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Concept 4.3: The water balance of organisms is determined by
exchanges of water and solutes with the external environment.
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Concept 4.2: The temperature of organisms is determined by
exchanges of energy with the external environment.
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Concept 4.1: Each species has a range of environmental tolerances that determines
its potential geographic distribution.
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Environmental temperatures ------------ throughout the biosphere.Some habitats experience little variation, while others have large seasonal or daily variation.
vary greatly
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Some organisms can survive periods of extreme heat or cold by entering
a state of dormancy, in which little or no metabolic activity occurs.
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Bacteria in hot springs have enzymes that are stable up to
100°C.
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Energy exchange with the environment can be by:
Conduction—Convection—Latent heat transfer—
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Conduction—
transfer of energy from warmer to cooler molecules.
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Convection—
heat energy is carried by moving water or air.
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Latent heat transfer—
water absorbs heat as it changes state from liquid to gas.
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For terrestrial plants, energy inputs include---------
Losses of energy include -----------
- sunlight and longwave (infrared) radiation from surrounding objects.
- emission of infrared radiation to the environment, and through evapotranspiration.
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Transpiration rates can be controlled by
specialized guard cells surrounding a pore, called a stomate.Variation in the size of the opening and number of stomates control the rate of transpiration and thus control leaf temperature.
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pubescence—
hairs on leaf surfaces that reflect solar energy. But hairs also reduce conductive heat loss.
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If soil water is limited------------is not a good mechanism.
, transpirational cooling
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If air temperature is lower than leaf temperature, heat can be lost by --------, dependent on --------------
- convection,
- speed of air moving across the leaf surface.
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Know that long equation thingie
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Ectotherms:
: Primarily regulate body temperature through energy exchange with the external environment.
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Endotherms:
- Rely primarily on internal heat
- generation, mostly birds and mammals.
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Larger surface area allows ----------, but makes it harder to ----------------
- greater heat exchange
- maintain internal temperature.
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A smaller surface area relative to volume ------------ the animal’s ---------------
- decreases
- ability to gain or lose heat.
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As body size increases, surface area-to-volume ratio decreases, and ------------ are thus improbable.This had led to speculation that
- large ectotherms
- large dinosaurs may have had some degree of endothermy.
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Some large ectotherms can maintain body temperature above the environmental temperature, such as...
Skipjack tuna use muscle activity in conjunction with heat exchange between blood vessels to maintain a body temperature as much as 14°C warmer than the surrounding seawater.
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Many terrestrial ectotherms can------- to adjust temperature.
move
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Many insects and reptiles --------- to warm up after a cold night. Because this increases risk from predators, many are -----------
- bask in the sun
- also camouflaged.
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Ectotherms in temperate and polar regions must avoid or tolerate freezing.Avoidance behavior includes
seasonal migration to lower latitudes or microsites that are above freezing (e.g., burrows in soil).
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Small endotherms may regularly undergo ------------ to minimize energy needed during cold nights.Long-term torpor is possible only for animals that have enough food and can store enough energy reserves, such as -------------
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Three problems must be overcome for an organism to withstand freezing:
- 1Water forms needle-like ice crystals that can pierce cell membranes.
- 2Oxygen supply to tissues is restricted due to lack of breathing and circulation.
- 3When ice forms, it pulls water from cells.
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Concept 4.3: The water balance of organisms is determined by
exchanges of water and solutes with the external environment.
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Water is the medium in
which all biochemical reactions necessary for life occur.
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Water has unique properties that make it a
universal solvent for biologically important solutes.
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-------------- have the highest resistance to water loss.The outer exoskeleton of -----is covered by ------that are impervious to water.
- Desert invertebrates
- chitin is covered by waxy hydrocarbons
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Reptiles have been very successful in dry environments. They have thick skin with layers of
dead cells, fatty coatings, and plates or scales.
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Mammals and birds have ------------- and ------- or ------ minimize water loss.
similar skin, and fur or feathers to
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