Vertebrates
Vertebrates
• All vertebrates belong to the phylum chordata
• They are often called chordates
• All vertebrates have a back bone (vertebra)
Characteristics of Chordates
• All chordate embryo’s have a notochord
• The notochord is a flexible rod that extends
through much of the length of the body
• In vertebrates the only remnant of the
notochord is found in the cartilagenous discs
of the backbone
Characteristics of Chordates
• In addition to the notochord all chordate
embryos share three other features
• All have a dorsal hollow nerve cord that will
eventually develop into the brain and spine
• All have pharyngeal slits these develop into
the organs of respiration, hearing or the
mouth in various species
• All chordates have a tail that extends beyond
the anus
Invertebrate Chordates
• In two species (Tunicates and Lancets) the
larval stage has all the characteristics of a
chordate, however they are invertebrates in
the adult stage
Tunicate
Lancet
General Characteristics of Vertebrates
• In addition to the skull and backbone
• All vertebrates have an endoskeleton that may
be composed of bone and cartilage (humans)
or entirely of cartilage (sharks)
• All vertebrates have a hinged jaw. In mammals
in unhinges in an up and down fashion. In
reptiles (snakes) it unhinges up and down as
well as left to right
Classes of Vertebrates
• Fish
• Amphibians
• Reptiles
• Birds
• Mammals
Classes of Vertebrates
• Fish
• Fish are divided into two groups
- Cartilagenous fish (Chondrichthyes) so named
because they have a flexible skeleton composed
entirely of cartilage - These include the sharks and
rays
Classes of Vertebrates
• Fish
• Fish are divided into two groups
- Cartilagenous fish (Chondrichthyes) so named
because they have a flexible skeleton composed
entirely of cartilag - These include the sharks and
rays
- Bony fish (Osteichthyes) so named because they
contain a true skeleton composed of hardened
calcium components – This includes all other fish
Fish Adaptations
• Lateral Line System – is a series of sensory organs
running along each side of the body that allows
the shark to detect minute changes in water
pressure indicating the presence of animals
swimming by
• Swim bladder (bony fish) is a gas filled sac that
enables a fish to control it density and therefore
its depth in the water. Bony fish can remain
motionless in water without sinking, sharks
cannot
• All fish have a two-chambered heart
Classes of Vertebrates
• Amphibians
• Amphibians include the frogs and
salamanders
• Amphibians are tetrapods – organisms with
four limbs
Classes of Vertebrates - Amphibians
• Characteristics
- Live part of their lifecycle in the water and
part on land
- The larval stage is generally spent in the
water and the adult form on land
- Larval amphibians have gills adults have
lungs
- The eggs of amphibians do not have shells
and will dry out if left on land
Classes of Vertebrates - Amphibians
• All amphibians have a three-chambered heart
(two atria and one ventricle) there is mixing of
oxygenated and deoxygenated blood. This is
why amphibians cannot maintain there body
temperature and are called cold-blooded
(ectotherms)
Classes of Vertebrates - Reptiles
• Reptiles were the first amniotes
• Amniotes (Reptiles, birds and Mammals) have
an amniotic egg, internal fertilization and
water tight skin
• Reptiles include snakes, turtles, tortoises,
lizards, alligators and crocodiles
Classes of Vertebrates - Reptiles
• Amniotic egg – The amniotic egg means that it is
water proof and has a shell. One membrane the
amnion develops from the embryo. The amnion
protects the embryo from drying out. Other
membranes allow for gas exchange and
cushioning.
• The amniotic eggs makes it possible for an
embryo to develop on land. It was a tremendous
evolutionary leap from amphibians
Classes of Vertebrates - Reptiles
• Internal fertilization – During internal
fertilization the male deposits sperm into the
female that swim toward the fallopian tubes
for fertilization. External fertilization which
can occur in water would be impossible on
land
Classes of Vertebrates - Reptiles
• Water-tight skin – Amniotes have a water tight
skin enriched with a waterproofing material
called keratin. This “keratiniztion” prevents
dehydration. Keratin is found in the scales of
reptiles, the feathers of birds, and in the hair,
nails and horns of mammals
Classes of Vertebrates - Reptiles
• There are about 6,500 classes of reptiles
• Reptiles began to evolve about 300 million
years ago, however the true age of reptile and
an explosion in diversity occurred about 55
million years ago.
American Alligator
Saltwater Crocodile
Classes of Vertebrates – Aves (Birds)
• Molecular and fossil evidence indicates that
dinosaurs, crocodiles and birds are very
closely related
Classes of Vertebrates – Aves (Birds)
• Birds are endothermic amniotes with special
adaptations for flight
• These adaptations include: Wing shape that
provides lift for flight, feathers for flight and
endothermy, and weight reducing features in
the bone and among their internal organs
(such as having only one ovary and not having
teeth)
Classes of Vertebrates – Aves (Birds)
• Like mammals, birds have a very efficient four
chambered heart with a two-loop circulation
Classes of Vertebrates – Aves (Birds)
• Gizzard- The gizzard is a muscular organ often
containing small stones that are used for
grinding seeds. Both crocodiles and alligators
have a gizzard. Fossil evidence shows that
some dinosaurs also had a gizzard
• Crop – The crop is a temporary storage site for
food before it continues onto the stomach
Classes of Vertebrates – Aves (Birds)
• Cloaca – Like amphibians and reptiles, birds
have a cloaca, the common opening for urine,
feces, sperm and eggs
The Bernoulli Principle and flight
Classes of Vertebrates – Mammalia
(Mammals)
• Mammals are endothermic animals that have
body hair, produce live young (with three
exceptions), have modified sweat glands that
produce milk, nurse their young, have seven
cervical vertebrae, have a solid lower jaw
bone, have three bones in the ear (hammer,
anvil, stirrup), have a diaphragm, and have
one primary artery (the aorta) leaving the
heart and bending to the left
Diversity Among Mammals
• All mammals are divided into three groups
• Monotremes – These are the egg laying
mammals they are represented by the platypus
and the echidnas. Monotremes have sloped
shoulders like reptiles and a cloaca. However,
they have hair, produce milk and nurse their
young and are therefore classified as mammals
• DNA evidence shows that monotremes are very
primitive and closely related to reptiles
Platypus
Short-beaked Echidna
Long-beaked Echidna
Diversity Among Mammals
• Marsupials – Marsupials also known as
pouched mammals. The embryo’s of
marsupials are born before they are fully
mature, with 12-16 days in most species. The
embryo’s finish their development in an
external pouch
Diversity Among Mammals
• Placental Mammals – In placental or eutherian
mammals the embryo completes its development
while protected within the mother’s uterus.
• Inside the uterus an organ called the placenta
provides the embryo with nutrition and oxygen
and removes waste
• The embryo is bathed in fluid called the amniotic
fluid (this is what leaks when a woman’s “water”
breaks
Diversity Among Mammals
• From our perspective the most important
group of mammals are the primates
• The primates include the new and old World
monkeys as well as the apes
• The apes include gibbons, orangutans,
chimpanzees, gorillas and man
• Humans and chimpanzees share 97% of the
same DNA
• That 3% makes all the difference!
The “Great Ape”
Family