We are all animals!
Life expresses itself in innumerable ways.
Basically, life forms can be divided in five great kingdoms:
bacteria, higher unicellular life, fungus, plant life
(or flora), and animal life (also called fauna). Fauna
includes all animals that exist, from the smallest to
the biggest, including humans!
There are many sorts of animals, and
over the course of history they have been classified
in several categories defined by certain characteristics.
Most of the animals we are familiar with and easily
recognize are mammals, birds, fishes, reptiles, amphibians,
crustaceans (or shellfish), mollusks and insects.
Most mammals are almost all fur-bearing and give birth
to fully developed babies.They are all nourished with
their mothers' milk and require maternal care and attention
in the early stages of their life. Most of them live
on land (humans, dogs, moose, etc.) but some have adapted
to sea life (seals and whales) and others have even
learned to fly (bats).
Birds are feather-bearing and lay eggs.
Most of them fly, but some have lost that ability to
do so (like chickens, wild turkeys, partridges and the
now extinct dodo...), and some have even adapted their
wings to function within a marine habitat (penguins).
Fishes are scale-bearing and also lay
eggs. They all live in either salt water or fresh water.
They don't breath air with lungs but rather extract
the oxygen in the water through gills. Some are big
(sharks, sturgeons...), some are small (herrings, goldfish...),
and some are funny looking (sea horses...), but they
are all fishes.
Reptiles are scale-bearing and again,
many lay eggs. They are generally land animals (lizards,
turtles) even if some don't have legs (snakes). Some
live most of their life in water (alligators, crocodiles)
while others live in the desert or the tropical forest.
Amphibians have smooth and moist skin
and they lay eggs without shells. They live in either
water or humid environments (frogs, toads, salamanders).
All of the animals from the preceeding
groups have one main, common characteristic: they are
vertebrates, which means they all have a spinal column.
Other animals in the categories below do not have a
Crustaceans, or shellfish, live in water,
with few exceptions, such as the wood louse. Their skeleton
is their skin, and this is why it is called an exoskeleton.
The exoskeleton is not made of bone but rather of chitin.
The most well-known representatives of crustaceans are
lobsters, crabs, and shrimps.
Mollusks have no skeleton (like squids
and octopuses). Many live in shells (like mussels, clams,
oysters, etc.) or have cartilage-like internal structures.
Most of them live in water, with the exception of land
Insects are small six-legged animals
with well over a million different species represented.
Insects are the most adaptable of all animals and we
find them on land, in water and flying through the air.
Many other animals belong to other less
known categories that have not been mentioned here.
For example, spiders and scorpions are arachnids, sea
urchins and sea stars are echinoderms, jellyfish and
anemones are cnidarians, andthe thousands of sorts of
worms and sponges come from many more different classes.
As you can see, the animals kingdom is incredibly numerous
and varied. Animals live all around us, on land, in
the sky, in the water, underground, and even on or inside
us, such as parasites like head lice or pinworms!