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 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 3 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 5 Fig. 40.4
Hierarchical Organization 6 See Fig. 1.4 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
Functions? 7
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 8
Muscle Body movement Actin & myosin filaments Skeletal, smooth & cardiac Nervous Tissue types Sense stimuli, process information and transmit signals 9 Fig. 40.5
Coordination & Control 10 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
Nervous System Coordination & Control 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 11
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 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 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 Fig. 40.7 13
Homeostasis 14 Sensor/Receptor Integrator/Control Center Effector/Response Set point Normal or target value/range for the controlled variable See Fig. 40.8
Homeostasis 15 Fig. 40.8
Homeostasis 16 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
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 20 Insulation Reduces flow of heat between animal and environment Trap air layer under fur or feathers Body fat
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 22 Circulatory adaptations Countercurrent heat exchange Transfer of heat between adjacent fluids flowing in opposite directions Maximizes transfer of heat (or solutes) Fig. 40.12
Mechanisms of Thermoregulation 23 Evaporative cooling Water absorbs heat when it evaporates Water vapor carries heat away from body Kangaroos lick their skin to increase evaporative cooling
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 26 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
Acclimatization 27 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)