This Document Contains Chapters 31 to 33 CHAPTER 31: THE LIVING PLANT WHERE DOES IT ALL FIT IN? Chapter 31 is a follow-up of Chapter 30 and builds upon the general information on plants provided in Chapters 29 and 30. A quick summary of Chapter 30 is essential for success at covering Chapter 31. In addition, students should be encouraged to recall the principles of eukaryotic cell structure and evolution associated with the particular features of plants. SYNOPSIS There are two major challenges facing land plants: having sufficient structural support for upright growth and maintaining water balance. In herbaceous plants, turgor pressure helps keep plants upright while secondary growth of vascular tissues allows trees to achieve great heights. The vascular system transports water, minerals, and carbohydrates over great distances. Water and minerals enter plants through root hairs and then move through the xylem tissues, in part from root pressure “pushing,” but primarily through evapo-transpirational “pulling.” Adhesion of water molecules to cell walls and cohesion of water molecules to each other, as well as bulk flow, contribute to the tenacity and extent of the water column. At the cellular level, water movement through channels called aquaporins, transport channels that also exist in animals, augments osmosis. Water movement within plants is explained in terms of water potential, () composed of such physical forces as gravity and cell walls, and the concentration of solutes in each solution. Water always moves from a solution of greater water potential to one of less water potential. Turgor pressure is the force exerted by water in the vacuole pushing against cell walls, and is referred to as pressure potential (p); as turgor pressure increases, water pressure increases. regulates movement of water through entire plants as well as across cell membranes. The equation for water potential is = p + s wherein s is solute (osmotic) pressure. s describes the smallest amount of pressure that arrests osmosis. Root hairs’ s is generally greater than that in the surrounding soil, due to the active pumping of mineral ions into cells through proton pumps. Ions pass between cell walls non-selectively until they reach the endodermis and its unique Casparian strips which impose selectivity. Once in the xylem, ions move with the water. Since more than 90% of water taken in by roots is lost to the atmosphere through transpiration, as vapor, the rate of transpiration, hence water and ion movement, depends on such conditions as temperature, humidity, and time of day. Transpiration generates the negative pressure responsible for water movement. Root pressure may occur during the night, causing guttation, the loss of water through specialized cells. In the short term, stomatal action, regulated by turgor pressure in the guard cells, governs the rate of transpiration. CO2 levels, light, and temperature also affect the opening and closing of stomata. K+ concentration in guard cells is responsible for turgor pressure. Dormancy, deciduousness, and various leaf modifications are among water loss prevention strategies that have evolved in plants. Flooding stresses plants because it reduces the amount of available oxygen in the soil, thus interfering with minerals and carbohydrates transport in roots, and inducing hormonal changes as well. Adaptations as aerenchyma, loose parenchymal tissue with large air spaces, allow some plants to inhabit fresh water environments. Pneumatophores, above ground root portions where oxygen can enter through lenticels, allow some plants, for example, mangroves, to live in salt water. Translocation is the process whereby carbohydrates, manufactured in leaves, is distributed throughout plants through the phloem tissues that also transport hormones. Dissolved carbohydrates flow from sources such as photosynthetic and food-storage tissues to such sinks as other food-storage tissues and meristems. Phloem loading occurs when carbohydrates enter sieve tubes, an active transport event. • Plants require vast amounts of energy during their life cycles, beyond the carbohydrates synthesized as a result of photosynthesis and the minerals they absorb from the soil. Additionally, they require numerous inorganic nutrients. Nine of these are macronutrients, which plants need, in larger amounts than the necessary micronutrients. Macronutrients include carbon, hydrogen, oxygen, nitrogen, potassium, calcium, magnesium, phosphorus, and sulfur. Some of these are major components of organic molecules; others are components of cells walls, membranes, nucleic acids, and proteins including chlorophyll. Essential micronutrients may be required only in trace amounts, and include iron, chlorine, copper, manganese, zinc, boron, and molybdenum. Specific requirements for different plants are determined through hydroponic culture. Deficiencies of any element may harm plant growth and development. Today, food fortification programs, whereby uptake of some minerals is increased, providing nutrient-enriched plants in the field, is an active area of research. In some cases, genes that code for certain plasma membrane transport proteins have been cloned and bred into crop plants. • Plants, as all organisms, interact with their environments; in fact, their growth and survival depend on abiotic factors. Hormones are important in plants’ interpretation of signals received at the cell level and expressed at the macroscopic level. Light is an important trigger, helping to initiate seed germination, etiolation, flowering, and other developmental events, a complex non-directional phenomenon called photomorphogenesis. Directional development, in response to light, accounts for phototropisms. Plants exhibit three primary kinds of tropism: phototropism, gravitropism, and thigmotropism Red light receptors, especially the pigment-containing protein phytochrome, are especially important. It exists in two interconvertible forms, responding in turn to red light, Pr, and far-red, Pfr, light, bringing about various morphogenetic responses as well as plant spacing. Evidence indicates that phytochrome systems evolved among the green algae, as they are present in all plants. • Phototropism is the bending of plants toward a unidirectional light source consisting of blue wavelengths (460 nm range). The consequent positioning of leaves and stems is clearly of adaptive value to plants, exposing them to optimal light. Auxin is involved in all phototropic responses. Gravitropism is a plant’s response to gravity. It causes stems to grow upward (positive gravitropic response) and roots to grow downward (negative gravitropic response). In shoots, the gravity-sensing cells are in the endodermis. In roots, they are located in root cap cells. Plants’ perception of gravity may be associated with the position and movement of amyloplasts in individual cell. This signal reception is mediated primarily by auxins. However, roots of some plants in the tropics may grow up the stems of neighboring plants, suggesting a complex interaction of receptors and hormones and environments. Thigmotropism and thigmonasty relate to plant responses to touch. The former involves the directional growth response of a plant or plant part toward contact with other objects, whereas thigmonasty describes a direction of plant growth irrespective of the direction of the signal; in other words, tendrils exhibit a thigmotropic response when they grow toward an object but tendrils of some species may always coil clockwise, regardless of their contact with the object and signal. There exists other topic responses to stimuli, including electricity, chemicals, trauma, temperature, oxygen, darkness, water, and magnetic fields. Some touch-induced plant movements are not growth responses as are tropisms but result from reversible changes in the turgor pressure of specific cells. This process is called turgor movement. Basically, if water exits from cells with high turgor pressure, the cells make collapse, causing plant movement. Reversing the turgidity likewise causes movement. Many plants become dormant during adverse conditions, due to such environmental signals as light, temperature, and moisture. In temperate climates, dormancy is associated with winter when water is unavailable. Many trees drop their leaves; new buds remain dormant; perennials subsist as underground parts; and annuals persist as seeds. In seasonally dry climates, largely inhabited by annuals, seeds dormancy occurs during the dry season. They germinate in response to sufficient water, then grow rapidly, flower, and produce new seeds before the drought conditions return. Seeds of some species in any climate may remain dormant for indeterminate amounts of time, even many thousands of years. Shoot and root dormancies are released in response to temperatures and day length, in addition to water availability. Hormones are involved in plant responses to environmental triggers, as well as in the internally regulated processes that may alter plant morphology and physiology during their adjustments to environmental stress. Hormones are chemicals produced in minute quantities and transported to other locations where they elicit specific physiological or developmental responses. In animals, hormones are usually produced in specialized tissues, usually organs, but in plants, they are produced in tissues that carry out normal, obvious functions, such as apical meristems, young leaves, and seeds. There are seven major kinds of naturally occurring plant hormones, and they are involved in many aspects of plant growth and development, sometimes alone, more often synergistically. Charles and Francis Darwin first observed the actions of auxins in the phototropic response of seedlings to light. Later experiments identified a chemical substance concentrated on the non- illuminated side of the seedling tip. This compound migrates from the light side to the dark side, producing an elongating effect on the cells and thereby causing the tip to bend toward the light. The only naturally occurring auxin is indoleacetic acid (IAA), a compound synthesized from tryptophan. It is produced in the shoot apex and diffuses downward to the base of the plant. It acts primarily by increasing the plasticity of young cell walls. Synthetic auxins are used in some commercial applications to promote flowering and fruiting in some plants, to prevent fruit drop, to induce root formation in cuttings, and as weed killers. Cytokinins are essential for cell division, promoting the synthesis or activation of proteins that are necessary for mitosis. In conjunction with auxins, they promote division and differentiation of cells from callus tissue in culture. Most are produced in root apical meristems. They are chemically derived from adenine, and transported throughout a plant. They function antagonistically with auxins, thereby promoting growth of lateral branches and inhibiting formation of lateral roots. Plant tissues can form shoots, roots, or undifferentiated masses of tissue, depending on relative amounts of auxin and cytokinin. Gibberellins, acidic in nature, are produced in the apical regions of stems and roots where they function in stem elongation. They also function in seed germination, as GA is a signal from the embryo that turns of transcription of one or more genes that encode hydrolytic enzymes that allow endosperm utilization. More than 100 chemically different gibberellins (GA) are known. They were first observed in abnormally tall rice plants infected with a fungus, Gibberella fujikuroi, after which they are named. Ethylene gas is a natural product of plant metabolism that interacts, in very small amounts, with other hormones. For example, auxin induces ethylene production around the lateral buds, thereby slowing down their growth. It also suppresses root and stem elongation and hastens fruit development and ripening. Its production increases rapidly when plants are stressed due to toxins, temperature extremes, drought, pathogens, and herbivory, resulting in various self- preservation processes. It is widely used commercially to time and enhance fruit ripening. Abscisic acid is produced in mature green leaves, fruits, and root caps. It induces formation of winter buds and the conversion of leaf primordia into bud scales. It may suppress growth of dormant lateral buds and it controls the opening and closing of stomata. It plays a role in seed dormancy, is antagonistic to gibberellins during seed germination. Its levels are greatly elevated with plant stress, particularly drought. The growth-regulating role of abscisic acid, present in all plants, suggests that it evolved early in the plant evolution story. LEARNING OUTCOMES 31.1 Movement of Materials Through a Plant Is Controlled by Water Transport 1. Use water potential to predict the movement of water. 2. Explain the role of aquaporins in determining water potential. 31.2 Water and Mineral Are Absorbed 1. Explain the possible pathways water can take to vascular tissue. 2. Describe the function of Casparian strips. 31.3 Xylem Transports Water from Root to Shoot 1. Describe the environmental conditions that produce root pressure. 2. Explain the effect of cavitation on the flow of water in the xylem. 31.4 Plants Adjust the Rate of Transpiration to Match the Weather 1. Explain the process by which guard cells regulate the opening of stomata. 31.5 Plants Are Adapted to Water Stress 1. List three drought adaptations in plants. 2. Describe the negative impacts of flooding on plant growth. 3. Outline plant adaptations to a salty environment. 31.6 Phloem Transports Organic Molecules 1. Define translocation. 2. Explain the pressure-flow hypothesis. 31.7 Plants Require a Variety of Nutrients 1. Distinguish between macronutrients and micronutrients. 31.8 Plant Growth Is Responsive to Light 1. Compare the pigments phytochrome and chlorophyll. 2. Describe the growth responses influenced by phytochromes. 3. Explain the mechanism of phototropism. 4. Explain how light entrains circadian cycles of plant growth. 31.9 Plant Growth Is Sensitive to Gravity 1. Identify the structures in plant cells that perceive gravity. 31.10 Plants Use Hormones to Coordinate Growth 1. Discuss the properties of plant hormones. 2. Explain the role of auxin in controlling plant growth. 3. Compare cytokinins with auxins. 4. Describe the effects of gibberellins on plant growth. 5. Describe how ethylene induces fruit ripening. 6. Describe the major roles of abscisic acid. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 31 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • Students are unaware that plants develop environmental adaptations. • Students believe that plants lack tissues and organs. • Students believe that capillary action alone is involved in plant transport. • Students to not equate turgor with plant rigidity. • Students do not know the role of phloem in cell transport. • Students believe phloem only has a passive downward transport. • Students believe the xylem transport is only upward and not lateral. • Students are unaware that water is taken up for photosynthesis and transport. • Students are unaware of all of the functions of roots. • Students are unaware of all of the functions of stems. • Students believe that only leaves only carry out photosynthesis. • Students believe that fertilizer is equivalent to “food.” • Students are unaware that plants develop environmental adaptations. • Students believe that plants do not produce hormones. • Students do not understand the environmental factors that induce plant hormones. • Students are unaware of plant movement responses. • Students are unfamiliar with the mechanisms of plant tropisms. • Students do not know the complexity of soil. INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE Visuals are important in making cell transport understandable to students, and in energizing students about soil and plant nutrition. Emphasize the variety of environmental conditions in which plants are responsible for carrying out transport. Explain how transport is important in successful agriculture and environmental conservation. Acquire teaching materials the Crop Science Society of America and the Soil Science Society of America. Explain that the subscript in Pr should be associated with the red light that it absorbs. Similarly, the fr of Pfr should be associated with far-red. Explain why day length rather than temperature or moisture is a better indicator of the seasons (for animals too!). Relate seed dormancy to the various animals that produce hard-walled eggs resistant to adverse conditions, like drought and cold. Compare plant dormancy to animal aestivation and hibernation. HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluate information from Chapter 31. Application • Have students describe relationship between turgor and the storage of fruits at the grocery store. • Have students explain houseplants must be placed in larger pots as the shoot grows. • Ask students to explain the possible habitat of a plant that has no apparent root system. • Have students describe how sterilizing soil in greenhouses could affect plant nutrient uptake. • Ask students to explain the possible source of nutrients for a plant that lacks apparent roots • Have students describe what happens when auxin is applied to the left side of a growing shoot. • Ask students to describe the effects of a chemical that inhibits gibberllin synthesis in seedlings. • Ask students to explain changes to auxin synthesis in a tall house plant that fell down on its side. Analysis • Ask students to explain the properties a plant would need to grow in dry soils. • Ask students to explain the properties a plant would need to grow in very wet soils. • Ask students to explain the benefits and limitations of an epiphyte lifestyle. • Have students explain relationship between water transport and a plant’s need for soil nutrients. • Have students explain how the nutritional value of plants eaten by humans is affected by fertilizer quality. • Have students explain how a potted plant would grow in the absence of gravity such as found on a space ship. • Have students explain the effectiveness of using abscisic acid as an herbicide for controlling weeds in a yard of grass. Synthesis • Ask students to explain how pollutants that dissolve fats would affect the uptake of water by roots. • Have students hypothesize the agricultural value of a plant gene that enhances the function of aquaporins. • Ask the students to design an experiment that tests the relative effectiveness of drought resistance in corn plants. • Ask students design an experiment to determine the effectiveness of using mycorrhizae to improve crop production. • Have students design an experiment to determine if two plants can transfer hormones between two through roots that intertwine and fuse when grown together. Evaluation • Ask students debate the environmental benefits and drawbacks of irrigating crops. • Ask students to evaluate the safety of an herbicide that prevents water uptake by roots of monocots. • Ask students to evaluate benefits and risks of breeding crops that have little need for phosphorus and nitrogen. • Ask students access the value of studying tropical plants as a model for reducing flooding in northern urban areas. • Ask students to evaluate the feasibility of using natural plant hormones in place of pesticides used in agriculture. • Ask students evaluate the benefits and consequences of using herbicides in agricultural practices. VISUAL RESOURCES There are excellent diagrammatic images of most of the processes involved in vascular transport of water, minerals, and carbohydrates in plants. Beyond using these as instructional models, have students either diagram or label diagrams to document their understanding of plant structure, the processes, directions of movement, components such as minerals and their charges, and the influence of external factors. IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Transport Issues. Introduction This demonstration permits faculty to play two animations that show the interrelationship between photosynthesis and plant transport. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to Cornell University Plant Transport Animations at http://cycas.cornell.edu/ebp/projects/laststraw/ise/tut.water.html Procedure & Inquiry 1. Briefly review with students the role of water transport in plant survival 2. Load up the website and click on the icon under “Can plants control how much water they lose during photosynthesis? 3. Have the class explain the process going on. 4. Load up the website and click on the icon under “How do plants transport water from the soil to their leaves? 5. Have the class explain the process going on. 6. Ask the students to briefly review and explain the concepts of the animations. B. Nutrient Calculator for Plants. Introduction This demonstration shows students that application of nutrient uptake information in agriculture. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to USDA Plant Nutrient Calculator at http://npk.nrcs.usda.gov/ Procedure & Inquiry 7. Explain to the students that you want to demonstrate the importance of precise plant nutrient uptake in plants 8. Have the students describe why different crops require specific amounts of particular nutrients 9. Load up the website and ask the students to select a crop group or specific crop 10. Then type in some yield information and acreage (optional) 11. Calculate the nutrient needs 12. Ask the class to recall the uses of each nutrient in the plant 13. Repeat this for three other unrelated crops and compare the different nutrient needs 14. Ask the students to briefly explain why different crops have different nutrient needs C. Plant Hormones as Herbicides Introduction This video demonstration shows students the mechanisms of action of plant hormones that serve as herbicides Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to Library of Crop Technology website at http://croptechnology.unl.edu/viewLesson.cgi?LessonID=998688536. Procedure & Inquiry 15. Explain to the students that plant hormones can also serve as herbicides by interfering with normal plant development. 16. Load up the website and go the Animation link. 17. Click on the “Overall Picture of Auxinic Herbicide Action” link. 18. Have the students answer questions about the sequence of events being shown throughout the animation. 19. Click on the “Auxin and Auxinic Herbicide Mechanisms of Action” animation link 20. Have the students answer questions about the sequence of events being shown throughout the animation. 21. Have the students briefly discuss the similarities in natural auxin and auxin herbicide action. LABORATORY IDEAS A. Osmolarity of Plant Transport This activity asks students to design an experiment that determines the osmolarity or solute concentration on xylem function. a. Review the concepts associated plant water uptake. b. Tell students that they will be designing an experiment to determine solute concentration of soil on xylem function. c. Provide students with the following materials: a. Fresh celery stalks b. Food coloring c. Sodium chloride (table salt) d. Balance e. Small beakers f. Distilled water d. Instruct the students how to make percent concentrations of salt solutions e. Then ask them how they will track the rate up water uptake in the plants f. Have them come up with an experimental design and critique the design to ensure accuracy of their model. g. They should record the different rates uptake and discuss if salt concentration of fluid entering a plant influences xylem function. LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. 1. Have students do a community presentation on the value of plants in reducing urban and suburban flooding. 2. Have students tutor high school students learning about plant function. 3. Have students tutor high school students learning about plant hormones. 4. Have students volunteer with a garden club on a community garden project. 5. Have students give a demonstration on plant on plant growth to elementary school students. 6. Have students volunteer on environmental restoration projects with a local conservation group. 7. Have students volunteer at botanical garden or nature center. CHAPTER 32: ANIMAL FORM AND FUNCTION WHERE DOES IT ALL FIT IN? Chapter 32 builds on the foundations of Chapter 27 and provides detailed information about animal form and function Students should be encouraged to recall the principles of eukaryotic cell structure and evolution associated with the particular features of animal cells. Multicellularity should also be reviewed. The information in chapter 32 does not stand alone and fits in with the remaining chapters on animals. Students should know that animals and other organisms are interrelated and originated from a common ancestor of all living creatures on Earth. SYNOPSIS The human organism is a vertebrate, therefore it is also a deuterostome and a coelomic animal. The diaphragm divides the body into the thoracic cavity containing the lungs and the heart and the peritoneal cavity containing the stomach, liver, intestines, and various other organs. It is supported by an internal skeleton of jointed bones. A skull surrounds the brain and the hollow vertebral column surrounds the dorsal nerve cord. All vertebrates are organized in successively more inclusive levels: cells to tissues to organs to organ systems. Humans contain eleven principal organ systems, each a collection of functional units composed of several different tissues. The tissues themselves are derived from embryonic endoderm, mesoderm, and ectoderm and are of four main types: epithelial, connective, muscle, and nervous tissue. Epithelium protects other tissues from dehydration and damage and provides a selective barrier. Simple epithelium is only a single cell layer thick; the cells may exhibit squamous (flattened, irregular), cuboidal, or columnar shapes. Stratified epithelium is a few cell layers thick and is made up of a combination of cell shapes. The outer epithelium of terrestrial vertebrates is highly keratinized for protection against abrasion and dehydration. Glands are epithelial tissues that serve a secretory function. Exocrine glands are connected to epithelium by ducts while endocrine glands are ductless and secrete their hormonal products directly into the blood system. Connective tissues are derived from mesoderm and divided into connective tissue proper and special connective tissue. Connective tissues are composed of widely-spaced cells imbedded in an extracellular matrix. Loose connective tissues contain cells scattered in an amorphous protein substance, strengthened by collagen, elastin, or reticulin. Dense connective tissues contain tightly packed collagen fibers. Regular dense connective tissue, like tendons and ligaments, have collagen fibers aligned in parallel. Irregular tissue fibers are not regularly oriented and compose the tissues that cover organs, muscles, nerves, and bones. The special connective tissues are cartilage, bone, and blood. Each has unique cells and extracellular matrix allowing specialized function. Cartilage is composed of collagen fibers interspersed with living chondrocyte cells. Bone is composed of cartilage fibers coated with calcium salts. Even though embedded in a calcium matrix, the osteocytes remain alive. New bone is formed by osteoblast cells in concentric layers around nerve and blood vessel-containing Haversian canals. Numerous types of cells are found within the liquid matrix of the blood. They include erythrocytes (red cells), leukocytes (white cells), and thrombocytes (platelets). There are several types of white cells: neutrophils, eosinophils, and basophils are named by their special affinity to biological stains. Monocytes and macrophages are phagocytes, while lymphocytes comprise an important part of the immune system. All types of connective tissue are similar in their composition of abundant matrix as well as the cell nomenclature of -blast and -cyte. Muscle tissue is also derived from mesoderm and exhibits the unique function of contractibility. These cells possess a great concentration of actin and myosin containing myofibrils. There are three general types of muscles, categorized by their location and cellular structure. Smooth muscle cells surround various internal organs and are composed of uninucleate spindle-shaped cells. Two types of contractions occur in smooth muscle. Muscles lining blood vessels and those in the iris of the eye contract with nerve stimulation. Other smooth muscles, like those in the walls of the digestive tract contract spontaneously. Nerves simply regulate their activity. Skeletal muscle connects bones to one another and underlies the skin. It is composed of multinucleate fibers produced by the fusion of many individual cells. These cells contract only when stimulated by nerves. Cardiac muscle is found in the heart and is composed of specially arranged striated muscle fibers. Certain cells in the myocardium generate a spontaneous electrical impulse which causes all cells in the myocardium to contract in unison. Nerve tissue is composed of neurons and supporting cells. An individual neuron is composed of a processing cell body, receiving dendrites, and a transmitting axon. They are capable of conducting an electrical current and thereby transmit information. The brain and spinal cord comprise the central nervous system (CNS) while nerves and ganglia make up the peripheral nervous system (PNS). Animals possess three types of skeletons. Hydrostatic skeletons, found in soft-bodied invertebrates, are fluid-filled cavities surrounded by muscle fibers. Exoskeletons are hard, chitinous cases that surround the bodies of arthropods. Vertebrates and echinoderms possess endoskeletons in which muscles are attached to a rigid internal skeleton. The human body is composed of 206 bones divided into the appendicular skeleton (limbs, pectoral, and pelvic girdles) and the axial skeleton (skull, backbone, and ribcage). Joints permit flexible range of motions determined by the type of joint. Bones connect to one another at immovable, slightly movable, or freely movable joints and are connected to muscles via cartilaginous tendons. Skeletal muscles provide movement in vertebrate organisms. Synergistic muscles work together to cause movement while antagonistic muscles oppose each other, moving a bone in opposite directions. Vertebrate skeletal muscle cells contain a great number of muscle fibers that are the key to their ability to contract. The cytoplasm of this fiber is called sarcoplasm; the central myofibrils are constructed of repeating sarcomere units. An individual sarcomere consists of Z lines to which actin filaments are attached. The actin filaments do not reach completely from one Z line to the next, the gap is bridged by myosin filaments. Both ends of a myosin filament move simultaneously, pull the Z lines together, and shorten the sarcomere. Synchronous contraction of all sarcomeres within a myofibril shortens the entire myofibril. Uniform contraction of all of the myofibrils results in compression of the entire muscle. On a molecular level, muscle contraction occurs when the myosin heads form cross-bridges with the actin fibers, each requiring the expenditure of one ATP molecule. Calcium plays an integral role in the control of muscle contraction. The myosin heads are normally bound by tropomyosin held in place by troponin molecules. Calcium alters the shape of the troponin molecules, which repositions the tropomyosin away from the myosin. Only then can the myosin heads bind to the actin filaments, resulting in muscle shortening. Vertebrate skeletal muscle contraction is initiated by impulses from nerves. A neuromuscular junction occurs where a nerve innervates a muscle fiber. Stimulation of the motor neuron causes the release of acetylcholine which causes the muscle fiber to initiate its own electrical impulses. Those impulses are carried to the T tubules and the sarcoplasmic reticulum, which results in the release of calcium and shortening of the muscle fibers. When the stimulus stops, the calcium is taken back up by the sarcoplasmic reticulum and the fibers relax. This entire process is called excitation-¬contraction coupling. Whole units of muscle tissue contract smoothly because of the recruitment of muscle fibers within a motor unit A twitch is a single brief contraction of a muscle. A second impulse immediately after the first causes summation as the contraction adds to that of the first. Tetanus results when there is no visible relaxation between twitches and there is a smooth, sustained muscle contraction. Skeletal muscle is composed of two distinctly different types of fibers. Type I fibers, also called slow twitch fibers, require a substantial length of time (in milliseconds) to reach maximum tension. As expected, type II or fast-twitch fibers, reach maximum tension in just a few milliseconds. Slow-twitch fibers have substantial resistance to fatigue and have a high capacity for aerobic respiration. They have a rich capillary supply, numerous mitochondria, and a high concentration of myoglobin to improve delivery of oxygen. Fast-twitch fibers have fewer capillaries and mitochondria and are better adapted to respire anaerobically due to high concentrations of glycolytic enzymes. Animals are mobile organisms that have evolved the ability to move in water, on land, and in the air. Many aquatic animals move through the water through undulations of their bodies against the water. Other animals use the same locomotor actions to swim as they would to walk on land. Terrestrial animals exhibit particular walking gaits depending on the number of legs that they possess. In general, tetrapods are capable of speedier movement on land than arthropods. Only four groups of animals have evolved flight. In all of them, propulsion is achieved as the wings press downward against the air. LEARNING OUTCOMES 32.1 The Vertebrate Body Has a Hierarchical Organization 1. List the levels of organization within the vertebrate body. 2. Describe how body cavities are organized in vertebrates. 32.2 Epithelial Tissue Forms Barriers Within the Body 1. Describe the structure and function of an epithelium. 2. Compare and contrast the different kinds of epithelia. 32.3 Nerve Tissue Conducts Signals Rapidly 1. Describe the basic structure of neurons and their supporting cells. 32.4 Connective Tissue Supports the Body 1. Differentiate the structure and function of loose and dense connective tissue. 2. Describe cartilage, bone, and blood tissue. 32.5 Muscle Tissue Powers the Body’s Movements 1. Contrast the three kinds of muscle and muscle cells. 32.6 Skeletal Systems Anchor the Body’s Muscles 1. Describe how animals with a hydrostatic skeleton move about. 2. Discuss the limitations of exoskeletons. 3. Compare endoskeletons to exoskeletons. 32.7 Vertebrate Endoskeletons Are Made of Bone 1. Compare intramembranous and endochondral development. 2. Compare the structure of different parts of a long bone. 3. Explain how bone remodeling occurs. 4. Describe how antagonistic muscles work at joints. 32.8 Muscles Contract Because Their Myofilaments Shorten 1. Explain the sliding filament mechanism of muscle contraction. 2. Explain how muscle contraction is linked to a nerve impulse. 32.9 Animal Locomotion Takes Many Forms 1. Describe how swimming uses muscular forces to overcome frictional drag. 2. Describe how friction and gravity affect terrestrial locomotion. 3. Describe how wings create lift. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 32 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • Students do not understand the evolution of endosymbionts in animal cells • Students are unsure that many of the lower animals are classified as animals • Students think that all animals evolved at about the same time • Students believe that most animals do not feel pain • Students believe that animals can sense emotions and danger • Students believe that only humans have a well-developed body regulation • Students believe that animals are purely instinctual • Students believe that most animals are vertebrates • Students do not equate humans with being animals • Students believe that all animals have identical organ system structures • Students believe that most animals have internal skeletons • Students believe that all muscles produce locomotion and are unfamiliar with postural muscles INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE Compare the organization of the human body to (organs). These are then combined to form entire the construction of a house. The screws, nails, rooms (organ systems) that finally comprise the wood, glass, and pipes (tissues) combine to make whole house (the body). interior walls, ceilings, floors, and windows Discuss bone healing associated with electrical currents which speed bone growth along natural stress lines. Exercise has an effect on bone growth as indicated by the diameter of a pitcher’s pitching versus non-pitching arm. It may also help combat bone deterioration that occurs with age and osteoporosis. Discuss the physiology of muscular dystrophy, myasthenia gravis, and/or atrophy of unused muscles. Discuss the physiology of loss of bone density in astronauts. Myosin and actin are not simply interdigitated, illustrated by interposing the fingers of the left and right hand with each set of fingers representing a protein. Rather, the fingers of both hands are actin, adding myosin is like holding short pencils between your fingers when they are placed tip to tip. As contraction proceeds, your fingertips get closer together, as do your hands (representing the Z lines). HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluate information from Chapter 42. Application • Have students describe the how the digestive system works together with the nervous system. • Have students describe the how the muscles work together with the skeletal system. • Ask students to explain the benefits separating body functions into anatomically distinct systems. • Have students describe the similarities of differences of endoskeleton and exoskeletons • Ask students to explain why calcium is needed for bone and muscle function. • Ask students to explain the importance of the nervous system Musculoskeletal system control. Analysis • Have students explain the similarities and difference of muscle and nerve tissue. • Have students explain why respiratory systems of animals have a high degree of variation compared to other organ systems. • Ask students to use organ system anatomy to explain the evidence supporting a common ancestor for protostomes and deuterostomes. • Have students explain why large terrestrial animals have an endoskeleton instead of an exoskeleton. • Have students explain the benefits and limitations of an exoskeleton. • Ask students explain if muscles can also serve the role of a skeletal system. Synthesis • Ask students to explain how evolution of the vertebral column impacted the anatomical features of the nervous system. • Have students design an experiment to test the effectiveness of epithelium on forming a barrier against the spread of bacteria. • Ask the students to find a medical application for knowledge that all vertebrates use identical proteins to synthesize connective tissues. • Ask students to design a model for testing the maximum size an exoskeleton can reach on land and in water. Evaluation • Ask students to evaluate the claim the vertebrates are less evolved than insects. • Ask students to evaluate the accuracy of studying chicken eggs to get a better understanding of human organ system formation during embryological development. • Ask students to evaluate the effectiveness and safety using medications that regulate the activities of antagonistic effectors. • Ask students evaluate the effectiveness of producing artificial muscles to replace damaged body parts. • Ask students evaluate the accuracy of using insect flight to design better airplanes. VISUAL RESOURCES Obtain a number of animal organs to illustrate how they are made up of various tissues. Samples from the grocery are best, but in very large classes they may be substituted with photographs. Bring in examples of bone and muscle tissue, readily obtained at the local meat market. Ask the butcher to bisect a long bone in both directions to show the internal structure. Place a pencil (actin) on a smooth surface (even the overhead projector) “walk” your fingers (myosin heads) along its length so that it moves backward under your fingers. IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Virtual Histology Introduction This demonstration permits the class to see histological sections of animal organ systems mentioned in this chapter. It can be used to demonstrate form and function in tissues and cellular organization. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to LUMEN at http://www.meddean.luc.edu/lumen/MedEd/HISTO/frames/histo_frames.html. Procedure & Inquiry 1. Ask the class if they can recognize the function of a tissue by looking at its cellular organization. 2. Load up the Lumen website. 3. Then click on a tissue category and show the images to the students. 4. Then ask the class to determine the function of the tissue in animal. They should justify their answers and explain the characteristics that determine the function. 5. Repeat this for the major tissue and cell types of vertebrates. B. Muscles in Action Introduction This demonstration uses animations to help students review muscle action by seeing the events occurs. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to Skeletal Muscle: Biceps, Fibers, Fibrils and Sarcomeres website at http://harveyproject.science.wayne.edu/development/muscle/strufast.html Procedure & Inquiry 6. Ask the class what they know about endocrine system feedback of blood sugar. 7. Load up the Skeletal Muscle website and click on the following links in the sequence below. a. The muscle fiber to the sarcomere animation b. The structure of the thick filament and M-line animation c. The structure of the thin filament and Z-line animation d. The gross physiology of skeletal muscle animation e. Levers and joints animation 8. Have students review the concepts after each sequence. 9. Ask the students to briefly explain the full sequence of events of a skeletal muscle contraction. LABORATORY IDEAS A. Comparative Animal Systems This activity has students evaluate the differences and similarities of representative protostome and deuterostome animal organ systems. a. Explain to students how all animals have a common ancestor and that all animals address similar survival issues. b. Tell students that they will be investigating the similarities and differences in two representative animals: the clamworm, a protostome, and the fish, a deuterostome. c. Provide students with the following materials a. Preserved fish specimen b. Preserved clamworm specimen c. Dissecting microscope d. Dissecting equipment e. Small ruler d. Instruct the students to describe the following features of while comparing each organism: a. Relative complexity of organ systems b. Relative size proportion of organ systems c. Evidence of conservation of organ system structure and function d. Evidence of organ system specialization e. Degree of integration of organ systems e. The students reports should include an explanation of the similarities considering the great differences in lineage of clamworms and fish. B. Comparing Vertebrae This activity has students has students investigate the role of developmental form and function of vertebral bones. a. Explain to the students that vertebrae vary within an organism and between organisms to carry out specific functions. b. Then tell them that they will be investigating differences and similarities of vertebral bones. c. Provide students with the following materials: a. Preserved specimen of fish b. Preserved specimen of frog c. Human skeleton with intact vertebral column d. Cat or dog skeleton with intact vertebral column e. Dissecting equipment f. Dissecting microscope d. Instruct students to expose the vertebral columns of the fish and the frog. e. Tell them to note the differences and similarities of the vertebral bone variation between the two specimens. f. Then have them compare the fish to the human and cat or dog specimens. g. Have them record any observations about form and function of any variance in the bones within one specimen. h. Then have the students record any observations about form and function of any variance in the bones between the specimens. Also have the students hypothesize about the genetic control of vertebral bone shape. LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. 1. Have students do a lesson or do a hands-on program on the animal homeostasis. 2. Have students tutor high school students studying animal anatomy and physiology. 3. Have students prepare a PowerPoint presentation on muscle action for high school teachers. 4. Have students volunteer on environmental restoration projects with a local conservation group. 5. Have students volunteer at the educational center of a zoo or marine park. CHAPTER 33: THE NERVOUS SYSTEM WHERE DOES IT ALL FIT IN? Chapter 33 builds on the foundations of Chapter 32 and provides detailed information about animal form and function Students should be encouraged to recall the principles of eukaryotic cell structure and evolution associated with the particular features of animal cells. Multicellularity should also be reviewed. The information in chapter 33 does not stand alone and fits in with the remaining chapters on animals. Students should know that animals and other organisms are interrelated and originated from a common ancestor of all living creatures on Earth. SYNOPSIS Communication by neurons is extremely fast acting and provides information to specific locations. The nervous systems of vertebrates are composed of the brain, afferent nerves that send information to the brain, and efferent nerves that transmit commands from the brain. The two functional divisions are the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is composed of the brain and the spinal cord. The PNS is composed of all of the nerve pathways outside the CNS. Within the PNS, the afferent nerves are sensory pathways and the efferent nerves are motor pathways. Motor pathways are divided into the voluntary (somatic) nervous system that innervate the skeletal muscles and the involuntary (autonomic) nervous system that innervate glands and non-¬skeletal muscles. Electrical impulses are transmitted along individual neurons. The highly branched dendrites carry incoming impulses from many different sources to the cell body. Its surface integrates the information arriving from many dendrites and acts as the central processing unit. Generally a neuron has only a single potentially lengthy axon. It carries electrical impulses away from the cell body to a target cell. The end of the axon contains packets of neurotransmitters that chemically transmit the nerve impulse to the next neuron or target cell. Specialized Schwann cells wrap around the axon at specific intervals insulating the axon and forming the myelin sheath. This insulation is interrupted at locations called nodes of Ranvier. Schwann cells produce myelin in the PNS while oligodendrocytes produce myelin in the CNS. These cells are 2 of the most important kinds of neurolglia in vertebrates. A neuron’s resting potential results from the charge differential between the inside and the outside of the neuron. This gradient results from active outward transport of sodium and inward active transport of potassium through voltage-gated membrane channels. This results in a cell that is slightly more negative on the outside than on the inside. Graded potential, caused by the opening of ligand-gated channels, can depolarize or hyperpolarize the membrane. Depolarizing graded potentials summate, resulting in the rapid inward diffusion of sodium through sodium channels [depolarization] wiping out the local electrical potential difference. This is followed by the outward diffusion of potassium through potassium channels [repolarization]. This rapid change in the membrane potential is called an action potential. The action potential of a neuron is an all-or-nothing event, although the actual electrical value differs among various types of neurons. A membrane is unable to respond to a new stimulus during the refractory period. Saltatory conduction is an extremely rapid form of transmission that jumps from one node of Ranvier to the next. An axon synapses with other neuron dendrites, with sites on muscles or with secretory cells. The gap between the axon and the target cell is called the synaptic cleft. Nerve signals cross this gap chemically. Chemicals released from the presynaptic side cause ion channels on the postsynaptic side to open initiating depolarization in the target cell. Different chemicals in different junctions allow a variety of responses not possible through direct electrical conduction. The neuromuscular junction is a typical synapse in which acetylcholine is the neurotransmitter. This chemical is rapidly degraded by acetylcholinesterase to allow for subsequent transmission. The cell body integrates signals from inhibitory and excitatory synapses. The signals either cancel or reinforce one another and affect the resulting signal sent out along the cell body’s axon. Many other neurotransmitters occur throughout the nervous system. These include glutamate, glycine, GABA, epinephrine, dopamine, norepinephrine, serotonin, neuropeptides, substance P, and even a gas, nitric oxide. Addictive drugs alter a post-synaptic neuron’s response to neurotransmitters. The vertebrate brain is divided into three regions: the hindbrain, the midbrain, and the forebrain. The diencephalon of the forebrain integrates sensory information, while the telencephalon is devoted to associative activity. Mammalian brains are particularly large with respect to overall body mass as compared to those of fish and reptiles. In humans, there is great enlargement of the cerebrum which functions in correlation, association, and learning. The human brain is divided into left and right hemispheres connected by the corpus callosum. Each hemisphere is further divided into frontal, parietal, temporal, and occipital lobes. The outer layer of the cerebrum is the cerebral cortex, the site of most neural activity. Sensory integration is directed mostly by the thalamus. The hypothalamus controls visceral responses, like temperature, respiration, and heartbeat and secretions of the pituitary gland. It is connected to the cerebral cortex via the limbic system, the center for emotional responses. The reticular activating system monitors all signals to the brain and sorts out important signals. The reticular system is also involved with sleep, which is studied via electroencephalograms. Higher cerebral functions are associated with the motor, sensory, and associative areas of the cerebral cortex. These regions direct sensory and motor input, higher mental activities, language, and memory. Voluntary bodily functions are under direct conscious control of the associative cortex. Involuntary homeostatic functions are not subject to conscious control. The spinal cord relays messages to and from the brain and functions in relfexes. Most neuromuscular control is regulated by feedback loops, the most simple being the muscle stretch receptors. Monosynaptic reflex arcs also provide feedback without involving the CNS. Neurovisceral control is directed by either the parasympathetic or the sympathetic divisions of the autonomic nervous system. The neurotransmitter at the synapse between the CNS axon and the autonomic dendrite is acetylcholine in both the sympathetic and the parasympathetic systems. The second neurotransmitter in the parasympathetic system, between the autonomic axon and the target organ, is again acetylcholine, while the sympathetic system uses epinephrine or norepinephrine. The actions of the two neurotransmitters on a target organ are completely opposite. In general, the parasympathetic system stimulates activity of normal body functions while the sympathetic system prepares the body for greater, emergency activity. Sensory information reaches the central nervous system through the processes of stimulation, transduction, transmission, and interpretation. The three classes of environmental stimuli use different classes of receptors. Exteroceptors sense external, environmental conditions that affect the body, while interoceptors sense internal conditions of the body. The external environment is sensed at many levels. The least encompassing determines only that an object is present. Another level senses information indicating both the location and direction of an object, thereby providing a three-dimensional image of the object and its surroundings. Many of the interoreceptors are simpler than those that monitor the external environment and are believed to be similar to primitive sensory receptors. In general, sensory receptors initiate nerve impulses by opening stimulus-gated ion channels that cause depolarization. The simplest receptors are bare nerve endings that depolarize in response to direct physical stimulation. Such receptors sense changes in temperature by detecting heat and cold. Simple mechanical receptors include nociceptors that sense pain, spindle fibers that fire when a muscle is stretched, and baroreceptors that alter their rate of firing with changes in blood pressure. Mechanoreceptors also sense changes in mechanical force thereby detecting changes in muscle length and tension through muscle spindles and blood pressure through baroreceptors in certain blood vessels. Some sensory cell membranes contain special proteins that bind to certain chemicals in the environment or a cell’s extracellular fluid The simplest receptors are chemical in nature and sense what we call taste and smell. Sensing the chemical environment is accomplished by taste receptors all over a fish’s body and by smell receptors in the nasal cavity of terrestrial vertebrates. Internal chemoreceptors also sense changes in blood chemistry by measuring concentrations of pH and oxygen. Fish possess receptors that sense changes in the patterns of pressure waves in water. This is the lateral line system located in grooves on either side of the body. Various receptors provide information on the body’s position in space. Statocysts are gravity receptors located in hollow chambers within the inner ear of vertebrates. Angular acceleration in all planes is detected by the motion of fluid in three semicircular canals, also within the inner ear. Mechanical receptors within the ears of land animals sense pressure waves in air as the lateral line receptors sense pressure waves in water. Structures in the middle ear amplify the sound waves since they are weaker in air than in water. The auditory receptors are located within the cochlea of the inner ear. Sonar is an auditory sense that provides information analogous to vision as it allows for three-dimensional imaging. • The stimulus for vision is electromagnetic energy detected by the visual pigment cis-retinal within rod and cone cells in the eye. Although many groups of animals independently evolved eyes of some sort, all utilize the same pigment. The retina is composed of three layers of cells. Light passes through ganglion and bipolar cells before reaching the rods and cones closest to the external surface of the eyeball. The visual nerve impulse is unusual in that it is initiated by a hyperpolarization event. Predator eyes are located at the front of their head to increase stereoscopic vision; prey eyes are at the side to enlarge their field of view. Vertebrates sense a variety of environmental stimuli in addition to sound and light waves. Vipers sense heat, a form of electromagnetic radiation of longer wavelengths than light. Extremely accurate stereoscopic imaging is possible due to the location of the receptors. Many aquatic organisms utilize electrical charges to send and receive information much as bats utilize sonar. Terrestrial animals have not evolved such sensory mechanisms because air is a very poor conductor of electricity. Recent studies indicate that great numbers of organisms, from bacteria to birds, are able to sense the earth’s magnetic field. Little is known about the nature of magnetic receptors. • LEARNING OUTCOMES 33.1 The Nervous System Directs the Body’s Actions 1. Distinguish the subdivisions of the vertebrate nervous system. 33.2 Neurons Maintain a Resting Potential Across the Plasma Membrane 1. Describe the production of the resting potential. 33.3 Action Potentials Propagate Nerve Impulses 1. Explain how the action of voltage-gated channels produces an action potential. 2. Describe how action potentials are propagated along axons. 33.4 Synapses Are Where Neurons Communicate With Other Cells 1. Describe how cells communicate across synapses. 2. Contrast the effects of excitatory and inhibitory neurotransmitters. 3. Explain how a neuron integrates the input from many other neurons. 33.5 The Central Nervous system Includes the Brain and Spinal Cord 1. Describe the organization of the brain in vertebrates. 2. Describe the organization of the brain in vertebrates 3. Explain how a simple reflex works. 33.6 The Peripheral Nervous System Consists of Both Sensory and Motor Neurons 1. Distinguish between somatic, autonomic, sympathetic and parasympathetic systems. 33.7 Sensory Receptors Provide Information About the Body’s Environment 1. Explain how sensory information is conveyed from sensory receptors to the CNS. 2. Describe how gated ion channels work. 33.8 Mechanoreceptors Sense Touch and Pressure 1. Describe how nociceptors detect pain. 2. Describe how proprioceptors detect limb position and movement. 3. Distinguish between proprioceptors and baroreceptors. 33.9 Sounds and Body Position Are Sensed by Vibration Detectors 1. Describe how the lateral line system allows fish to navigate to prey in the dark. 2. Explain how sound waves in the environment lead to production of action potentials in the inner ear. 3. Explain how mammals differentiate between sounds of different frequency. 4. Explain how the body’s position in space is monitored by structures in the inner ear. 33.10 Taste, Smell, and pH Senses Utilize Chemoreceptors 1. List the five taste categories and describe how their receptors function. 2. Describe how olfactory receptors function. 3. Describe how the body monitors blood pH. 33.11 Vision Employs Photoreceptors to Perceive Objects at a Distance 1. Compare invertebrate and vertebrate eyes. 2. Describe how photoreceptors function. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 33 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • Students do not understand the evolution of endosymbionts in animal cells • Students are unsure that many of the lower animals are classified as animals • Students think that all animals evolved at about the same time • Students believe that most animals do not feel pain • Students believe that animals can sense emotions and danger • Students believe that only humans have a well-developed nervous system • Students believe that animals are purely instinctual • Students believe that most animals are vertebrates • Students do not equate humans with being animals • Students believe that all animals have identical organ system structures INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE Discuss the similarities and differences between a typical electrical system and the vertebrate nervous system. Which of the events typical with nervous conduction are lacking in electrical conduction? Short-term memory is analogous to files stored in a computer’s RAM (random access memory), a volatile memory that requires a constant input of electricity. When the computer is shut off, these files are lost. Long-term memory is analogous to ROM (read only memory) present in special microchips or to files that have been written to or saved on a hard disk, floppy disk, zip disk, or CD; they still exist when the power is off. The few absolutely necessary bits of information (like time and date) are maintained in most computers by a tiny, internal battery on the mother board. Discuss the affects of the following on the function of synapses: cocaine, anti-depressants known as SSRIs [selective seratonin re-uptake inhibitors], strychnine, and tetanus toxin. Explain how death occurs due to strychnine and tetanus toxin and explain the addiction of cocaine. Stress the need for all types of sensory systems, not just those we associate with communication. Senses are needed to provide the brain with information so it can direct the motor systems. Sensory systems are closely integrated with and adapted to the environment. Speculate on the changes that might occur with humans under different environmental conditions such as the silence and weightlessness associated with space. Discuss how hearing and olfaction are altered with colds and allergies. Point out that the red spots that you see when you observe your tongue in the mirror are not taste buds but papillae. HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluate information from Chapter 33. Application • Have students explain the effects of diseases that cause a loss of myelination. • Have students explain the effects of blocking the movement of sodium ions on nervous system function. • Ask students to explain the peripheral nervous system components needed to walk up the steps. • Have students describe why olfaction is essential for tasting food. • Have students explain why deafness due to damage to the ear bones can be corrected with hearing assist devices such as hearing aids. • Ask students to explain the inability to see color does not affect seeing things at night. Analysis • Have students describe the effects of blocking acetylcholine on the autonomic nervous system. • Have students assess the effects on the nervous system of too much calcium in the diet. • Ask students to explain why complete damage to the brain still leaves the body with many intact functions. • Have students describe why fish use a lateral line instead of an ear structure for “hearing”. • Have students explain whether fresh water animals can benefit from receptors that detect electrical fields. • Ask students analyze the pros and cons of relying on vision as the primary sense for animals that live on land. Synthesis • Ask students explain why certain people are able to control autonomic nervous system responses. • Have students find a medical application for a chemical that blocks sodium transport across the cell membrane. • Ask the students design an experiment to investigate the role of oligodendrites on central nervous system function. • Ask students to design an experiment to test if other senses are enhanced by the loss of another sense. • Ask the students design an experiment to test whether a snake uses vision or heat perception to locate its prey. • Have students design an experiment to test is an animal has a sensory structure for detecting the direction of magnetic fields. Evaluation • Ask students evaluate the benefits and risks of using mood altering drugs that inhibit the uptake of certain brain neurotransmitters. • Ask students to evaluate the accuracy science fiction books that envision a future in which human thoughts are controlled by drugs. • Ask students to evaluate the effectiveness and safety of wasp control insecticides that block the action of acetylcholine. • Ask students evaluate the claims that extrasensory perception or ESP in humans is due to the ability to sense electrical signals given off by the brains of other organisms. • Ask students evaluate the benefits and risks of using flavor enhancers in foods that work by blocking the bitter receptors on the tongue. • Ask students evaluate the effectiveness using electrical impulses on the skin to reduce pain associated in injury and childbirth. VISUAL RESOURCES Pass a message around the room using three different methods. Have students verbally pass instructions from one to another across a row to represent communication via gap junctions. Have another set of students walk a written message from one end of a row to another imitating hormonal communication. The third method requires buying or borrowing a pair of walkie talkies to simulate nervous communication. The speed at which the message passes should be obvious to your students. They may additionally find that the slowest is also the least accurate as the message may get garbled especially if it is complicated. A copper wire wrapped with electrical tape resembles a myelinated nerve both in structure and function. A very simple mechanical associative activity is illustrated by a light that is activated only when it is dark outside (photosensitive) or when there is someone in the vicinity (heat, sound, or motion sensitive). IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Virtual Neurophysiology Introduction This demonstration uses a virtual electrophysiology to teach nervous system function in animal models. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to Biological Clocks Bio-interactive website at http://www.hhmi.org/biointeractive/vlabs/neurophysiology/index2.html Procedure & Inquiry 1. Explain to the class that they are going to observe a virtual neurophysiology demonstration using a model experimental system. 2. Load up the website and click on “Overview of equipment used in the lab”. 3. Then follow the sequence until completed with the virtual demonstration. 4. Then ask the class to the class to review what they saw and explain why the leech is used as an animal neurophysiology model. B. Mechanisms of Circadian Rhythm Introduction This demonstration uses animations to teach the cellular mechanisms of circadian rhythm. It models the functions of other sensory information used in homeostasis. Materials • Computer with Media Player and Internet access • LCD hooked up to computer • Web browser linked to Bio interactive Clocks at http://www.hhmi.org/biointeractive/clocks/animations.html#drosophmm. Procedure & Inquiry 5. Ask the class what they know about circadian rhythms. 6. Load up the “Clocks” website and click on “Step 1” of the “The Drosophila Molecular Clock Model”. 7. Ask the students briefly explain what is happening. Then click on the “Learn More” associated with “Step 1”. 8. Continue with the series and summarize the mechanism. 9. Repeat the process with “The Mammalian Molecular Clock Model” sequence. 10. Ask the students to compare and contrast the two circadian rhythm mechanisms. LABORATORY IDEAS A. Brine Shrimp as a Nervous System Model This activity has students design an experiment in which brine shrimp are used as a model of nervous system function. a. Explain to students how animals and animal cells are used in medicine and research as models for human studies. b. Provide students with the following materials a. Large brine shrimp at room temperature b. Microscope c. Microscope slides d. Plastic pipettes e. Test reagents : i. 3% W/V sodium chloride solution ii. 3% W/V potassium chloride solution iii. 3% W/V calcium chloride solution iv. 1-2 dilution organophosphate insecticide v. Black coffee c. Ask students to design an experiment to test the effects of the different solutions on the nervous system activity of the brine shrimp. Review the experiment before they progress with the activity. d. Have them record their findings and look up the potential effects of the treatments on the nervous system. e. Students should explain if their findings are consistent with the expected results. LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. 1. Have students do a lesson do a hands-on program on the animal behavior. 2. Have students do a lesson do a hands-on program on the animal homeostasis. 3. Have students tutor high school students studying animal anatomy and physiology. 4. Have students volunteer on environmental restoration projects with a local conservation group. 5. Have students volunteer at the educational center of a zoo or marine park. Instructor Manual for Understanding Biology Kenneth Mason, George Johnson, Jonathan Losos, Susan Singer 9780073532295, 9781259592416
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