Whittaker s Biomes. Regulating T b : Heat Loss & Heat Gain. Gain. Loss. Fertilizer: basis of Leibig s Law of the Minimum Shelford s Law of Tolerance

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1 Skunk Cabbage An exothermic plant Whittaker s Biomes Whittaker's diagram showing how the type of plant community found in an area varies with temperature and precipitation. Text Fertilizer: basis of Leibig s Law of the Minimum Shelford s Law of Tolerance Let s look at heat... Heat Loss & Heat Gain Gain Radiation Convection Conduction Metabolism Loss Radiation Convection Conduction

2 Ectotherm Thermoregulation Grasshoppers, beetles, & lizards behaviorally modify their radiant heat gain. Endotherm Thermoregulation Endotherm Thermoregulation Aquatic animals lose heat quickly. What does tuna T b graph show? How do they do it? Even Some Insects Do It

3 Shifting T a s, Shifting Strategies Endothermy allows activity at any time But it s cheaper to be ectothermic Some enter torpor for shorter stints Some hibernate for long cold periods Shifting T a s, Shifting Capabilities Sprinting speeds of desert night lizards acclimated to 20 C at a range of different temperatures. (After Kaufmann and Bennett 1989) Shifting T a s, Shifting Capabilities Popn Growth in Bacteria enzymes set rates of reactions T b Affects Enzyme Function Temperature-dependent rattling

4 Enzymes catalyze chemical reactions. How do you measure enzyme activity? Directly -Measure activity of enzyme Indirectly Thermal Physiology: Adaptation & Acclimation -Measure rate of processes requiring enzymes Nerve transmission is crucial to animals. Photosynthesis is crucial to plants. Physiological acclimation can also occur. Thermal Physiology: Acclimation Neurotransmission in trout acclimated to different T as. Photosynthesis in two plants Arctic moss Desert Atriplex winter summer Cuttings from one saltbush (Atriplex) in Death Valley. Why was this done? Some were grown under hot conditions At 43 C day & 30 C night Some were grown under cool conditions At 23 C day & 18 C night Thermal Physiology: Acclimation Thermal Balance The heat balance equation has five processes, shown above, which move heat into and out of the k-rat. These must all balance (summing to zero) for the k-rat to maintain homeostasis.

5 Water Balance The simplest way for an organism to obtain water is to ingest it (e.g., via drinking or direct absorption). Metabolizing carbs makes water as a by-product. Organisms absorb lose water due to osmosis through surfaces in contact with liquid water. This is important in aquatic organisms. Heat energy can cause water to change state from liquid to gas and evaporate into the atmosphere. Animals lose water when they secrete waste products. Two Photosynthetic Reactions: Light vs. Dark ADP + P Sunlight ATP CO 2 + H 2 O C 6 H 12 O 6 + O 2 CO 2 from stomata, H 2 O from roots Light reaction forms ATP. Using energy from photons. Dark reaction fixes carbon. Using energy from ATP. Two Photosynthetic Pathways: C 3 (most plants) vs. C 4 (grasses) Form 3-carbon molecule 1st. Many open stomata = high CO 2 entry = high water loss Form 4-carbon 1st Few open stomata = dark reaction rate = H 2 0 loss Arid Land Pathways: C 4 & CAM Photosynthesis Succulents have dark reaction at night, light during day Slow growth & water-wise Water to make 1g plant tissue: C g C g CAM 50g

6 Energy Limitations: Sun vs. Shade Plants light photosynthetic rates The photosynthetic response curve flattens. food consumption rates. The functional response curve flattens. Heterotrophs: Variation in Nutritive Value Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), Phosphorus (P) = 95% N is for proteins, it is limited. An organism s C:N ratio α its food value. Dead leaves have <1/2 N of live leaves. Fresher leaves = more 2 compounds. Mouse-Elephant Curve Metabolic rates in mammals and all other living organisms increase with body size, as shown on the orange line. However, metabolic rates increase more slowly than mass, as shown by the black line, which plots metabolic rate per kilogram of body mass.