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Fish
All fish are cold-blooded animals that live in the water.
They have backbones, fins, and gills.
Fish come in more varieties than any other group of
vertebrate animals. There are 32,000 different species
of fish. There are two major types of fish including
cartilaginous, and bony fish. Sharks are cartilaginous
fish and the blue marlin is a bony fish. Bony fishes have
a swim bladder, a gas-filled sac, that they can inflate or
deflate allowing them to float in the water even when
not swimming.
All fish have gills that allow them to breathe water. Just like we use our lungs to exchange oxygen for
carbon dioxide from the air, the gills of a fish perform a similar function from water. So fish still need
oxygen to live, they just get it from the water instead of the air.
Some fish eat plant life. Some fish, called predators, prey on other fish and animals. The shark is a
noted predator that hunts for prey.
The biggest, or heaviest, fish is the ocean sunfish which can weigh as much as 5,000 pounds.
The longest fish is the whale shark which has been known to grow to over 40 feet long.
The fastest fish is a sailfish which can swim as fast as 68 miles per hour.
The smallest fish is the dwarf goby at only 9 mm long.
There are some animals that live in the water and we may think of as fish, but really aren't classified
by scientists as fish. These include whales, dolphins, octopus, and jellyfish.
Amphibians
Amphibians lay their eggs in water, and the tadpole, or
newborn frog, is born and lives in water. It has a tail that
allows it to swim like a fish. It also has gills so that it can
breathe under water. As the tadpole grow into a frog, it
loses its gills and tail, and develops legs for moving on land.
Most amphibians can both walk and swim in water.
Depending on the species of amphibian, breathing can take
place in gills, lungs, the lining of the mouth, the skin, or some combination of these.
Like fish and reptiles, amphibians and cold-blooded. This means their bodies don't automatically
regulate their temperature. They must cool off and warm up by using their surroundings. In cold
climates, amphibians hibernate during the winter.
Adult amphibians are carnivores and predators. They eat a variety of food including spiders, beetles,
and worms. Some of them, like frogs, have long tongues with sticky ends that they flick out to catch
their prey.
The largest amphibian is the Chinese Giant Salamander. It can grow to 6 feet long and weigh 140
pounds. The largest frog is the Goliath Frog which can grow to 15 inches long (not counting the legs)
and weigh over 8 pounds.
The smallest amphibian is a frog called the paedophryne amauensis. It is also the world's smallest
vertebrate animal. It is about 0.3 inches long.
Reptiles
Reptiles are often called cold-blooded because they can't regulate
their own body temperature. Their body temperature depends on
the external temperature. They will lay in the sun to heat their body,
or hide in the ground, under a rock or in water to cool their body.
The majority of reptiles lay eggs to give birth to their young.
Crocodiles and alligators are large reptiles that spend much of their
time on land and in water. They can walk on land using their feet.
They can also use their long tail to swim in water. Crocodiles feed
on large animals they catch on land or in water. They have
powerful jaws and teeth to tear apart their prey.
Lizards are four legged animals with a long tail. Many lizards can
shed their tail to escape from predators. They can then grow a new
tail. Some lizards, such as the chameleon, can change colors to
blend into their environment. This camouflage helps to protect
them from predators.
Snakes don't have limbs. They move by slithering along the ground. Some snakes are poisonous, or
venomous.
Gecko, iguana, tortoise, turtle, and viper also belong to the class of reptiles.
Birds
There are over 8,000 species of birds. Birds have 3 major
differentiating characteristics: wings for flight, feathers, and a
beak rather than teeth.
Birds have adapted their vertebrate skeleton for flight. Their
bones and skull are very thin, making their bodies extremely
light.
To support flight also required other changes to their skeleton.
Obvious changes are the addition of wings.
Although an important characteristic of most birds is flying,
not all birds fly. Some birds that don't fly are penguins, kiwis,
and ostriches. Penguins actually spend a good portion of time
in the water where they are prolific swimmers. Ostriches on the
other hand are very fast runners. An ostrich can outrun a horse!
There are all sizes of birds. Hummingbirds are some of the
smallest birds, while ostriches are some of the biggest.
Birds also lay eggs, like reptiles, however they are warmblooded, like mammals.
A bird's respiratory system is also adapted to make it easier to breathe at high elevations, where air is
thinner.
Mammals
What makes an animal a mammal are several things.
First, they must have glands that give milk. This is to
feed their babies. Second, they are warm-blooded.
Third, all mammals have fur or hair. Humans are
mammals and so are dogs, whales, elephants, and
horses.
Mammals live in all sorts of environments including
the ocean, underground, and on land. Some mammals,
bats for example, can even fly.
Most mammals give birth to live young, whereas some of them are marsupials or egg laying.
Marsupials carry their young in a pouch (like the kangaroo, the koala, and the opossum) whereas egg
laying mammals laying eggs like birds or reptiles.
The largest mammal is the Blue Whale which lives in the ocean and can grow to over 80 feet long.
The largest land mammal is the elephant. The smallest mammal is the Kitty's hog-nosed bat. This bat
is 1.2 inches long and weighs less than 1/2 a pound.
Mammals have unique brains and are often very intelligent. Humans are the most intelligent. Other
intelligent mammals include the dolphin, the elephant, the chimpanzee, and the pig. That's right, pigs
are thought to be one of the smartest animals!
Mammals that eat meat are called carnivores. Carnivores include lions, tigers, seals, and the largest
carnivore mammal which is the polar bear. Mammals that eat only plants are called herbivores. Some
herbivores are cows, elephants, and giraffes. Mammals that eat both meat and plants are called
omnivores. Humans are omnivores.