Fish, Amphibians, and Reptiles

Objectives

• Explain how fish reproduce and develop
• Describe amphibian structure and function
• Outline reproduction and development of amphibians
• Describe reptile structure and function
• Describe the amniotic egg and reptile reproduction

Most fish are oviparous. Sharks are ovoviviparous.

Spawning increases the chances of fertilization taking place.

Mouth brooding is an exception.

Larva

• Attached to yolk sac
• Goes through metamorphosis

Amphibians

• First true tetrapods
• 1 cm to 1.5 m
• Skin contains keratin
• Ectothermic
• Three-chambered heart

Amphibians

• Gills as larvae; lungs as adults
• Oxygen absorbed through skin
• Skin kept moist with mucus

Digestive, excretory, and reproductive systems share cloaca.

Amphibian Reproduction

• No amniotic eggs so must lay eggs in water
• Lay a large number of eggs at a time
• Tadpole resembles a fish
• Larvae undergo metamorphosis

Reptiles

Reptile scales are made of keratin to prevent injury and water loss.

Reptiles

• Lungs more efficient than amphibians'
• Crocs and alligators have a diaphragm
• Ectotherms
• Three-chambered heart (crocs and alligators 4)

Reptile Reproduction

• Amniotic eggs (with yolk)
• NO larval stage