28.1 Levels of Organization

Transcription

1 SECTION 28.1 Plan and Prepare Objectives Describe cell specialization and levels of organization. Identify how levels of organization work together in an organism. Section Resources Unit Resource Book Study Guide pp. 1 2 Power Notes p. 3 Reinforcement p. 4 Pre-AP Activity pp Interactive Reader Chapter 28 Spanish Study Guide pp Biology Toolkit pp. C6, C19, D3, D9 Technology Power Presentation 28.1 Media Gallery DVD Online Quiz 28.1 Activate Prior Knowledge Have students think about the way employees in a large company are organized. Ask, How would you describe the relationship between different jobs, divisions, and levels of responsibility in a company? Every part of the company is dependent on every other part functioning properly and efficiently. Tell students that in this section, they will learn about how the body levels of organization work together. Teach TEACH FROM VISUALS FIGURE 28.1 Have students observe the differences in appearance of the cells. Ask In what way are all the cells in the body alike? have the same DNA What accounts for the differences in these two cells? Different genes are turned off and on depending on cell type. Remind students of the Hox genes they learned about in genetics. 852 Unit 9: Human Biology 28.1 Levels of Organization KEY CONCEPT The human body has five levels of organization. 4.c Describe and differentiate among the organizational levels of organisms (e.g., cells, tissues, organs, systems, types of tissue). FIGURE 28.1 The disk-shaped red blood cells (top) carry oxygen to all parts of the body. The neuron (bottom), through its extensions, receives and transmits messages from and to other neurons. (colored SEMs; magnifications: blood cells 2800 ; neuron about 1600 ) 852 Unit 9: Human Biology Differentiated Instruction hspe indd 852 MAIN IDEAS Specialized cells develop from a single zygote. Specialized cells function together in tissues, organs, organ systems, and the whole organism. ENGLISH LEARNERS Have students preview the chapter by having them look at headings, illustrations, and key terms. Ask them to predict what will be important and why they think so. Set up a four-column table with the headings: What I Know I Know, What I Think I Know, What I Think I ll Learn, What I Learned. Have students fill in the first three columns, leaving the last column empty until they complete the chapter. Biology Toolkit, DRTA, p. C6 VOCABULARY determination, p. 852 differentiation, p. 853 tissue, p. 854 organ, p. 854 organ system, p. 854 Review cell, stem cell, zygote Connect Climbing a wall of ice requires careful interaction among all parts of the body. You probably know that the brain and muscles work together to coordinate the climber s movements. The heart and lungs also have to work together to help provide energy for the climb. Yet every human body starts out as a single cell, a fertilized zygote. How does a single cell give rise to all the different types of cells, tissues, and organs in the human body? Further, how do such different parts coordinate their activities to keep the body functioning? MAIN IDEA Specialized cells develop from a single zygote. If you were to watch an emergency medical team in action, you would quickly notice that each person has a special job. One keeps in radio contact with the main hospital. Another monitors the patient s vital signs. Still others perform life-saving procedures. All emergency teams are made up of people, but each person within the group has a different job. Likewise, multicellular organisms are made up of cells, but different cells in the organism have different functions. Take a moment to study the images of the blood cells and nerve cells, or neurons, in FIGURE You will notice that the red blood cells are round with a concave center. This structure gives them more surface area to help deliver oxygen to all parts of the body. In contrast, neurons develop extensions that transmit and receive messages from other neurons. Humans, like almost all multicellular organisms, are collections of specialized cells that work together. These cells arise from a single cell, the zygote, which is formed by the union of an egg and sperm. The zygote divides and differentiates into more than 200 different types of human cells. These cells allow you to do everything from lifting a glass, to learning people s names, to maintaining your body temperature on a cold day. Cell specialization involves two main steps: determination and differentiation. Determination The cells produced during the first few divisions of the zygote are known as embryonic stem cells. These cells have the potential to become any type of specialized cell in the body. Within a few weeks, however, a process called determination occurs in which most stem cells become committed to develop 9/9/09 7:46:52 PM

2 A into only one type of cell. For instance, a stem cell might become a cardiac muscle cell or a spinal neuron. These committed cells still retain all of the genetic information needed to build an entire organism. However, during determination, they lose their ability to express some of this information. Once a cell is committed to becoming a specialized cell, it will develop into only that type of cell. For instance, a cell that will become a neuron can only be a neuron, even if it is transplanted into another part of the body. During normal development, determination cannot be reversed. Differentiation Differentiation is the process by which committed cells acquire the structures differentiation and functions of highly specialized cells. Differentiation occurs because supporting detail specific genes in each cell are turned on and off in a complex, regulated pattern. The different structures of these specialized cells, such as those shown in FIGURE 28.2, allow them to perform specific functions within the body. The function of muscle cells, for example, is to produce movement by contracting and relaxing. However, skeletal muscle and smooth muscle cells have different structures. Skeletal muscle cells align in bands of orderly rows and contain many nuclei. They are responsible for nearly all voluntary muscle movements, such as lifting your foot to kick a ball. In contrast, FIGURE 28.2 Cell Differentiation smooth muscle cells are shorter Cells develop specialized structures and functions during differentiation. and have only one nucleus. They perform involuntary movements, such as raising the hairs on your Connective cells Smooth muscle cells in arms and legs. in skin intestinal wall Other cells have even more specialized structures and functions. Sperm cells, for instance, develop whiplike tails that enable them to swim. Cells lining the gut are elongated and tightly packed to provide more surface area for the absorption of nutrients. Not all cells continue to develop into specialized cells. The process of programmed cell death, called apoptosis (AP-uhp-TOH-sihs), is also a normal part of development. For example, when your hands first formed, your fingers resembled a mitten. The death of cells between the fingers allowed individual fingers to develop. Analyze What are some of the reasons that multicellular organisms need specialized cells? Bone cells Epithelial cells in skin BELOW LEVEL Have students note how key vocabulary are used in the text. In their notebooks, have them write what each word means based on their reading of the text. Have them check the definition in the Glossary. Then have students use the word in a sentence and draw a picture that will help them remember the meaning. B ZYGOTE Sperm cells TAKING NOTES Use a supporting main ideas strategy to take notes about processes such as cell specialization. Specialized cells develop from embryonic stem cells. determination cells are committed to be one type of cell Skeletal muscle cells Epithelial cells in stomach lining Contrast How do the structures of sperm cells and epithelial cells in the stomach differ? Chapter 28: Human Systems and Homeostasis 853 b10hspe indd 853 8/13/08 2:22:23 Biology Toolkit, Student Vocabulary, p. D3 PRE-AP Tell students that there are about 25 trillion red blood cells in the human body, each with a life span of about days. Red blood cells that are worn out and die are replaced by new cells produced in the bone marrow and stored in the spleen. Have students calculate the number of blood cells the human body loses due to natural cell death each second. 25 trillion cells 10.4 million seconds 2.4 million cells per second This is about half the number of red blood cells in one cubic millimeter of blood. Vocabulary Greek and Latin Word Origins Students know the word species, which shares the same Latin root as the word special, meaning of a certain kind. Tell students that it is possible to think of specialized cells as belonging to a species. A species of muscle cell is distinct from a species of skin cell, in a similar sense that one species of bird is different, yet similar, to another. The Inside Story What does it mean that you are 16 or 17 years old if your cells regularly replace themselves? Dr. Jonas Frisén, a stem-cell biologist at the Karolinska Institute in Stockholm, has developed a way to estimate the ages of human cells. He developed a scale for converting the carbon-14 in tissues into calendar dates. Using this dating technique, Dr. Frisén estimates the average age of all the cells in an adult s body may be seven to ten years. A hotly debated topic is whether the brain generates new neurons. Using his technique, Dr. Frisén has shown that cells from the visual cortex in the brain are the same age as the individual. These are the cells that enable you to see and interpret what you see. Still to be determined are whether the cells associated with the cerebral cortex, involved with memories and consciousness, are also as old as you are. A Analyze Multicellular organisms need specialized cells to build specialized tissues and organs that carry out functions such as respiration, digestion, and elimination. Specialization also allows multicellular species to become much larger than unicellular species can. B Contrast Sperm have a head and a long tail that enables them to move. Epithelial cells are elongated, are tightly packed, and have hairlike cilia at the surface to move materials. 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3 Teach continued ONLINE BIOLOGY Go to the chapter Resource Center at ClassZone.com for additional resources and information on levels of organization. Science Trivia Skin is the largest organ of the human body. Unlike other organs that are distinct and separate structures, skin covers the entire body. Adults have about 1.7 square meters (20 ft 2 ) of skin. Skin makes up about percent of a person s body weight. Every minute approximately 30,000 40,000 dead skin cells are removed from the body. In a person s lifetime, he or she will lose around 18 kilograms (40 lb) of dead skin. Your body will produce an entirely new layer of skin in one month s time. Connecting CONCEPTS Digestion and Elimination In addition to serving as a protective layer, epithelial tissue can absorb materials and secrete special types of fluids. Your ability to digest food and eliminate waste depends in part on the specialized functions of epithelial tissue, as you will learn in Chapter 32. MAIN IDEA Specialized cells function together in tissues, organs, organ systems, and the whole organism. Specialized, or differentiated, cells are only the first level of organization in a multicellular organism. Scientists organize multicellular structures into five basic levels, beginning with cells and moving to increasingly complex levels tissues, organs, organ systems, and the whole organism. These five levels in the human body are shown in FIGURE Cells Each type of specialized cell has a particular structure and a chemical makeup that enable it to perform a specific task. Some cells in the lungs, for instance, are involved in the exchange of gases. Others secrete mucus that helps to trap foreign particles and to protect the lungs from pathogens, such as bacteria and viruses. 2 Tissues Groups of similar cells that work together to perform a specialized function are known as tissues. The human body is made up of four general types of tissues. Epithelial tissue consists of protective sheets of tightly packed cells connected by special junctions. The skin and the membranes that line the stomach, the lungs, and other organs are epithelial tissues. Connective tissue serves to support, bind together, and protect other tissues and organs. Tendons, ligaments, bone, and cartilage are all connective tissues. Muscle tissue is capable of contracting to produce movement. The human body contains skeletal, cardiac, and smooth muscle tissues. Nervous tissue transmits and receives impulses in response to stimuli, processes information, and regulates the body s response to its environment. 3 Organs Different types of tissue that function together form an organ. For example, the lungs are organs composed of all four types of tissues. Muscle and connective tissues expand and contract the lungs. Nervous tissue sends and receives messages that help regulate gas exchange in the lungs and the rate at which a person breathes. Epithelial tissue forms the inner lining of the lungs. 4 Organ systems Two or more organs working in a coordinated way form an organ system. The organ system that allows you to breathe includes not only the lungs but also the sinuses, the nasal passages, the pharynx, and the larynx (the voice box). Organ systems perform the most complex activities in the body. 5 Organism Together, the organ systems make up the entire organism. For you or any other organism to stay alive, all of the systems must interact and work together. As a result, anything that harms one organ or organ system will affect the health of the entire body. Differentiated Instruction 854 Unit 9: Human Biology TEACH WITH TECHNOLOGY Students might enjoy viewing a portion of the 1966 film Fantastic Voyage. In this science fiction film, a miniaturized medical team is inserted into the human bloodstream with the goal of removing a blood clot in the brain of an important scientist. The film was made long before the advent of computer animation yet provides an entertaining realization of the body. hspe indd Sec1:854 PRE-AP The human body, with its five levels of organization, can be compared to the structure of an ecosystem with its different levels of organization. Have students explore this analogy by developing a visual presentation that illustrates their interpretation of this idea. Students should provide a written explanation of the thinking behind their interpretation bh i dd d d 6/6/ AM Biology Toolkit, Analogies, p. D9 6/6/06 11:31:39 AM 854 Unit 9: Human Biology

4 FIGURE 28.3 Five Levels of Organization All levels of organization interact and work together to maintain the body s health. 3 2 ORGANS Lungs The lungs are composed of four types of tissue. The lungs are the site where gases are exchanged. 4 ORGAN SYSTEMS Respiratory System This system includes the lungs, trachea, larynx, pharynx, sinuses, and nose. The nose and sinuses filter, moisten, and warm the air before it enters the lungs. 1 CELLS Epithelial Lung Cell These cells have tiny hairlike structures (cilia) at the top. TISSUES Epithelial Lung Tissue Cells with cilia are packed together in the lung s inner lining. They act like a conveyor belt to move foreign particles and pathogens out of the lungs. BIOLOGY Explore the human organ systems at ClassZone.com. TEACH FROM VISUALS FIGURE 28.3 Point out to students that the numbers in the diagram correspond to the numbered list on page 854. Ask What cells are featured in the figure, and what system do they belong to? epithelial cells of the lung and respiratory system Looking at the drawing of the girl and the organs identified in caption 4, what parts of the respiratory system lead from the nose to the lungs? nose leads to pharynx and larynx, then to trachea and into lungs What is the primary function of the respiratory system? exchange of gases, supply oxygen needed to release energy, remove waste carbon dioxide Science Trivia The size of an average human body cell is ten micrometers. It would take over 39 million cells to cover the floor of a high school basketball court. It would take 6000 cells to cover a sheet of notebook paper. Roughly 1000 cells would be needed to cover a dollar bill. A CRITICAL VIEWING 5 ORGANISM Human The respiratory system is one of several organ systems that work together to keep the human body functioning properly. How might a sinus infection affect the rest of the respiratory system? BELOW LEVEL Have students look at the full list of systems in FIGURE Point out that the first letter of each system can be used to make the words miners and cider. After reviewing the information, have students close their books. Give them five minutes to write down as many systems as they can remember and a function for each. To help them remember, remind them that miners like cider. Chapter 28: Human Systems and Homeostasis 855 bhspe indd Sec1:855 6/6/06 11:31:44 Biology Toolkit, Quick-Write, p. C19 A Critical Viewing Air first enters through the nose and sinuses, where it is filtered, moistened, and warmed. If the sinuses were blocked by infection, the person would have to breathe through the mouth and there would be a greater chance of harmful pathogens or foreign matter entering the lungs. Drainage from the sinuses could also spread pathogens to the airways, producing a lower respiratory infection. Chapter 28: Human Systems and Homeostasis 855

5 Teach continued Take It Further In 1989, the National Library of Medicine set out to create a digital atlas of the human body called the Visible Human Project. The University of Colorado Heath Sciences Center created the atlas by combining CT and MRI images of cross sections of a male and a female cadaver. Both bodies, from a 39-year-old male and a 59-year-old female, had been donated to science. The Visible Human Project provides medical, research, and educational communities with the unique opportunity to see organs and systems in relation to one another, along the entire length of the human body. A Compare and Contrast Tissues are composed of one specific type of differentiated cell. Organs consist of two or more types of tissues. Organ systems are composed of two or more organs working in a coordinated fashion. Organs and organ systems perform more complex activities than tissues do. FIGURE 28.4 Major Organ Systems SYSTEM MAJOR TISSUES AND ORGANS PRIMARY FUNCTION Circulatory Digestive Endocrine heart, blood vessels, blood, lymph nodes, lymphatic vessels mouth, pharynx, esophagus, stomach, small large intestines, pancreas, gallbladder, liver hypothalamus, pituitary, thyroid, parathyroid, adrenals, pancreas, ovaries, testes transports oxygen, nutrients, wastes; helps regulate body temperature; collects fluid lost from blood vessels and returns it to circulatory system breaks down and absorbs nutrients, salts, and water; eliminates some wastes influences growth, development, metabolism; helps maintain homeostasis Excretory skin, lungs, kidneys, bladder eliminates waste products; helps maintain homeostasis Immune white blood cells, thymus, spleen protects against disease; stores and generates white blood cells Integumentary skin, hair, nails, sweat and oil glands acts as a barrier against infection, injury, UV radiation; helps regulate body temperature Muscular skeletal, smooth, and cardiac muscles produces voluntary and involuntary movements; helps to circulate blood and move food through digestive system Nervous brain, spinal cord, peripheral nerves regulates body s response to changes in internal and external environment; processes information Reproductive male: testes, penis, associated ducts and glands female: ovaries, fallopian tubes, uterus, vagina produces reproductive cells; in females, provides environment for embryo Respiratory nose, sinuses, pharynx, larynx, trachea, lungs brings in O 2 for cells; expels CO 2 and water vapor Skeletal bones, cartilage, ligaments, tendons supports and protects vital organs; allows movement; stores minerals; serves as the site for red blood cell production A The major organ systems in the human body, including their main parts and primary functions, are listed in FIGURE Keep in mind that all of the organs in these systems developed from specialized cells and tissues that arose from a single cell, the zygote. The major parts and functions of each organ system are examined in greater detail in Chapters 29 through 34. How do these complex organs and organ systems keep functioning and working together properly? As you will read in Section 28.2, the body has sophisticated mechanisms for maintaining a stable internal environment. Compare and Contrast How do tissues differ from organs and organ systems? Assess and Reteach Assess Use the Online Quiz or Section Quiz (Assessment Book, p. 553). Reteach Have students make a graphic organizer that shows the hierarchical relationships among cells, tissues, organs, organ systems, and organism ASSESSMENT REVIEWING MAIN IDEAS 1. How does the process of cell determination differ from the process of cell differentiation? 2. Briefly define and give an example of each of the five levels of organization in multicellular organisms. CRITICAL THINKING 3. Apply What organ systems must work together to bring oxygen to the body s cells? 4. Predict A cell has undergone determination to become an endocrine gland cell. If it is transplanted to a leg muscle, what do you think will happen to this cell? ONLINE QUIZ ClassZone.com Connecting CONCEPTS 5. Cell Cycle In the spring, tadpoles lose their tails as part of their life cycle. At a certain stage in development, the human fetus acquires individual fingers and toes. What occurs in some cells of both species to explain these changes? 28.1 ASSESSMENT 1. In cell determination, stem cells commit to becoming a certain type of cell, such as a muscle cell. In cell differentiation, cells develop the actual structures and functions that make them specialized cells. 2. A cell is the smallest unit of life (example: neuron). A tissue is a group of similar cells that work together to perform a specialized function (example: nerve tissue). Organs consist of two or more types of 856 Unit 9: Human Biology tissues that function together (example: brain). Organ systems consist of two or more organs working together (example: brain and spinal cord). 3. The respiratory system brings oxygen into the body. Part of the muscular system coordinates the movement of the lungs. The circulatory system picks up oxygen from the lungs and delivers it to body cells. 4. Because determination is usually not reversible, the cell and its daughter cells will continue to develop as endocrine cells. 5. Both are examples of programmed cell death, or apoptosis. 856 Unit 9: Human Biology

6 CHAPTER 28 MATERIALS jump rope stop watch PROCESS SKILLS Observing Collecting data 1.c Apply the components of scientific processes and methods in classroom and laboratory investigations. 1.d Construct and analyze graphs. 1.g Communicate and defend a scientific argument in oral, written, and graphic form. INVESTIGATION Homeostasis and Exercise Your body s temperature, heart rate, and blood pressure need to remain within certain set ranges. In this lab, you will work in groups to examine the effects of exercise on the circulatory and respiratory systems and on perspiration level. PROBLEM How does exercise affect a person s heart rate, breathing rate, and perspiration level? PROCEDURE 1. Choose one person to jump rope. Measure the person s heart rate by taking his or her pulse for 15 seconds. Multiply this number by four to calculate beats per minute. (Caution: If the person exercising feels discomfort at any time, stop the experiment and inform your teacher.) 2. Measure the person s breathing rate by counting the number of breaths taken in 15 seconds. Multiply this number by four to calculate breaths per minute. 3. Rate the person s perspiration level from 1 to 5 (1 = none; 5 = droplets dripping down the face). 4. Design a data table like the one shown below. Write a hypothesis about the effect of exercise on the dependent variables that you are measuring. 5. Have the person jump rope for 2 minutes. When the person stops, measure heart rate, breathing rate, and perspiration level and record the data. Repeat step 5 three more times and record your data at each point. 6. After the final recording of the dependent variables, wait 1 minute and measure all of the variables again. TABLE 1. EFFECTS OF EXERCISE Time (Min) Heart Rate (Beats/Minute) Breathing Rate (Breaths/Minute) Perspiration Level ANALYZE AND CONCLUDE 1. Identify Variables What is the independent variable in this experiment? 2. Organize Data Graph the relationship between the independent and dependent variables. You may choose one graph to display all of your data, or you may use separate graphs for each of the dependent variables. Explain your graph choice. 3. Summarize What are the effects of exercise over time on the circulatory and respiratory systems and on perspiration level? 4. Synthesize What other processes could you have measured to determine the external and internal effects of exercise on the body? 5. Infer How is perspiration level related to body temperature? How is perspiration related to homeostasis? INVESTIGATION Time 45 minutes Teacher Preparation Student Difficulty Lab Binder Human Bio, pp. 1 4 Purpose Measure the effects of exercise on body systems. Overview Student teams will test the effect of exercise on the circulatory, respiratory, and integumentary systems. They will predict the effect of exercise on heart rate, breathing rate, and perspiration level graph the relationships between the independent and dependent variables, using the data collected LAB PREPARATION Move furniture to create an open space. LAB MANAGEMENT Ask for one or two volunteers to jump rope for the experiment. Extend the readings at the end of the investigation to see how long it takes to return to the resting rates. Safety Caution students to stop jumping if they feel uncomfortable and to inform you right away. Any student who has a health problem that could be exacerbated by physical activity should not be allowed to jump rope. POST-LAB DISCUSSION Sample Data For a sample of student graphs from this lab, go to page R108. Chapter 28: Human Systems and Homeostasis 857 b10hspe ci.indd 857 8/18/09 11:50:50 A Analyze and Conclude 1. amount of time spent exercising 2. Graphs can be line graphs, bar graphs, or a combination of both. Heart and breathing rates can be placed on one y-axis with perspiration level on a second. 3. Exercise leads to increased heart rate, breathing rate, and perspiration level. 4. Sample Answer: blood pressure and body temperature 5. Higher perspiration level indicates higher body temperature. Perspiration is one way the body cools itself to maintain a fairly constant body temperature. Relate the variables tested to homeostasis. Ask, Why do heart rate and breathing rate increase with exercise? During exercise, muscle cells demand more energy. More oxygen must be taken in for cellular respiration to produce energy, so the breathing rate increases. The heart rate increases so that the blood can quickly deliver oxygen to the muscles. Teacher Note Students are able to make connections beyond homeostasis and inquire about relationships between breathing and heart rate. Chapter 28: Human Systems and Homeostasis 857