Page 113 - Science Class 06

HUMAN SKELETAL SYSTEM

Human skeletal system consists of bones of

Bone is very hard material. It is made up the skull, the backbone, ribs and limbs.
of living cells, calcium phosphate (a The main func on of the skeletal system is to
mineral salt), and collagen (a protein). give a shape to the body and to support the
Car lage is more elas c and resilient than
body. Besides, it also protects vital internal
bone, but not so hard. Chalk or chi n is
organs like brain, lungs, heart, etc. The
the hard substance of which insect’s
skeletal system also helps in body movement.
exoskeleton are made.

Invertebrates
Invertebrates can be simply iden fied as

animals that don’t have a backbone. They
are found almost everywhere, from the
ho est deserts and the deepest water
bodies to the darkest caves and tallest
mountains.

To compensate for the lack of an internal
skeleton, most invertebrates have an
external skeleton that protects their so ,
inner body. This material is usually made
from chi n, a deriva ve of glucose.

Invertebrates cons tute more than 97 per-

cent of all species in the animal kingdom.
The number of invertebrates exceeds more
than 2 million species, with more being
found almost every other day.

Invertebrates are generally unicellular org-
anisms such as hydra, amoeba, parame-
cium, etc. Some mul cellular invertebrate
animals are earthworm, starfish, leech, etc.

Human Skeletal System

Some living organisms have an endo-
skeleton, some have an exoskeleton and
some have both. Let us see how an
Invertebrates endoskeleton differs from exoskeleton!

Science-6 113