Ch 8 explains how humans and animals move. Students learn about the human skeleton, different types of joints, the role of muscles, and how animals like earthworms, snails, fish, snakes, and birds move.
The skeleton gives shape and support. Ball-and-socket joint (shoulder, hip) allows movement in all directions. Hinge joint (elbow, knee) allows movement in one direction. Pivotal joint (neck) allows rotation. Fixed joints (skull) allow no movement.
Earthworm: uses alternate contraction/expansion of body muscles with tiny bristles (setae). Snail: uses a muscular foot. Fish: uses fins and tail to push through water. Snake: curves body to push off the ground. Birds: fly using wings with lightweight hollow bones.
Download: https://ncert.nic.in/textbook/pdf/fesc108.pdf | Complete book: https://ncert.nic.in/textbook/pdf/fesc1ps.zip
Muscles are attached to bones by tendons. When muscles contract (shorten), they pull the bones and cause movement. Muscles work in pairs — when one contracts, the other relaxes. Without muscles, bones cannot move on their own.
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