SBI3U - Unit 1 - Phylum Chordata and its Classes

Characteristics of chordata

A notochord, which typically becomes the brain and spinal chord, and a dorsal nerve chord

Notochord

A flexible, rod-shaped structure found in chordate animals; during vertebrate development it is replaced by the spine

Chordata classes

Agnatha, chondrichthyes, osteichthyes, amphibia, reptilia, aves, and mammalia

Agnatha

Fish without jaws that do not have paired fins, which use suction to hold onto food

Gnathostomata

Fish with paired fins and jaws

Chondrichthyes

Sharks and rays with a skeleton made of cartilage

Osteichthyes

Fish with skeletons made of bone, and also have swim bladders to rise and sink

Amphibia

Ectothermic vertebrates with moist skin that inhabit wet ecosystems

The class of the first tetrapods to live partially on land

Amphibians

Tetrapod

A vertebrate with two pairs of limbs; an amphibian, reptile, bird, or mammal

Gas exchange in amphibians

They use their moist skin

Orders of Amphibia

Anura (frogs and toads), and Urodela (salamanders)

Reptilia

Land-dwelling chordates that have scales and lay amniotic eggs

Orders of reptiles

Lizards and snakes, turtles, and crocodilians

Use of scales in reptiles

Keep moisture locked and prevent dehydration

Gas exchange in reptiles

Using their lungs

Fertilization in reptiles

Fertilization is internal, which creates an amniotic egg with several layers of membranes to prevent it from drying out

Temperature and reptilian offspring

The incubation temperature can determine the sex of the offspring

Ectothermic

The reliance on environmental heat for determining internal body temperature

Hearts of reptiles

Three-chambered

Aves

Endothermic, calcareous egg-laying vertebrates that have feathers, hollow bones, a toothless skull, and a compact body

Endothermic

The use of metabolic heat to maintain a high, constant body temperature

Relation of birds to dinosaurs

Related to at least one group of dinosaurs by nature of their wings and scales

Bodies of aves

Four-chambered hearts, high body temperatures, and unique respiratory systems that promote the one-way movement of air

Mammalia

Endothermic vertebrates with mammary glands in females, hair, hearts with four chambers, and highly developed brains

Mammary Gland

A mammalian gland that produces and secretes milk for nourishing and developing young

Monotremes

Egg-laying mammals

Marsupials

Pouched mammals that have a short gestation period

Placental Mammals

Mammals with a placenta

Placenta

An organ in the pregnant uterus that exchanges nutrients and oxygen between the mother and developing offspring