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Animal Form and Function (Animal body plan influences (Tissue type and…

- - - - Animals that generate their own heat through metabolism are endotherms
      - Includes mammals, birds and some fish and insects
      - Disadvantage: must eat a lot of food Advantage: Can exist in a large temperature range
    - - Animals that get heat from their environment are ectotherms
      - Includes amphibians, reptiles, many fishes, and most invertebrates
      - Generate heat through behavior (basking in the sun)
      - Limited habitats (they don't live in Antarctica) but require less food (10% of what endotherms need)
    - - Poikilotherms are animals whose body temperatures vary with the environment
      - Homeotherms can relatively constant body temperatures
      - No fixed relation between these two and endothermy and ectothermy
    - - Insulation
        
        Includes hair, feathers, fat, and fur
        
        When animals raise their fur or feathers, it traps a thick layer of air, contributing to a higher insulating power
        
        Humans lack feathers and fur, and rely on fat for warmth
        
        Apparently goosebumps are a vestige in humans, but they do actually contribute to warmth
        
        Marine animals have a thick layer of insulating fat, called blubber, which helps keep them warm in frigid temperatures
      - Circulation
        
        Circulatory systems are a major route for heat flow; blood carries heat
        
        Thermoregulation is maintained via vasoconstriction or vasodilation
        
        Countercurrent heat exchange
        
        In many birds and mammals, veins and arteries run parallel, which conserves heat; warm blood from the core moves to the veins, bringing the heat back into the core
        
        Explains why fingers and toes are the first to get cold
      - Evaporation
        
        Only way that animals cool down
        
        Panting, sweating, and bathing increase evaporation
      - Behavior
        
        Primary way for ectotherms to cool down
        
        Includes sun basking, seeking shade,orienting the body to maximize or minimize sun exposure, and huddling together
        
        Long term methods include hibernation and migration
      - Metabolism
        
        Primary way for endotherms to combat heat loss and utilize thermogenesis
        
        Movement (shivering) generates heat through increased muscle movement
        
        Some animal use hormone to cause mitochondria to create heat instead of energy (nonshivering thermogenesis)
        
        Takes place in brown fat, adipose tissue designed for rapid heat production
        
        In human babies, brown fat accounts for 5% of body weight, although it is present in adults as well
      - Acclimatization is a physiological adjustment to an environmental factor
        
        Growing more feathers or altering the cell membrane in the cold
        
        Sensors for thermoregulation exist in the hypothalamus