Page 99 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

It has four chambers – the upper two chambers are called the right and the left

atrium (plural atria) while the lower two chambers are called the right and the left
ventricles. Right atrium receives carbon

dioxide-rich via vena cava. Blood from
the right atrium enters the right ventricle,

which contracts and pumps the blood to

the lungs via pulmonary artery. On the
other hand, oxygen-rich blood from the

lungs returns to the left atrium from
pulmonary vein. From the left atrium,

blood enters the left ventricle. The left
ventricle contracts and pumps the blood to all the body parts via aorta. Hence, the
rhythmic contraction and expansion of various chambers of the heart maintains the

transport of oxygen to all parts of the body. The valves present between different
chambers of the heart ensure that the blood flows only in a particular direction. They

prevent the backflow of blood in the heart, thereby maintaining a healthy blood
circulation.
3. How does water move from roots to the leaves in plants?

Ans. Water moves from the roots to the leaves in plants through a process called
transpiration.

First, water is absorbed by tiny root hair from the soil. Then it travels up through the
plant with the help of a vascular tissue called xylem. Xylem acts like straws, helping
the water move upwards. As water evaporates from the leaves, it creates a pulling

force, which draws more water up from the roots. This continuous movement of
water provides the plant with the necessary hydration and nutrients it needs to stay
healthy & grow.

4. What will happen if there are no platelets in the blood?
Ans. Platelets are those components of the blood that play a crucial role in helping it
to clot. When we get a cut or injury, platelets rush to the site & form a mesh on

the wound to stop bleeding. Without platelets, the blood would not be able to clot
properly.

This means even small clots or injuries could lead to continuous bleeding, which can
be very dangerous. Additionally, without platelets, a person might be injured easily
because the blood vessels under the skin could break & bleed, leading to a large

injury. Moreover, there could be internal bleeding in organs, which is hard to detect
and can be life threatening. Therefore platelets are essential for stopping bleeding

and protecting our body from excessive blood loss.

99