Biology 205Ecology and Adaptation

Lecture 5 Temperature relations

How different organisms regulate or adapt to changing temperature

environments?

Dr. Erik D. Davenport

Outline

Temperature in the environment:– Microclimates – climate in a small area over short time period.– Aquatic Temperatures -- less variation.

Temperature and living organisms– Temperature and Animal Performance– Extreme Temperature and Photosynthesis– Temperature and Microbial Activity

Body Temperature Regulation: Balancing Heat Gain Against Heat Loss– Plants– Ectothermic Animals– Endothermic Animals

Climate: the average or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years

Climate pattern in a large scale area that is mainly determined by temperature and precipitation, (which is represented by climate diagrams).

Microclimate: is the climate variation in a small scale (few kilometer to meters), and usually measured over short time period Altitude:

– Higher altitude: low air temperature, low pressure, and less trapped heat.

Aspect:– Topography, shape of

the land, north or south facing slopes of the valley

Vegetation:– Can provide the

shade, moisture, affect airflow.

Color of the ground:– Dark color absorb

more heat, and light color reflect more heat

4-2     Source: Parmenter, Parameter, and Cheney 1989

“Macroclimate interacts with local landscape to produce microclimate”

– latent heat of water evaporation - absorb heat when water evaporates.

– Latent heat of fusion – heat give off when water freezes. 1 g of water gives off 80 cal as it freezes.

“Aquatic environments generally show less

variation in temperature than terrestrial environments.” Why??

Specific heat: a capacity of water to absorb large amount of heat energy with a little change of temperature. 1 cal energy to heat 1 cm3 of water 1 C. Air - .0003 cal

4-5     Source: Ward 1985

Riparian vegetation influences stream temperature by

providing shade.

“Macroclimate interacts with local landscape to produce microclimate”

“Most species perform best in a fairly narrow range of temperatures”

Temperature effects:– physiology and

behavior of organisms.

– Rate of growth.– Rate of

reproduction.– Rate of

movement (i.e.,run, fly, or swim).

– Predator avoidance

– Etc….

“Biology relies on chemistry at molecular levels.”

Enzymes are very important in the bio-chemistry reactions.

Enzymes usually work best in the intermediate, narrow range of temperatures.

Low temperature will decrease the enzyme activity, and high temperature will damage the enzyme structures.

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

Temperature effects

photosynthesis Extreme

temperature reduces the rate of photosynthesis.

Plants could adapt for maximum photosynthesis rates at different temperatures. Different plants have different optimal photosynthesis temperature.

6CO2 + 12H2O C6H12O6 + 6O2 + 6H20

4-8     Source: Berry and Björkman 1980, after Pearcy 1977

Plant responses to temperature, as well as those of animals, can reflect the short term physiological adjustments call acclimation.

“Plants can adapt for maximum photosynthesis rates at different temperatures. “

Temperature effects Microbial Activity

– Some growth recorded in temperatures as cold as ----5.5o C.

Morita studied the effect of temperature on

population growth among psychrophilic marine

bacteria around Antarctica.

-Grew fastest at 4o C

Some thermophilic microbes have been found to grow best in temperatures as hot as 110o C.

Temperature effects Microbial Activity

“Many organisms

have evolved ways to

compensate for variations

in environmental temperature by regulating

body temperature.”

Heat Balance

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 radiation

– He = Lost via evaporation

Heat Exchange Pathways

“Plants could use morphology and behavior to alter the heat exchange

with the environments.”Desert plants:

– Decrease heat by conduction.

– Increase rate of convective cooling

– Reducing rates of radiative heating.

Thermoregulation by Plants

Arctic and Alpine Plants Two main options to stay warm:

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

Temperature regulation by ectothermic animals

Ectothermic animals: fish, reptiles, and invertebrates etc, all use external sources of energy to regulate body temperature.

They could vary the body size, shape and pigmentation to regulate the body temperature.

Behavior regulation is more important to animals than plants.

Temperature Regulation by Ectothermic Animals

Liolaemus Lizards– Thrive in cold

environments. Burrows Dark

pigmentation Sun Basking

Liolaemus multiformis

Rearing temperature/pigmentation of grasshopper

4-16    

Grasshoppers– Some species

can adjust for radiative heating by varying intensity of pigmentation during development.

Temperature Regulation by Ectothermic Animals

Temperature regulation by Endothermic animals

Most significantly, Endothermic animals rely a great deal more on metabolic heat to maintain the constant body temperature.

They also have the anatomical and behavioral adaptations to regulate the body temperature.

Examples: mammals, birds.

However, when the temperature falls below or raise above the thermal neutral zone, the metabolic rate will increase rapidly. Why??????

The breadth of the thermal neutral zone varies greatly among different species.

Thermal neutral zone: the range of environmental temperature over which the metabolic rate of a endothermic animal does not change.

Thermoregulation in aquatic birds and mammals

It is hard to regulate the body temperature in the aquatic environments, so only a few aquatic species are truly endothermic. (penguins, seals, and whales)

They all breathe air and don’t expose a large amount of surface area to the surrounding waters.

They are well insulated from the environment by a thick layer of fat or fur.

– Inactivity: avoid extreme environmental temperature by seeking shelter during the hottest or coldest time for the day

– Reducing metabolic rate

“Many organisms avoid the extreme temperatures

by entering a resting stage.”

Hummingbirds could enter a stage of Torpor (a state of low metabolic rate and lowered body temperature, from usual 39 to 12-17 degrees).

Hibernation: is a state in which an animal is inactive for many days or weeks. In deep hibernation the animal's body temperature drops to around five degrees.

Key concepts

Macroclimate interacts with local landscape to produce the microclimate (temperature variation in a small area).

Most species perform best in a fairly narrow range of temperature.

Many organisms have evolved ways to compensate for variations in environmental temperature by regulating body temperature.

Many organisms avoid extreme temperature by entering a resting stage.