Chapter 3

Phylum Chordata

At some point of their lives, all have a:- notochord

- hollow nerve cord- pharyngeal pouches- tail

Three groups of Chordates

• Lancelets• Tunicates • Vertebrates – largest group – has a backbone

No backbone

Vertebrates

• Backbone or vertebral column - Protects spine

- Support• Endoskeleton

-Support -Shape -grows with the organism

Groups of Chordates

• Eight Groups- Six are ectotherms

-Rely on environment for heat - “cold blooded”

- Two are endotherms - Maintain their body heat - “warm blooded”

FISH• Evolved 540 mya• Ectotherms• Water dwelling vertebrates• Scales (most)• Fins• Gills• Most do external fertilization

Jawless Fish• Most primitive• No scales, fins, bones or

jaw• Has skeleton made of

cartilage• Examples- hagfish and

lamprey

Cartilaginous Fish• Skeleton made of

cartilage• Tooth-like scales• No swim bladder• Sharks, skates, and

rays

Bony Fish

• Have a swim bladder -Gives the ability to float or sink• Color vision• Lateral line that senses movement

AMPHIBIANS• Evolved 350 mya• Ectotherms• Lungs• Breathe through skin• Term amphibian means “double life”• Live on land and water – soft eggs• Goes through metamorphosis• Ecological indicators

Caecilians• Legless amphibian• Lives in damp soil in

the tropics• Eats small

invertebrates• Thin moist skin• Small eyes under skin

but are blind

Salamander

• 390 known species• Eats small vertebrates• Long tail and four

small legs

How Frogs and Toads are Alike • 90% of all amphibians are frogs and toads• Found all over the world• Highly adapted for life on land• Sticky tongues that are attached to the front of

the mouth instead of the back• Strong legs for jumping• Ears• Vocal cords

How Frogs and Toads are Different

frogs• Smooth skin• Moist skin• Lay eggs in bunches

toads• Bumpy skin• Dry skin• Lay eggs in strings

Frog Life Cycle

REPTILES• Thick, dry, water tight skin• Ectotherms• Lungs to breathe• Evolved 300 mya • Strong vertical legs • Most lay thick rubbery eggs. This allows them

to reproduce on land• Internal fertilization

Reptile eggs

• Shell - protects the egg• Albumen – provides water and protein• Amniotic sac - protects embryo• Yolk - provides food• Allantois – stores waste and passes oxygen

ter

Lizards • About 4,000 species• Live in deserts, jungle, forests and grasslands• Most eat small invertebrates and plants but

some are strictly herbivores• The tail of some lizards separate from the

body when the lizard is grabbed. The tail that is left behind wriggles, confusing the other animal.

Turtles and Tortoises

• 250 species• Slow and inflexible• Protective shell• Tortoises live on land and have bumpy shell• Turtles live on land and have smooth shells

Snakes

• About 1600 species• No legs• Scales on belly pull snake

forward• Carnivores with a good

sense of smell

Alligators and Crocodiles

• Eyes and nose on top of head so they can hide under water

• Alligators have a rounded snout, crocodiles have a narrow snout

Alligators and Crocodiles