Phylum Chordata

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Phylum Chordata
Chordates have four defining characteristics that
occur AT SOME POINT in their lifecycle. Some of
these characteristics are only present in the
embryonic stage in many chordates. Characteristic
s 1. Notochord in the back (this is replaced by
vertebrae in the vertebrates) 2. Dorsal nerve
cord (spinal cord in the back) 3. Pharngeal
grooves or gill slits 4. Tail that extends past
the anus
Most chordates belong to a large group of animals
commonly known as the vertebrates (99). These
include fish, amphibians, reptiles, birds and
mammals.
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Elaboration please

• Notochord
• 1) This dorsal supporting rod is located
  dorsally just below the nerve cord.
• 2) It provides support and is replaced by
  vertebral column in vertebrates.
• Dorsal Hollow Nerve Cord 1) This cord contains
  a fluid-filled canal. 2) In vertebrates, the
  spinal cord is protected by vertebrae.
• Pharyngeal Gill Slits 1) These openings function
  in feeding, gas exchange, or both. 2) They are
  seen only during embryonic development in most
  vertebrates. 3) In invertebrate chordates, fish,
  and amphibian larvae, they become functioning
  gills. 4) In terrestrial vertebrates, the
  pouches are modified for various purposes. 5) In
  humans, the first pouches become auditory tubes,
  the second become tonsils, and the third and
  fourth pairs become thymus and parathyroid
  glands.
• A post-anal tail extends beyond the anus in
  some, this only appear in embryos.

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Offspring Births
Oviparous species lay eggs Viviparous species
have the embryos develop inside the female,
nourished by the placenta. Born
live. Ovoviviparous species have the embryo
develop in an egg within the female's body.
Cold vs Warm Blooded
Ectotherms cold blooded. Rely on environment
for body temp cannot control body temp. Allows
these organisms to live on less food than
endotherms. Endotherms warm blooded. Regulate
body temp as part of homeostasis.
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The Circulatory Systems of Vertebrates
Double-Loop Circulatory System
Single-LoopCirculatory System
Section 33-3
FISHES
CROCODILIANS, BIRDS,AND MAMMALS
AMPHIBIANS MOST REPTILES

• 2 Chambered Heart
• 1 ventricle, 1 atrium
• One loop from the heart round the body, passing
  through the gills on the way
• Ventricle pumps blood to gills and newly
  oxgenated blood continues throughout the body
  WITHOUT being pumped again.
• Lower blood pressure than in double looped
  organisms.

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The Circulatory Systems of Vertebrates
Double-Loop Circulatory System
Single-LoopCirculatory System
Section 33-3
FISHES
CROCODILIANS, BIRDS,AND MAMMALS
AMPHIBIANS MOST REPTILES

• Double Loop Circulatory Systems
• 2 loop system blood travels from the heart, to
  the lungs, back to the heart, and then to the
  rest of the body.
• Double loop circulation is more efficient,
  because it gives the heart an extra pump to move
  blood to the body
• Deoxygenated blood enters the right atrium, moves
  into the right ventricle and is pumped to the
  lungs. Oxygenated blood enters the left atrium,
  moves into the left ventrical and is pumped to
  the rest of body.

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The Circulatory Systems of Vertebrates
Double-Loop Circulatory System
Single-LoopCirculatory System
Section 33-3
FISHES
AMPHIBIANS MOST REPTILES
CROCODILIANS, BIRDS,AND MAMMALS

• 3 Chambered Heart
• 1 ventricle, 2 atria
• Oxgenated and deoxygenated blood are kept
  somewhat separate, largely as a result of the
  timing of the contractions of the left and right
  atria. OFTEN SAID TO MIX, but
• The blood returning from the right atrium is
  pumped by the ventricle into pulmonary
  circulation.
• After most of the deoxygenated blood has left the
  ventricle, oxygenated blood is pushed in and
  pumped through the bodytherefore, limited mixing
  due to the pulsing of the heart muscle.

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The Circulatory Systems of Vertebrates
Double-Loop Circulatory System
Single-LoopCirculatory System
Section 33-3
FISHES
CROCODILIANS, BIRDS,AND MAMMALS
AMPHIBIANS MOST REPTILES

• 4 Chambered Heart
• 2 ventricles, 2 atrias
• Oxygenated and deoxygenated blood is completely
  separated
• Right ventricle pumps blood to the lungs through
  the pulmonary artery

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Major Vessels
Aorta - pumps blood to the body (it connects to
the left ventricle) Pulmonary artery - connects
to right ventricle, pumps oxygen-poor blood to
the lungs Pulmonary veins - bring oxygen rich
blood from the lungs to the left atrium Superior
Vena Cava - brings oxygen poor blood from the
upper body to the right atrium Inferior Vena
Cava - brings oxygen poor blood from the lower
part of the body to the right atrium Coronary
Arteries - located on the outside of the heart,
these vessels supply blood to the heart itself, a
blockage in these arteries can lead to a heart
attack.
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An important message about blood color
Blood is NEVER blue. Blood is described as dark
red deoxygenated blood or bright red oxgenated
blood. Our veins look blue because we are
looking at them through our skin (light is
diffused through the skin). The blood inside
them is dark red and it doesn't reflect light
very well. BLUE is an artistic
interpretationnot an actual blood color!
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Most Chordates are Vertebrates
Most chordates belong to a large group of animals
commonly known as the vertebrates (99). These
include fish, amphibians, reptiles, birds and
mammals.

• Vertebrate a chordate that has a strong
  supporting structure called the vertebral column
  or backbone which is made up of bony vertebrae
• In vertebrates, the dorsal, hollow nerve cord
  becomes the spinal cord
• Vertebrates have an endoskeleton which grows as
  the org grows, and is made up of living cells
  which produce non-living material

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Nonvertebrate Chordates
Two groups do NOT have backbones 1. Tunicates
filter feeders, larval form has chordate
characteristics, adults do not 2. Lancelets
small, fish-like, live on sandy ocean bottom
Lancelets
Not to be confused with invertebrates because
nonvertebrate chordates have the 4 key
characteristics at some point in their life
cycle, invertebrates do not.
Tunicates
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Vertebrate Chordates
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Class Agnatha

• Examples lamprey and hagfish
• These fish lack a jaw.
• These organisms lack the paired pelvic and
  pectoral fins.
• Skeleton made of cartilage.
• Soft skin that does not contain scales.
• They lack a swim bladder, and gill covers.
• Have 7 gill slits on each side of the head.
• The lamprey are parasitic and the hagfish are
  scavengers.
• Ectothermic
• Oviparous (egg laying)
• Has a pressure sensitive organ in the skin called
  a lateral line.
• 2 chambered heart.
• Gills are used for respiration

hagfish
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Class Chondrichthyes

• Examples sharks, rays, skates
• Skeleton made of cartilage.
• A notochord is present in adults.
• Body covered with triangular placoidscales.
• Ventral mouth with several rows of triangular
  teeth.
• Large caudal fin with the dorsal section larger
  than the ventral one.
• Paired pectoral and pelvic fins are stiff and
  non-flexable.
• They lack a swim bladder. This makes them unable
  to float in the water.
• Ectothermic
• Oviparous or ovoviviparous
• Has a lateral line.
• 2 chambered heart.
• Gills used for respiration.

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Ovoviviparous  
Ovoviviparous animals develop within eggs that
remain within the mother's body up until they
hatch or are about to hatch. This strategy of
birth is known as ovoviviparity. It is similar to
vivipary in that the embryo develops within the
mother's body. Unlike the embryos of viviparous
species, ovoviviparous embryos are nourished by
the egg yolk rather than by the mother's body.
However, the mother's body does provide gas
exchange.
Actual birth of of a lemon shark pup. This event
which had never been seen in a shark in the wild
before, took place in Bimini Lagoon in the
Bahamas. The mother which was about 8.5 feet
long-had been captured for study and was anchored
to the scientists boat by a hook in her mouth and
a rope around her tail. As each pup was born it
would lie briefly on the ocean floor, before
swimming away, straining against the umbilical
cord until it broke, leaving a small depression
in the baby sharks belly. 
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Shark Pups
All baby sharks are called pups. All pups do not
grow in the same exact way. Some grow in an egg
in their mother's stomach. This is called
ovoviviparity. Pups pop out through the opening
in their mother's body. They are joined to their
mother by a big cord that has a whole bunch of
tiny cords that break as the pup leaves the
mother's body. The sharks are then born live in
the ocean. When the pup is born the mother leaves
the pup on its own to take care of itself. Some
shark embryos get their food first from a yolk.
They use up all the food in the yolk. The yolk
will turn into a placenta that attaches to the
female's womb. Nutrients and oxygen from the
mother then go to the placenta and through
umbilical cord, so the shark embryo can
grow. This shark gets its nutrients and oxygen
from a yolk sac which is provided by the mother.
This shark only needs one yolk sac. Each shark
embryo is in a seperate chamber in the uterus.
When the nutrients from the yolk sac are used up
the embryo is ready to come out of the mother's
body.  This embryo is provided with many
eggcases. The sharks will immediately start
feeding on the eggcases. The oldest shark is the
one that will that will be able to feed on his or
her brothers and sisters. These eggcases are
swallowed and digested very easily. That's how
these embryos get their nutrients and oxygen.
Others grow in eggcases that are left in the
ocean and are oviparous. The eggcases are put in
different places. Cat sharks' egg cases have tiny
tendrils will that wrap tightly onto plants in
the ocean. A horn shark's eggcase settles in big
cracks in the ocean's rocks. Many other egg cases
settle on the soft seabed.     Each little egg
is in a hardened sack. It hardens to protect the
small pup. Egg cases are very long lasting. The
eggs take nine months to hatch, just like a human
baby. The pups look exactly like their parents,
only tinier. The pup is hatched when it is
nearly full grown. It wanders off to some place
safe. Many pups are eaten as soon as they are
born by other sharks. Dogfish shark lay about 20
eggs, usually in a pile of seaweed. Each egg case
contains a yolk sac just for the pup to feed off
as it grows.
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Class Osteichthyes

• Examples tuna, carp, salmon, sturgeon
• Skeleton made of bone.
• 2 chambered heart
• Operculum covering the gills.
• They have a swim bladder.
• Ectothermic rely on environment and behavior to
  regulate body temperature
• Paired fins made of rays and spines,or lobed fins
  lacking the rays and spines.
• Various types of scales (ctenoid,ganoid, or
  cycloid).
• Gills used for respiration
• External fertilization. Spawning. Oviparous.

Class Osteichthyes are fish with a bony skeleton.
Their gill slits are covered by a flap called the
operculum. Their body is covered with
scales. The bony fish are the most diverse and
abundant of all the vertebrates.
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Class Amphibia
The Class Amphibia includes salamanders, frogs
and toads. They have moist skin that secretes
mucus. Amphibians must return to water to
reproduce.
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Class Amphibia

• Examples caecilians, salamanders, newts, frogs
  and toads.
• Amphibians have smooth moist skin. The toad is an
  exception with rough dry skin.
• The majority of amphibians contain 4 limbs with
  no claws on their digits (toes).
• They contain a 3 chambered heart. There is a
  possibility of the oxygenated and unoxygenated
  blood mixing in the ventricle.
• Ectothermic rely on environment and behavior to
  regulate body temperature
• During extreme environmental conditions they
  either hibernate (winter) or aestivate (summer).
• They carry on external fertilization. Their
  offspring develop through a process called
  metamorphosis. Tadpoles (aquatic larvae)
  resemble fish. Over a period of time they change
  in form into the adult amphibian.
• They respire through poorly developed lungs and
  moist skin.
• They contain a well developed muscular system.
• The digestive system is adapted to digest whole
  prey, swallowed by the organism.
• Two kidneys rid the body of nitrogenous waste.
  The amphibian liver carries on several functions
  detoxifying poisons, producing bile, and storing
  glucose in the form of glycogen.
• The cloaca is a sac that collects discharge from
  the large intestine, urinary bladder, and gonads
  before it is eliminated from the body.
• Their brain is well developed and is attached to
  a dorsal nerve cord.
• Most amphibians contain 3 eye lids. Two are
  normal and one is transparent.
• These are the first animals to possess a pressure
  releasing canal called the euscachian tube. The
  tube connects the mouth cavity with the tympanic
  membrane in the ear.

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Metamorphosis
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Dual life of a frog (Rana temporaria)
EXTERNAL FERTILIZATION!!!
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Class Reptilia

• Examples turtles/tortoises, snakes, lizards,
  crocodiles/alligators
• Reptiles are considered the first true land
  animals since it was the development of the
  amniote egg that allowed the reptiles to conquer
  the land.
• Reptiles molt/shed as they grow.
• Reproduction is sexual with internal
  fertilization. Males do NOT have a penis, but
  rather two hemipenes. These reversible
  structures aid in delivering sperm into the
  cloaca of a female snake during internal
  fertilization.
• Some females have stored sperm for a year or more
  before allowing eggs to be fertilized. There is
  a special organ used to store sperm within the
  female.
• Most are oviparous, while some snakes and lizards
  are either ovoviviparous or viviparous.
• Respiration occurs through well developed lungs,
  and in some turtles a moist choacal surface.
• Ectotherms depend on environment and behavior to
  regulate body temperature.
• Most reptiles contain a 3 chambered heart with a
  partially divided ventricle. Crocodiles contain a
  4 chambered heart.

One way to sex a snake is to use a special
probe. Depending on the depth the probe descends
into the cloaca can help a herpetologist
determine a snakes sex. If the snake is a male,
the probe will slide down into one or the other
hemipenis to a depth more than the width of the
tail base.
Another method to sex a snake is to pop its
cloaca. A female will have tiny spots whereas a
male will extrude its two hemipenes.
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Amniote Egg
This egg is a water proof structure composed of a
shell, embryonic membranes, and the living
embryo. Chorion-aids in the exchange of gases
between the environment and the embryo.
Allantois-a sac-like structure that grows out of
the digestive tract of the embryo. It functions
in gas exchange and collects metabolic wastes
from the embryo. Amnion-fluid filled sac that
surrounds the embryo and the fluid it secretes
cushions the embryo. Yolk sac-contains the food
for the embryo.
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Amniote Egg
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Class Reptilia
The Class Reptilia includes lizards, snakes,
alligators, crocodiles and turtles. Their body is
covered with scales. Reptiles are unable to
maintain their body temperature like birds and
mammals. They are cold blooded.
Reptiles were the first vertebrates to be able to
live away from water. They produce an amniote egg
that retains water for the embryo.
Most reptiles have peg-like teeth that are
similar in shape. Crocodiles transport their
young in their mouths.
Snakes are reptiles that have lost their legs. A
few snakes have vestigial legs and a vestigial
pelvis.
Turtles live inside a shell that is attached to
their skeleton. They can pull their head and legs
into their shell when danger is present. Turtles
do not have teeth.
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Lets Shed a Tail, Shall We?
SOME lizards lose their tails to throw off
predators. Even after a tail detaches, nervous
spasms make a newly dropped lizard tail wag
around as if it's alive. The headless appendage
startles predators and gives tailless lizards a
few precious moments to escape, relatively
unharmed. The trauma jumpstarts cells to build
a new tail out of cartilage. Original tails are
made of bony vertebrae. Regeneration can use up
a lot of energy, and as lizards get older their
tails actually become less colorful, and
therefore less attractive to predators.
How does this occur? Most lizards have a
standard, rather complex mechanism for shedding
the tail, in which breakage takes place through
the body of a vertebra (transvertebral autotomy).
All vertebrae in the tail, except the first few,
have fracture planes running across them. These
are often visible in skeletons as partial splits.
The planes of weakness continue through the fat,
muscles and skin surrounding the vertebrae, so
that the tail can break right across at these
points. When a predator grasps the tail, muscles
in the tail contract, causing the vertebra lying
just in front of the point of contact to break.
This ensures that the lizard loses the smallest
piece of its tail necessary to allow escape. The
shed part of the tail often thrashes vigorously,
sometimes for five minutes or more, frequently
holding the attention of the predator while the
lizard flees. The tail muscles of some lizards
respire anaerobically for longer than muscles in
other parts of the body, which explains why the
tail can keep moving for so long after it is
detached from the body. The missing part usually
regenerates within a few weeks. Although it often
looks perfect from the outside, internally the
regenerated tail is very different, with a simple
tube of cartilage in place of the vertebrae. Once
it has regrown, the tail can be broken again, but
only in front of the regenerated section, where
there are still vertebrae with planes of
weakness. Although this is what happens in most
lizards, there are exceptions. For instance, some
species have no tail-shedding mechanism at all
others have a simpler method in which breakage
takes place between vertebrae (intervertebral
autotomy) and these animals do not always grow a
replacement part. Complete absence of autotomy
and intervertebral breakage are not, as we might
expect, successive stages in the development of
the widespread transvertebral mechanism. Rather,
they are derived from it. During the course of
evolution, the complex transvertebral mechanism
has been lost many times, and breakage between
the vertebrae seems to be a rather inferior
redevelopment of the strategy which has appeared
as many as eight times.
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Class Aves

• Birds are flight orientated organisms. Each part
  of its anatomy is modified in some way to allow
  it to keep its body light and energic for flight.
• Very active metabolism. They can eat, digest, and
  eliminate the waste in a short amount of time.
  Their body temperature is rather high 102-103
  degrees F. They are endothermic.
• They contain a 4 chambered heart.
• Their skeleton is constructed of light weight
  bones supported by an inner meshwork of bony
  material to give extra support while flying.
• They have no teeth and their beak is made of a
  light protein called keratin..
• They contain feathers, also made of keratin.
• They have an extensive air sac system attached to
  the lungs. Functions to make sure the lungs are
  always oxgenated
• Birds and reptiles have the same kind of amniote
  egg. This enables them to reproduce away from
  water. They develop from the amniote egg. Bird
  egg shells are hardened with calcium carbonate
  for added protection.
• They have a well developed nervous system. Acute
  vision, and external ears.
• Well developed muscles. The keel ,a part of the
  sternum, allows large pectoral muscles to be
  attached to the skeleton.
• Their forelimbs are modifies as wings. These
  wings are homologous to the limbs of the
  reptiles, amphibians, and mammals.
• Their hind limbs are modified for various jobs
  based on the structure of their claws.
• Many birds migrate over long distances to find
  suitable breeding grounds and protection from
  major climatic changes.

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The Anatomy of a Pigeon
Section 31-2
Brain
Esophagus
Lung
When a bird eats, food moves down the esophagus
and is stored in the crop.
Heart
1
Kidney
Crop
Air sac
Liver
Moistened food passes to the stomach, a two-part
chamber. The first chamber secretes acid and
enzymes. The partially digested food moves to the
second chamber, the gizzard.
2
Firstchamberof stomach
Pancreas
Large intestine
Gizzard
Smallintestine
Undigested food is excreted through the cloaca.
Cloaca
5
The muscular walls of the gizzard squeeze the
contents, while small stones grind the food.
3
As digestion continues, the food moves
through the intestines.
4
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Respiration (this is important!)

• Bird lungs do not expand or contract like the
  lungs of mammals. They do not have a diaphram.
• The respiratory system of birds is more efficient
  than that of mammals, transferring more oxygen
  with each breath.
• The air sacs permit a unidirectional flow of air
  through the lungs. Unidirectional flow means that
  air moving through bird lungs is largely 'fresh'
  air has a higher oxygen content.
• In contrast, air flow is 'bidirectional' in
  mammals, moving back forth into out of the
  lungs.
• As a result, air coming into a mammal's lungs is
  mixed with 'old' air (air that has been in the
  lungs for a while) this 'mixed air' has less
  oxygen.
• So, in bird lungs, more oxygen is available to
  diffuse into the blood

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Form fits function
For added strength, the hollow bones are
supported by internal struts (much like the
struts that support the hollow wings of planes).
A bird's streamlining for flight is perhaps best
exemplified in the evolution of the skull, which
is composed mainly of thin, hollow bones. A
bird's skull is extremely light in proportion to
the rest of its body due to elimination of a
heavy jaw, jaw muscles, and teeth the job of
chewing has largely replaced by the gizzard. The
skull usually represents less than 1 percent of a
bird's total body weight.
Feathers are made of keratin, a protein which is
also used to make horn and hair by different
animals and beaks by birds. Owls have the outer
ends of their flight feathers lacking in
barbules they are unzipped - this makes the
edges softer and reduces the noise they make,
silent flight helps an owl catch its prey.
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Class Mammalia
Mammals have hair or fur and mammary glands for
nursing their young. They have an advanced
nervous system and exhibit complex behavior.
Mammals care for their young much more than other
animals. They are able to maintain their body
temperature. Mammals descended from reptiles.
Embryos of mammals have the same four embryonic
membranes as found in the amniote egg of reptiles.
Mammals have specialized teeth. Unlike reptiles
that swallow their food whole, mammals are able
to cut and chew their food. Mammalian teeth have
evolved into many different shapes to fit various
life styles.
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Class Mammalia

• Possess hair/fur which is made of keratine.
  Hair/fur provides insulation .
• Endothermic. The majority of the heat energy is
  used to maintain their body temp.
• 4 chambered heart.
• Mammary glands are used to produce milk to
  nourish their young. Female glands are the only
  functional glands.
• The diaphramgm is a muscle that separates the
  thoracic cavity from the abdominal cavity.
• 7 cervical vertebrae (neck bones) are present in
  most mammals.
• Most are viviparous though some are oviparous.
• Well developed brain.
• Have specialized teeth. Unlike reptiles that
• swallow their food whole, mammals are able
• to cut and chew their
• food. Mammalian
• teeth have evolved
• into many different
• shapes to fit various
• life styles.

Incisors
Canines
Premolars
Molars
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Major Groups of Mammals
Monotremes. Characterized by the duckbilled
platypus and the spiny anteaters, lay eggs and
maintain some reptilian characteristics. They do
not contain true mammary glands, but produce a
fatty sweat (milk) from glands in the skin. The
milk collects and drips down tufts of hair into
the offspring's mouth. They are found in
Australia and New Guinea. Marsupials. These
mammals contain a pouch (marsupium). Opossums,
koalas, kangaroos, and other examples live in
Australia as a result of the break up of the
super continent Pangea. The young are born during
the early stages of development. The new born
crawls up to the mother's pouch, where it clings
on to a nipple and hangs there until it fully
develops. Placental Mammals. These mammals are
the most abundant and diverse of the class. The
placenta,is a reproductive structure, is housed
in the uterus of the female. Here the offspring
receives all that it needs to develop into a
fully developed organism. This period of
development (gestation) varies with the species
of mammal. Whales gestate for 2 years, while a
mouse develops in 21 days.
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The platypus is a member of the most primitive
group of mammals, the monotremes. They have fur
like other mammals, but they lay eggs like a
reptile. They are a transitional species with
both mammalian and reptilian traits. Placental
mammals out competed the monotremes and drove
them to extinction in most of the world.
Primates include humans, apes, monkeys, baboons
and other similar animals. All primates have the
following characteristics 1.Grasping fingers 2.
Fingernails instead of claws 3.
Forward-pointing eyes for binocular vision
Australian monotremes and marsupials echidna
(top left), marsupial mouse (lower left), sugar
glider (right)
The kangaroo is a marsupial mammal. Marsupials
have a short gestation period and give birth to
underdeveloped young. The offspring complete
their development in a pouch. Most marsupials
could not compete with placentals. Placentals are
the most successful of the mammals. A notable
exception is the opossum.
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