Chapter 40. Basic Principles of Animal Form and Function. Physical Laws and Animal Form. The need to exchange materials with the environment place certain limits on the range of animal forms The ability to perform certain actions depends on an animal’s shape and size
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Basic Principles of Animal Form and Function
(b) Two cell layers
A microscopic view of the lung reveals
that it is much more spongelike than
balloonlike. This construction provides
an expansive wet surface for gas
exchange with the environment (SEM).
The lining of the small intestine, a diges-
tive organ, is elaborated with fingerlike
projections that expand the surface area
for nutrient absorption (cross-section, SEM).
Inside a kidney is a mass of microscopic
tubules that exhange chemicals with
blood flowing through a web of tiny
vessels called capillaries (SEM).
Organisms with more complex body plans have highly folded internal surfaces specialized for exchanging materials
Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often
located where secretion or active absorption of substances is an important function.
A stratified columnar
Stratified squamous epithelia
Simple squamous epithelia
Loose connective tissue
Fibrous connective tissue
Red blood cells
White blood cell
Mucosa. The mucosa is an
epithelial layer that lines
Submucosa. The submucosa is
a matrix of connective tissue
that contains blood vessels
Muscularis. The muscularis consistsmainly of smooth muscle tissue.
Serosa. External to the muscularis is the serosa,a thin layer of connective and epithelial tissue.
0.2 mmOrgans and Organ Systems
in body cells
This photograph shows a ghost crab in arespirometer. Temperature is held constant in thechamber, with air of known O2 concentration flow-ing through. The crab’s metabolic rate is calculatedfrom the difference between the amount of O2entering and the amount of O2 leaving therespirometer. This crab is on a treadmill, runningat a constant speed as measurements are made.
(b) Similarly, the metabolic rate of a manfitted with a breathing apparatus isbeing monitored while he works outon a stationary bike.Measuring Metabolic rate
Annual energy expenditure (kcal/yr)
0.025-kg female deer mouse
4-kg male Adélie penguin
from Antarctica (brooding)
60-kg female human
from temperate climate
4-kg female python
Total annual energy expenditures
Energy expenditure per unit mass
Energy expenditures per unit mass (kcal/kg•day)
producedMechanisms of Homeostasis
River otter (endotherm)
Body temperature (°C)
Largemouth bass (ectotherm)
Ambient (environmental) temperature (°C)Ectotherms and Endotherms
A few reptiles, fish, and insects are endotherms!
waves by all objects warmer than absolute
zero. Radiation can transfer heat between
objects that are not in direct contact, as when
a lizard absorbs heat radiating from the sun.
Evaporation is the removal of heat from the surface of a
liquid that is losing some of its molecules as gas.
Evaporation of water from a lizard’s moist surfaces that
are exposed to the environment has a strong cooling effect.
Conduction is the direct transfer of thermal motion (heat)
between molecules of objects in direct contact with each
other, as when a lizard sits on a hot rock.
Convection is the transfer of heat by the
movement of air or liquid past a surface,
as when a breeze contributes to heat loss
from a lizard’s dry skin, or blood moves
heat from the body core to the extremities.Modes of Heat Exchange
Skin provides protection from mechanical injury, infection and dessication
Skin is important in thermoregulation
Adipose tissue of the hypodermis supplies insulation of varying amount depending upon the species
legs of a goose or the flippers of a dolphin
are in close contact with veins conveying
cool blood in the opposite direction, back
toward the trunk of the body. This
arrangement facilitates heat transfer
from arteries to veins (black
arrows) along the entire length
of the blood vessels.
Near the end of the leg or flipper, where
arterial blood has been cooled to far below
the animal’s core temperature, the artery
can still transfer heat to the even colder
blood of an adjacent vein. The venous blood
continues to absorb heat as it passes warmer
and warmer arterial blood traveling in the
In the flippers of a dolphin, each artery is
surrounded by several veins in a
countercurrent arrangement, allowing
efficient heat exchange between arterial
and venous blood.
As the venous blood approaches the
center of the body, it is almost as warm
as the body core, minimizing the heat lost
as a result of supplying blood to body parts
immersed in cold water.
3Countercurrent Heat Exchangers
Dorsal aortaCountercurrent Heat Exchangers
(a)Bluefin tuna. Unlike most fishes, the bluefin tuna maintains
temperatures in its main swimming muscles that are much higher
than the surrounding water (colors indicate swimming muscles cut
in transverse section). These temperatures were recorded for a tuna
in 19°C water.
(b)Great white shark. Like the bluefin tuna, the great white shark
has a countercurrent heat exchanger in its swimming muscles that
reduces the loss of metabolic heat. All bony fishes and sharks lose
heat to the surrounding water when their blood passes through the
gills. However, endothermic sharks have a small dorsal aorta,
and as a result, relatively little cold blood from the gills goes directly
to the core of the body. Instead, most of the blood leaving the gills
is conveyed via large arteries just under the skin, keeping cool blood
away from the body core. As shown in the enlargement, small
arteries carrying cool blood inward from the large arteries under the
skin are paralleled by small veins carrying warm blood outward from
the inner body. This countercurrent flow retains heat in the muscles.
Red areas indicate areas of high temp in this winter-active moth
sweat that evaporates,
cooling the body.
in skin dilate:
with warm blood;
heat radiates from
as when exercising
or in hot
shuts off cooling
Internal body temperature
of approximately 36–38C
shuts off warming
(such as when
Blood vessels in skin
constrict, diverting blood
from skin to deeper tissues
and reducing heat loss
from skin surface.
Skeletal muscles rapidly
contract, causing shivering,
which generates heat.Feedback Mechanisms in Thermoregulation
Periodic arousals may be needed to carry out some body functions that require a high temperature
Additional metabolism that would be
necessary to stay active in winter
(kcal per day)
Belding’s ground squirrel
Hibernating black bears can go months without eating, drinking, urinating, defecating or exercising
The body temperature of a hibernating black bear dips only to about 88 degrees. Much less of a drop than that seen in many hibernating rodents
Hibernation in black bears does not involve the periodic arousals seen in many hibernating rodents. Bears also slumber less deeply than the rodents.