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Chapter 28: Common Challenges

This chapter explores the challenges faced by organisms in high elevations, including scarcity of oxygen and intense UV radiation. It also discusses the concept of homeostasis and how organisms maintain a stable internal fluid environment. The chapter also examines recurring challenges that all plants and animals must accomplish, as well as long-term adaptations and variations among different habitats. Additionally, it delves into the mechanisms of homeostasis and how the body responds to external stimuli to maintain stability.

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Chapter 28: Common Challenges

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  1. Chapter 28: Common Challenges

  2. Fig. 28-1, p.478

  3. p.479

  4. Living the High Life (1) • At high elevations, oxygen is scarce • Barheaded goose has hemoglobin that binds oxygen more tightly than human hemoglobin • What’s the difference? A single amino acid substitution

  5. Living the High Life (2) • At high elevations, UV radiation and winds are intense • Leontopodium alpinum forms short, tight, cushions • Flowers are covered with wooly hairs that protect against UV and help retain moisture

  6. Anatomy and Physiology • Anatomy is the study of an organism’s form • Physiology is the study of how the body functions • Some aspects of anatomy and physiology are adaptations to past or present environmental conditions

  7. Levels of Organization Bodies of multicelled organisms show division of labor • Tissues • Organs • Organ system

  8. reproductive organ (flower) stem tissues, cross-section, for support, storage, water distribution, food distribution shoot system (aboveground parts) root system (belowground parts, mostly) root water-conducting cells, longitudinal section Fig. 28-2, p.480

  9. Growth and Development • Growth is an increase in the number, size, and volume of cells • Quantitative • Development refers to successive stages in the formation of specialized tissues, organs, and organ systems • Qualitative

  10. Homeostasis • Maintaining a stable internal environment • Cells are filled with and bathed in fluid • Extracellular fluids are an internal environment • Both plants and animals must maintain stable fluid environments for all living cells

  11. Evolutionary History • Land plants and land animals arose from aquatic ancestors • Both face new challenges in the drier environment • Their form and physiology are answers to these challenges

  12. Fig. 28-3, p.481

  13. Recurring Challenges • All plants and animals must accomplish certain tasks • Gas exchange • Internal transport • Maintaining solute-water balance • Integrating signals

  14. Long-Term Adaptation • A heritable aspect of form, function, behavior, or development that contributes to the fit between an individual and its environment • Salt-tolerant tomatoes • Desert oryx

  15. Adaptation to What? • Not all traits are adaptations to present environment • Camel and llama have hemoglobin with high affinity for oxygen • Only the llama lives at high altitudes • Hemoglobin is not an adaptation to high altitude

  16. Defining Fluids • Fluid inside and outside of animal cells • Fluid outside of cells is extracellular fluid • Interstitial fluid lies between cells • Plasma is the fluid portion of the blood

  17. Fluid Balance • Changes in extracellular fluid cause changes in cells • The component parts of every animal work to maintain a stable fluid environment for living cells

  18. Fig. 28-5a, p.483

  19. Fig. 28-5b, p.483

  20. Fig. 28-5c, p.483

  21. Fig. 28-5d, p.483

  22. Variations • Challenges differ among habitats • Physical resources vary • Water • Nutrients • Temperature • Biological components vary • Predators • Competition

  23. Homeostasis • Stable operating conditions in the internal environment • Three components interact RECEPTOR (e.g., free nerve ending in the skin) INTEGRATOR (such as the brain) EFFECTOR (a muscle or a gland)

  24. Negative Feedback • Some activity alters a condition in the internal environment • Alteration triggers a response • Response reverses the altered condition

  25. SKELETAL MUSCLES Husky rests, starts to pant (behavioral changes). SMOOTH MUSCLE IN BLOOD VESSELS Blood carrying metabolically generated heat shunted to skin, some heat lost to surroundings. SALIVARY GLANDS Secretions from glands increase; evaporation from tongue. Both have a cooling effect, especially on the brain. ADRENAL GLANDS Output drops, husky is less stimulated. STIMULUS The husky is overactive on a hot, dry day and its body surface temperature rises. RECEPTORS in skin and elsewhere detect the temperature change. An INTEGRATOR (the hypothalamus, a brain region) compares input from the receptors against a set point. Some EFFECTORS (pituitary gland and thyroid gland) trigger widespread adjustments. RESPONSE Temperature of circulating blood starts decreasing. Many EFFECTORS carry out specific responses: Activity of the body in general slows down (behavioral change). The overall slowdown in activities results in less metabolically generated heat. Figure 28.8 Page 484

  26. dead, flattened skin cells sweat gland pore Fig. 28-8a, p.484

  27. STIMULUS receptors integrator effectors After over-exertion on a hot, dry day, surface temp-erature of body skyrockets. The hypothalamus, a brain region, compares input from the receptors against the set point for the body. Pituitary gland and thyroid gland trigger widespread adjustments in many organs. In skin and elsewhere detect the temperature change. RESPONSE Body temper-ature falls, receptors initiate shifts in effector output. effectors These carry out specific, not general, responses: Skeletal muscles in chest wall work to get additional oxygen into lungs. Smooth muscle in blood vessels dilates; blood transporting metabolic heat shunted to skin; some heat lost to surroundings. Sweat glands secrete more, with cooling effect on the brain especially. Adrenal gland stimulatory signals drop off. Overall slowdown in activities results in less metabolically generated heat. Fig. 28-8b, p.484

  28. STIMULUS input into the system receptor integrator effector (such as a free nerve ending in the skin) (such as the brain or spinal cord) (a muscle or gland) RESPONSE to stimulus causes change. The change is “fed back” to receptor. In negative feedback, the system’s response cancels or counters the effect of the original stimulus. Fig. 28-7, p.484

  29. Positive Feedback • Some activity alters the internal environment • The alteration triggers a response • The response intensifies the change in the internal condition

  30. Fig. 28-9, p.485

  31. Compartmentalization • Plant response to a wound or pathogen • Walls around area thicken • Toxins and resins are produced at site • Tree species vary in their responses • Strong response can stop an infection

  32. strong moderate weak Fig. 28-10, p.486

  33. Fig. 28-11a, p.487

  34. Fig. 28-11b, p.487

  35. Leaf-Folding in Lupine • Leaves of the yellow bush lupine make a homeostatic response to environment • Leaves fold during strong winds and during hottest part of day • Folding reduces evaporative water loss

  36. Rhythmic Leaf Folding • A circadian rhythm • Bean plant spreads leaves during day, folds them in at night • Leaf movements persist even in complete darkness • May help plant maintain temperature at night

  37. Rhythmic Leaf Folding Fig. 28-12, p.487

  38. Cell Communication • Molecular mechanisms • Activation of a receptor • Usually membrane protein • Transduction of the signal • Functional response

  39. ABC Model • Three groups of genes are master switches for floral development • Genes encode factors that govern transcription of other genes • Products of those genes reprogram the mass of dividing cells to form floral components

  40. Apoptosis • The process of programmed cell death

  41. signal reception signal transduction cellular response Fig. 28-13a, p.488

  42. Signal to die docks at receptor. Signal leads to activation of protein-destroying enzymes. Fig. 28-13b, p.488

  43. Apoptosis • When Apoptosis fails:

  44. Fig. 28-14a, p.489

  45. Fig. 28-14b, p.489

  46. Fig. 28-15, p.489

  47. Vertebrate Nervous System • When receptors on neurons bind a signaling molecule, ion channels open • Ions flow across the membrane, changing the charge • Signal is self-propagating • Multiple sclerosis interferes with signaling

  48. Fig. 28-16a, p.490

  49. Fig. 28-16b, p.490

  50. Fig. 28-16c, p.490

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