the world is full of many different
types of animals some swim some fly some
breathe air and some breathe underwater
some have skeletons and others don't
to help us understand the differences
between the animals in our world
scientists classify or sort animals into
different groups that share important
characteristics the two largest groups
of animals are vertebrates and
invertebrates vertebrates are animals
that have spines or backbones
invertebrates are animals that do not
have backbones most of the animals in
the world are invertebrates some
examples of invertebrates are octopus
and squid insects arachnids starfish and
sea urchins jellyfish crabs and lobsters
clams and many more creatures on land
most invertebrates are fairly small but
in the water they may grow to much
larger sizes as the water will support
them even without a skeleton
vertebrates make up less than 5% of all
animal species on earth but if I asked
you to think of an animal you would
probably choose a vertebrate vertebrates
are divided into different classes or
groups several of these classes are
specific types of fish for example
jawless fish like lampreys and hagfish
and cartilaginous fish like sharks and
rays
for simplicity's sake these other
classes are usually lumped together with
bony fish and just called fish the four
remaining classes of vertebrates will
all be very familiar amphibians reptiles
birds and mammals let's look at the
characteristics that make an animal a
fish fish live in the water and they can
breathe underwater they use gills not
lungs to get oxygen from the water
around them fish have scales and fins
they are cold blooded which means that
they cannot control their own body
temperature which changes based on the
temperature of the environment around
them most fish also lay eggs
amphibians are a group of animals that
include frogs toads newts salamanders
and more amphibians like fish are
cold-blooded unlike fish amphibians can
live on land and in the water and have
smooth moist skin amphibians lay their
delicate jelly covered eggs in the water
when the eggs hatch the young may not
look much like their parents because
some amphibians must go through
metamorphosis or a big change to become
adults aside from some fish amphibians
are the only vertebrates that undergo
metamorphosis reptiles you might know
our turtles snakes crocodiles and
lizards like fish and amphibians
reptiles are cold-blooded unlike them
reptiles are air-breathing animals and
cannot breathe underwater even reptiles
that live in the water must come to the
surface to breathe you can tell if an
animal is a reptile instead of an
amphibian if it has dry scaly skin most
reptiles lay eggs but they are very
different from the eggs of amphibians or
fish their eggs are laid out of the
water and have a protective shell for
the most part reptile eggs have soft
leathery shells
birds are easy to recognize they are the
only type of animals in the world to
have feathers like reptiles birds can
only breathe air
all birds have two legs and all birds
also have wings but not all birds fly
unlike fish amphibians and reptiles
birds are warm-blooded that means that
they can maintain a constant body
temperature birds lay eggs but unlike
the eggs of reptiles birds eggs have
hard shells the last group of animals we
are going to talk about is mammals
mammals are the group of animals that
humans belong to like birds mammals are
warm-blooded and breathe air even
mammals that live in water must come to
the surface to breathe all mammals have
at least some fur or hair although some
have less than others almost all mammals
give birth to live young instead of
laying eggs and all mammals feed their
babies milk a fun fact about mammals is
that mammals are the only animals to
have ears that stick out the animal
kingdom is classified into many
different groups based on animal
characteristics to help us understand
the world around us saying an animal is
an invertebrate a vertebrate a fish
amphibian reptile bird or mammal tells
us many things about it that can help us
to understand its needs and behavior I
hope you enjoyed learning about animal
classification today goodbye until next
time
you