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Temperature Relations

Chapter 5

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Outline• Microclimates• Aquatic Temperatures• The Principle of Allocation• Temperature and Animal Performance• Extreme Temperature and Photosynthesis• Temperature and Microbial Activity• Balancing Heat Gain Against Heat Loss• Body Temperature Regulation• Surviving Extreme Temperatures

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Microclimates

• Macroclimate: Large scale weather variation.• Microclimate: Small scale weather variation,

usually measured over shorter time period. Altitude

Higher altitude - lower temperature. Aspect

Offers contrasting environments. Vegetation

Ecologically important microclimates.

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Microclimates

• Ground Color Darker colors absorb more visible light.

• Boulders / Burrows Create shaded, cooler environments.

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Aquatic Temperatures

• Specific Heat Absorbs heat without changing

temperature. 1 cal energy to heat 1 cm3 of water 1o C.

Air - .0003 cal• Latent Heat of Evaporation

1 cal can cool 580 g of water.• Latent Heat of Fusion

1 g of water gives off 80 cal as it freezes.

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Aquatic Temperatures

• Riparian vegetation influences stream temperature by providing shade.

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The Principle of Allocation

• Organisms allocate limited energy to a certain function which then reduces the amount for other functions.

This trade-off in energy allocation will differ among environments with functions that include growth, reproduction, and defense against predators

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The Principle of Allocation

• Levins concluded that the evolutionary consequences of this trade-off results in populations having high fitness in one environment, but lowered fitness in another environment.

• Bennett and Lenski found support for Levins’ Principle of Allocation using experiments with Escherichia coli grown in different temperature environments.

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The Principle of Allocation

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Temperature and Animal Performance

• Biomolecular Level Most enzymes have rigid, predictable

shape at low temperatures Low temperatures cause low reaction

rates, while excessively high temperatures destroy the shape.

Baldwin and Hochachka studied the influence of temperature on performance of acetylcholinesterase in rainbow trout (Oncorhynchus mykiss).

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Extreme Temperatures and Photosynthesis

• Photosynthesis

6CO2 + 12H2O C6H12O6 + 6CO2 + 6H20

Extreme temperatures usually reduce rate of photosynthesis.

Different plants have different optimal temperatures.

Acclimation: Physiological changes in response to temperature.

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Optimal Photosynthetic Temperatures

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Temperature and Microbial Activity

• Morita studied the effect of temperature on population growth among psychrophilic marine bacteria around Antarctica. Grew fastest at 4o C. Some growth recorded in temperatures as

cold as - 5.5o C.• Some thermophilic microbes have been

found to grow best in temperatures as hot as 110o C.

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Optimal Growth Temperatures

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Balancing Heat Gain Against Heat Loss

• HS = Hm Hcd Hcv Hr - He

HS = Total heat stored in an organism

Hm = Gained via metabolism

Hcd = Gained / lost via conduction

Hcv = Gained / lost via convection

Hr = Gained / lost via electromag. radiation

He = Lost via evaporation

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Heat Exchange Pathways

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Body Temperature Regulation

• Poikilotherms Body temperature varies directly with

environmental temperature.• Ectotherms

Rely mainly on external energy sources.• Endotherms

Rely heavily on metabolic energy. Homeotherms maintain a relatively

constant internal environment.

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Temperature Regulation by Plants

• Desert Plants: Must reduce heat storage. Hs = Hcd Hcv Hr

To avoid heating, plants have (3) options: Decrease heating via conduction (Hcd).

Increase conductive cooling (Hcv).

Reduce radiative heating (Hr).

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Temperature Regulation by Plants

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Temperature Regulation by Plants

• Arctic and Alpine Plants Two main options to stay warm:

Increase radiative heating (Hr). Decrease Convective Cooling (Hcv).

• Tropic Alpine Plants Rosette plants generally retain dead

leaves, which insulate and protect the stem from freezing.

Thick pubescence increases leaf temperature.

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Temperature Regulation by Ectothermic Animals

• Eastern Fence Lizard (Sceloporus undulatus) Metabolizable energy intake maximized at

33ºC Preferred temperature closely matches the

temperature at which metabolizable energy intake is maximized

• Grasshoppers Some species can adjust for radiative

heating by varying intensity of pigmentation during development.

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Temperature Regulation by Endothermic Animals

• Thermal neutral zone is the range of environmental temperatures over which the metabolic rate of a homeothermic animal does not change. Breadth varies among endothermic

species.

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Thermal Neutral Zones

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Temperature Regulation by Endothermic Animals

• Swimming Muscles of Large Marine Fish Lateral swimming muscles of many fish

(Mackerel, Sharks, Tuna) are well supplied with blood vessels that function as countercurrent heat-exchangers.

Keep body temperature above that of surrounding water.

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Countercurrent Heat Exchange

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Temperature Regulation by Endothermic Animals

• Warming Insect Flight Muscles Bumblebees maintain temperature of

thorax between 30o and 37o C regardless of air temperature.

Sphinx moths (Manduca sexta) increase thoracic temperature due to flight activity.

Thermoregulates by transferring heat from the thorax to the abdomen

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Moth Circulation and Thermoregulation

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Temperature Regulation by Thermogenic Plants

• Almost all plants are poikilothermic ectotherms. Plants in family Araceae use metabolic

energy to heat flowers. Skunk Cabbage (Symplocarpus foetidus)

stores large quantities of starch in large root, and then translocate it to the inflorescence where it is metabolized thus generating heat.

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Eastern Skunk Cabbage

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Surviving Extreme Temperatures

• Inactivity Seek shelter during extreme periods.

• Reducing Metabolic Rate Hummingbirds enter a state of torpor

when food is scarce and night temps are extreme.

Hibernation - Winter Estivation - Summer

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Review• Microclimates• Aquatic Temperatures• The Principle of Allocation• Temperature and Animal Performance• Extreme Temperature and Photosynthesis• Temperature and Microbial Activity• Balancing Heat Gain Against Heat Loss• Body Temperature Regulation• Surviving Extreme Temperatures

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