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Animal Form & Function Lecture 10 Winter 2014 Physical Constraints on Form & Function 1 • Anatomy & physiology (define) • Environmental constraints on form – Convergent evolution • Larger organisms – Need thicker skeletons to maintain support – Larger muscles for movement of larger mass Fig. 40.2 Physical Constraints on Form & Function 2 • Exchange with environment – Substances dissolved in aqueous medium move across plasma membranes of cells – Plasma membranes must be kept moist to maintain integrity • What materials need to be exchanged with environment? • Limits with surface to volume ratios – Rates of exchange (for nutrients, waste, gases) are proportional to membrane surface area – Amount of material that needs to be exchanged to sustain life is proportional to volume Physical Constraints on Form & Function 3 • Single-cell organism: entire surface area contacts environment • Simple organization in multicellular organisms – Hydra: two cells thick with gastrovascular cavity allows for all cells to have direct with the environment – Tapeworm: Thin & flat - can keep most cells in contact with external environment • More challenging for more multicellular organisms • As the number of cells increase, the ratio of outer surface area to total volume decreases Fig. 40.3 Physical Constraints on Form & Function 4 • How to bathe every cell in fluid in order to have exchange? • Specialized surfaces that are extensively branched or folded – Most surfaces within body – Example lungs, blood vessels, intestines of humans • Interstitial fluid – Fluid in spaces between cells – exchanges nutrients, gases, waste, etc. with circulatory fluid (e.g., blood in humans) Physical Constraints on Form & Function Fig. 40.4 5 Hierarchical Organization 6 • Tissue – Integrated group of cell with a common function, structure or both • Organ – Specialized center of body function composed of several different types of tissues • Organ System – Group of organs that work together in performing vital body functions See Fig. 1.4 7 Functions? 8 Tissue types • Note: For tissue types, only focus on function (as listed here) • Epithelial – Covers outside of body – Lines organs and cavities in body – Protection against mechanical injury, pathogens, fluid loss – Forms active interface with environment (e.g., nasal cavity) • Connective – Bind and support other tissues in body – Includes loose connective tissue, fibrous connective tissue, cartilage, bone, adipose tissue, blood Tissue types • Muscle – Body movement – Actin & myosin filaments – Skeletal, smooth & cardiac • Nervous – Sense stimuli, process information and transmit signals Fig. 40.5 9 Coordination & Control • Endocrine System – Signaling molecules released into bloodstream reach all locations in body – Signaling molecule: hormones – Cell must have receptor for hormone – Slower acting – Coordinates growth, development, reproduction, metabolic processes,. digestion • Note: overview only – we will look at details in later chapter 10 Coordination & Control 11 • Nervous System – Neurons transmit signals between specific locations in body – Fast actingCordinating immediate & rapid response to environment, locomotion & behavior – Both endocrine and nervous system often work together • Note: overview only – we will look at details in later chapter Fig. 40.6 Homeostasis Homeostasis • The maintenance of a relatively constant chemical and physical environment within an organism Examples of conditions in the body that need to be maintained? 12 Homeostasis 13 • Regulator – Uses internal control mechanisms to moderate internal change in the face of external changes • Conformer – Allows its internal condition to vary with certain external Fig. 40.7 changes • An animal may be both regulator and conformer depending on the variable • Example: Bass is a conformer for temperature, but a regulator for solute concentration of blood and interstitial fluid Homeostasis • Sensor/Receptor • Integrator/Control Center • Effector/Response Set point • Normal or target value/range for the controlled variable See Fig. 40.8 14 Homeostasis Fig. 40.8 15 Homeostasis Negative Feedback Loops • Corrective response in which effectors reduce or oppose the change in internal conditions • Moves a system back towards a set point or normal range Fig 40.16 16 Regulation of Systems 17 Positive Feedback loop • Increased temperatures = increased melting • Increased melting = less ice/snow cover • Less ice/snow cover = less light reflection • Less light reflection = more light absorption • More light absorption = increased temperature Positive feedback loops • Moves a system further away from a set point • Amplifies the disturbance E.g., Albedo Effect • Ice & snow reflect sunlight • Rocks/soil absorb sunlight Thermoregulation 18 • Process which organisms maintain an internal temperature within a tolerable range • Why is this important? • Heat transfer always from warmer temperatures to colder temperatures Fig. 40.11 Mechanisms of Thermoregulation 19 • Endotherm – An organism that uses its metabolism to generate heat for body • Ectothermic – An organism that uses external heat sources for body heat • Why aren’t all organisms endothermic? • Poikilotherm – Organism whose body temperature varies with its environment • Homeotherm – Organism whose body temperature is relatively constant Fig. 40.10 Mechanisms of Thermoregulation • Insulation – Reduces flow of heat between animal and environment – Trap air layer under fur or feathers – Body fat 20 Mechanisms of Thermoregulation Circulatory adaptations • Vasodilation – Widening of superficial blood vessels, increases blood flow • Warms skin & increases heat transfer from body • Vasoconstriction – Decreases diameter of superficial blood vessels, reduces blood flow & heat transfer • Conserves body heat to central core – E.g., ears of jackrabbit in very hot environment • Prevents heat absorbed by ears from being transferred to body 21 Mechanisms of Thermoregulation Circulatory adaptations • Countercurrent heat exchange – Transfer of heat between adjacent fluids flowing in opposite directions – Maximizes transfer of heat (or solutes) 22 Fig. 40.12 Mechanisms of Thermoregulation • Evaporative cooling – Water absorbs heat when it evaporates – Water vapor carries heat away from body • Kangaroos lick their skin to increase evaporative cooling 23 Mechanisms of Thermoregulation Behavioral responses • Positional/postural – Orientation to sun • Social behavior – Honeybees & penguins huddle to keep warm & rotate positions 24 Mechanisms of Thermoregulation Behavioral responses • Topor – State of low physical and metabolic activity – Short-term – Anna’s hummingbird in Seattle winter – torpor state overnight when too cold • Hibernation – Long-term 25 Mechanisms of Thermoregulation • Thermogenesis • Heat production • Shivering – E.g., chickadees, hawkmoth& bumblebee pre-flight warm-up, python incubating eggs • Non-shivering thermogenesis – Increase metabolic activity to produce heat (rather than ATP) Fig. 40.15 26 27 Acclimatization • A temporary adjustment to changes in an organism’s external environment – Change in altitude causes change in production of red blood cells – Seasonal changes • Thicker fur, or shedding • Proportion of saturated vs. unsaturated lipids in cell membrane • Acclimatization is not Adaptation • Pgs 868-871 (Concept 40.4 Energy requirements are related to animal size..) will be covered with the next chapter (Animal Nutrition)