee- oh-STAY-sihs). Your body is constantly regulating such things as your body tempera- ture, the amount of sugar in your blood, even your posture. The processes that take place in your body occur within a particular set of conditions.

    The body’s many levels of organization, from cells to organ systems, work constantly to maintain the balance needed for the survival of the organism. For example, on a hot day, you may sweat. Sweating keeps the temperature inside your body constant, even though the temperature of your surroundings changes.

    homeostasis

    organ system

    KEY CONCEPTS 1. Draw a diagram that shows

    the relationship among cells, tissues, organs, and organ systems.

    2. Make a chart of the four basic tissue groups that includes names, functions, and examples.

    3. Identify three functions per- formed by organ systems.

    CRITICAL THINKING 4. Apply How does drinking

    water after you sweat help maintain homeostasis?

    5. Compare and Contrast Compare and contrast the four basic tissue groups. How would all four types of tissue be involved in a simple activity, like raising your hand?

    CHALLENGE 6. Apply Describe an object,

    such as a car, that can be used as a model of the human body. Explain how the parts of the model relate to the body.

    574 Unit 5: Human Biology

    INFER This student is drinking water after exercising. Why is it important to drink fluids after you sweat?

    reading tip

    The word homeostasis contains two word roots. Homeo comes from a root meaning “same.” Stasis comes from a root meaning “stand still” or “stay.”

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