Adapting to a Varying Environment

FIELD BIOLOGY & METHODOLOGYFall 2014 Althoff

Lecture

09

Background considerations...

• Each type of organism has an ___________--the habitats which sustain its population

• Environmental conditions _______:a) hourlyb) dailyc) seasonallyd) annually

_______ changes – response of giant red velvet mite to changing environmental conditions

Ricklefs Fig. 9.2, p181, 5th edition

…in response to change

• Individuals can make “________” adjustments (shiver, sweat, lower body temperature, etc.) and stay-put

• Individuals can _____ to “_______” conditions require less internal adjustments

• ….or some _____________ of these responses.

____________________ to changes in light and surface reflectance = change in environmental conditions

Ricklefs Fig. 6.17, p128

Homeostasis

The ability of an individual to maintain constant __________ conditions in the face of a varying __________ environment

Not all animals do this constantly…when they don’t they may become inactive (think of “cold-blooded” species) and/or physiological functions not as efficient or finely-tuned.

How does a rabbit do this?

• “Internal adjustments”

a) hourly

b) daily

c) seasonally

How does a rabbit do this?

• “External adjustments--habitat selection”

a) hourly

b) daily

c) seasonally

Ricklefs Fig. 9.5, p185, 5th edition

Desert iguana regulates body temperatureby _____________________

Based on negative feedback

• Analogous to thermostat in a house• Influence by internal conditions and external

environment• Examine Ricklefs- Fig. 3.22, page 565 (next slide)

a) hypothalamusb) body organsc) body temperature

“____________ GOAL”

SET POINT

Neg

ative

Fee

dbac

k Sy

stem

• ______________--maintain constant bodytemperature

• ______________--use of elevatedmetabolism to counteract cooling

• ______________--reliance on external sources to maintain body temp.

• ______________--failure to regulate bodytemperature. Often referred to as

“cold-blooded” but...

Source of Heat? Advantage?

• Ectotherms: ___________ex: reptiles & amphibians & insects

advantage(s):

• Endotherms: ___________ex: birds & mammals

advantage(s):

• Newton’s law of cooling: “heat loss varies in direct proportion to the gradient between body and ambient temperature”

• Endotherms counteract this with the varying rate of metabolism

• To maintain a constant “internal” temperature, a BMR must be achieved

Rates of Cooling

________________- BMR

The amount of energy expended by an animal at____________, that is required to maintain its body temperature at least at the lower ambient critical temperature.

BMR & Ambient Temperature

• Tlc - _______________________Temperature When body temperature goes below Tlc then metabolism must increase (i.e., heat production must increase) to maintain Tlc

• See next slide….

• This applies to homeothermic species (i.e., birds and mammals)

Met

abo

lism

temperatureFDVMK Fig. 9.2, p158

BMR & Tlc

• Body produces sufficient heat to maintain body temperature above Tlc

• Influenced by __________________: as body size increases, BMR increases more rapidly than body surface area. ___________ fur and feathers reduce thermal conductance.

BMR & Tlc…con’t

• By reducing thermal conductance, Tlc decreases with increasing size of the animal.

• Comparison:a) sparrow Tlc is 30Cb) penguin Tlc is 0C

__________________ Heat Exchange

• Evolved as an adaptation for homeotherms when more energy required than an individual can provide. It is an “__________ _____________”

• Some portion of the body, usually an “uncovered, uninsulated” extremity, can survive at ___________ temperatures than the rest of the body.

Countercurrent Heat Exchange

• Example of gulls, ducks, other birds without feathers on tarsa as illustrated in Ricklefs - Fig. 3.24, page 57 - next slide

• Arterial blood vessels anatomically in ______ ________ to venous blood vessels allows for “transfer of heat” before blood goes out to extremity and “warming up” on way back

Ricklefs Fig. 3.24, p57

_________ - another adaptation

• DEFINED = a voluntary, reversible condition of lowered body temperature and inactivity. Differs from hibernation in length of time and degree of “shutdown” by the body

• Exhibited by some species, in cool climates (or occasionally cool climates) that would starve otherwise (Fig. 3.23, page 57 - hummingbirds)

Ricklefs Fig. 3.24, p57

Activity Space

The “space” which an organism ___________. It is usually a limited range of conditions. The concept applies to all aspect’s of the individual’s life…

….have somewhat already introduced this concept with the “zone of tolerances” material

Activity Space - examples

• Seeds of a plant: “everything must be just right to germinate & grow” (Jack pine -- soil, light, fire, etc.)

• Southern Flying Squirrel

• Grasshoppers

Microhabitats

• __________________ of the habitat

• Create ___________________ (temperature, light, pH, DO2, wind velocity, availability of foods etc.) that enable the individual to most efficiently obtain food (energy intake) or reduce heat loss (energy expended)…or some combination

Microhabitat Selection

• Choosing one “habitat” ________________ to its availability

• Contrasts habitat “use”• Example: Verdin nest

opening orientation

In summary…

• Most traits of organisms ________ in response to environments

• Individual organisms can respond to changes in their environment by altering their ___________________________________.

• Organisms have characteristic activity spaces defined by the conditions within they can ______ AND ______________

• Animal ___________________ whose physical conditions fall within their activity space