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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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chapter 40

Chapter 40

Basic Principles of Animal Form and Function

physical laws and animal form
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
    • Evolutionary convergence reflects different species’ independent adaptation to a similar environmental challenge
    • Fusiform shape in fast swimmers 

Tuna

Shark

Penguin

Dolphin

Seal

exchange with the environment
Exchange with the Environment
  • An animal’s size and shape have a direct effect on how the animal exchanges energy and materials with its surroundings
  • Exchange with the environment occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes
unicellular organism

Diffusion

(a) Single cell

Unicellular organism
  • A single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm
multicellular organism simple
Multicellular Organism…simple
  • Multicellular organisms with a sac body plan have body walls that are only two cells thick, facilitating diffusion of materials

Mouth

Gastrovascular

cavity

Diffusion

Diffusion

Hydra

(b) Two cell layers

multicellular organism complex
Multicellular Organism … complex

External environment

Food

CO2

O2

Mouth

Animal

body

Respiratory

system

Blood

50 µm

0.5 cm

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).

Cells

Heart

Nutrients

Circulatory

system

10 µm

Interstitial

fluid

Digestive

system

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).

Excretory

system

Inside a kidney is a mass of microscopic

tubules that exhange chemicals with

blood flowing through a web of tiny

vessels called capillaries (SEM).

Anus

Unabsorbed

matter (feces)

Metabolic waste

products (urine)

Organisms with more complex body plans have highly folded internal surfaces specialized for exchanging materials

levels of organization
Levels of organization
  • Animals are composed of cells
  • Groups of cells with a common structure and function make up tissues
  • Different tissues make up organs
  • Which together make up organ systems
tissue structure and function
Tissue Structure and Function
  • Different types of tissues have different structures that are suited to their functions
  • Tissues are classified into four main categories
    • Epithelial
    • Connective
    • Muscle
    • nervous
epithelial tissue
Epithelial Tissue
  • Epithelial tissue
    • Covers the outside of the body and lines organs and cavities within the body
    • Contains cells that are closely joined
epithelial tissue10
Epithelial tissue

EPITHELIAL TISSUE

Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often

located where secretion or active absorption of substances is an important function.

  • Simple
  • Stratified
  • Columnar
  • Cuboidal
  • Squamous
  • Pseudostratified

A simple

columnar

epithelium

A stratified columnar

epithelium

A pseudostratified

ciliated columnar

epithelium

Stratified squamous epithelia

Cuboidal epithelia

Simple squamous epithelia

Basement membrane

40 µm

connective tissue
Connective Tissue
  • Connective tissue
    • Functions mainly to bind and support other tissues
    • Contains sparsely packed cells scattered throughout an extracellular matrix
connective tissue12
Connective tissue

CONNECTIVE TISSUE

100 µm

Chondrocytes

Collagenous

fiber

Chondroitin

sulfate

Elastic

fiber

100 µm

  • Loose
  • Adipose
  • Fibrous
  • Cartilage
  • Bone
  • Blood

Cartilage

Loose connective tissue

Adipose tissue

Fibrous connective tissue

Fat droplets

Nuclei

150 µm

30 µm

Blood

Bone

Central

canal

Red blood cells

White blood cell

Osteon

Plasma

700 µm

55 µm

muscle tissue
Muscle Tissue
  • Muscle tissue
    • Is composed of long cells called muscle fibers capable of contracting in response to nerve signals
    • Three types
      • Skeletal
      • Cardiac
      • Smooth
nervous tissue
Nervous Tissue
  • Nervous tissue
    • Senses stimuli and transmits signals throughout the animal
    • Neurons
      • Cell body
      • Axon
      • Dendrite
muscle and nervous tissue
Muscle and Nervous tissue

MUSCLE TISSUE

100 µm

Skeletal muscle

Multiple

nuclei

Muscle fiber

Sarcomere

Cardiac muscle

50 µm

Nucleus

Intercalated

disk

Smooth muscle

Nucleus

Muscle

fibers

25 µm

NERVOUS TISSUE

Process

Neurons

Cell body

Nucleus

50 µm

organs and organ systems

Lumen of

stomach

Mucosa. The mucosa is an

epithelial layer that lines

the lumen.

Submucosa. The submucosa is

a matrix of connective tissue

that contains blood vessels

and nerves.

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 mm

Organs and Organ Systems
  • In all but the simplest animals different tissues are organized into organs
  • In some organs (like the stomach) tissues are arranged in layers
  • At a higher level of organization, organ systems carry out the major body functions of most animals
organ systems
Organ Systems
  • Organ systems in mammals
bioenergetics
Bioenergetics
  • Animals are Heterotrophs
  • Animals consume food for the chemical energy stored in the molecules
  • Energy is required for all life processes
  • The flow of energy through an animal, its bioenergetics
    • Ultimately limits the animal’s behavior, growth, and reproduction
    • Determines how much food it needs
bioenergetics overview
Bioenergetics overview
  • After the energetic needs of staying alive are met, any remaining molecules from food can be used in biosynthesis

Organic molecules

in food

External

environment

Animal

body

Digestion and

absorption

Heat

Energy

lost in

feces

Nutrient molecules

in body cells

Energy

lost in

urine

Cellular

respiration

Carbon

skeletons

Heat

ATP

Biosynthesis:

growth,

storage, and

reproduction

Cellular

work

Heat

Heat

metabolic rate
Metabolic rate
  • The amount of energy an animal uses in a unit of time
measuring metabolic rate

(a)

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
  • One way is to determine the amount of oxygen consumed or carbon dioxide produced by an organism
bioenergetic strategies
Bioenergetic Strategies
  • Birds and mammals are mainly endothermic
    • Bodies are warmed mostly by heat generated by metabolism
    • They typically have higher metabolic rates
    • Capable of intense, long-duration activity
  • Amphibians and reptiles other than birds are ectothermic
    • They gain their heat mostly from external sources
    • They have lower metabolic rates
    • Incapable of intense activity over long periods
size and metabolic rate
Size and Metabolic Rate
  • Metabolic rate per gram
    • Is inversely related to body size among similar animals
    • Each gram of mouse consumes 20 times the calories as each gram of elephant
activity and metabolic rate
Activity and Metabolic Rate
  • Basal metabolic rate (BMR)
    • Is the metabolic rate of an endotherm at rest
  • Standard metabolic rate (SMR)
    • Is the metabolic rate of an ectotherm at rest
  • For both endotherms and ectotherms
    • Activity has a large effect on metabolic rate
energy budgets

Endotherms

Ectotherm

Reproduction

800,000

Temperature

regulation costs

Basal

metabolic

rate

Growth

340,000

Activity

costs

Annual energy expenditure (kcal/yr)

8,000

4,000

0.025-kg female deer mouse

from temperate

North America

4-kg male Adélie penguin

from Antarctica (brooding)

60-kg female human

from temperate climate

4-kg female python

from Australia

Total annual energy expenditures

(a)

438

Human

233

Energy expenditure per unit mass

(kcal/kg•day)

Python

Deer mouse

Adélie penguin

36.5

5.5

Energy expenditures per unit mass (kcal/kg•day)

(b)

Energy Budgets
  • Different species of animals use the energy and materials in food in different ways, depending on their environment
  • An animal’s use of energy is partitioned to BMR (or SMR), activity, homeostasis, growth, and reproduction
regulating the internal environment
Regulating the Internal Environment
  • Animals regulate their internal environment within relatively narrow limits
  • The internal environment of vertebrates (where our cells live) is the interstitial fluid. It is very different from the external environment
  • Homeostasis
    • A dynamic balance between external changes and the animal’s internal control mechanisms that oppose the changes
regulating and conforming
Regulating and Conforming
  • Regulating and conforming are two extremes in how animals cope with environmental fluctuations
  • Regulator
    • Uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
  • Conformer
    • Allows its internal condition to vary with certain external changes
mechanisms of homeostasis

Response

No heat

produced

Heater

turned

off

Room

temperature

decreases

Set

point

Too

hot

Set point

Too

cold

Set

point

Control center:

thermostat

Room

temperature

increases

Heater

turned

on

Response

Heat

produced

Mechanisms of Homeostasis
  • Mechanisms of homeostasis moderate changes in the internal environment
  • A homeostatic control system has three functional components
    • receptor
    • control center
    • effector
feedback circuits
Feedback Circuits
  • Negative feedback
    • Where buildup of the end product of the system shuts the system off
  • Positive feedback
    • Involves a change in some variable that triggers mechanisms that amplify the change
thermoregulation
Thermoregulation
  • The process by which animals maintain an internal temperature within a tolerable range
ectotherms and endotherms

40

River otter (endotherm)

30

Body temperature (°C)

20

Largemouth bass (ectotherm)

10

0

10

20

30

40

Ambient (environmental) temperature (°C)

Ectotherms and Endotherms
  • Ectotherms
    • Include most (but not all) invertebrates, fishes, amphibians, and non-bird reptiles
    • Tolerate greater variation in internal temperature than endotherms
  • Endotherms
    • Include birds and mammals
    • More energetically expensive than ectothermy

A few reptiles, fish, and insects are endotherms!

modes of heat exchange

Radiation is the emission of electromagnetic

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
  • Radiation
  • Evaporation
  • Convection
  • Conduction
insulation
Insulation
  • Insulation, which is a major thermoregulatory adaptation in mammals and birds
    • Reduces the flow of heat between an animal and its environment
    • May include feathers, fur, or blubber

Cedar Waxwing

mammalian integument as insulation
Mammalian integument as insulation

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

Hair

Epidermis

Sweat

pore

Muscle

Dermis

Nerve

Sweat

gland

Hypodermis

Adipose tissue

Blood vessels

Oil gland

Hair follicle

circulatory adaptations
Circulatory Adaptations
  • Many endotherms and some ectotherms
    • Can alter the amount of blood flowing between the body core and the skin
  • Vasodilation
    • Blood flow in the skin increases, facilitating heat loss
  • Vasoconstriction
    • Blood flow in the skin decreases, lowering heat loss
countercurrent heat exchangers

Arteries carrying warm blood down the

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.

Pacific

bottlenose

dolphin

1

Canada

goose

Blood flow

1

Artery

Vein

Vein

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

opposite direction.

2

Artery

3

35°C

33°

3

30º

27º

20º

18º

2

10º

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.

2

3

Countercurrent Heat Exchangers
  • Many marine mammals and birds have arrangements of blood vessels that are important for reducing heat loss

3

1

countercurrent heat exchangers39

21º

23º

25º

27º

29º

31º

Body cavity

Skin

Artery

Vein

Blood

vessels

in gills

Capillary

network within

muscle

Heart

Artery and

vein under

the skin

Dorsal aorta

Countercurrent Heat Exchangers
  • Some specialized ENDOTHERMIC bony fishes and sharks also possess countercurrent 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.

endothermic insects
Endothermic Insects
  • Many endothermic insects have countercurrent heat exchangers that help maintain a high temperature in the thorax
  • Strong flight muscles generate large amounts of heat when operating

Red areas indicate areas of high temp in this winter-active moth

cooling by evaporative heat loss
Cooling by Evaporative Heat Loss
  • Heat is lost through the evaporation of water in sweat
  • Some animals pant to cool their bodies
  • Bathing moistens the skin which helps to cool an animal down
behavioral responses
Behavioral Responses
  • Posture: Some terrestrial invertebrates have certain postures that enable them to minimize or maximize their absorption of heat from the sun
  • Adjustment of metabolic heat production
    • Many species of flying insects use shivering to warm up before taking flight
feedback mechanisms in thermoregulation

Sweat glands secrete

sweat that evaporates,

cooling the body.

Thermostat in

hypothalamus

activates cooling

mechanisms.

Blood vessels

in skin dilate:

capillaries fill

with warm blood;

heat radiates from

skin surface.

Increased body

temperature (such

as when exercising

or in hot

surroundings)

Body temperature

decreases;

thermostat

shuts off cooling

mechanisms.

Homeostasis:

Internal body temperature

of approximately 36–38C

Body temperature

increases;

thermostat

shuts off warming

mechanisms.

Decreased body

temperature

(such as when

in cold

surroundings)

Blood vessels in skin

constrict, diverting blood

from skin to deeper tissues

and reducing heat loss

from skin surface.

Thermostat in

hypothalamus

activates

warming

mechanisms.

Skeletal muscles rapidly

contract, causing shivering,

which generates heat.

Feedback Mechanisms in Thermoregulation
  • Mammals regulate their body temperature by a complex negative feedback system that involves several organ systems
  • In humans the hypothalamus contains a group of nerve cells that function as a thermostat
adjustment to changing temperatures
Adjustment to Changing Temperatures
  • Acclimatization
    • Many animals can adjust to a new range of environmental temperatures over a period of days or weeks
    • May involve cellular adjustments (esp. in ectotherms)
      • Change in membrane lipid composition
      • Production of cryoprotectant (antifreezing) molecules
    • Birds and mammals can make adjustments of insulation and metabolic heat production
torpor and energy conservation
Torpor and Energy Conservation
  • Torpor
    • An adaptation that enables animals to save energy while avoiding difficult and dangerous conditions
    • A physiological state in which activity is low and metabolism decreases
  • Estivation, or summer torpor
    • Enables animals to survive long periods of high temperatures and scarce water supplies
  • Daily torpor
    • Is exhibited by many small mammals and birds and seems to be adapted to their feeding patterns
    • Nocturnally feeding bats enter torpor while roosting during the daylight hours
    • A hummingbird may enter turpor on a cold night and have its body temp lower by 25-30 degrees centigrade
hibernation is long term torpor
Hibernation is long-term torpor
  • An adaptation to winter cold and food scarcity during which the animal’s body temperature declines

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

200

Actual

metabolism

100

Metabolic rate

(kcal per day)

0

Arousals

35

Body

temperature

30

25

20

Temperature (°C)

15

10

5

0

Outside

temperature

Burrow

temperature

-5

-10

-15

June

August

October

December

February

April

Belding’s ground squirrel

slide47

Bears

Grizzly

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

Kodiak Brown

Polar

Hibernation in black bears does not involve the periodic arousals seen in many hibernating rodents. Bears also slumber less deeply than the rodents.