0.5 cm Nutrients Digestive system Lining of small intestine Mouth Food External environment Animal body CO 2 O2O2 Circulatory system Heart Respiratory system Cells Interstitial fluid Excretory system Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) Kidney tubules 10 µm 50 µm Lung tissue
Stimulus Hormone Endocrine cell Signal travels everywhere via the bloodstream. Blood vessel Response Signaling by hormones Stimulus Neuron Axon Signal Signal travels along axon to a specific location. Signal Axons Response Signaling by neurons
Response: Heater turned off Stimulus: Control center (thermostat) reads too hot Room temperature decreases Set point: 20ºC Room temperature increases Stimulus: Control center (thermostat) reads too cold Response: Heater turned on
Organic molecules in food External environment Animal body Digestion and absorption Nutrient molecules in body cells Carbon skeletons Cellular respiration ATP Heat Energy lost in feces Energy lost in nitrogenous waste Heat Biosynthesis Heat Cellular work
Shrew Harvest mouse Mouse Ground squirrel Rat Cat Dog Sheep Human Horse Elephant Body mass (kg) (log scale) BMR (L O 2 /hr) (log scale) (a) Relationship of BMR to body size 10 –3 10 –2 10 –1 1 1 10 10 2 10 3 10 10 2 10 3
10 2 10 1 10 –1 10 –2 10 –3 0 1 2 3 4 5 6 7 8 Body mass (kg) (log scale) (b) Relationship of BMR per kilogram of body mass to body size BMR (L O 2 /hr) (per kg) Shrew Harvest mouse Mouse Rat Ground squirrel Cat Sheep Dog Human Horse Elephant
Additional metabolism that would be necessary to stay active in winter Actual metabolism Arousals Body temperature Outside temperature Burrow temperature Metabolic rate (kcal per day) Temperature (°C) JuneAugustOctoberDecemberFebruaryApril –15 –10 –5 0 5 15 10 25 20 35 30 0 100 200
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