Childrens Illustrated Encyclopedia

24

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internal organs of

an invertebrate

a complicated invertebrate, such as

a prawn (right), does have internal

organs, but they are generally more

simple than those of a vertebrate.

Prawns are crustaceans and have

jointed legs like insects and spiders.

When a prawn sheds its skeleton,

even the delicate coverings of its

feelers and eyes are cast off.

A human

being is

one of

the larger

mammals.

vertebrates

fish, amphibians, reptiles, birds,

and mammals comprise vertebrate

animals. birds and mammals are

warm-blooded. their bodies generate

heat so they can stay active in cold

conditions. fish, reptiles, and

amphibians are cold-blooded,

and can regulate their body

temperature by sunbathing

or seeking shade.

Birds include

pelicans, eagles,

and gulls.

Mollusks include snails,

shellfish, and octopuses.

Cnidarians include

jellyfish, corals, and

Crustaceans include crabs, sea anemones.

lobsters, and barnacles.

Abdominal

muscles, part of

musculoskeletal system

Brain, control center

of body and part of

nervous system

Antenna

(large feeler)

Antennule

(small feeler)

Pincer on first

walking leg

One of five

pairs of jointed

walking legs

Pleopods

(swimmerets)

Uropod

(tail fan)

Intestine, part of

digestive system

Bladder, part of

excretory system

external skeletons

Many invertebrate animals, such as

insects and spiders, have an outer

skeleton. it forms an exoskeleton—a

tough outer casing around the body.

the exoskeleton has flexible joints,

and muscles pull on it from the

inside, so that the animal can move.

it also supports and protects the

internal organs. the exoskeleton is

hard, so it must be shed, or cast off,

as the animal grows larger. this

process is known as ecdysis.

Centipedes

Echinoderms include

starfish, sea urchins,

and sea cucumbers.

Millipedes

Annelid worms

include earthworms

and leeches.

Arachnids

include

spiders,

scorpions,

and mites.

Insects

include

beetles,

flies, and

fleas.

Nematode

worms include

roundworms

and hookworms.

The prawn is a crustacean, a relative

of shrimps, crabs, and lobsters.

invertebrates

some invertebrates, such as

snails, have fleshy bodies

protected by shells. others,

such as jellyfish, have soft,

unprotected bodies. insects

are the largest single group

of invertebrates. there are

more than one million

kinds of insects. the smallest

invertebrates are visible only

under a microscope. the

largest is the colossal squid,

with a total length of

65 ft (20 m).

Bryozoans include sea

mats and moss animals.

Sponges

Fish include

sharks, rays,

and salmon.

Reptiles include

tortoises,

crocodiles,

snakes, and

lizards.

Mammals include mice,

cats, and koalas.

Heart, part of

circulatory system

Amphibians

include

newts, frogs,

and toads.

Image-

forming eye

Flatworms include

tapeworms and flukes. Find out more

birds

frogs

and other amphibians

insects

Mammals

reptiles

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