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 first animal with a backbone (fish) appeared about 450 million years ago.

The animal kingdom has many more species of invertebrates than vertebrates. About 11 phylum of invertebrates to 1 phylum with 3 subphylum of vertebrates.

Phylum Chordata…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

In most Chordates it will eventually become the spinal chord.

Notochord

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 Phylum Chordata is divided into 3 subphylum:into 3 subphylum:

1. Urochordata

2. Cephalochordata

3. Vertebrata

1. Urochordates…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.

Sea squirt larva

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.

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…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…Amphioxus…

5 – 6 inches in length

Brain located in the front – eel-like.

Filter feeder

They maintain their notochord throughout their entire life.

Also a filter feeder – considered a primitive trait because gill slits used for respiration as well as feeding.

They also keep their nerve chord which does not become the spinal chord.

3. Subphylum Vertebrata…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…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

3. Osteichthyes

4. Amphibia

5. Reptilia

6. Aves

7. Mammalia

Fish

Amphibians

Reptiles

Birds

Mammals

Agnatha is the jawless fish.

They have a mouth designed for sucking – parasite.

There are 2 species of jawless fish alive today- Hag Fish and Sea Lamprey.

Chondrichthyes...Chondrichthyes...

Called the cartilage fish – all members of this group have an endoskeleton made entirely of cartilage.

Members include sharks, skates, and rays.

Rays and skates are closely related to sharks.

Osteicthyes are the bony Osteicthyes are the bony fish.fish.

Unlike sharks, skates, and Unlike sharks, skates, and rays – the bony fish have a rays – the bony fish have a skeleton made of bone.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.

Amphibians include salamanders and sirens, frogs and toads, and the worm-like apoda.

Siren

Salamander

Toad

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.

There are three major groups of mammals:

1. Monotremes

2. Marsupials

3. Placental

Other mammalian characteristics include: hair and nursing of young.

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 duckbilled platypus.

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…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

That’s all

folks!Now start studying for the test!