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The study of the kingdom Animalia is called zoology.
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There are more than a million animal species
with new species being discovered every day.
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It is hard to answer the question “What is an
animal?” There are so many different types of animals, from worms to people, cows
to jellyfish, etc. Even though there are a lot of differences between different
animal species, there are some characteristics that are the same no matter what
member of Kingdom Animalia.
o
Movement:
Most animals are able to do some type of locomotion to obtain their food, but
in the case of animals that are fixed in their location; they move the
environment around them.
o
Support:
Small animals require less structure than larger animals, but nevertheless, all
animals have some sort of support system. Some have their support system on the
outside (exoskeleton), such as crabs, lobster, and cray fish, while
others have it on the inside (endoskeleton).
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| The cartilage of a squid |
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| Scorpion with its exoskeleton |
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| Armadillo with protective shell |
o Nutrition:
All members of Kingdom Animalia are heterotrophs, meaning they depend on other
organisms for their food. There are other kingdoms with heterotrophic members.
What sets Animalia apart? All members of this kingdom ingest à digest à absorb their food.
o
Excretion:
All animals eliminate the waste that their bodies produce.
o
Respiration:
Some animals only have respiration at a cellular level, but others exchange
CO2 for O2 directly with their environments. The means of
obtaining oxygen differs depending on the organism. For example, humans have
lungs to obtain oxygen from the air while fish have gills to obtain oxygen from
water.
o
Circulation:
This is the transport of materials throughout the animal. This helps feed and
maintain tissues and organs. If there is no circulation to tissues, they can
die or be damaged. Blood or a similar fluid is used to transport these materials
in either a closed or open system.
o
Response:
The ability to perceive and respond to stimuli in the environment. Except for
sponges, all multicellular organisms have nerve cells that make response to
their environment possible. Some possess brains that are capable of memory and
emotion.
o
Reproduction:
While some animals can reproduce asexually, sexual reproduction is a
characteristic of the animal kingdom. This involves the union of two gametes to
form a zygote. The fertilized zygote then goes through embryonic states
as it develops into an independent organism. Some animals have larval stages
(not like adult) as they mature.
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| Fly larva |
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| Embryonic stages of a human |
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