Transcript 3.5 Animals, Vertebratesx

Animals, Part 2
Vertebrates
VERTEBRATES

CHORDATA: dorsal, hollow nerve cord

CRANIATES: have a skull (hagfish)
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VERTEBRATES: have a backbone (lampreys)
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GNATHOSTOMES: have jaws (extinct)
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CHONDRICHTHYANS: cartilage skeleton (sharks and rays)
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OSTEICHTHYANS: bony skeleton (fishes)
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TETRAPODS: four feet (amphibians: frogs, salamanders)
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AMNIOTES: have a yolk egg (reptiles: turtles, snakes, crocodiles, birds)
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MAMMALS: have hair and produce milk (marsupials, etc)
CHORDATA
 Chordates have a notochord and a dorsal, hollow nerve
cord. They are not quite invertebrates, but are more
closely related to vertebrates than to invertebrates. A
notochord is a long, flexible rod located between the
digestive tube and the nerve cord. It provides skeletal
support throughout most of the length of the back. It
differs from vertebrates in that it is not jointed; the
notochord in humans is reduced to discs sandwiched
between the vertebrae, known intervertebral discs. A
dorsal, hollow nerve cord is unique to chordates. Other
animals have solid nerve cords. The nerve cord of a
chordate embryo develops into the central nervous
system including the brain and spinal cord. Rather than
a fully developed brain, chordates have only a slightly
swollen tip at the anterior end of their dorsal nerve cord.
CRANIATES
 Craniates are chordates that have a skull. One example is the
hagfish, which have a skull made out of cartilage, but they
lack jaws and vertebrae. They swim in a snake like fashion by
using their muscles. Hagfish have a small brain, eyes, ears,
and a nasal opening that connects with the phalanx. They also
have tooth like formations made out of protein in their mouth.
All species are marine, and measure up to 60 cm in length.
Most are bottom dwelling scavengers that feed on worms or
sick or dead fish. A hagfish has rows of slime glands that
secrete a slime to repulse other scavengers. When a hagfish is
attacked, it can produce several liters of slime in less than a
minute. This slime coats the gills of an attacking fish, forcing it
to retreat or suffocate. Scientists are investigating the
properties of hagfish slime in hopes of producing it as a spacefilling gel which can be used to stop bleeding during surgery.
VERTEBRATES
 Vertebrates are craniates that have a backbone. They have a
more complex nervous system and a more elaborate skeleton, and
have become active predators.

In most vertebrates, the vertebrae enclose the spinal cord.
Aquatic vertebrates also acquired dorsal, ventral, and anal fins
which provide thrust and steering control during swimming.
They also adapted more efficient gas exchange systems in their
gills.
 Lampreys differ from fishes in that they lack jaws and they lack
paired fins. They represent the oldest of the vertebrates. Most are
parasites that feed by clamping their round, jawless mouth onto
the flank of a live fish. They then use their rasping tong to
penetrate the skin of the fish and ingest the fish's blood. Their
skeleton mostly consists of cartilage. Collectively, jawless fish
are referred to as agnathans (“no jaw”)
GNATHOSTOMES
 Gnathostomes (“jaw mouth”) are vertebrates that have
jaws. A jaw is a hinged structure that, with help of the
teeth, enables gnathostomes to grip food firmly and slice
it up. Their forebrain is enlarged compared to that of
other craniates, which allows them enhanced senses of
smell and vision. Running the length of each side of the
body in aquatic gnathostomes is the lateral line system, a
row of microscopic organs sensitive to vibrations in the
surrounding water. Additionally, they have a
mineralized endoskeleton. All of the vertebrates that we
will discuss are descents of this clade; the species that are
only gnathostomes are all extinct.
CHONDRICHTHYANS
 Chondrichthyans have a skeleton and that is
predominately cartilage, impregnated with
calcium. Examples include sharks and rays. They
are the biggest and most successful vertebrate
predators in the ocean.
SHARKS
 Sharks have hinged jaws, vertebrae, a flexible skeleton made of
cartilage, and a lateral line system. A lateral line system is a row
of sensory organs running along each side that are sensitive to
changes in water pressure and can detect vibrations caused by
animals swimming nearby. They have a streamlined body and are
swift swimmers, but they do not maneuver very well. Powerful
movements of the trunk and tailfin propel them forward. The
dorsal fins function mainly as stabilizers. They do not have a
swim bladder. A swim bladder is a gas-filled sac that can help
keep a fish afloat. Instead, the shark gets buoyancy by storing a
large amount of oil in its huge liver, the animal is still denser than
water, and if it stops swimming it sinks. Continual swimming
also ensures that water flows into the shark’s mouth and out
through the gills, where gas exchange occurs. However, some
sharks spend a good deal of time resting on the seafloor. When
resting, they use muscles of their jaw to pass water over the gills.
SHARKS
 The largest sharks and rays are suspension feeders
that consume plankton (algae). Most sharks,
however, are carnivores that swallow their prey
whole or use their powerful jaws and sharp teeth to
tear flesh from animals too large to swallow in one
piece. Sharks have several rows of teeth that
gradually move to the front of the mouth as old
teeth are lost.
SHARKS
 Acute senses are adaptations that go along with the
active, carnivorous lifestyle of sharks. Sharks have
sharp vision but cannot distinguish colors. The
nostrils of sharks function only for smelling, not for
breathing. Sharks also have a pair of regions in the
skin of their head that can detect electric fields
generated by muscle contractions of nearby animals.
Like other aquatic vertebrates, sharks have no
eardrums to transmit sound waves. Sound reaches
a shark through water, and the animal's entire body
transmits the sound to the hearing organs of the
inner ear.
RAYS
 Rays are closely related to sharks, but they have
adapted a very different lifestyle. Most rays are
flattened bottom-dwellers that feed by using their
jaws to crush mollusks and crustaceans. They use
their greatly enlarged pectoral fins like water wings
to propel themselves through the water. The tail of
many rays is whip-like and in some species, have
poisonous barbs that function in defense. Sharks
and rays are severely threatened with overfishing.
In 2003, sharks in the Northwest Atlantic declined
75% in 15 years.
OSTEICHTHYANS
 OSTEICHTHYANS
 Osteichthyan means “bony fish”. They have a bony
skeleton made out of calcium phosphate.
Informally, we call these “fish”. They breathe by
drawing water over four or five pairs of gills located
in chambers covered by a protective bony flap
called the operculum.
OSTEICHTHYANS
 Most fish control their buoyancy with an air sac
known as a swim bladder. Movement of gases
from the blood to the swim bladder increases
buoyancy, making the animal rise. This skin is
often covered by flattened, bony scales that differ in
structure and function from the tooth-like scales of
sharks. Glands in the skin secrete a slimy mucus
over the skin to reduce drag during swimming.
Like sharks, boney fish have a lateral line system.
There are two main types of fishes: Ray-finned and
lobe-fins.
Ray-Finned Fishes
 Ray-finned fishes have an operculum, a lateral
line system, a swim bladder, and flattened scales
cohering the skin, but they do not have a flexible
skeleton made of cartilage. Nearly all of the
osteichthyans we are familiar with are among the
ray-finned fishes. Examples include bass, trout,
perks, tuna, and herring. The fins are modified for
maneuvering, defense, and other functions. Rayfinned fishes originated in fresh water and spread to
the seas. Some species have returned to fresh water
at some point in their evolution.
Ray-Finned Fishes
 Some of them, including salmon and trout, replay
their evolutionary round-trip from freshwater to sea
water and back to fresh water during their lifecycle.
Ray-finned fishes serve as a major source of protein
for humans. However, industrial-scale fishing
operations now threaten some of the world's biggest
fisheries with collapse. Ray- finned fishes also face
other pressures from humans, such as the diversion
of rivers by dams.
Lobe-Fin Fishes
 The key derived characteristic of lobe-finned fish is a
series of rod-shaped bones in their fins surrounded by
a thick layer of muscle in their pectoral and pelvic fins.
During their evolution, they lived in brackish waters
where they probably used their lobed fins to swim and
“walk” underwater across the bottom. Today only two
main types of lobe-fins survive. One is called the
coelacanths, which shifted to the ocean. Scientists once
thought that coelacanths had become extinct 75 million
years ago, but in 1938, fishermen caught a living
coelacanth in the western Indian Ocean. A second
species has been discovered in Indonesia.
Lobe-Fin Fishes
 Another lineage of living lobe-fin is a lung fish
which are found in the southern hemisphere. They
are found only in fresh water stagnant ponds and
swamps. They have gills as well as lungs; they
surface to pull air into their lungs. They also have
gills for additional gas exchange. When ponds
shrink during the dry season; they burrow into the
mud and wait for conditions to improve.
Fish: the Good News and
the Bad News
 Fish is a good source of protein and, unlike fatty
meat products, it’s not high in saturated fat. It’s also
a good source of omega-3 fatty acids, which benefit
heart health. The American Heart Association
recommends eating fish at least twice a week.
However, some types of fish may contain high
levels of mercury and other environmental
contaminants. Levels of these substances are
generally highest in older, larger, predatory fish and
marine mammals.
Fish: the Good News and
the Bad News
 Fish with the highest levels of mercury are shark,
swordfish, golden bass or golden snapper, and king
mackerel. These fish should be avoided by pregnant and
nursing women and by young children.
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 Five of the most commonly eaten fish that are low in
mercury are shrimp, canned light tuna, salmon, pollock,
and catfish. Albacore ("white") tuna has more mercury
than canned light tuna; you may eat up to 6 ounces (one
average meal) of albacore tuna per week. Fish sticks and
"fast-food" sandwiches are commonly made from fish
that are low in mercury.
TETRAPODS
 Tetrapods (“four feet”) are gnathostomes that have
limbs and feet which evolved from the fins of lobe-fin
fish. Once tetrapods moved onto land, they eventually
took on many new forms, from leaping frogs to flying
eagles.
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 The limbs can support their weight on land and their feet
allow them to walk. They do not have gills slits. The
ears are adapted to the detection of airborne sounds.
Some species developed wings, while others, such as
whales, retained the shape of a fish. The first tetrapods to
evolve were amphibians, represented by salamanders
(with tails), frogs (tail-less), and caecilians (legless).
TETRAPODS
 Most salamanders that live on land walk with a side to
side bending of the body. Adult frogs use their powerful
hind legs to hop along the terrain. A frog nabs insects by
flicking out its long, sticky tongue, which is attached to
the front of the mouth. Frogs display a great variety of
adaptations that help them avoid being eaten by larger
predators. Their skin glands secrete distasteful or even
poisonous mucus. Many poisonous species have bright
coloration, which predators apparently associated with
danger. Other frogs have caller patterns that
camouflage. Caecilians are legless and nearly blind, and
superficially they resembled earthworms. They inhabit
tropical areas and burrow in moist forest soil.
Amphibians
 Amphibians were the first terrestrial vertebrates. Most
amphibian life cycles include a metamorphosis, and larval
amphibians have a lateral line system resembling that in
fishes. Amphibian means “two lives”. The larval stage of a
frog, called a tadpole, is an aquatic herbivore with a long tail.
Larval amphibians have a lateral line system like bony
fishes and sharks. The tadpole initially lacks legs and swims
by its tail. During the metamorphosis that leads to the second
life, the tadpole develops legs, lungs, a pair of external
eardrums, and a digestive system adapted to a carnivorous
diet. At the same time, the gills disappear. The young frog
crawls onto shore and becomes a terrestrial hunter. Lungs and
appendages for support did NOT evolve first in amphibians.
Lungs evolved from the swim bladders of fish, and
appendages evolved from their fins.
Amphibians
 Most amphibians are found in damp habitats such
as swamps and rain forests. Even those that are
adapted to drier habitats spend much of their time
in burrows or under moist leave, where the
humidity is high. Amphibians generally rely
heavily on their moist skin for gas exchange with
the environment.
Amphibians
 They usually lay their eggs in water. Fertilization is
external and most amphibians; the male grasps the
female and spills his sperm over the eggs as the
female sheds them. Adults display various types of
parental care. Depending on the species, either
males or females may house eggs on their back, in
their mouths, or even in their stomach. Some species
make nests, and others abandon their eggs in water
or in moist environments on land.
Amphibians
 Many amphibians exhibit complex and diverse
social behaviors, especially during their breeding
seasons. Frogs are usually quiet, but the males of
many species vocalize to defend their breeding
territory or to attract females.
Amphibians
 Over the past 25 years, there has been a rapid
decline in amphibian populations throughout the
world. There appears to be several causes,
including habitat degradation, fungal pathogens,
and acid rain. One difference between an
amphibian and a reptile is that amphibians do not
have an amniotic egg.
AMNIOTES
 Amniotes have an amniotic (yolk) egg, such as
reptiles (including birds). An amniotic egg is one
that contains specialized membranes that protect
the embryo. They function in gas exchange, waste
storage, and the transfer of storage nutrients to the
embryo. The amnion is the layer that contains fluid
and acts as a shock absorber. In contrast to the
shell-less eggs of amphibians, the amniotic eggs of
most reptiles and some mammals have a shell.
AMNIOTES
 The shells of bird eggs are made of breakable
calcium carbonate, while the shells of many reptile
eggs are leathery and flexible. The shell
significantly slows dehydration of the egg in the air,
an adaptation that allowed amniotes to occupy a
wider range of terrestrial habitats than amphibians.
Most mammals no longer have a shell, and the
embryo develops within the mother. Amniotes also
acquired other adaptations to terrestrial life,
including less permeable skin and the ability to use
the rib cage to ventilate the lungs. They also walk
with a more elevated stance.
Reptiles
 Reptiles include snakes, lizards, turtles, crocodiles,
and birds. Reptiles have scales, amniotic eggs, and
waterproof skin, but no lateral line system in
larvae. Unlike amphibians, reptiles have scales that
contain the protein keratin. Scales create a
waterproof area that helps prevent dehydration in
dry air. Scales prevent reptiles from breathing
through their skin like amphibians; most reptiles
rely on their lungs alone for gas exchange. Turtles
are the exception to this rule; many turtles also use
the moist surfaces of their skin for gas exchange.
Reptiles
 Reptiles include snakes, lizards, turtles, crocodiles,
and birds. Reptiles have scales, amniotic eggs, and
waterproof skin, but no lateral line system in
larvae. Unlike amphibians, reptiles have scales that
contain the protein keratin. Scales create a
waterproof area that helps prevent dehydration in
dry air. Scales prevent reptiles from breathing
through their skin like amphibians; most reptiles
rely on their lungs alone for gas exchange. Turtles
are the exception to this rule; many turtles also use
the moist surfaces of their skin for gas exchange.
Reptiles
 The adaptation of an amniotic egg allowed reptiles
to complete their life cycles on land. Most reptiles
lay shelled eggs on land. Fertilization must occur
internally, before the shell is secreted. Many species
of snakes and lizards are viviparous; they're
amniotic membranes form a placenta that enables
the embryo to obtain nutrients from its mother.

Reptiles
 Many reptiles are sometimes said to be “cold-blooded”
because they do not is their metabolism to control their
body temperature. However, they do regulate their
body temperature by using behavioral adaptations. For
example, many lizards bask in the sun when the air is
cool and seek the shade when the air is too warm. A
more accurate description of these reptiles is to say they
are ectothermic. By heating their bodies directly with
solar energy rather than through metabolic breakdown
of food, an ectothermic reptile can survive on less than
10% of the food required by a mammal of the same size.
Ectothermic animals include frogs, lizards, turtles, and
alligators.
Snakes
 A snake is a scaly, limbless, elongate reptile. Snakes
descended from an extinct lizard-like ancestor that was
venomous. All snakes are carnivorous. Some snakes
have a venomous bite, which they use to kill their prey
before eating it. Other snakes kill their prey by
constriction. Still others swallow their prey whole and
alive. A snake smells by using its forked tongue to collect
airborne particles then passing them to an organ in their
mouth to examine them. The term poisonous snake is
false - poison is inhaled or ingested whereas venom is
injected. Snake venom is used in biotechnology to
rapidly stop excessive bleeding during vascular surgery
and major trauma.
Lizards
 Lizards normally possess four legs, external ear
openings and movable eyelids. They can range in
size from a few centimeters (geckos) to nearly three
meters (Komodo Dragons).
Turtles
 Turtles are the most distinctive group of reptiles
alive today. All turtles had a box like shell made of
upper and lower shields that are fused to the
vertebrae. In most species, the shell is hard,
providing excellent defense against predators. The
earliest turtles could not retract their heads into
their shell; mechanisms for doing so evolved
independently in two separate branches of turtles.
The side-necked turtles fold their neck horizontally,
while the vertical-neck turtles fold their neck
vertically.
Turtles
 Some turtles have adapted to deserts, and others
live almost entirely in ponds and rivers. Still others
have returned to the sea. Sea turtles have a reduced
shell and enlarged forelimbs that function as
flippers. They are the largest living turtles and can
weigh over 1500 kg. They feed on jellyfish and dive
as deep as 60 m. They are endangered by fishing
boats that accidentally catch them in their nets, as
well as by the humans’ development of the beaches
where turtles lay their eggs.
Alligators and Crocodiles
 Alligators and crocodiles are collectively called
crocodilians. They are confined to the warmer
regions of the world. Alligators in the United States
have made a strong comeback after spending years
on the endangered species list.
Birds
 Birds are in the same category as reptiles; they evolved
from dinosaurs when they developed hollow bones,
then some feathers, then flight feathers, then two toes
in front and two in back. Although they are reptiles,
their reptilian anatomy has undergone adaptations that
are weight saving modifications to make flying more
efficient. Adaptations for flight include the absence of
teeth, very short tail bones, large breast muscles, efficient
lungs, lack of a urinary bladder, an extremely high rate
of metabolism, and the females of most species only have
one ovary. The skull is especially light and the bones are
hollow, although a bird skeleton as a whole is no lighter
in relation to body weight than the skeleton of a mammal
of similar size.
Birds
 Birds also have relatively large brains and possibly the best
vision of all vertebrates. Although most birds are fabulous
flyers, some birds are flightless. Birds generally display very
complex behaviors, particularly during breeding season, when
they engage in elaborate courtship rituals. Fertilization is
internal and the amniotic egg of birds has a hard outer shell.
Male and female frequently share responsibility for the
incubation and care of the young.

 Although their general body form is similar, different species
can be distinguished by their body profile, flying style,
behavior, feather colors, beak shape, and foot structure.
MAMMALS
 Mammals evolved from reptiles. Mammals have hair
and have mammary glands which produce milk. All
mammalian mothers nurse their young with milk, a
balanced diet rich in fats, sugars, proteins, minerals, and
vitamins. Hair and a fat layer under the skin help to
retain the body heat. Like birds, mammals are
endothermic, and most have a high metabolic rate. This
is supported by an efficient respiratory system with a
diaphragm and efficient circulatory system, including a
four-chambered heart. Live births are not limited to
mammals (some reptiles have live births), and some
mammals lay eggs.
MAMMALS
 Mammals generally have a larger brain than other
vertebrates of equivalent size. A relatively long
duration of parental care extends the time for
offspring to learn important survival skills by
observing their parents.
MAMMALS
 Mammals are endothermic (warm-blooded). They
use heat generated by metabolism to maintain a
warm, steady body temperature. Differentiation of
teeth is another important mammalian trait. The
teeth of mammals come in a variety of sizes and
shapes adapted for chewing many types of food.
Humans, for example, have teeth modified for
shearing and for crushing and grinding. The three
major groups of mammals are the monotremes,
marsupials, and eutherians.
Monotremes
 Monotremes are found only in Australia and New
Guinea and are represented by the platypus and
spiny anteater. Like all mammals, monotremes have
hair and produce milk, but they lay eggs and they
lack nipples; the baby sucks milk from the mother’s
fur.
Marsupials
 Examples are opossums, kangaroos, and koalas. A
marsupial is born very early in its development and
completes its development while nursing in a
maternal pouch called a marsupium. A red
kangaroo is about the size of a honey bee at its birth,
just 33 days after fertilization. Its hind legs are
merely buds, but it's forelegs are strong enough for
it to crawl from the exit of its mother's reproductive
tract to a pouch that opens to the front of her body,
a journey that lasts a few minutes.
Marsupials
 Australia has not been in contact with another
continent for about 65 million years. Most
marsupials evolved after South America and
Australia broke off from the other landmasses. That
is why kangaroos and koalas are only found in
Australia. Australia’s native species face serious
challenges from introduced, alien species.
Eutherians
 Eutherians (placental mammals)
 Eutherians are commonly called placental mammals
because their placentas are more complex than
those of marsupials and they have a longer period
of pregnancy. Eutherians complete their embryonic
development within the uterus. The major order of
eutherians we will discuss is the Primates.
Primates
 This order includes the lemurs, the tarsiers, the
monkeys, and the apes. Humans are members of
the ape group. Most primates have hands and feet
adapted for grasping, and their digits have flat nails
instead of claws. Additionally, the fingers have skin
ridges (fingerprints). Primates have a larger brain
than other mammals, and short jaws, giving them a
flat face. There have forward-looking eyes that are
close together on the front of the face. Primates also
have relatively well-developed parental care and
complex social behavior.
Primates
 The earliest primates were probably tree dwellers, and
many of the characteristics of primates are adaptation to
the demands of living in trees. All modern primates,
except humans, have a big toe that is widely separated
from the other toes, enabling them to grasp branches
with their feet. All primates have a thumb that is
relatively mobile and separate from the fingers, but only
monkeys, apes, and humans have a fully opposable
thumb; that is, they can touch the tip of all four fingers
with the fingerprint surface of the thumb of the same
hand. In humans, a distinctive bone structure at the base
of the thumb allows it to be used for more precise
manipulation. Having two eyes facing forward causes
and overlapping of visual fields, which enhances depth
perception.
Primates
 There are three main groups of living primates: the
lemurs of Madagascar, the tarsiers of South East Asia,
and the anthropoids, which include monkeys, apes, and
humans. After South America and Africa a drifted apart,
South America is called the New World and Africa and
Asia are called the Old World. New World monkeys and
Old World monkeys underwent separate adaptive
evolutions. All species of New World monkeys live in
trees, have prehensile tails, and nostrils that open to the
sides. Old World monkeys include ground dwelling as
well as tree-dwelling species, lack a prehensile tail, and
their nostrils open downward. Most monkeys in both
groups are active during the day and usually live in
bands held together by social behavior.
Primates
 The other group of anthropoids, the hominoids,
consists of primates informally called the apes. This
group includes gibbons, orangutans, gorillas,
chimpanzees, and humans. Hominoids have
relatively long arms, short legs, no tail, and a larger
brain in proportion to their body size than other
primates.
Humans
 “Homo sapiens” (wise or rational man) is the genus
and species for humans. Humans are the only
living members of the Homo genus. A number of
characteristics distinguish humans from other
hominoids. Humans have a much larger brain, and
are capable of written language, symbolic thought,
and they can manufacture and use complex tools.
Humans also have reduced jawbones and jaw
muscles and a shorter digestive tract. Humans are
99% genetically identical to chimpanzees, but that
1% translates into a large number of differences in a
genetic sequence that contains 3 billion genes.
Humans
 The characteristics of humans have been
reconsidered recently; a gorilla named Coco
demonstrated knowledge and use of sign language.
An African gray parrot named Alex has also
demonstrated an understanding of spoken
vocabulary, and not just mimicry. And many
species of mammals make their own tools to obtain
food, however they are not complex tools that
humans make.
Other Orders of Eutherians
(not on the exam)

Proboscidea: elephants

Sirenia: manatees

Xenarthra: sloths, anteaters, armadillos

Lagomorpha: rabbits

Carnivora: dogs, wolves, bears, cats, weasels, otters, seals, walruses

Artiodactyls: sheep, pigs, cattle, deer, giraffes

Cetaceans: whales, dolphins, porpoises

Rodentia: squirrels, beavers, rats, porcupines, mice

Perissodactyla: horses, zebras, rhinoceroses
ANIMAL FORM AND
FUNCTION
 Structure Fits Function in the Animal Body
 Anatomy is the study of an organism's structures;
physiology is the study of the function of an
organism's structures. The structure of an organism
fits its adaptive function. For instance, a gecko’s
anatomy includes tiny hairs on its feet that allow it
to climb vertical walls; a physiologist would study
the functioning of these hairs in order to understand
how they work.
ANIMAL FORM AND
FUNCTION
 Another example is the flight apparatus of birds. Feathers
give the wing its broad shape without adding much weight to
the body. They remain dry because they are lightly coated
with oil, and they also trap air, which provides insulation that
helps a bird to maintain its high body temperature and
metabolism. The function of feathers results from their unique
structure. Feathers consist entirely of nonliving material,
mainly the protein keratin. A flight feather has a hollow shaft
that provides a central support with minimum weight. Small
flat rods called barbs extend from both sides of the shaft. Still
finer rods called barbules extend from the sides of the barbs.
Each barbule has tiny hooks that interlock with adjacent
barbules. This gives a feather a particular shape and rigidity
that support flight. When a bird preens, it draws its feathers
through its beak, hooking the barbules back together like
zipping up a zipper.
ANIMAL FORM AND
FUNCTION
 The muscles and bones in a bird wing also show the
relationship between structure and function.
Muscles provide power, and the bones provide
support for flight. The flight muscles are situated
on the breast and around the base of the wings,
keeping most of the weight off the wings and
helping maintain the birds balance in flight.
ANIMAL FORM AND
FUNCTION
 The bones in a bird wing are similar to those in a
human arm, but the number of the bones is fewer.
The bird wing only has three fingers, and only the
middle one has a complete set of bones. This
adaptation helps make the wing lighter but less
flexible than a human hand. This reduced flexibility
stabilizes the wing and helps it function as a unit in
flight.
Animal Structure Has a
Hierarchy
 Just as there is a progression from atoms to
molecules to cells, the progression continues within
an animal. Cells connect with other cells of similar
function in and coordinate themselves, making up a
tissue. For instance, cardiac muscle cells are
branched and can communicate with each other. A
tissue is a group of similar cells that perform a
specific function, for instance, cardiac tissue. An
organ is a group of tissues that work together to
perform a specific task, for example, the heart.
Animal Structure Has a
Hierarchy
 An organ system consists of multiple organs that
together perform a vital bodily function, for
instance, the circulatory system consists of the heart
and blood vessels. An organism contains a number
of organ systems, each specialized for certain
functions and all functioning together as a
coordinated unit. For example, the pelican’s
circulatory system cannot function without the
oxygen supplied by the respiratory system and
nutrients supplied by the digestive system. And it
takes the coordination of muscle and bone systems
to enable the bird to fly.
ORGAN SYSTEMS
 Digestive System: ingests and breaks down food to be absorbed.
 Respiratory System: exchanges gases with the environment, supplies
blood with oxygen
 Circulatory System: delivers oxygen into the body cells
 Immune System: Defends the body against infections
 Lymphatic System: filters and cleans the fluid that leaks out from
blood vessels.
 Excretory System: removes waste products
 Endocrine System: secretes hormones that regulate body activities
 Nervous System: coordinates body activities
 Integumentary System: protects against injury, infection,
temperature, and dryness
 Skeletal System: supports the body and protects internal organs
 Muscular System: produces movement of the body, maintains
posture
 Reproductive System: produces gametes and sex hormones.