Basic Principles of Animal Form and Function What
Basic Principles of Animal Form and Function
What you must know: • How feedback systems function to maintain homeostasis • One example of positive feedback and one example of negative feedback
STRUCTURE FUNCTIONS
Coordination and control within a body • Endocrine System: transmits chemical signals (hormones) to all locations in the body through the bloodstream • Slow acting, long-lasting effects • Info received by: cells with specific receptors for released hormone • Nervous System: neurons transmit info between specific locations • Very fast! • Info received by: neurons, muscle cells, endocrine cells
Homeostasis • Maintain a “steady state” or internal balance regardless of external environment • Fluctuations above/below a set point serve as a stimulus; these are detected by a sensor and trigger a response • The response returns the variable to the set point
Negative Feedback • “More gets you less. ” • Return changing conditions back to set point • Examples: – Temperature – Blood glucose levels – Blood p. H Plants: response to water limitations Positive Feedback • “More gets you more. ” • Response moves variable further away from set point • Stimulus amplifies a response • Examples: – Lactation in mammals – Onset of labor in childbirth Plants: ripening of fruit
Temperature Regulation
• Maintain an internal temperature within a tolerable range • Endothermic animals generate heat by metabolism (birds and mammals) • Ectothermic animals gain heat from external sources (invertebrates, fishes, amphibians, and nonavian reptiles) • Q: Which is more active at greater temperature variations? • Q: Which requires more energy?
Energy Use • Metabolic rate: total amount of energy an animal uses in a unit of time • Ectotherms have much lower metabolic rates than endotherms of a comparable size
Metabolic rate is inversely related to body size among similar animals
Balancing Heat Loss and Gain • Organisms exchange heat by four physical processes: radiation, evaporation, convection, and conduction
Five adaptations for thermoregulation: • Insulation (skin, feather, fur, blubber) • Circulatory adaptations (countercurrent exchange) • Cooling by evaporative heat loss (sweat) • Behavioral responses (shivering) • Cellular adjustments (“antifreeze” proteins, membrane lipids, enzyme variants)
Countercurrent heat exchange
Torpor and Energy Conservation • Torpor is a physiological state in which activity is low and metabolism decreases • Save energy while avoiding difficult and dangerous conditions • Hibernation: torpor during winter cold and food scarcity • Estivation: summer torpor, survive long periods of high temperatures and scarce water
Osmoregulation Marine vs. Freshwater Fish Nitrogenous wastes
Osmoregulation Mammalian Excretory System
Nephron: blood filtration and water concentration in the human kidney
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