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Plants and Animals – Common Challenges Chapter 27 Impacts, Issues A Cautionary Tale A multicelled organism must keep conditions inside its body within a range cells can tolerate; Korey Stringer died from heat stroke after football practice on a hot, humid day Introduction to Anatomy and Physiology Anatomy • The study of body form (structures) Physiology • The study of how body parts are put to use (function) 27.1 Levels of Structural Organization Tissue • One or more cell types (and often extracellular matrix) that collectively perform a specific task Organ • Two or more tissues in specific proportions that interact to carry out a specific task Organ system • Organs that interact in one or more tasks Growth Versus Development Growth • An increase in number, size, and volume of cells (quantitative) Development • A series of stages in which specialized tissues, organs and organ systems form in heritable patterns (qualitative) Evolution of Form and Function All anatomical and physiological traits have a genetic basis and have been affected by natural selection Plants and animals adapted to life on dry land with structures to move gases and retain moisture Anatomy of a Tomato Plant Flower, a reproductive organ shoot system (aboveground parts) root system (belowground parts, mostly) Cross-section of a leaf, an organ of photosynthesis and gas exchange Cross-section of a stem, an organ of structural support, storage, and distribution of water and food Fig. 27-2, p. 462 The Human Respiratory System Ciliated cells and mucussecreting cells of a tissue that lines respiratory airways Organs (lungs), part of an organ system (the respiratory tract) of a whole organism Lung tissue (tiny air sacs) laced with blood capillaries— one-cell-thick tubular structures that hold blood, which is a fluid connective tissue Fig. 27-3, p. 463 The Internal Environment Plant and animal cells are surrounded by their internal environment: extracellular fluid (ECF) To keep cells alive, body parts work together to keep the internal environment within tolerable limits (homeostasis) A Body’s Tasks Essential functions of plants and animals: • Maintain favorable conditions for cells • Acquire and distribute water, nutrients and other raw materials, and dispose of wastes • Defend against pathogens • Reproduce • Nourish and protect gametes and embryos 27.1 Key Concepts Many Levels of Structure and Function Cells of plants and animals are organized in tissues Tissues make up organs, which work together in organ systems This organization arises as the plant or animal grows and develops Interactions among cells and among body parts keep the body alive 27.2 Common Challenges Although plants and animals differ in many ways, they share some common challenges Animation: Morphology of a tomato plant Gas Exchange Diffusion • Ions or molecules of a substance move from a place where they are concentrated to one where they are scarce Aerobic respiration • The pathway that releases energy from food or photosynthetic products using oxygen and releasing carbon dioxide Internal Transport Very small organisms can exchange materials with the environment by diffusion; larger organisms have vascular tissues Plants have xylem and phloem Animals have a circulatory system with blood vessels Internal Transport Maintaining the Water-Solute Balance Passive transport • A material moves in or out of ECF down its concentration gradient through a transport protein Active transport • A protein pumps one specific solute from a region of lower concentration to a region of higher concentration (requires energy) Cell-to-Cell Communication Specialized cells release signal molecules that help control and coordinate events in the body • • • • Growth Development Maintenance Reproduction Variations in Resources and Threats Each habitat has a specific set of resources (water, nutrients, light, temperature) and challenges (predators, pathogens, parasites) Competition and variation in these factors promotes diversity of form and function Forms of Protection 27.2 Key Concepts Similarities Between Animals and Plants Animals and plants exchange gases with their environment, transport materials through their body, maintain volume and composition of their internal environment, and coordinate cell activities They also respond to threats and to variations in available resources 27.3 Homeostasis in Animals Detecting and responding to changes is a characteristic trait of all living things and the key to homeostasis Three Components Maintain Homeostasis in Animals STIMULUS Sensory input into the system Receptor Integrator Effector such as a free nerve ending in the skin such as the brain or the spinal cord a muscle or a gland Fig. 27-7, p. 466 Negative Feedback Negative feedback mechanisms • A change leads to a response that reverses that change • Example: A furnace turns off and on to maintain a set temperature; similar mechanisms maintain human body temperature Homeostatic Controls of Human Body Temperature STIMULUS Body’s surface temperature skyrockets after exertion on a hot, dry day. RESPONSE Body’s surface temperature falls, which causes sensory receptors to initiate shift in effector output. Receptors Sensory receptors in skin and elsewhere detect the change in temperature. Integrator Hypothalamus (a brain region) compares input from receptors against a set point for the body. Effectors Pituitary gland and thyroid gland trigger adjustments in activity of many organs. Effectors Different types of effectors carry out specific (not general) responses: Skeletal muscles Blood vessels in skin Sweat gland Adrenal in chest wall expand as muscle in secretions gland contract more their wall relaxes; more increase; the secretions frequently; faster metabolic heat gets evaporation drop off; breathing speeds heat transfer from shunted to skin, where of sweat cools excitement it dissipates into the air. body surfaces. declines. lungs to air. Effectors collectively call for an overall slowdown in activities, so the body generates less metabolic heat. Fig. 27-8a, p. 466 STIMULUS Body’s surface temperature skyrockets after exertion on a hot, dry day. RESPONSE Body’s surface temperature falls, which causes sensory receptors to initiate shift in effector output. Receptors Sensory receptors in skin and elsewhere detect the change in temperature. Integrator Hypothalamus (a brain region) compares input from receptors against a set point for the body. Effectors Pituitary gland and thyroid gland trigger adjustments in activity of many organs. Effectors Different types of effectors carry out specific (not general) responses: Skeletal muscles Blood vessels in skin Sweat gland Adrenal in chest wall expand as muscle in secretions gland contract more their wall relaxes; more increase; the secretions frequently; faster metabolic heat gets evaporation drop off; breathing speeds heat transfer from shunted to skin, where of sweat cools excitement it dissipates into the air. body surfaces. declines. lungs to air. Effectors collectively call for an overall slowdown in activities, so the body generates less metabolic heat. Stepped Art Fig. 27-8a, p. 466 dead, flattened skin cell sweat gland pore Fig. 27-8b, p. 466 Animation: Control of human body temperature Positive Feedback Positive feedback mechanisms • A chain of events intensifies the change from the original condition, leading to a change that ends feedback • Example: Childbirth contractions 27.4 Heat-Related Illness Heat stroke is a failure of homeostasis that can cause irreversible brain damage or death Symptoms: dizziness, blurred vision, muscle cramping, weakness, nausea and vomiting Risk factors: Sweating, heat and humidity, age, medical condition, pregnancy First aid: Water, ice packs, call for medical aid 27.5 Does Homeostasis Occur in Plants? Mechanisms that control homeostasis in plants are not centrally controlled Systemic acquired resistance: Affected cells release signaling molecules that cause release of protective organic compounds Compartmentalization walls injured and infected tissues with resins and toxic compounds Compartmentalization Response A Strong B Moderate C Weak Fig. 27-9, p. 468 Animation: Compartmentalization responses Sand, Wind, and Yellow Beach Lupine Lupine adaptations to beach environment: • Nitrogen-fixing bacteria provide nutrients • Hairs trap moisture that evaporates from stomata • Leaves fold in hot, windy conditions Rhythmic Leaf Folding Circadian rhythm • A biological activity pattern in plants or animals that recurs with a 24-hour cycle • Example: Rhythmic leaf folding might help reduce heat loss at night Rhythmic Leaf Folding 1 A.M. 6 A.M. Noon 3 P.M. 10 P.M. Midnight Fig. 27-11, p. 469 Animation: Rhythmic leaf movements 27.3-27.5 Key Concepts Homeostasis Homeostasis is the process of keeping conditions in the body’s internal environment stable The feedback mechanisms that often play a role in homeostasis involve receptors that detect stimuli, an integrating center, and effectors that carry out responses 27.6 How Cells Receive and Respond to Signals Communication among distant body cells requires special molecules that travel through ECF, blood, or plant vascular systems • Signal reception • Signal transduction • Cellular response Example: Apoptosis (programmed cell death) Three Steps in Signaling Signal Reception Signal binds to a receptor, usually at the cell surface. Signal Transduction Binding brings about changes in cell properties, activities, or both. Cellular Response Changes alter cell metabolism, gene expression, or rate of division. Fig. 27-12a, p. 470 Signal Transduction Pathway Signal to die docks at receptor. Signal leads to activation of proteindestroying enzymes. Fig. 27-12b, p. 470 Apoptosis Apoptosis: When Cell Signaling Fails 27.6 Key Concepts Cell Communication in Multicelled Bodies Cells of tissues and organs communicate by secreting chemical molecules into extracellular fluid, and by responding to signals secreted by other cells Animation: Formation of human fingers Animation: Negative feedback system Animation: Structures that function in human respiration Video: Too hot to handle