Chordates (Chordata)

Our phylum

Chordates have a backbone1. Dorsal hallow nerve cord2. _________________: strong rod that separates digestive and nerve cord3. Pharyngeal slits: ______________________________________________4. Post anal tail (behind the anus)• Invertebrate chordates: (no backbone but do have major hallmarks of

chordates!)– _______________ (only have these structures in their larval stages)– ___________________: (another invertebrate chordate, have

segmented muscle structure)

Fish to JAWS (literally)

• Fish started without jaws– Agnathans/Lampreys are a group

of vertebrates that ________ ___________________________. Mud suckers and suspension feeders

• The Jaw allowed for a variety of prey– Chondrichthyes:

_______________ _____________ (sharks, rays and skates)• Use a ____________________

to detect changes in water pressure and nearby swimming creatures (predators or prey)

More on fish evolution

• Another kind of fish with a jaw is the ______________ (boney fish)– Have an operculum which

allows for gas exchange even when they aren’t moving

– Contain a ________________ which keeps them buoyant (lung like structures that fill with air but don’t exchange gases)

Amphibians lead a double life• Dependent on water for their eggs

to develop• Larva swim in water • _____________________________

____________________________________________________________________________

• After metamorphosis the adolescent crawls onto land

• Largest population during the Carboniferous period before reptiles or mammals

** Currently undergoing a rapid decline due to acid rain (high amount so carbon dioxide in the air)

Reptiles• Amniotic egg: like the seed,

__________________________________________________________________

• Scales that protect their bodies from water loss

• _____________________: don’t use metabolism to regulate body temp. (cold blooded)

• Some dinosaurs may have been endothermic (using metabolism for body temp.)

• Include– Lizards– Snakes (lost legs secondarily)– Turtles– Crocodiles– Alligators

How a reptile became a bird

• Derived from a group of small 2 legged dinosaurs

• _________________________________________________________________(Archaeopteryx)

• Archaeopteryx is not an ancestor but it give us info about what they would be like– Scales on feet, vertebral tail, scales

on claws, feathers on arms, webbed fingers

– Many birds died with the dinosaurs, those that survived went on to be modern birds

More on Birds• Every aspect of birds has been

evolved for flight… they “trimmed the fat”– Hallow feathers– ___________________– No teeth– ___________________

• Different styles of wings are excellent at different things, some are for soaring, some for quick maneuverability, Some to be able to stay still. – Some rare birds of course don’t fly (like

the ostrich!)• Endothermic!!!• 4 chambered heart

(___________________________)

Mammals come from reptiles too!

• Mammals diverged from reptiles long before even dinosaurs evolved!

• Independent 4 chambered heart• Lived a meager existence until the fall of

the dinosaurs opened up the availability for them to survive.

• ________________________________________________________________________________

• ______________________… have a placenta which bridges the gap between mother and child

• Marsupials are a kind of mammal that has a very short gestation then carries the young nursing them after they are born until they are able to live on their own.

Phylogeny of animals summary