Chapter 40
Basic Principles of Animal Form
and Function
Overview: Diverse Forms, Common
Challenges
• Anatomy is the study of the biological form of an
organism
• Physiology is the study of the biological
functions an organism performs
• The comparative study of animals reveals that
form and function are closely correlated
Table 40.1
Chapter 41
Animal Nutrition
Overview: The Need to Feed
• In general, animals fall into three categories:
– Herbivores eat mainly plants and algae
– Carnivores eat other animals
– Omnivores regularly consume animals as well
as plants or algae
• Most animals are also opportunistic feeders
Concept 41.1: An animal’s diet must supply
chemical energy, organic molecules, and
essential nutrients
• An animal’s diet provides:
– Chemical energy, which is converted into ATP to
power cellular processes
– Organic building blocks, such as organic carbon
and organic nitrogen, to synthesize a variety of
organic molecules
– Essential nutrients, which are required by cells
and must be obtained from dietary sources
Essential Nutrients
• There are four classes of essential nutrients:
–
–
–
–
Essential amino acids
Essential fatty acids
Vitamins
Minerals
• Digestion is the process of breaking food down
into molecules small enough to absorb
– Mechanical digestion, including chewing, increases
the surface area of food
– Chemical digestion splits food into small molecules
that can pass through membranes; these are used to
build larger molecules
Concept 41.2: The main stages of food
processing are ingestion, digestion,
absorption, and elimination
• Ingestion is the act of eating
• Absorption is uptake of nutrients by body cells
• Elimination is the passage of undigested
material out of the digestive system
Suspension and Filter Feeders
• Many aquatic animals such as clam and oyster
are suspension feeders, which sift small food
particles from the water
• Humpback whale is a filter feeder
Substrate Feeders
• Substrate feeders are animals that live in or on
their food source
Figure 41.6b
Bulk Feeders
Fluid Feeders
• Fluid feeders suck nutrient-rich fluid from a
living host
• Examples: mosquitos, aphids and hummingbirds
• Bulk feeders such as human seat relatively large
pieces of food
Figure 41.6d A rock python eats a gazelle
Digestive Compartments
• Most animals process food in specialized
compartments
• These compartments reduce the risk of an
animal digesting its own cells and tissues
Intracellular Digestion
• In intracellular digestion, food particles are
engulfed by phagocytosis
• Food vacuoles, containing food, fuse with
lysosomes containing hydrolytic enzymes
Figure 41.7
Extracellular Digestion
• Extracellular digestion is the breakdown of
food particles outside of cells
• It occurs in compartments that are continuous
with the outside of the animal’s body
• Animals with simple body plans have a
gastrovascular cavity that functions in both
digestion and distribution of nutrients
Mouth
Tentacles
Food
1 Digestive
enzymes released
2 Food
particles broken
down
3 Food particles
engulfed and
digested
Epidermis
Gastrodermis
Figure 41.8
Esophagus
Crop
Gizzard
Intestine
Pharynx
• More complex animals have a digestive tube with
two openings, a mouth and an anus
• This digestive tube is called a complete
digestive tract or an alimentary canal
• It can have specialized regions that carry out
digestion and absorption in a stepwise fashion
Anus
Mouth
(a) Earthworm
Foregut Midgut Hindgut
Esophagus
Rectum
Anus
Esophagus
Crop
Stomach
Gizzard
Intestine
Mouth
Crop
Gastric cecae
Mouth
(b) Grasshopper
Concept 41.3: Organs specialized for
sequential stages of food processing
form the mammalian digestive system
• The mammalian digestive system consists of an
alimentary canal and accessory glands that
secrete digestive juices through ducts
• Mammalian accessory glands are the salivary
glands, the pancreas, the liver, and the
gallbladder
Concept 42.1: Circulatory systems link
exchange surfaces with cells throughout
the body
• Diffusion time is proportional to the square of the
distance
• Diffusion is only efficient over small distances
• In small and/or thin animals, cells can exchange
materials directly with the surrounding medium
• In most animals, cells exchange materials with the
environment via a fluid-filled circulatory system
Anus
(c) Bird
Chapter 42
Circulation and Gas Exchange
Gastrovascular Cavities
• Some animals lack a circulatory system
• Some cnidarians, such as jellies, have elaborate
gastrovascular cavities
• A gastrovascular cavity functions in both digestion
and distribution of substances throughout the body
• The body wall that encloses the gastrovascular
cavity is only two cells thick
• Flatworms have a gastrovascular cavity and a
large surface area to volume ratio
Figure 42.2
General Properties of Circulatory Systems
Circular
canal
• A circulatory system has
Mouth
Gastrovascular
cavity
– A circulatory fluid
– A set of interconnecting vessels
– A muscular pump, the heart
Mouth
Pharynx
Radial canals
5 cm
2 mm
(a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm
• The circulatory system connects the fluid that
surrounds cells with the organs that exchange
gases, absorb nutrients, and dispose of wastes
• Circulatory systems can be open or closed, and
vary in the number of circuits in the body
Figure 42.3a
Open and Closed Circulatory Systems
(a) An open circulatory system
Heart
• In insects, other arthropods, and most molluscs,
blood bathes the organs directly in an open
circulatory system
• In an open circulatory system, there is no
distinction between blood and interstitial fluid, and
this general body fluid is called hemolymph
Hemolymph in sinuses
surrounding organs
Pores
Tubular heart
Figure 42.3b
(b) A closed circulatory system
• In a closed circulatory system, blood is
confined to vessels and is distinct from the
interstitial fluid
• Closed systems are more efficient at transporting
circulatory fluids to tissues and cells
• Annelids, cephalopods, and vertebrates have
closed circulatory systems
Heart
Interstitial fluid
Blood
Small branch
vessels in
each organ
Dorsal
Auxiliary
vessel
hearts
(main heart)
Ventral vessels
Organization of Vertebrate Circulatory
Systems
• Humans and other vertebrates have a closed
circulatory system called the cardiovascular
system
• The three main types of blood vessels are arteries,
veins, and capillaries
• Blood flow is one way in these vessels
• Arteries and veins are distinguished by the
direction of blood flow, not by O2 content
• Vertebrate hearts contain two or more chambers
• Blood enters through an atrium and is pumped
out through a ventricle
Figure 42.4a
(a) Single circulation
Single Circulation
Gill
capillaries
• Bony fishes, rays, and sharks have single
circulation with a two-chambered heart
• In single circulation, blood leaving the heart
passes through two capillary beds before returning
Artery
Heart:
Atrium (A)
Ventricle (V)
Vein
Body
capillaries
Key
Oxygen-rich blood
Oxygen-poor blood
Figure 42.4b
(b) Double circulation
Double Circulation
Pulmonary circuit
Lung
capillaries
• Amphibian, reptiles, and mammals have double
circulation
• Oxygen-poor and oxygen-rich blood are pumped
separately from the right and left sides of the heart
A
V
Right
A
V
Left
Systemic
capillaries
Key
Systemic circuit
Oxygen-rich blood
Oxygen-poor blood
• In reptiles and mammals, oxygen-poor blood flows
through the pulmonary circuit to pick up oxygen
through the lungs
• In amphibians, oxygen-poor blood flows through a
pulmocutaneous circuit to pick up oxygen
through the lungs and skin
• Oxygen-rich blood delivers oxygen through the
systemic circuit
• Double circulation maintains higher blood pressure
in the organs than does single circulation
Adaptations of Double Circulatory Systems
• Hearts vary in different vertebrate groups
Figure 42.5a
Amphibians
Pulmocutaneous circuit
Amphibians
Lung
and skin
capillaries
• Frogs and other amphibians have a threechambered heart: two atria and one ventricle
• The ventricle pumps blood into a forked artery that
splits the ventricle’s output into the
pulmocutaneous circuit and the systemic circuit
• When underwater, blood flow to the lungs is nearly
shut off
Atrium
(A)
Atrium
(A)
Right
Left
Ventricle (V)
Systemic
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Figure 42.5b
Reptiles (Except Birds)
Pulmonary circuit
Reptiles (Except Birds)
• Turtles, snakes, and lizards have a threechambered heart: two atria and one ventricle
• In alligators, caimans, and other crocodilians a
septum divides the ventricle
• Reptiles have double circulation, with a pulmonary
circuit (lungs) and a systemic circuit
Lung
capillaries
Right
systemic
aorta
Atrium
(A)
Ventricle
(V)
A
Right
V
Left
Left
systemic
aorta
Incomplete
septum
Systemic
capillaries
Systemic circuit
Key
Oxygen-rich blood
Oxygen-poor blood
Figure 42.5c
Mammals and Birds
Pulmonary circuit
Mammals and Birds
• Mammals and birds have a four-chambered heart
with two atria and two ventricles
• The left side of the heart pumps and receives only
oxygen-rich blood, while the right side receives
and pumps only oxygen-poor blood
• Mammals and birds are endotherms and require
more O2 than ectotherms
Lung
capillaries
A
Atrium
(A)
Ventricle
(V)
Right
V
Left
Systemic
capillaries
Systemic circuit
Concept 42.5: Gas exchange occurs across
specialized respiratory surfaces
• Gas exchange supplies O2 for cellular respiration
and disposes of CO2
Respiratory Surfaces
• Animals require large, moist respiratory surfaces
for exchange of gases between their cells and the
respiratory medium, either air or water
• Gas exchange across respiratory surfaces takes
place by diffusion
• Respiratory surfaces vary by animal and can
include the outer surface, skin, gills, tracheae, and
lungs
Key
Oxygen-rich blood
Oxygen-poor blood
Respiratory Media
• Animals can use air or water as a source of O2, or
respiratory medium
• In a given volume, there is less O2 available in
water than in air
• Obtaining O2 from water requires greater
efficiency than air breathing
Gills in Aquatic Animals
• Gills are outfoldings of the body that create a large
surface area for gas exchange
Figure 42.23
O2-poor blood
• Ventilation moves the respiratory medium over
the respiratory surface
• Aquatic animals move through water or move
water over their gills for ventilation
• Fish gills use a countercurrent exchange
system, where blood flows in the opposite
direction to water passing over the gills; blood is
always less saturated with O2 than the water it
meets
Gill
arch
O2-rich blood
Lamella
Blood
vessels
Gill arch
Water
flow
Operculum
Water flow
Blood flow
Countercurrent exchange
PO (mm Hg) in water
2
150 120 90 60 30
Gill filaments
Net diffusion of O2
Figure 42.24
Tracheoles Mitochondria
140 110 80 50 20
PO (mm Hg)
2
in blood
Muscle fiber
• The tracheal system of insects consists of tiny
branching tubes that penetrate the body
• The tracheal tubes supply O2 directly to body cells
• The respiratory and circulatory systems are
separate
• Larger insects must ventilate their tracheal system
to meet O2 demands
2.5 µ m
Tracheal Systems in Insects
Tracheae
Air sacs
Body
cell
Air
sac
Tracheole
Trachea
External opening
Air
Lungs
Chapter 44
• Lungs are an infolding of the body surface
• The circulatory system (open or closed) transports
gases between the lungs and the rest of the body
• The size and complexity of lungs correlate with an
animal’s metabolic rate
Osmoregulation and Excretion
Overview: A Balancing Act
• Osmoregulation regulates solute
concentrations and balances the gain and loss
of water
• Excretion gets rid of nitrogenous metabolites
and other waste products
Concept 44.1: Osmoregulation balances the
uptake and loss of water and solutes
• Osmoregulation is based largely on controlled
movement of solutes between internal fluids
and the external environment
Osmotic Challenges
• Osmoconformers, consisting only of some
marine animals, are isoosmotic with their
surroundings and do not regulate their
osmolarity
• Osmoregulators expend energy to control
water uptake and loss in a hyperosmotic or
hypoosmotic environment
• Most animals are stenohaline; they cannot
tolerate substantial changes in external
osmolarity
• Euryhaline animals can survive large
fluctuations in external osmolarity
Figure 44.3a
(a) Osmoregulation in a marine fish
Marine Animals
• Most marine invertebrates are osmoconformers
• Most marine vertebrates and some invertebrates
are osmoregulators
• Marine bony fishes are hypoosmotic to sea
water
• They lose water by osmosis and gain salt by
diffusion and from food
• They balance water loss by drinking seawater
and excreting salts
Gain of water
and salt ions
from food
Gain of water
and salt ions
from drinking
seawater
Excretion
of salt ions
from gills
Osmotic water
loss through gills
and other parts
of body surface
Excretion of salt ions and
small amounts of water in
scanty urine from kidneys
Key
Water
Salt
Figure 44.3b
(b) Osmoregulation in a freshwater fish
Freshwater Animals
• Freshwater animals constantly take in water by
osmosis from their hypoosmotic environment
• They lose salts by diffusion and maintain water
balance by excreting large amounts of dilute
urine
• Salts lost by diffusion are replaced in foods and
by uptake across the gills
Gain of water
and some ions
in food
Key
Water
Uptake of
salt ions
by gills
Osmotic water
gain through
gills and other
parts of body
surface
Excretion of salt ions and
large amounts of water in
dilute urine from kidneys
Salt
Animals That Live in Temporary Waters
• Some aquatic invertebrates in temporary ponds
lose almost all their body water and survive in a
dormant state
• This adaptation is called anhydrobiosis
Figure 44.5
Land Animals
• Adaptations to reduce water loss are key to
survival on land
• Body coverings of most terrestrial animals help
prevent dehydration
• Desert animals get major water savings from
simple anatomical features and behaviors such
as a nocturnal life style
• Land animals maintain water balance by eating
moist food and producing water metabolically
through cellular respiration
Figure 44.6
Water balance in
a kangaroo rat
(2 mL/day)
Ingested
in food (0.2)
Water
gain
(mL)
Derived from
metabolism (1.8)
Water balance in
a human
(2,500 mL/day)
Ingested
in food (750)
Ingested
in liquid
(1,500)
Derived from
metabolism (250)
Feces (100)
Feces (0.09)
Water
loss
(mL)
Urine
(0.45)
Evaporation (1.46)
Urine
(1,500)
Evaporation (900)
Concept 44.2: An animal’s nitrogenous
wastes reflect its phylogeny and habitat
• The type and quantity of an animal’s
waste products may greatly affect its
water balance
• Among the most significant wastes are
nitrogenous breakdown products of
proteins and nucleic acids
Forms of Nitrogenous Wastes
• Animals excrete nitrogenous wastes in different
forms: ammonia, urea, or uric acid
• These differ in toxicity and the energy costs of
producing them
• Ammonia (NH3) is very toxic. Animals that
excrete nitrogenous wastes as ammonia need
access to lots of water
• Urea is
Urea
• The liver of mammals and most adult
amphibians converts ammonia to the less toxic
urea
• The circulatory system carries urea to the
kidneys, where it is excreted
• Conversion of ammonia to urea is energetically
expensive; excretion of urea requires less
water than ammonia
Figure 44.8
Uric Acid
• Insects, land snails, and many reptiles, including
birds, mainly excrete uric acid
• Uric acid is relatively nontoxic and does not
dissolve readily in water
• It can be secreted as a paste with little water
loss
• Uric acid is more energetically expensive to
produce than urea
• Excretory systems regulate solute movement
between internal fluids and the external
environment
Nucleic acids
Amino
acids
Nitrogenous
bases
—NH2
Amino groups
Most aquatic
animals, including
most bony fishes
Ammonia
Concept 44.3: Diverse excretory systems
are variations on a tubular theme
Proteins
Mammals, most
amphibians, sharks,
some bony fishes
Urea
Many reptiles
(including birds),
insects, land snails
Uric acid
Excretory Processes
• Most excretory systems produce urine by
refining a filtrate derived from body fluids
• Key functions of most excretory systems
– Filtration: Filtering of body fluids
– Reabsorption: Reclaiming valuable solutes
– Secretion: Adding nonessential solutes and
wastes from the body fluids to the filtrate
– Excretion: Processed filtrate containing
nitrogenous wastes, released from the body
Figure 44.10
Protonephridia
1 Filtration
Capillary
Filtrate
Excretory
tubule
2 Reabsorption
• A protonephridium is a network of dead-end
tubules connected to external openings
• The smallest branches of the network are
capped by a cellular unit called a flame bulb
• These tubules excrete a dilute fluid and function
in osmoregulation
3 Secretion
Urine
4 Excretion
Metanephridia
Malpighian Tubules
• Each segment of an earthworm has a pair of
open-ended metanephridia
• Metanephridia consist of tubules that collect
coelomic fluid and produce dilute urine for
excretion
• In insects and other terrestrial arthropods,
Malpighian tubules remove nitrogenous
wastes from hemolymph and function in
osmoregulation
• Insects produce a relatively dry waste matter,
mainly uric acid, an important adaptation to
terrestrial life
• Some terrestrial insects can also take up water
from the air
Figure 44.12
Figure 44.13
Digestive tract
Kidneys
Rectum
Hindgut
Intestine
Midgut
Malpighian
(stomach)
tubules
Salt, water, and
Feces
nitrogenous
and urine
wastes
To anus
Malpighian
tubule
Rectum
Reabsorption
HEMOLYMPH
• Kidneys, the excretory organs of vertebrates,
function in both excretion and osmoregulation
Chapter 46
Animal Reproduction
Concept 46.1: Both asexual and sexual
reproduction occur in the animal kingdom
• Sexual reproduction is the creation of an
offspring by fusion of a male gamete (sperm) and
female gamete (egg) to form a zygote
• Asexual reproduction is creation of offspring
without the fusion of egg and sperm
Mechanisms of Asexual Reproduction
• Many invertebrates reproduce asexually by
fission, separation of a parent into two or more
individuals of about the same size
• In budding, new individuals arise from outgrowths
of existing ones (hydra)
• Fragmentation is breaking of the body into pieces,
some or all of which develop into adults
• Fragmentation must be accompanied by
regeneration, regrowth of lost body parts ( some
annelids, sponges, cnidarians, bristle worms and
sea squirts)
Sexual Reproduction: An Evolutionary
Enigma
• Parthenogenesis is the development of
a new individual from an unfertilized egg
– Bees, aphids, wasps and ants, rotifers,
komodo dragon and hummerhead shark
• Sexual females have half as many daughters as
asexual females; this is the “twofold cost” of
sexual reproduction
• Despite this, almost all eukaryotic species
reproduce sexually
Variation in Patterns of Sexual
Reproduction
• Hermaphroditism, in which each individual has
male and female reproductive systems
– Sea slugs
• Some species exhibit male to female reversal (for
example, certain oysters), while others exhibit
female to male reversal (for example, a coral reef
fish)
Concept 46.2: Fertilization depends on
mechanisms that bring together sperm
and eggs of the same species
• The mechanisms of fertilization, the union of egg
and sperm, play an important part in sexual
reproduction
• In external fertilization, eggs shed by the female
are fertilized by sperm in the external environment
• In internal fertilization, sperm are deposited in or
near the female reproductive tract, and fertilization
occurs within the tract
Ensuring the Survival of Offspring
• Internal fertilization is typically associated with
production of fewer gametes but the survival of a
higher fraction of zygotes
• Internal fertilization is also often associated with
mechanisms to provide protection of embryos and
parental care of young
• The embryos of some terrestrial animals develop
in eggs with calcium- and protein-containing shells
and several internal membranes
• Some other animals retain the embryo, which
develops inside the female
• In many animals, parental care helps ensure
survival of offspring
Gamete Production and Delivery
• To reproduce sexually, animals must produce
gametes
• In most species individuals have gonads, organs
that produce gametes
• Some simple systems do not have gonads, but
gametes form from undifferentiated tissue
• More elaborate systems include sets of accessory
tubes and glands that carry, nourish, and protect
gametes and developing embryos
• Most insects have separate sexes with complex
reproductive systems
• In many insects, the female has a spermatheca in
which sperm is stored during copulation
Chapter 49
• A cloaca is a common opening between the
external environment and the digestive, excretory,
and reproductive systems
• A cloaca is common in nonmammalian
vertebrates; mammals usually have a separate
opening to the digestive tract
Nervous Systems
• The simplest animals with nervous systems, the
cnidarians, have neurons arranged in nerve nets
• A nerve net is a series of interconnected nerve
cells
• More complex animals have nerves
• Nerves are bundles that consist of the axons of
multiple nerve cells
• Sea stars have a nerve net in each arm
connected by radial nerves to a central nerve
ring
• Bilaterally symmetrical animals exhibit
cephalization, the clustering of sensory organs
at the front end of the body
• Relatively simple cephalized animals, such as
flatworms, have a central nervous system (CNS)
• The CNS consists of a brain and longitudinal
nerve cords
• Annelids and arthropods have segmentally
arranged clusters of neurons called ganglia
• Nervous system organization usually correlates
with lifestyle
• Sessile molluscs (for example, clams and
chitons) have simple systems, whereas more
complex molluscs (for example, octopuses and
squids) have more sophisticated systems
• In vertebrates
– The central nervous system (CNS) is
composed of the brain and spinal cord
– The peripheral nervous system (PNS) is
composed of nerves and ganglia