Chapter 5 - Temperature Relations

Macro and Microclimates

Macroclimate - Large scale variation

Microclimate - Small scale variation

-Ground Color

• Darker color absorbs more visible light

• Since it absorbs more visible light, it is warmer

-Boulders/Burrowos

• Shaded, cooler environment

-Aspect:

• Directional; North-facing = colder (facing away from the sun)

-Altitude

• Greater the elevation, the cooler the temperature

Aquatic Temperatures and Stability

Aquatic temperatures are relatively stable due to:

1. Specific Heat

-Ability to absorb a lot of heat without changing temperature

-3000x more for water than for air

2. Latent Heat of Vapourization

-Heat absorbed during evaporation of water is large, results in an increase in cooling of the body of water

3. Latent Heat of Fusion

-When water freezes, it gives up heat to its environment, decreasing the cooling of water

Consequences of Water Temperature Change

Two major consequences of temperature change

1. Effect on aquatic organisms

2. Effect on dissolved O2

Law of Toleration

-Most species perform best in a narrow range of temperatures

-Consists of an optimum range where performance is maximized, and a range of tolerance, where growth/reproduction can still occur, followed by a mortality range

-Leads to Principle to Allocation

• Includes metabolism, respiration, movement, defence, feeding in order to lead reporduction

Temperature and Biomolecular Performance

Also affects organisms at a biomolecular level

-Enzymes have rigid, predictable shapes than can change based on temperatures

-Decrease in temperatures typically leads to a decrease in reaction rate

-Likewise, increase in temperature can result in molecular shape being destroyed/altered

Rainbow Trout

-Temperature influenced acetylcholinesterase in rainbow trout

-Two types were then produced; Winter and Summer

-Both adapted to two temperature ranges in response to temperature changes

Temperature Change and Photosynthesis

-Extreme temperatures leads to a decrease in photosynthesis

-Different plants have different optimal temperatures

-Acclimation - physiological changes as a result of temperature changes

Temperature and Microbial Activity

-Controls flow of energy and nutrients

-Change in microbial activity is a significant consequence for other organisms, since they serve as the base of the food-chain

-Extremely sensitive to temperature and temperature changes

-Adaptations to cold OR hot, have a very narrow range for living

Balancing Heat Gain and Heat Loss

-Organisms must evolve ways to compensate for variations in environmental temperature regulation

-Uses heat manipulation;

Hs = Hm ± Hcd ± Hcv ± Hr - He

Hs - total heat stored in an organisms

Hm - gained via metabolism

Hcd - gained/lost via conduction

• Transfer of heat between objects in direct contact

Hcv - gained/lost via convection

• Process of heat flow between a solid body and a moving fluid (like between you and wind)

Hr - gained/lost via radiation

• Transference of heat based on electromagnetic radiation; like heat from our sun

He - lost via evaporation

-Evaporation is always heat loss, metabolism is always heat gain

Body Temperature Regulation

Metabolic Rate

-Endotherms

-Ectotherms

Body Temperature Maintenance

-Poikilotherms

-Homeotherms

Most land birds and mammals - endothermic/homeothermic

Most fish, amphibians, reptiles - ectothermic/poikilothermic

Endotherms

-High metabolic rate

-Conserve Hm with insulation and other adaptations

-Most birds and mammals

Ecotherms

-Low metabolic rate

-External energy source

-Consists of invertebrates: fish, amphibians, reptiles

Poikilotherms

-Temperature varies directly with the environment

-Generally, they are ectotherms

-But some can be endothermic

Homeotherms

-Maintain a constant internal environment

-Generally are endotherms, but can be ectothermic

Temperature Regulation by Plants

Arctic Plants - must increase heat gain but redice their heat loss, so they have to store heat

Three Options:

1. Increase radiative heating

2. Decrease convective cooling

3. Increase heating via conduction

Desert Plants - must drop heat storage and increase coolings

Three Options:

-Decrease heating via conduction

-Increase convective cooling

-Decrease radiative heating

Temperature Regulation by Ectothermic Animals

-Fish, amphibians, reptiles, invertebrates

-Means analagous to those of plants (similar to plants)

-But have additional options since they can move (behaviours)

Eastern Fence Lizards

Energy intake is maximized at 33C

-Anything above that will result in them hiding

Grasshoppers

-Varies the intensity of pigmentation during development, changes pigmentation based on the amount of sunlight in differrent seasons

Temperature Regulation by Endothermic Animals

-Use the same anatomic and behavioural tricks at ectothermic animals

-But contain and increased metabolic heat (advantageous in colder environments)

Aquatic Species and Ecto/Endo

-Very few aquatic species are truly endothermic, most are ectotherms

1. Air Breathers (large respiratory areas unexposed to water

2. Endothermic aquatic species have Insulation with thick fat or fur

3. Uninsulated endotherms have countercurrent heat exchangers

Flying Insects - Circulation and Thermoregulation

-Creating a lot of heat by moving their wings

Temperature Regulation by Thermogenic Plants

Most plants are poikilothermic ectotherms

-But some can produce and utilize metabolic heat

Ex; Araceae (Arum Family) - metabolic energy to heat flowers

-Used by skunk cabbagaes to produce heat during the winter

-High metabolic rate can melt the snow around them, allowing them to be pollinated

Would be classified as an endothermic poikilotherm

Surviving Extreme Temperatures

Energy Budgets - describes how an organism allocates energy to essential life activities

-Extreme temperatures affects the energy budget of an organism

Strategies in the Case of Extreme Temperatures

Death - annual plants, many insects

-Die, but leave a lot of eggs/seeds

Migration - many birds, some butterflies

Resistance - Adaptations to the weather

-Fur, fat, feathers

-Acclimation: Seasonal toleration

-Inactivity/avoidance

Reduce/Stop Metabolic Rate

-Estivation - Prolonged period of reduced/no metabolic rate during the summer

-Torpor - Temporary lowering of the body temperature via reduced metabolic rate

-Hibernation - Prolonged period of reduced/no metabolic rate during the winter

-Freeze Tolerance

-Diapause