Animals are multicellular, eukaryotic
organisms of the kingdom Animalia (also
called Metazoa). The animal kingdom
emerged as a clade within Apoikozoa as
the sister group to the
choanoflagellates. Animals are motile,
meaning they can move spontaneously and
independently a few point their particular
lives. Themselves plan eventually becomes
fixed which they develop, while many
undergo a process of metamorphosis later
in their lives. All animals are
heterotrophs: they should ingest other
organisms or their products for
sustenance.
Most known animal phyla appeared the actual world
fossil record as marine species during
the Cambrian explosion, about 542 million
years your past. Animals can be divided broadly
into vertebrates and invertebrates.
Vertebrates possess a backbone or spine
(vertebral column), and make up less
than 5 % of all described animal
species. Consist of fish, amphibians,
reptiles, birds and mammals. The
remaining animals are the invertebrates,
which lack a vertebrae. These include
molluscs (clams, oysters, octopuses,
squid, snails); arthropods (millipedes,
centipedes, insects, spiders, scorpions,
crabs, lobsters, shrimp); annelids
(earthworms, leeches), nematodes
(filarial worms, hookworms), flatworms
(tapeworms, liver flukes), cnidarians
(jellyfish, sea anemones, corals),
ctenophores (comb jellies), and sponges.
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