Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The human skeleton is a framework of bones and cartilage that provides shape, support, and protection to internal organs. An adult human body has bones.
Ball and Socket Joint: Allows movement in all directions. Examples include the joint between the upper arm and the shoulder, and the hip joint.
Hinge Joint: Allows movement in only one plane (back and forth), similar to the hinges of a door. Examples include the elbow and the knee.
Pivot Joint: Where a cylindrical bone rotates in a ring. For example, the joint where our neck joins the head, allowing us to bend our head forward/backward and turn it left/right.
Fixed Joints: Joints where bones cannot move. Example: The joints between the bones of the skull (except the lower jaw).
Cartilage: A structure that is not as hard as bone and can be bent. It is found in the upper part of the ear and at the ends of bones at joints to reduce friction.
Muscle Movement: Muscles work in pairs. When one muscle contracts (becomes shorter, stiffer, and thicker), it pulls the bone. To move the bone in the opposite direction, the second muscle contracts while the first one relaxes. A muscle can only pull, it cannot push.
Gait of Animals: Different animals have different mechanisms for movement. For example, Earthworms use (bristles) and muscular expansion/contraction; Fish use a streamlined body and fins; Birds have hollow bones to reduce weight for flight.
📐Formulae
💡Examples
Problem 1:
Why can we move our upper arm in a circular motion but not our elbow?
Solution:
The shoulder and the elbow have different types of joints.
Explanation:
The shoulder contains a Ball and Socket Joint, which allows movement in all directions (360 degrees). However, the elbow contains a Hinge Joint, which only allows back-and-forth movement, similar to a door hinge.
Problem 2:
How does an earthworm move without having any bones?
Solution:
An earthworm moves using muscles and tiny hair-like bristles called .
Explanation:
The earthworm first extends the front part of its body while keeping the rear portion fixed to the ground. Then it fixes the front end and releases the rear end, shortening the body and pulling it forward. The help in getting a good grip on the ground.
Problem 3:
Identify the adaptation in birds that helps them fly.
Solution:
Hollow bones and modified forelimbs.
Explanation:
Birds have bones that are hollow and light, reducing the total body mass (). Their forelimbs are modified into wings, and strong breast muscles provide the force needed to flap the wings for flight.