Major Divisions of Animals
Invertebrates
To identify an animal as an invertebrate, it should have these
characteristics:
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Invertebrates have no backbone! Any animal that doesn't have a
spine is an invertebrate.
Invertebrates are cold-blooded. They cannot regulate their own body
temperature.
That's it! There are so many different types of invertebrates that
making a list of uniting characteristics is almost impossible.
Invertebrates are a very diverse group of species, including:
Insects
Spiders
Crustaceans (lobsters and crabs)
Worms
Mollusks (squids, snails and clams)
Coral
Sponges
Characteristics of Porifera:
1)No definite symmetry.
2)Body multicellular, few tissues, no organs.
3)Cells and tissues surround a water filled space but there is no true body
cavity.
4)All are sessile, (live attached to something as an adult).
5)Reproduce sexually or asexually, sexual reproduction can be either
gonochoristic or hermaphroditic.
6)Has no nervous system.
7)Has a distinct larval stage which is planktonic.
8)Lives in aquatic environments, mostly marine.
9)All are filter feeders.
10)Often have a skeleton of spicules
Mollusks
Mollusca is a taxonomic phylum that contains a diverse array of organisms
(referred to as 'mollusks'), and the taxonomic classes that include snails, sea
slugs, octopuses, squid, and bivalves such as clams, mussels and oysters.
From 50,000 to 200,000 species are estimated to belong to this phylum.
Imagine the obvious differences between an octopus and a clam, and you'll
get an idea of the diversity
Characteristics common to all mollusks:
They have a soft body
They have a usually distinguishable 'head' and 'foot' region. They use their
muscular foot to move.
Some may have a hard covering, or exoskeleton.
They have a heart that pumps blood through their blood vessels, digestive
system, and a nervous system.
Classification:
Kingdom: Animalia
Phylum: Mollusca
Feeding: Many mollusks feed using a radula, which is basically a series of
teeth on a cartilage base. The radula can be used for complex tasks, from
grazing on marine algae or drilling a hole in another animal's shell.
Reproduction: Some mollusks have separate genders, with males and
females represented in the species. Others are hermaphroditic (reproductive
organs associated with both male and female).
Distribution: Mollusks may live in salt water, in fresh water, and even on
land.
http://marinelife.about.com/od/invertebrates/p/Mollusca-PhylumMollusca.htm
Echinoderms
There are 5 related classes in the phylum Echinodermata (the Latin name
means "spiny-skinned"). For a detailed list with all classifications click here:
Sea star or starfish (Asteroidea)
Brittle stars, basket stars, serpent stars (Ophiuroidea)
Sea urchins, heart urchins and sanddollars (Echinoidea)
Holothurians or sea cucumbers (Holothuroidea)
Feather stars and sea lilies (Crinoidea).
Characteristics of Echinoderms
Echinoderms are characterized by radial symmetry, several arms (5 or more,
mostly grouped 2 left - 1 middle - 2 right) radiating from a central body (=
pentamerous). The body actually consists of five equal segments, each
containing a duplicate set of various internal organs. They have no heart,
brain, nor eyes, but some brittle stars seem to have light sensitive parts on
their arms. Their mouth is situated on the underside and their anus on top
(except feather stars, sea cucumbers and some urchins).
Echinoderms have tentacle-like structures called tube feet with suction pads
situated at their extremities. These tube feet are hydraulically controlled by
a remarkable vascular system. This system supplies water through canals of
small muscular tubes to the tube feet (= ambulacral feet). As the tube feet
press against a moving object, water is withdrawn from them, resulting in a
suction effect. When water returns to the canals, suction is released. The
resulting locomotion is generally very slow.
Behavior of Echinoderms
Some echinoderms are carnivorous (for example starfish) others are detritus
foragers (for example some sea cucumbers) or planktonic feeders (for
example basket stars).
Reproduction is carried out by the release of sperm and eggs into the water.
Most species produce pelagic (= free floating) planktonic larvae which feed
on plankton. These larvae are bilaterally symmetrical, unlike their parents
(illustration of a larvae of a sea star below). When they settle to the bottom
they change to the typical echinoderm features.
Echinoderms can regenerate missing limbs, arms, spines - even intestines
(for example sea cucumbers). Some brittle stars and sea stars can
reproduce asexually by breaking a ray or arm or by deliberately splitting the
body in half. Each half then becomes a whole new animal.
Echinoderms are protected through their spiny skins and spines. But they
are still preyed upon by shells (like the triton shell), some fish (like the
trigger fish), crabs and shrimps and by other echinoderms like starfish which
are carnivorous. Many echinoderms only show themselves at night (=
nocturnal), therefore reducing the threat from the day time predators.
Echinoderms serve as hosts to a large variety of symbiotic organisms
including shrimps, crabs, worms, snails and even fishes.
http://www.starfish.ch/reef/echinoderms.html
Arthropods
Arthropods, members of the phylum Arthropoda, are a diverse group of
animals including insects, crustaceans, spiders, scorpions and centipedes.
However, the members of this phylum, despite their incredible diversity and
sheer numbers, share a number of important distinguishing characteristics.
Exoskeleton
Arthropods are invertebrates, which means their bodies do not have internal
bones for support. To compensate for this, they produce a hard exoskeleton
made of chitin, a mixture of lipids, carbohydrates and protein, which covers
and protects their bodies like a suit of armor. As arthropods grow, they must
shed or molt their exoskeletons. They first produce new, softer exoskeletons
underneath the old ones. Once their hardened, old coverings crack and shed,
they sport roomier, albeit soft, exoskeletons. Arthropods are incredibly
vulnerable during the molting process, and will often hide until their new
exoskeletons harden.
Segmented Bodies
Arthropods have bodies that are internally and externally segmented. The
number of segments depends on the individual species; millipedes, for
example, have more segments than lobsters.
Jointed Appendages
The name arthropod actually comes from the Greek “arthro,” meaning joint,
and “pod,” meaning foot. All arthropods have jointed limbs attached to their
hard exoskeletons that allow for flexibility and movement. The joints
generally bend in only one direction but allow for sufficient predatory and
defensive actions.
Bilateral Symmetry
An arthropod's body can be divided vertically into two mirror images. This is
called bilateral symmetry. An arthropod shares this symmetry with many
other animals such as fish, mice and even humans. Other animals such as
the jellyfish and sea star exhibit radial symmetry, while coral and sea
sponge are asymmetrical -- exhibiting no pattern at all.
Open Circulatory System
An arthropod has an open circulatory system. This means instead of a closed
circulatory system of interconnected veins and capillaries, an arthropod’s
blood is pumped through open spaces called sinuses in order to reach
tissues. An arthropod does, however, have a heart which pumps blood into
the hemocoel, the cavity where the organs are located, where it surrounds
the organs and tissues.
http://animals.pawnation.com/5-characteristics-arthropod-5177.html
Chordates
Animals in the phylum Chordata share four key features: a notochord, a
dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
https://www.boundless.com/biology/textbooks/boundless-biologytextbook/vertebrates-29/chordates-171/characteristics-of-chordata-66311884/
Reptiles
To identify an animal as a reptile, it should have each of these
characteristics:
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Reptiles have a backbone. They are vertebrates.
Reptiles are covered in scales.
Reptiles breathe with lungs.
Most reptiles lay eggs. Some reptiles, like the boa constrictor, give
birth to live young.
Almost all reptiles are cold-blooded. One of the exceptions is the
leatherback sea turtle, which can regulate its body temperature to
some degree.
Some common reptiles are the American alligator, garter snakes, sea
turtles and a monitor lizard.
Amphibians
To identify an animal as an amphibian, it should have each of these
characteristics:
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Amphibians have a backbone. They are vertebrates.
Amphibians are cold-blooded. They cannot regulate their own body
temperature.
Amphibians spend at least part of their lives in water and on land.
Amphibians do not have scales and their skin is permeable (molecules
and gases can pass through).
Amphibians have gills for at least part of their lives. Some species
have gills only as larvae, while others can have gills throughout their
lives.
Most amphibians go through metamorphosis.
Amphibians are frogs, toads, salamanders, caecilians and newts. Some
common amphibians are bullfrogs, American toads, mole salamanders
and hellbenders.
Birds
To identify an animal as a bird, it should have these characteristics:
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Feathers! All birds have feathers.
Birds have a backbone. They are vertebrates.
All birds are warm-blooded. They can regulate their body temperature.
Female birds lay eggs. Their young develop inside of the egg.
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Birds have wings, but not all birds use them to fly. Penguins and
ostriches are examples of birds that do not fly.
 Some common birds are blue jays, pigeons, eagles, vultures, mallards
and hummingbirds.
http://www.nwf.org/Wildlife/Wildlife-Library/Birds.aspx
Fish
Modern fishes are divided into three classes:
• Agnatha, the jawless fishes.
• Chondrichthyes, jawed fishes that possess skeletons made of cartilage;
and sharks, rays, skates and ratfishes.
• Osteichthyes, jawed fishes that have skeletons made of bone.
To identify an animal as a fish, it should have these characteristics:
 Fish live in water.
 Fish have a backbone. They are vertebrates.
 Fish breathe using gills. They absorb oxygen through the gills.
 Almost all fish are cold-blooded. ...
 Some fish have scales.
http://www.nwf.org/wildlife/wildlife-library/amphibians-reptiles-andfish.aspx
Mammals
To identify an animal as a mammal, it should have these characteristics:
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Mammals have a backbone. They are vertebrates.
All mammals are warm-blooded. They can regulate their body
temperature.
 Female mammals produce milk to nourish their young
 Almost all mammals give birth to live young (except for the platypus
and echidna)
 Mammals have hair.
 Some common mammals are rodents, deer, whales, bears, dogs,
elephants, bats, lions, monkeys and humans!
http://www.nwf.org/Wildlife/Wildlife-Library/Mammals.aspx