Phylum Chordata Unit
Objectives:
Student will…
•Understand the characteristics of animals with
backbones
•Know the 7 classes of vertebrates
MIF – Students will determine their own grade.
Approx. – 20 min.
WIF – Students will take notes and answer essay
questions in complete sentences. Approx. 20 min.
State of New Mexico Content
Standards…
Benchmark I – Understanding how survival of
species depends on biodiversity…
Performance standard 10 – Understand
variations among organisms…
Approximate time – 1.5 weeks
The animal kingdom is usually divided into 2
groups – 1) those that lack a backbone, the
invertebrates - and 2) those that have a
backbone, the vertebrates.
The first living organisms were invertebrates and
today they are considered more primitive.
The animal kingdom has many more species of
invertebrates than vertebrates. About 11 phylum of
invertebrates to 1 phylum with 3 subphylum of
vertebrates.
The first animal with a backbone (fish) appeared
about 450 million years ago.
Phylum Chordata…
All animals which have a backbone are
members of Phylum Chordata.
To be a chordate, you must have all 3 of these
characteristics:
1. Must have a notochord at some point.
Notochord – flexible, rod-like structure
made of cartilage which runs down the
back of an individual. In most, it is found
only in the embryonic stage and becomes
the backbone before birth.
2. Must have a dorsal, hollow, nerve chord at some point
in development.
Forms during embryonic
development when the
ectoderm pinches in.
Forms just above the
notochord
Notochord
In most Chordates it will eventually become the
spinal chord.
3. Must have gill slits at some point in development.
Forms in the pharynx region and is used for
respiration and filter feeding in some organisms.
In non-aquatic species, the gill slits disappear
before birth or hatching.
Some other Chordate characteristics that are
nonexclusive:
Bilateral symmetry
Muscle segmentation
True colon
Phylum Chordata is divided
into 3 subphylum:
1. Urochordata
2. Cephalochordata
3. Vertebrata
1. Urochordates…
About 2000 different
species, all are
marine and all are
filter feeders.
Sea squirt or
tunicates are sessile
as adults.
The Chordate characteristics are only present during
the larval stage of development when it is free
swimming and looks similar to a small tadpole.
The sea squirt larva has a
notochord which does not
change into a backbone and
gill slits that are used for both
respiration and filter feeding.
Sea squirt larva
The larva settles onto a rock and becomes sessile as
an adult loosing its notochord, gill slits, and brain.
The adult form is very different than the larval
stage.
2. Subphylum Cephalochordata…
The Cephalochordata is an intermediate
between the more primitive Urochordata
and the more advanced Vertebrata.
The word Cephalochordata means “chordate with a
head”
Approximately 200 species of Cephalochordata
All live in shallow water environments
The Amphioxus or lancelets is a good example of
Cephalochordata
Amphioxus…
5 – 6 inches in
length
Brain located
in the front –
eel-like.
Filter feeder
They maintain their notochord
throughout their entire life.
They also keep their nerve
chord which does not become
the spinal chord.
Also a filter feeder – considered
a primitive trait because gill
slits used for respiration as well
as feeding.
3. Subphylum Vertebrata…
All have bones that surround the spinal chord
which developed from the notochord.
Largest of the 3 Chordate subphylum with
over 40,000 species.
It is also the most advanced and complex
phylum of the animal kingdom.
All have an endoskeleton made of bone or
cartilage.
An endoskeleton is an internal skeleton.
Endoskeleton…
Purpose:
Protection – especially protects important body
structures such as brain (skull), spinal chord
(backbone), and heart & lungs (ribs).
Movement – allows attachment of muscles to
allow body movement.
Storage – allows body a place to keep in
reserve valuable minerals such as calcium
and phosphorous for future use.
All endoskeletons, whether fish or human, have a
similar plan.
Skull
Vertebral
Column &
Ribs
Axial skeleton
Pectoral
Girdle Pelvic
Girdle &
Limb Bones
Appendicular
skeleton
Axial skeleton
is in green while
the
appendicular
skeleton is in
yellow.
Other vertebrate characteristics…
Closed circulatory system
Ventral heart with specialized
chambers
Developed brain concentrated in the top
end of the animal
Subphylum Vertebrata is divided into 7
classes of still living organisms.
1. Agnatha
2. Chondrichthyes
Fish
3. Osteichthyes
4. Amphibia
Amphibians
5. Reptilia
Reptiles
6. Aves
Birds
7. Mammalia
Mammals
Agnatha is the jawless fish.
There are 2 species of jawless fish
alive today- Hag Fish and Sea
Lamprey.
They have a
mouth
designed for
sucking –
parasite.
Chondrichthyes...
Members include sharks, skates, and rays.
Called the cartilage fish – all members
of this group have an endoskeleton made
entirely of cartilage.
Rays and skates are
closely related to sharks.
Osteicthyes are the bony
fish.
Unlike sharks, skates, and
rays – the bony fish have a
skeleton made of bone.
Amphibians
Frog
Amphibians need to return to the water to
reproduce. Laying eggs in the water that hatch
into an aquatic larva stage called a tadpole.
Siren
Salamander
Toad
Apoda
Amphibians include salamanders and sirens,
frogs and toads, and the worm-like apoda.
Reptiles…
Unlike amphibians, reptiles do not need to
return to the water to reproduce.
The living groups of reptiles include the
crocodiles, snakes/lizards, turtles, and the
rare tuatara.
Crocs, alligators, and caimans all belong to
the same order.
Lizards and snakes belong to the same order.
Some lizards even look like
snakes…
The rare tuatara looks
like a lizard but it’s
not. It’s the only
member of a lost
group of reptiles that
live only in New
Zealand.
The tuatara has a 3rd vestigial eye in the center
of it’s forehead.
Turtles and
tortoises are the
fourth group of
reptiles.
A tortoise lives on
land…
While turtles live
mostly in the water…
Class Aves are the birds…
Birds are associated with two important
characteristics… feathers and flight.
Not all birds have
the power of
flight…
Mammals…
Like birds, mammals are warm blooded and also
like birds have a large number of orders and
families compared to the reptiles and amphibians.
Other mammalian characteristics include: hair
and nursing of young.
There are three major groups of mammals:
1. Monotremes
2. Marsupials
3. Placental
The duckbilled
platypus.
Monotremes are egg
laying mammals.
They are the most
primitive of all
mammals, being
almost a missing link
between reptiles and
mammals.
Monotremes still nurse their young
and have hair like other mammals
even though they lay eggs.
There are two species of monotremes
alive today.
The spiny anteater
Marsupials are more
advanced than the
monotremes. They have
live birth of young, but…
The young are born
premature and crawl into a
pouch where they will finish
their development.
Marsupials and monotremes are considered
more primitive than placental mammals. With
one exception they are found only in places that
are isolated from placental mammals –
Australia and New Zealand. In these places
they did not have to compete with the more
advanced placentals.
The one exception is the
opossum which live in the
Americas.
The placental mammals are the most advanced
animals on the planet. They can be found on …
Land….
Sky…
And Sea…
Evolutionary Trends…
Primitive
Advanced
(Urochordates
Mammals)
2 chamber heart
4 chamber heart
Cold blooded
Warm blooded
Egg laying
Live birth
Small or no cerebrum
Larger cerebrum
Now start studying for the test!