Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal Organization and Homeostasis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 2.A.1: All living systems require constant input of free energy. – a. Life requires a highly ordered system – b. Living systems do not violate the second law of thermodynamics, which states that entropy increases over time. – c. Energy-related pathways in biological systems are sequential and may be entered at multiple points in the pathway. – d. Organisms use free energy to maintain organization, grow and reproduce.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – e. Changes in free energy availability can result in changes in population size. – f. Changes in free energy availability can result in disruptions to an ecosystem.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. – a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 2.C.1: – b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change. – c. Alteration in the mechanisms of feedback often results in deleterious consequences.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 2.C.2: Organisms respond to changes in their external environments. – a. Organisms respond to changes in their environment through behavioral and physiological mechanisms.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 2.D.2: Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. – a. Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions. – b. Organisms have various mechanisms for obtaining nutrients and eliminating wastes. – c. Homeostatic control systems in species of microbes, plants and animals support common ancestry.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential knowledge 4.C.2: Environmental factors influence the expression of the genotype in an organism. – a. Environmental factors influence many traits both directly and indirectly. – b. An organism’s adaptation to the local environment reflects a flexible response of its genome.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homeostasis Animals are covered by protective skin to protect and prevent water loss-this makes exchange of materials with the environment more difficult Most animals have low surface area to volume ratio-this means they must have specialized internal exchange surface adaptations to create large surface area

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Living cells must be bathed in aqueous solution to keep the membrane intact Molecules must be dissolved in aqueous solution to diffuse across the cell membrane Materials diffuse from blood to interstitial fluid, and from interstitial fluid into body cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organisms with complex body plans h ave highly folded internal surfaces specialized for exchanging materials

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The internal environment of vertebrates is called the interstitial fluid, and is very different from the external environment Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanisms of homeostasis – Moderate changes in the internal environment Mechanisms of Homeostasis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A homeostatic control system has three functional components – A receptor, a control center, and an effector

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Homeostasis The organ systems of the human body contribute to homeostasis – The digestive system Takes in and digests food Provides nutrient molecules that re-place used nutrients – The respiratory system Adds oxygen to the blood – The liver Store excess glucose as glycogen Later, glycogen is broken down to replace the glucose used The hormone insulin regulates glycogen storage – The kidneys

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A homeostatic control system has three functional components –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most homeostatic control systems function by negative feedback –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Negative Feedback Homeostatic Control – Partially controlled by hormones – Ultimately controlled by the nervous system Negative Feedback is the primary homeostatic mechanism that keeps a variable close to a set value – Sensor detects change in environment – Regulatory Center activates an effector – Effector reverses the changes –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A second type of homeostatic control system is positive feedback –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Positive Feedback During positive feedback, an event increases the likelihood of another event – Childbirth Process – Urge to urinate – Estrogen release in menstrual cycle Positive Feedback – Does not result in equilibrium –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammals regulate their body temperature – By a complex negative feedback system that involves several organ systems Feedback Mechanisms in Thermoregulation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In humans, a specific part of the brain, the hypothalamus – Contains a group of nerve cells that function as a thermostat

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Thermoregulation contributes to homeostasis and involves anatomy, physiology, and behavior Thermoregulation –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ectotherms – Include most invertebrates, fishes, amphibians, and non-bird reptiles Endotherms – Ectotherms and Endotherms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Birds and mammals are mainly endothermic, meaning that – Their bodies are warmed mostly by heat generated by metabolism – They typically have higher metabolic rates – Commonly called “warm-blooded” – Endotherms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ectotherms Amphibians and reptiles other than birds are ectothermic, meaning that – They gain their heat mostly from external sources – They have lower metabolic rates – Body temp fluctuates with environmental temperatures – Commonly called “cold-blooded” –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endothermy is more energetically expensive than ectothermy – But buffers animals’ internal temperatures against external fluctuations –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endotherms and some ectotherms maintain a constant internal temperature as the external temperature fluctuates by changing the rate of heat production, or by changing the rate of heat gain or loss

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Insulation Insulation, which is a major thermoregulatory adaptation in mammals and birds – Reduces the flow of heat between an animal and its environment –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many endotherms and some ectotherms – Can alter the amount of blood flowing between the body core and the skin Circulatory Adaptations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooling by Evaporative Heat Loss Many types of animals – Lose heat through the evaporation of water in sweat –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Both endotherms and ectotherms use a variety of behavioral responses to control body temperature Animals may increase or decrease body heat by relocating-migration to a more suitable climate, basking in sun, huddling together They may burrow to escape the heat and seek cool damp areas, they may also bathe Behavioral Responses

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Torpor and Energy Conservation Torpor – Is an adaptation that enables animals to save energy while avoiding difficult and dangerous conditions – Is a physiological state in which activity is low and metabolism decreases (heart and respiratory rate slow down – Animals active in day undergo torpor at night –

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hibernation is long-term torpor – That is an adaptation to winter cold and food scarcity during which the animal’s body temperature declines

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Estivation, or summer torpor – Daily torpor – Is exhibited by many small mammals and birds and seems to be adapted to their feeding patterns

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ectotherms cannot survive extreme cold temps, because their body temp is too low to remain active They must lower metabolic rate and hibernate, which allows them to burn very little energy all winter