Chordates and Their Vertebrate Classes

Notochord

A flexible rod that develops into cartilage discs in vertebrates.

Dorsal Hollow Nerve Cord

Becomes the brain and spinal cord.

Pharyngeal Gill Slits

May form gills, jaws, or ear structures.

Post-Anal Tail

Extends beyond the anus.

Endoskeleton

Skeleton inside the body.

Hinged Jaw

Present in most vertebrates.

Tetrapods

Four-limbed vertebrates.

Agnatha

Jawless fish (e.g., lamprey, hagfish).

Chondrichthyes

Cartilaginous fish (e.g., sharks, rays).

Osteichthyes

Bony fish (e.g., salmon, trout).

Operculum

Covers gills and pumps water over them.

Swim Bladder

Regulates buoyancy.

Two-Chambered Heart

Found in fish.

Double Life

Live on land but reproduce in water.

Three-Chambered Heart

Heart structure found in amphibians.

Moist, smooth skin

Facilitates gas exchange in amphibians.

Amniotic Eggs

Waterproof shell, embryo develops inside.

Internal Fertilization

Fertilization occurs inside the body.

Mostly 3-Chambered Heart

Heart structure in reptiles, except crocodilians (4 chambers).

Endothermic

Warm-blooded; regulate internal temperature.

Hollow Bones, Feathers, Wing Shape

Flight adaptations in birds.

Hard-shelled Eggs

Eggs with calcium carbonate shell.

Hair or Fur

Characteristic of mammals.

Mammary Glands

Produce milk in mammals.

Monotremes

Egg-laying mammals (e.g., platypus).

Marsupials

Pouch mammals (e.g., kangaroo).

Placentals

Develop in uterus with placenta.

Parental Care

Mammals care more for their young compared to fish.