BSU IN AFS meeting

• Tue Aug 23 TONIGHT!

• 5:00 pm

• CL 167

• Electrofishing demonstration

Genetics Club meeting

• Wed Aug 28

• 7:00 pm

• CL 268 (genetics lab)

• Biology jeopardy and snacks

Chapter 5 Temperature relations

Probably the most limiting factor in organism’s distributions

Active animal life limited between ~ 0˚ C and 50˚ C

Dilemma of life

• Organisms need energy + nutrients

Dilemma of life

• Organisms need energy + nutrients

• Enzymes function under narrow ranges of T

Dilemma of life

• Organisms need energy + nutrients

• Enzymes function under narrow ranges of T

• Internal environment differs from external = gradient

• = dilemma

T varies in time + space

• Temporal (daily, seasonal, multi-year, long-term changes)

T varies in time + space

• Temporal (daily, seasonal, multi-year, long-term changes)

• Spatial (latitude, elevation, aspect, microclimate)

T varies in time + space

• Temporal (daily, seasonal, multi-year, long-term changes)

• Spatial (latitude, elevation, aspect, microclimate)

• Less variable in aquatic habitats

Dealing With It: ADAPTATION

• Optimum conditions for physiological activity match the prevailing environmental conditions

• Downside: Species can only survive in specific environments

<<<<<<<<<< Range of Tolerance >>>>>>>>>>

Optimum

Range of Limitation ProteinDenaturation

Temperature

O2

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ake

Met

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ate

CO

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Temperature Response Curve

T response curve

• Species from warm vs cold environments differ in T responses

Adaptations to deal with extreme T

• Mechanisms to regulate body T– Control radiative heat gain/loss– Control convective heat gain/loss– Evaporative heat dissipation– Metabolic heat gain– Control T of critical tissues only

Adaptations to deal with extreme T

• Mechanisms to avoid extreme T– Seasonal migration– Daily/hourly movements– Physiological dormancy

Definitions:

• Acclimation = short-term change in morphology or physiology

• Adaptation = evolutionary change in morphology or physiology

Badlands, SD

Glacier National Park, MT

Acclimation example:

• Desert shrubs– A. glabriuscula saltbrush from cool coastal CA– T. oblongifolia from Death Valley

Acclimation example:Acclimation example:

• Desert shrubsDesert shrubs

Goldfish acclimation

Acclimation T

Le

tha

l T

10 40

10

40

Acclimation T

Le

tha

l T

10 40

10

40

Solid line = range of thermal toleranceDash = acclimation T

E.g., fish kept at 30 C has upper lethal limit of 38 C and lower lethal limit of 9 C

Trade-offs for T regulationTrade-offs for T regulation

• Poikilotherms: Poikilotherms: – Inactive when T is not optimumInactive when T is not optimum

• Result:Result:– Low energy needs for homeostasisLow energy needs for homeostasis

Poikilotherms can regulate T Poikilotherms can regulate T with behavior (ectothermic)with behavior (ectothermic)

• In deserts, shade under shrub can be 25˚CIn deserts, shade under shrub can be 25˚C

• Ground exposed to sun can be > 60˚ CGround exposed to sun can be > 60˚ C

• Desert iguana maintains body T 39 - 43˚C by Desert iguana maintains body T 39 - 43˚C by changing microhabitatschanging microhabitats

Trade-offs for T regulation• Homeotherms:

– Metabolic rate to heat– Evaporative water to cool

• Result:– Loss of resources for repro, growth, etc.

Cost-Benefit ofMetabolic Thermo-Regulation• Benefit: Species can be active in cold

environments (increases opportunity to acquire resources)

• Cost: Energy expended to generate heat is not available for growth or reproduction

• Most advantageous in environments where energy (food) is abundant

Eastern skunk cabbage

Air temperature and cabbage metabolic rate

Water temp and body temp of bluefin tuna

Minimizing Cost ofMetabolic Thermo-Regulation

• Increase RESISTANCE to heat loss / gain b/t body and environment.

– Fur, Feathers, Fat Layer (Insulation)– Low body surface-to-volume ratio

• Large body size• Shorter / Fewer appendages and

elongation

Answer a question:

• Are most organisms tolerant of a wide range of temperatures or a narrow range of temperatures?