Dictionary of Meaning
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Animal
*** Shopping-Tip: Animal
{{redirect|Animalia|the book by Graeme Base|
Animalia (book)}}{{otheruses}}
{{Taxobox
| color = pink
| name = Animal
| image = Sea nettles.jpg
| image_width = 250px
| image_caption =
Sea nettles, ''Chrysaora quinquecirrha''
| domain =
Eukaryote Eukaryota
| regnum = '''Animalia'''
| regnum_authority =
Carolus Linnaeus Linnaeus, 1758
| subdivision_ranks = Phyla
| subdivision =
*
Sponge Porifera (sponges)
*
Ctenophora (comb jellies)
*
Cnidaria (coral, jellyfish, anemones)
*
Trichoplax Placozoa (trichoplax)
*'''''Subregnum
Bilateria''''' (
symmetry (biology) bilateral symmetry)
**
Acoelomorpha (basal)
**
Orthonectida (parasitic to flatworms, echinoderms, etc.)
**
Rhombozoa (dicyemids)
**
Myxozoa (slime animals)
**'''Superphylum
Deuterostome Deuterostomia''' (blastopore becomes anus)
***
Chordate Chordata (vertebrates, etc.)
***
Hemichordata (acorn worms)
***
Echinodermata (starfish, urchins)
***
Chaetognatha (
arrow worms and
Pterobranchia)
**'''Superphylum
Ecdysozoa''' (shed exoskeleton)
***
Kinorhyncha (mud dragons)
***
Loricifera
***
Priapulida (priapulid worms)
***
Nematoda (roundworms)
***
Nematomorpha (horsehair worms)
***
Onychophora (velvet worms)
***
Tardigrada (water bears)
***
Arthropoda (insects, etc.)
**'''Superphylum
Platyzoa'''
***
Platyhelminthes (flatworms)
***
Gastrotricha (gastrotrichs)
***
Rotifera (rotifers)
***
Acanthocephala (acanthocephalans)
***
Gnathostomulida (jaw worms)
***
Micrognathozoa (limnognathia)
***
Cycliophora (pandora)
**'''Superphylum
Lophotrochozoa''' (trochophore larvae / lophophores)
***
Sipuncula (peanut worms)
***
Nemertea (ribbon worms)
***
Phoronida (horseshoe worms)
***
Bryozoa (moss animals)
***
Entoprocta (goblet worms)
***
Brachiopoda (brachipods)
***
Mollusca (mollusks)
***
Annelida (segmented worms)
}}
'''Animals''' are a major group of
organisms, classified as the
kingdom (biology) kingdom '''Animalia''' or '''Metazoa'''. In general they are
multicellular multicellular, capable of locomotion and responsive to their environment, and feed by consuming other organisms. Their body plan becomes fixed as they develop, usually early on in their
ontogeny development as
embryos, although some undergo a process of
metamorphosis (biology) metamorphosis later on.
The word "animal" comes from the
Latin word ''animal'', of which ''animalia'' is the plural, and ultimately from ''anima'', meaning vital breath or soul.
Characteristics
Animals have several characteristics that set them apart from other living things. Animals are
eukaryote eukaryotic and
multicellular, which separates them from
bacteria and most
protists. They are
heterotrophic, generally digesting food in an internal chamber, which separates them from
plants and
algae. They are also distinguished from plants, algae, and
fungus fungi by lacking
cell walls.
Structure
With a few exceptions, most notably the
sponges (Phylum Porifera), animals have bodies differentiated into separate
biological tissue tissues. These include
muscles, which are able to contract and control locomotion, and a
nervous system, which sends and processes signals. There is also typically an internal
digestion digestive chamber, with one or two openings. Animals with this sort of organization are called metazoans, or
eumetazoans when the former is used for animals in general.
All animals have
eukaryotic cells, surrounded by a characteristic extracellular matrix composed of
collagen and elastic
glycoproteins. This may be calcified to form structures like
shells,
bones, and
spicules. During development it forms a relatively flexible framework upon which cells can move about and be reorganized, making complex structures possible. In contrast, other multicellular organisms like plants and fungi have cells held in place by cell walls, and so develop by progressive growth. Also, unique to animal cells are the following intercellular junctions:
tight junctions,
gap junctions, and
desmosomes.
Reproduction and development
Nearly all animals undergo some form of
sexual reproduction. Adults are
diploid or occasionally
polyploid. They have a few specialized reproductive cells, which undergo
meiosis to produce smaller motile
spermatozoon spermatozoa or larger non-motile
ovum ova. These fuse to form
zygotes, which develop into new individuals.
Many animals are also capable of
asexual reproduction. This may take place through
parthenogenesis, where fertile eggs are produced without mating, or in some cases through fragmentation.
A
zygote initially develops into a hollow sphere, called a
blastula, which undergoes rearrangement and differentiation. In sponges, blastula larvae swim to a new location and develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement. It first
invagination invaginates to form a
gastrula with a digestive chamber, and two separate
germ layers - an external ectoderm and an internal endoderm. In most cases, a mesoderm also develops between them. These germ layers then differentiate to form tissues and organs.
Animals grow by indirectly using the energy of
sunlight. Plants use this
energy to turn air into simple
sugars using a process known as
photosynthesis. These sugars are then used as the building blocks which allow the plant to grow. When animals eat these plants (or eat other animals which have eaten plants), the sugars produced by the plant are used by the animal. They are either used directly to help the animal grow, or broken down, releasing stored solar energy, and giving the animal the energy required for motion. This process is known as
glycolysis.
Origin and fossil record
Animals are generally considered to have evolved from
flagellate protozoa. Their closest living relatives are the
choanoflagellates, collared flagellates that have the same structure as certain sponge cells do. Molecular studies place them in a supergroup called the
opisthokonts, which also include the
fungus fungi and a few small parasitic
protists. The name comes from the posterior location of the
flagellum in motile cells, such as most animal spermatozoa, whereas other
eukaryotes tend to have anterior flagella.
The first fossils that might represent animals appear towards the end of the
Precambrian, around 600 million years ago, and are known as the
Vendian biota. These are difficult to relate to later fossils, however. Some may represent precursors of modern phyla, but they may be separate groups, and it is possible they are not really animals at all. Aside from them, most known animal phyla make a more or less simultaneous appearance during the
Cambrian period, about 570 million years ago. It is still disputed whether this event, called the
Cambrian explosion, represents a rapid divergence between different groups or a change in conditions that made fossilization possible.
Groups of animals
Image:Elephant-ear-sponge.jpg thumb|left|Orange [[elephant ear sponge, ''Agelas clathrodes'', in foreground. Two corals in the background: a
sea fan, ''Iciligorgia schrammi'', and a
sea rod, ''Plexaurella nutans''.]]
The sponges (
Porifera) diverged from other animals early. As mentioned, they lack the complex organization found in most other phyla. Their cells are differentiated, but not organized into distinct tissues. Sponges are sessile and typically feed by drawing in water through
pores.
Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum.
Image:Brain_coral.jpg thumb|right|[[Brain coral, ''Diploria labyrinthiformis'']]
Among the eumetazoan phyla, two are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus. These are the
Cnidaria, which include
sea anemones,
corals, and
jellyfish, and the
Ctenophora or comb jellies. Both have distinct tissues, but they are not organized into
organ (anatomy) organs. There are only two main germ layers, the ectoderm and endoderm, with only scattered cells between them. As such, these animals are sometimes called
diploblastic. The tiny phylum
Placozoa is similar, but individuals do not have a permanent digestive chamber.
The remaining animals form a monophyletic group called the
Bilateria. For the most part, they are bilaterally symmetric, and often have a specialized head with feeding and sensory organs. The body is
triploblastic, i.e. all three germ layers are well-developed, and tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is also an internal body cavity called a coelom or pseudocoelom. There are exceptions to each of these characteristics, however - for instance adult
echinoderms are radially symmetric, and certain parasitic worms have extremely simplified body structures.
Image:Common_clownfish.jpg thumb|right|[[Ocellaris Clownfish, ''Amphiprion ocellaris'' in a
sea anemone.]]
Genetic studies have considerably changed our understanding of the relationships within the Bilateria. Most appear to belong to four major lineages:
#
Deuterostomes
#
Ecdysozoa
#
Platyzoa
#
Lophotrochozoa
In addition to these, there are a few small groups of bilaterians with relatively similar structure that appear to have diverged before these major groups. These include the
Acoelomorpha,
Rhombozoa, and
Orthonectida. The
Myxozoa, single-celled parasites that were originally considered Protozoa, are now believed to have developed from the Bilateria as well.
Image:Magellanic-penguin02.jpg thumb|left|[[Magellanic Penguin, ''Spheniscus magellanicus'']]
Deuterostomes
Deuterostomes differ from the other Bilateria, called
protostomes, in several ways. In both cases there is a complete digestive tract. However, in protostomes the initial opening (the
archenteron) develops into the mouth, and an anus forms separately. In deuterostomes this is reversed. In most protostomes cells simply fill in the interior of the gastrula to form the mesoderm, called schizocoelous development, but in deuterostomes it forms through
invagination of the endoderm, called enterocoelic pouching. Deuterostomes also have a dorsal, rather than a ventral, nerve chord and their embryos undergo different cleavage.
All this suggests the deuterostomes and protostomes are separate, monophyletic lineages. The main phyla of deuterostomes are the
Echinodermata and
Chordate Chordata. The former are radially symmetric and exclusively marine, such as
sea stars,
sea urchins, and
sea cucumbers. The latter are dominated by the
vertebrates, animals with backbones. These include
fish,
amphibians,
reptiles,
birds, and
mammals.
In addition to these, the deuterostomes also include the
Hemichordata or acorn worms. Although they are not especially prominent today, the important fossil
graptolites may belong to this group. The
Chaetognatha or arrow worms may also be deuterostomes, but this is less certain.
Ecdysozoa
Image:Sympetrum flaveolum - side (aka).jpg thumb|[[Yellow-winged Darter, ''Sympetrum flaveolum'']]
The
Ecdysozoa are protostomes, named after the common trait of growth by moulting or
ecdysis. The largest animal phylum belongs here, the
Arthropoda, including
insects,
spiders,
crabs, and their kin. All these organisms have a body divided into repeating segments, typically with paired appendages. Two smaller phyla, the
Onychophora and
Tardigrada, are close relatives of the arthropods and share these traits.
Image:roundworm.jpg thumb|left|[[Roundworm]]
The ecdysozoans also include the
Nematoda or roundworms, the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the
Nematomorpha or horsehair worms, which are visible to the unaided eye, and the
Kinorhyncha,
Priapulida, and
Loricifera, which are all microscopic. These groups have a reduced coelom, called a pseudocoelom.
The remaining two groups of protostomes are sometimes grouped together as the Spiralia, since in both embryos develop with spiral cleavage.
Image:Bedford's Flatworm.jpg thumb|left|[[Bedford's Flatworm, ''Pseudobiceros bedfordi'']]
Platyzoa
The
Platyzoa include the phylum
Platyhelminthes, the flatworms. These were originally considered some of the most primitive Bilateria, but it now appears they developed from more complex ancestors.
Image:Rotifer.jpg thumb|right|A [[rotifer, probably ''Philodina''.]]
A number of parasites are included in this group, such as the
flukes and
tapeworms. Flatworms lack a coelom, as do their closest relatives, the microscopic
Gastrotricha.
The other platyzoan phyla are microscopic and pseudocoelomate. The most prominent are the
Rotifera or rotifers, which are common in aqueous environments. They also include the
Acanthocephala or spiny-headed worms, the
Gnathostomulida,
Micrognathozoa, and possibly the
Cycliophora. These groups share the presence of complex jaws, from which they are called the
Gnathifera.
Lophotrochozoa
Image:Reef2063.jpg thumb|[[Big blue octopus, ''Octopus cyanea'']]
The
Lophotrochozoa include two of the most successful animal phyla, the
Mollusca and
Annelida. The former includes animals such as
snails,
clams, and
squids, and the latter comprises the segmented worms, such as
earthworms and
leeches. These two groups have long been considered close relatives because of the common presence of
trochophore larvae, but the annelids were considered closer to the arthropods, because they are both segmented. Now this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla.
The Lophotrochozoa also include the
Nemertea or ribbon worms, the
Sipuncula, and several phyla that have a fan of cilia around the mouth, called a
lophophore. These were traditionally grouped together as the lophophorates, but it now appears they are
paraphyletic, some closer to the Nemertea and some to the Mollusca and Annelida. They include the
Brachiopoda or lamp shells, which are prominent in the fossil record, the
Entoprocta, the
Phoronida, and possibly the
Bryozoa or moss animals.
History of classification
Image:Caerulea3 crop.jpg thumb|left|[[White's Tree Frog, ''Litoria caerulea''.]]
Image:Rød ræv (Vulpes vulpes).jpg thumb|[[Red fox, ''''Vulpes vulpes''.]]
Aristotle divided the living world between animals and
plants, and this was followed by
Carolus Linnaeus in the first hierarchical classification. Since then biologists have begun emphasizing evolutionary relationships, and so these groups have been restricted somewhat. For instance, microscopic
protozoa were originally considered animals because they move, but are now treated separately.
In
Carolus Linnaeus Linnaeus' original scheme, the animals were one of three kingdoms, divided into the classes of
Vermes,
Insecta,
Fish Pisces,
Amphibia,
bird Aves, and
Mammalia. Since then the last four have all been subsumed into a single phylum, the
chordate Chordata, whereas the various other forms have been separated out. The above lists represent our current understanding of the group, though there is some variation from source to source.
Usage of the word ''animal''
In everyday usage ''animal'' refers to any member of the
animal kingdom that is not a
human being, and sometimes excludes
insects (although including such arthropods as crabs). The use of the word ''animal'' in law typically reflects the common pre-scientific use of the word, roughly equivalent to what modern biology would classify as ''nonhuman mammal. '' For example,
wildlife laws commonly use phrases such as "animals, birds and fish."
Examples
{{see also|List of animal names}}
Some well-known types of animals, listed by their common names:
{{col-begin}}
{{col-5}}
*
aardvark
*
afghan hound
*
albatross
*
alligator
*
alpaca
*
anaconda
*
angelfish
*
anglerfish
*
ant
*
antlion
*
anteater
*
antelope
*
ape
*
aphid
*
armadillo
*
arrow crab
*
asp
*
donkey ass
*
baboon
*
badger (animal) badger
*
bald eagle
*
bandicoot
*
barnacle
*
common Basilisk basilisk
*
barracuda
*
bass (fish) bass
*
basset hound
*
bat
*
bear
*
beaver
*
bed bug
*
bee
*
beetle
*
bird
*
bison
*
blackbird (animal) blackbird
*
black panther
*
black widow
*
blue jay
*
blue whale
*
boa
*
bobcat
*
bobolink
*
booby
*
Box jellyfish
*
Boston Terrier boston terrier
*
bovid
*
bison buffalo
*
bug
*
bulldog
*
Bull Terrier bull terrier
*
butterfly
*
buzzard
*
camel
*
canid
*
cape buffalo
*
cardinal (bird)
*
caribou
*
carp
*
cat
*
caterpillar
*
catfish
*
centipede
*
cephalopod
*
chameleon
*
cheetah
*
chickadee
*
chicken
*
chihuahua (dog) chihuahua
*
chimpanzee
*
chinchilla
*
chipmunk
*
clam
*
clownfish
*
cobra (snake) cobra
*
cockroach
*
cod
*
collie
*
condor
*
constrictor
*
coral
*
cougar
*
coyote
{{col-5}}
*
cattle cow
*
crab
*
crane (bird) crane
*
crane fly
*
crawdad
*
crayfish
*
cricket (insect) cricket
*
crocodile
*
crow
*
cuckoo
*
daddy longlegs
*
damselfly
*
deer
*
dingo
*
dinosaur
*
dog
*
dolphin
*
donkey
*
dormouse
*
dove
*
dragonfly
*
duck
*
dung beetle
*
eagle
*
earthworm
*
earwig
*
eel
*
egret
*
elephant
*
Elephant Seal
*
Red Deer elk
*
emu
*
English Pointer english pointer
*
English Setter english setter
*
ermine
*
falcon
*
ferret
*
finch
*
firefly
*
fish
*
flamingo
*
flea
*
fly
*
flyingfish
*
fowl
*
fox
*
frog
*
fruit bat
*
gazelle
*
gecko
*
gerbil
*
German Shepherd Dog german shepherd
*
giant panda
*
giant squid
*
gibbon
*
gila monster
*
guanaco
*
guineafowl
*
giraffe
*
goat
*
golden retriever
*
goldfinch
*
goldfish
*
goose
*
gopher
*
gorilla
*
grasshopper
*
great blue heron
*
great dane
*
great white shark
*
greyhound
*
grizzly bear
*
grouse
*
guinea pig
*
gull
*
guppy
*
haddock
*
halibut
*
hammerhead shark
*
hamster
*
hare
*
harrier (bird) harrier
*
hawk
{{col-5}}
*
hedgehog
*
hermit crab
*
heron
*
herring
*
hippopotamus
*
hookworm
*
hornet
*
horse
*
hound
*
human
*
hummingbird
*
humpback whale
*
husky
*
hyena
*
iguana
*
impala
*
insect
*
Irish Setter irish setter
*
Irish Wolfhound irish wolfhound
*
Irukandji jellyfish
*
jackal
*
jaguar
*
jay
*
jellyfish
*
kangaroo
*
kangaroo mouse
*
kangaroo rat
*
kingfisher
*
kite (bird) kite
*
kiwi
*
koala
*
koi
*
komodo dragon
*
krill
*
labrador retriever
*
ladybug
*
lamprey
*
lark
*
leech
*
lemming
*
lemur
*
leopard
*
leopon
*
liger
*
lion
*
lizard
*
llama
*
lobster
*
locust
*
loon
*
louse
*
lungfish
*
lynx
*
macaw
*
mackerel
*
magpie
*
mammal
*
manta ray
*
marlin
*
marmoset
*
marmot
*
marsupial
*
marten
*
mastiff
*
meadowlark
*
meerkat
*
mink
*
minnow
*
mite
*
mockingbird
*
mole
*
mollusk
*
mongoose
*
monitor lizard
*
monkey
*
moose
*
mosquito
*
moth
*
mountain goat
*
mouse
*
mule
*
muskox
*
mussel
{{col-5}}
*
narwhal
*
newt
*
nightingale
*
ocelot
*
octopus
*
Old English Sheepdog old english sheepdog
*
opossum
*
orangutan
*
orca
*
ostrich
*
otter
*
owl
*
ox
*
oyster
*
panda
*
panther
*
panthera hybrid
*
parakeet
*
parrot
*
parrotfish
*
partridge
*
peacock
*
peafowl
*
pekingese
*
pelican
*
penguin
*
perch
*
Peregrine Falcon peregrine falcon
*
persian (cat) persian cat
*
pheasant
*
pig
*
pigeon
*
pike (fish) pike
*
pilot whale
*
piranha
*
platypus
*
polar bear
*
poodle
*
porcupine
*
porpoise
*
portuguese man o' war
*
possum
*
prairie dog
*
prawn
*
praying mantis
*
primate
*
puffin
*
puma
*
python
*
quail
*
rabbit
*
raccoon
*
rainbow trout
*
rat
*
rattlesnake
*
raven
*
red panda
*
reindeer
*
rhinoceros
*
right whale
*
roadrunner
*
robin
*
rodent
*
rook (bird) rook
*
roundworm
*
sailfish
*
St. Bernard (dog) saint bernard
*
salamander
*
salmon
*
sawfish
*
scallop
*
scorpion
*
hippocampus (fish) seahorse
*
sea lion
*
sea slug
*
sea urchin
*
setter
*
shark
*
sheep
*
sheepdog
*
shrew
*
shrimp
*
siamese (cat) siamese cat
*
silkworm
{{col-5}}
*
silverfish
*
skink
*
skunk
*
sloth
*
slug
*
smelt
*
snail
*
snake
*
snipe
*
snow leopard
*
sockeye salmon
*
sole
*
spaniel
*
sperm whale
*
spider
*
spider monkey
*
spoonbill
*
squid
*
squirrel
*
starfish
*
Star-nosed Mole star-nosed mole
*
steelhead trout
*
stoat
*
stork
*
sturgeon
*
swallow
*
swan
*
swift
*
swordfish
*
swordtail
*
tabby cat
*
tahr
*
takin
*
tapeworm
*
tapir
*
tarantula
*
tasmanian devil
*
termite
*
tern
*
terrier
*
thrush
*
tiger
*
tiger shark
*
tigon
*
toad
*
tortoise
*
toucan
*
Toy Poodle toy poodle
*
trapdoor spider
*
tree frog
*
trout
*
tuna
*
turkey
*
turtle
*
tyrannosaurus
*
urial
*
vampire bat
*
viper
*
vole
*
vulture
*
wallaby
*
walrus
*
wasp
*
warbler
*
water buffalo
*
weasel
*
whale
*
whitefish
*
whooping crane
*
wild cat
*
wildebeest
*
wildfowl
*
wolf
*
wolverine
*
wombat
*
woodpecker
*
worm
*
wren
*
yak
*
zebra
{{col-end}}
References
*Klaus Nielsen. ''Animal Evolution: Interrelationships of the Living Phyla'' (2nd edition). Oxford Univ. Press, 2001.
*Knut Schmidt-Nielsen. ''Animal Physiology: Adaptation and Environment''. (5th edition). Cambridge Univ. Press, 1997.
External links
{{Sisterlinks|Animalia}}
{{wikispecies| Animalia}}
-
Tree of Life Project
-
ARKive - multimedia database of worldwide endangered/protected species and of UK common species
-
Sounds of the World's Animals - animal sounds in many languages
Category:Animals
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an:Animal
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zh-min-nan:TÅ?ng-buÌ?t
ca:Animal
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el:Ζώα
es:Animal
eo:Animalo
fr:Animal
fy:Dier
ga:AinmhÃ
he:בעלי ×—×™×™×?
hr:Životinje
ko:�물
io:Animalo
id:Hewan
ia:Animal
it:Animali
kw:Enyval
ku:Ajal
la:Animalia
lv:Dzīvnieki
lt:Gyvūnų karalystė
lb:Déiereräich
li:Diere
mk:Животни
ms:Haiwan
nah:Yolkatl
nl:Dieren (rijk)
nds:Beest
ja:動物
no:Dyr
pl:Zwierzęta
pt:Animalia
ru:Животные
scn:Armali
simple:Animal
sl:Živali
sr:Животиња
fi:Eläinkunta
sv:Djur
th:สัตว์
uk:Тварини
zh:动物
vi:Ä?á»™ng váºt
chy:Hova
*** Shopping-Tip: Animal
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