Sci 10 Ch 9.pdf - 9 C H A P T E R From Cell to \u2022 How do plants use specialized cells to accomplish the same functions as a single cell but on a larger

Sci 10 Ch 9.pdf - 9 C H A P T E R From Cell to u2022 How...

This preview shows page 1 out of 42 pages.

You've reached the end of your free preview.

Want to read all 42 pages?

Unformatted text preview: 9 C H A P T E R From Cell to • How do plants use specialized cells to accomplish the same functions as a single cell, but on a larger scale? • How do transport systems move matter in, throughout, and out of plants? • What are the mechanisms that enable plants to respond to their environment? 318 318 MHR MHR •• Flow Unit of 3 Matter CyclinginofLiving MatterSystems in Living Systems Organism:Focus on Plants T g L n Groups of specialized leaf cells create sugars for the plant. Other cells form the vessels that transport water, nutrients, and wastes throughout the plant. The flower itself contains egg cells, sperm nuclei enclosed in pollen grains, and other cells specialized for sexual reproduction. The striking difference between the bloom and the stalk shows the great variety of cells as the basic unit of life. In Chapter 9, you will apply your understanding of cells as you investigate multicellular organisms. Using plants as model organisms, you will examine how specialized cells and structures perform basic life processes. You will learn how plants with vascular systems transport matter such as gases and fluids, and oki o even how plants themselves move. head A oki n o L g Look ahead to “Des ign Your Own Investigation: Inside Out: The Parts of Plants” at the end of this unit. In this investigation you wi ll examine the struc ture and organization of plants — from the microsc opic cell to the entire plant. Ge t a head start by co llecting the types of specimen s you may need for your investigation. Put aside liv e plants or note wh ere to find them, so that the pla nt materials are fre sh when you conduct your research. Make draw ings of the different plant struc tures. As you read this chapter, annotate your draw ings with informatio n about how the structures you have observed relate to these structures’ function s. head A he railroad in Canada stretches from coast to coast. It covers thousands of kilometres and leads through prairies, valleys, and mountain passes. Building the railroad was a monumental task. Clearly, it could not have been built without teamwork. In fact, its construction required the skill and labour of hundreds of individuals. The collective activities of many cells can also make extraordinary things possible — for example, the functioning of the human body, which is extremely complex. In multicellular organisms, numerous specialized cells function together to accomplish the same tasks as a single cell, but on a larger scale. The people who helped build the railroad included land surveyors, engineers, smiths to make the spikes, and hundreds of people to lay the tracks. Just as all of these people had specialized tasks, the different types of cells in a multicellular organism have specific functions. The prairie lily, shown on the facing page, has a complex structure. Chapter 9From FromCell CelltotoOrganism: Organism:Focus FocusononPlants Plants• • MHR MHR Solar Energy and Climates • MHR 319 319 319 9.1 Figure 9.1 Shown here is a photomicrograph of a cross section of a leaf. Notice how similar types of cells are grouped together. A chloroplast Specialized and Organized How does a plant, a multicellular organism, obtain food, water, and minerals? How does it respond to its environment? Most plants take up water and minerals through their roots and produce food in their leaves. In winter, some plants lose their leaves, and if they do not receive enough water, some plants may wilt. These actions are complex. What exactly are the structures that allow plants to perform these activities? How are these structures organized and how do they function? In single-celled organisms, one cell must be able to perform all the functions of life. Each organelle in the cell carries out a specific set of activities. By functioning together, the organelles meet all of the cell’s needs. In multicellular organisms, similar specialization takes place at the level of the cell. Many cells working together meet the needs of the organism. Groups of specialized cells, often with particular structures, perform specific tasks. For example, the cells lining the intestines are specialized to transport nutrients across their membranes and into the bloodstream. Other specialized cells of the body include muscle cells, nerve cells, and skin cells. Plants also show specialization of cells, as you can see in Figures 9.1 and 9.3. Specialized cells have particular traits that help them to carry out their activities efficiently. Those traits can include a particular cell shape, size, and location within the organism, as well as the types of organelles within the cell. simple sugars C6H12O6 ATP NADPH photosynthesis II carbon dioxide CO2 oxygen O2 photosynthesis I Cell Specialization in Leaves Leaves contain several types of specialized cells that function in one of the leaf’s most important activities: photosynthesis (see Figure 9.2). Light energy powers this biochemical process, in which carbon dioxide from the air and water from the soil are combined to create glucose. Glucose is a carbohydrate that both plant cells and animal cells use as a source of energy. Oxygen gas, an essential component of the air for plants and animals, is produced as a by-product during photosynthesis. As shown in Figure 9.3, different types of leaf cells have different structures and arrangements. How does a specific structure enable a leaf cell to perform specific activities? How does the location of a leaf cell within a leaf affect that cell’s function? Discover the answers to these questions in the Find Out Activity on page 322. water H2O light 320 photosynthesis 6CO2(g) + 6H2O(l) + light energy C6H12O6(s) + 6O2(g) MHR • Unit 3 Cycling of Matter in Living Systems Figure 9.2 Most photosynthesis in a plant occurs in its leaves. Chloroplasts inside the leaf cells contain a pigment molecule, chlorophyll, which traps light energy. This energy is used in a series of reactions that produce glucose and oxygen. A Epidermal Cells Just as skin cells protect your inner tissues, a protective layer covers a plant’s leaf. This layer, called the epidermis (also the scientific name for skin), is made up of epidermal cells. The epidermis covers the upper and lower surfaces of the leaf. The epidermal cells are flat and arranged in a tightly knit sheet that is one cell layer thick. A waxy substance (the cuticle) coats the cells to prevent evaporation of water from the leaf. Because their main function is to protect the leaf, rather than to perform photosynthesis, the epidermal cells do not have chloroplasts. They are mostly transparent to allow solar energy to pass through them to the layers of photosynthetic cells underneath. B Palisade Tissue Cells One of the main types of photosynthetic cells of plants are palisade tissue cells. This cell type forms a distinct layer within the leaf. The palisade tissue cells are long and narrow, like columns, and are packed closely together. Their shape and organization make photosynthesis within the palisade tissue cells very efficient. These cells lie just under the leaf’s upper surface, where they are exposed to sunlight striking the leaf. Palisade cells are packed with chloroplasts, thus, this is where most of leaf’s photosynthesis occurs. A palisade is a fence made of sharpened poles or stakes that forms a defensive barrier. Canada’s early forts were surrounded by palisades. In your notebook, write a few sentences comparing the appearance of a palisade fence to the appearance of palisade tissue cells. Include drawings, if you like. cuticle A upper epidermis C Spongy Tissue Cells Spongy tissue cells also contain chloroplasts and carry out photosynthesis. The spongy cells are layered just below the palisade tissue cells. These cells are round and loosely packed and have many air spaces between them, like a sponge. Their structure helps the cells to exchange gases and water with the environment. D Stomata and Guard Cells The epidermis provides leaf cells with valuable protection from the environment. However, if the epidermis prevented carbon dioxide from entering the leaf, photosynthesis could not occur. Small openings in the epidermal layer, called stomata (singular, “stoma”), allow gases in and out of the leaf. Carbon dioxide comes in to the leaf and oxygen is released from the leaf through the stomata. Water vapour also diffuses out of the leaf through these openings. Most stomata are on the underside of the leaf. Each stoma is flanked by two guard cells that regulate the stoma’s size. The shape of the guard cells can change to open or close the stomata. palisade tissue cells vascular bundle E xylem phloem lower epidermis stomata B D guard cells spongy tissue cells A C Figure 9.3 Pictured here is a cross section through a leaf showing specialized leaf cells. Try to recognize these cells in the photomicrograph shown in Figure 9.1. E Vascular Tissue Cells In addition to carbon dioxide and light energy, leaves need water to perform photosynthesis. Vascular tissue cells form a series of tubes that transport fluids throughout the plant. In the leaves, these are visible as leaf veins. Two kinds of vascular tissue, called xylem and phloem, make up the tubes. Xylem carries water and minerals from the roots to the leaves. Phloem carries sugars produced by the leaves to various parts of the plant. The tissues are arranged together in vascular bundles. The word “stoma” comes from the Greek word stoma, meaning “mouth.” This term is also used to name the small openings in some membranes and mouthlike openings in some animals, such as microscopic worms. Chapter 9 From Cell to Organism: Focus on Plants • MHR 321 Find Out Turn Over a New Leaf In this activity, you will use a microscope to examine the specialized cells of leaves. Materials 3. Prepare a wet mount of epidermis from a Tradescantia or Kalanchoe leaf. Tear one leaf at an angle perpendicular to the leaf veins. prepared slides of leaves in cross section compound light microscope Tradescantia (Spiderwort) or Kalanchoe (Bryophyllum) leaves tweezers 2–3 microscope slides medicine dropper tap water 2–3 cover slips Safety Precautions • Handle microscope slides and cover slips carefully so they do not break and cut you. • Be careful when using sharp objects such as tweezers. Procedure Performing and Recording 1. Place a prepared slide of a cross section of a leaf under the microscope. Examine the specimen under low power, and gradually increase the magnification as necessary. 2. Use the photomicrograph of stained cells below to help you identify the following cell types and structures: • • • • • 4. Find a section of the torn leaf edge where a thin layer of the epidermis has been pulled away from the tissue beneath. Using tweezers, place a bit of the epidermis on a clean microscope slide. Using a medicine dropper, put a drop of water on the tissue. Cover the sample with a cover slip. 5. Examine the epidermal tissue under the microscope. Start at low power, and then gradually increase to high power, until the stomata and guard cells are visible. What Did You Find Out? Analyzing and Interpreting 1. On which part of the leaf did you observe stomata? 2. If you observed both closed and open stomata, describe the difference in appearance of the guard cells in each case. epidermal cells palisade tissue cells spongy tissue cells stomata and guard cells vascular tissue cells 3. (a) What were the colours and shapes of the cells that you observed? palisade tissue epidermal cells (b) Explain how the colours and shapes of the cells relate to their functions. 4. (a) What was the arrangement of cells in the leaf? vascular tissue spongy tissue 322 stoma MHR • Unit 3 Cycling of Matter in Living Systems (b) Explain how the arrangement of cells in the leaf contributes to the efficiency of photosynthesis. Cell, Tissue, Organ, System Being a multicellular organism has many advantages. Compared with singlecelled organisms, multicellular organisms can have: • a larger size • a variety of specialized cells • an ability to thrive in a broader range of environments However, multicellularity also creates a new demand: organization. The human body, for example, contains an estimated 100 trillion cells. For so many cells to function in a co-ordinated way, a high degree of organization is needed. Within a cell, different functions are performed by specialized organelles. In multicellular organisms, groups of specialized cells are organized so that they can perform their functions efficiently. There are multiple levels of organization in organisms: cells, tissues, organs, and systems (see Figure 9.4). Cells are the most basic level of organization, while systems are the most complex. B Tissues Cells that are similar to each other are often clustered together to form tissues. For example, vascular tissue is formed from bundles of many vascular tissue cells. The epidermal tissue pictured here is made from layered sheets of epidermal cells. The cells making up a particular tissue share the same structure and function. A Cells Cells are the most basic unit of organization in organisms. C Organs Multiple tissues can be arranged in combination to form organs. An example of an organ is your heart, which contains muscle tissue, nerve tissue, and connective tissue. Plant organs include roots, stems, and leaves. The different tissues forming an organ work together to enable the organ to perform a specific function. A carnivorous plant plays the leading role in the musical Little Shop of Horrors. In this fictional tale, the plant, which resembles a Venus’s-flytrap, has a taste for human blood. As it gobbles up its fellow cast members, it grows from a modest houseplant into a people-eating giant intent on world domination. If such a plant really existed, what kinds of specializations would it have? Describe some of the features its cells and systems would require to be able to stalk and eat prey the size of humans. D Systems Organs, too, can function together at an even higher level of organization. In a system, organs and tissues throughout the body perform a shared complex function. For example, your teeth, tongue, stomach, and intestines are all part of your digestive system. The vascular system of plants, which carries water to all of the plant’s tissues, makes use of the roots, stem, and leaves. Figure 9.4 There are successive levels of organization in multicellular organisms. Chapter 9 From Cell to Organism: Focus on Plants • MHR 323 Humans are not the only organisms that reap health benefits from cell research. The study of plant cells helps scientists learn why some plants get sick. Plant pathologists specialize in the study of plant health. They work to understand the diseases of plants, the organisms that cause them, and how these diseases affect plant Find out more about career opportunities in the growth and survival. By improving plant health, plant pathologists contribute to field of plant pathology. Go to the web site above the quality of our food and environment. The field of plant pathology combines to find out where to go next. Investigate one such botany, crop science, ecology, biochemistry, and genetics. Plant pathologists career more fully and give a brief presentation to work in universities, government agencies, industries, and private consulting. your class, telling the class about the type Research a disease that affects plants. Find out what causes the disease, the of work involved in this career. name of the disease agent, and the plants it affects. What are the economic or social consequences of this plant disease? Summarize your findings in a short paragraph. A in d ok g Lo Section 9.1 Summary hea How do we know that plants are organized into cells, tissues, organs, and systems? How can you tell the difference between each kind of structure? Suggest a way of using plant samples to demonstrate how plants are structured and organized. Re-read “Design Your Own Investigation: Inside Out: The Parts of Plants” at the end of this unit. In this investigation, you will have an opportunity to answer these questions by designing your own experiment. With your group, brainstorm possible techniques you could use to address these questions. Record your ideas for future reference. In a multicellular organism, cells are specialized and work together to meet the needs of the organism. For example, a leaf has epidermal, palisade tissue, spongy tissue, and vascular tissue cells. Epidermal cells make up a thin sheet that protects the leaf’s interior. Most photosynthesis takes place in the palisade tissue cells, which are packed with chloroplasts. Much of the leaf is filled with round, loosely packed spongy tissue. Vascular tissues, the xylem and phloem, transport fluids throughout the plant. Multicellular organisms can grow larger and survive in a wider range of environments than unicellular organisms. However, multicellular organisms must also organize their cells in a co-ordinated way. Cells are organized into tissues, organs, and systems. Check Your Understanding 1. How are the activities of single-celled organisms similar to the activities of a specialized cell within a multicellular organism? 2. Explain how a plant tissue differs from a plant organ. 3. The epidermal cells of most leaves are transparent. Why is this beneficial to the plant? 4. Describe the roles of the two types of leaf cells that perform photosynthesis. 5. Thinking Critically Some leaf cells specialize in the exchange of water and gases with the environment. Other leaf cells do the opposite and prevent exchange of materials with the environment. Explain why leaves need both types of cells to survive and grow. 6. Apply Consider the following materials: a flowering African violet, a light, and an opaque piece of cloth. How could you demonstrate which plant organ is responsible for photosynthesis in the African violet? Indicate your controls, and the manipulated variable in your procedure. 7. Apply Some people wipe a thin layer of petroleum jelly on the leaves of houseplants to make the leaves shiny. What would be the effects of using petroleum jelly to cover: (a) the entire surface of each leaf; (b) the underside of the leaves; (c) the upper surface of the leaves. Explain your reasoning. 324 MHR • Unit 3 Cycling of Matter in Living Systems 9.2 Gas Exchange in Plants To supply oxygen to our body cells, we breathe. Air enters our lungs and oxygen diffuses into our blood and is distributed throughout our body. Plants, however, lack lungs and blood to take in gases from the air. How, then, do they exchange gases with their environment? The stomata in the outer tissues of the plant’s leaves allow gases to diffuse in and out of the leaf. Inside the leaf, between the upper and lower leaf surfaces, there are spaces between some of the cells. Gases move in and out of these intercellular spaces. Here, carbon dioxide, oxygen, and water vapour move by passive transport between the plant cells and the surrounding air. Something in the Air leaf hair Water and minerals enter leaf through xylem. palisade tissue cells air space leaf vein spongy tissue cells Sugar exits leaf through phloem. guard cell CO2 enters leaf O2 and H2O through stomata. exit leaf through stomata. The air we breathe is a mixture of oxygen, carbon dioxide, water vapour, nitrogen, and other gases. However, the ratio of these gases is different in the air we inhale and the air we exhale. To break down glucose and release its energy, our body cells consume oxygen and produce carbon dioxide waste. Therefore, the air we exhale has lower levels of oxygen and higher levels of carbon dioxide than the air we inhale. Plant cells, like animal cells, consume some oxygen and produce carbon dioxide and water during cellular respiration. During photosynthesis, however, plants also consume carbon dioxide and water and produce oxygen. In fact, when plants photosynthesize, they consume far more carbon dioxide than they...
View Full Document

  • Fall '15
  • Plants, Xylem, Living Systems

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture