Vertebrates

Fishes  All fishes are ectotherms.  Ectotherms- animals with body temperatures dependent upon the temperature of their surroundings.  Fish have a two chambered heart and breath through gills.  Different types of fishes are grouped into three different classes, jawless fishes, cartilaginous fishes and bony fishes.

Fishes cont. Jawless Fishes  Types of jawless fishes are lampreys and hagfishes.  Jawless fish have endoskeletons made of cartilage like sharks and types of rays.

Fishes cont. Cartilaginous fishes  Types of cartilaginous fishes are sharks, skates and rays.  Evidence has proven that jaws were first evolved in this type of fish.  Cartilaginous fish have endoskeletons made of cartilage like jawless fish.  Cartilaginous fish have paired fins and a lateral line system that enables them to detect movement and vibrations in water.

Fishes cont. Bony Fishes  Most fishes belong to the bony fish class.  All bony fishes have a bony skeleton, gills, paired fins, flattened bony scales and a lateral line system.  Bony fishes breath by drawing in water into their mouth then passing it over the gills where gas exchange occurs.  They adjust their depth in the water by regulating the amount of gas that diffuses out of their blood into the swim bladder.

Amphibians  Amphibians are ectothermic with three chambered hearts, lungs and thin moist skin.  Most gas exchange is carried out through the skin not the lungs.  Adult amphibians live on land but rely on water for reproduction.  Almost all amphibians go through the process of metamorphosis.  Metamorphosis- which the young hatch into tadpoles, then gradually lose their tails and gills as they develop legs, lungs and other adult structures.  Amphibians can be classified into three orders Anura, Caudata and Apoda.

Amphibians cont.  Anura are considered to be frogs and toads.  Anuras have vocal cords that can produce wide range sounds.  Frogs have think, smooth, moist skin.  While toads have thick bumpy skin with poison glands.  Caudata are considered to be salamanders and newts.  Salamanders have long, slender bodies with a neck and tail.  Apoda are considered to be legless caecilians.  Caecilians have long, wormlike bodies with no legs.

Reptiles  Reptiles are ectotherms with dry, scaly skin and clawed toes.  Types of reptiles are snakes, lizards, turtles, crocodiles and alligators.  All reptiles have four legs that are positioned under the body except snakes.  Most reptiles have a three chambered heart except for a crocodile it has a four chambered heart.  The scaly skin of reptiles reduces the loss of moisture on land scales also prevent the skin from absorbing or releasing gas.  Reptiles are dependent on lungs for the essential gas exchange.  Reptiles lay amniotic eggs to reproduce.

Birds  Birds are the only class of animals to have feathers.  Feathers are lightweight, modified scales, that help insulate birds and enable them to fly.  They have wings which are modified forelimbs.  Similar to reptiles birds have scales on their feet and clawed toes.  Unlike reptiles they are endotherms.  Endotherms- animals that maintain a constant body temperature.  Endotherms must eat frequently to provide energy needed for producing heat.

Birds cont.  Birds have thin hallow bones with cross braces that provide support for strong flight muscles while reducing their body weight.  Birds have a four chambered heart.  Birds have a unique respiratory system which oxygen is available through exhalation and inhalation.  Like reptiles birds lay amniotic eggs but unlike reptiles birds incubate their eggs in nests. The nest keeps the egg warm till the young birds hatch.

Mammals  Mammals are endotherms.  Mammals are named after their mammary glands, which produces milk to feed their young.  Most mammals have hair which is used to help insulate their bodies and sweat glands that help keep them cool.  Mammals need a high energy level for maintaining body temperature and high speeds of locomotion.  Mammals have a efficient four chambered heart and muscular diaphragm beneath the lungs to help deliver oxygen for their activities.

Mammals cont.  All mammals have internal fertilization and the young begin development inside the mothers uterus.  Mammals are divided into three large groups monotremes, marsupials and placental.  Monotremes are mammals that lay eggs.  Marsupials are mammals which the young complete a second stage of development after birth in a pouch made of skin and hair on the outside of the mothers body.  Placental mammals carry their young inside the uterus until development is nearly complete.  Mammals can also be classified by their teeth, how many they have and type.  Types of teeth are incisors, canines, molars and premolars.  Incisors are used to cut food.  Canines are long pointed teeth used to stab or hold food.  Molars or premolars have flat surfaces with ridges and are used to rind and chew food.