Temperature

Poikilotherms

Body temperature varies directly with environmental temperature.  

Ectotherms

Rely mainly on external energy sources to regulate body temperature. Endotherms: Rely heavily on metabolic energy.  

Homeotherms

maintain a relatively constant internal environment

Macroclimate

prevailing weather conditions over long time period.  

Microclimate

small scale weather variation, over shorter time periods.  

Microclimate is influenced by

landscape features (altitude, aspect, vegetation, ground color, etc.) 

Temperature 

the average kinetic energy of molecules in the mass of a substance. 

Heat

The kinetic energy in the mass of a substance

Organisms are best adapted to a

fairly narrow range of temperatures. 

Main source of heat

light

Generate heat through

visible and infrared light

Shorter wavelengths

have more energy, travel farther

Longer wavelengths

infrared radiation, more easily absorbed by our bodies

Black bodies

absorbs all radiation

Difference in preceived temperature is mainly due to

infrared radiation

Why do higher altitudes have lower temps?

Atmospheric pressure decreases, air expands and cools, less atmosphere to trap heat. 

Aspect

the direction of ground relative to the sun

Biophysics of temperature

Solar radiation can be direct or scattered (cooler). Some rays are absorbed, and some are reflected. Thermal heat radiates off the ground. Some heat is absorbed by the atmosphere, radiates heat. Clouds trap heat. Air flow convection changes temp: air velocity increase further away from the ground (friction). As we get closer to the ground, Air temperature gets closer to ground temp.  

Why burrow?

more constant temperature

Urban heat islands

urban cores retain heat

Most enzymes work..

best at moderate temperatures where they retain proper shape and flexibility.

Photosynthesis rate reduced by

extreme temperatures

Acclimation

species responses to temperature can reflect short term physiological adjustments

acclimation is generally

reversible

Microbes

are found in water of all temps, but no species is found at all temps 

Evolutionary trade off

Adapting to one set of environmental conditions generally reduces a population’s fitness in other environments.  

Fitness =

number of years of survival times number of offspring

All organisms are adapted to a limited range of environmental conditions due to

energy limitations, physiological processes operating best at different temperatures  

The Principle of Allocation

Organisms have access to limited energy supplies. Energy allocated to one life function reduces amount for other functions.

Reductionism:

practice of analyzing a complex system in terms of phenomena that are held to represent a simpler level, especially when this is said to provide a sufficient explanation. 

Holism

holds that not all properties of a system can be explained in terms of its constituent parts and their interactions.

In terms of temperature regulation, most of life

Actively manipulates heat gain and loss

Endotherms preferred body temperature

has been manufactured

Ectotherms preferred body temperature

is from how they use their environment

Heat exchange pathways for plants

Heat loss and gain by radiation, wind, metabolism, ect. 

Desert plants temperature regulation must rely on

morphology and behavior, NOT evaporative cooling

Temperature regulation of arctic, alpine, and tropical alpine plants

Increase radiative heating, decrease convective cooling

Endotherms rely more on __ to maintain internal temperature

metabolic heat

Thermal neutral zone

is the range of environmental temperatures over which the metabolic rate of a homeothermic animal does not change.  

At low temps, metabolic rate rises

shivering, fat metabolism

At high temperatures,

heart rate and blood flow to skin increase, sweating may occur

Thermal neutral zone breadth

varies

Thermal neutral zone of tropic species are __ than arctic

narrower

Endothermic Aquatic Animals Aquatic environment is a heat sink -

limits ways organisms can regulate body temperature

Very few aquatic animals

are endothermic

Aquatic birds and mammals are __ due to breathing air and insulating layer of fat or fur. Appendages have countercurrent heat exchange

homeothermic

Insects thermoregulate by

transferring heat from thorax to abdomen

Temperature Regulation by Thermogenic Plants

Almost all plants are poikilothermic ectotherms.

Skunk cabbage uses metabolic energy to heat flowers:

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

Main organisms survive extreme temperatures by entering a

resting stage

Resting stage during extreme temperatures involves

inactivity, may seek shelter, reduce metabolic rate to save energy

Torpor

Short term resting stage

Hibernation

reduced metabolism in winter

Estivation

reduced metabolism in summer

Penguins mitigate heat from huddles by

disbanding after 50 minutes, eating snow

Fat tailed lemur hibernation

Active for 5 months, hibernates for 7. Hibernates during dry season, when food is scarce. Survives on the fat stored in tail and elsewhere during the wet season when food is abundant.  

Land snails disappearance

Climate change and urban heat island resulted in high temperatures that stopped embryonic development