CBSE Class 7 Science Advanced Biology Transportation in Plants and Animals Short Answer Questions Set 01

Short Answer Questions

Question 1. What is transpiration? Name the cells that regulate transpiration.
Answer:
Transpiration is the loss of water in the form of water vapour through the stomata. Stomata are small openings on the leaves, and each is enclosed by two kidney-shaped cells called guard cells.
The guard cells open and close the stomata, and in this way control the rate of transpiration.
In simple words: Water vapour leaves the leaf through stomata, and guard cells control how much.

Teacher's Note:
1. Name both parts: the process (transpiration) and the controlling cells (guard cells).
2. The guard cells swell to open the pore and shrink to close it.

Teacher's Note:
1. Write in a two-column table to score full marks.
2. Always include the direction of flow and the elements.

Teacher's Note:
1. The exceptions (pulmonary artery and pulmonary vein) are often asked, so mention them.
2. Valves are present only in veins.

Question 4. What is blood and what are the various components of blood?
Answer:
Blood is a red-coloured fluid that flows through the body and carries materials from one place to another. It is a connective tissue.
Blood has two main parts: plasma and blood cells.
Plasma: the straw-coloured liquid part of blood.
Red blood cells (RBCs): biconcave and contain haemoglobin, the red pigment that carries oxygen.
White blood cells (WBCs): of various shapes and mainly involved in defence against germs.
Platelets: help in clotting of blood.
In simple words: Blood is plasma with three types of cells floating in it.

Teacher's Note:
1. Remember the three blood cells as RBC, WBC and platelets.
2. Give one function for each component to complete the answer.

Question 5. 'All arteries do not carry oxygenated blood'. Justify the statement.
Answer:
Normally the arteries carry oxygenated (pure) blood from the heart to the various body parts.
The pulmonary artery, however, carries impure (deoxygenated) blood from the heart to the lungs.
Therefore it is true that not all arteries carry oxygenated blood.
In simple words: The pulmonary artery is an artery that carries impure blood.

Teacher's Note:
1. Always name the exception: pulmonary artery.
2. The same idea applies in reverse to the pulmonary vein.

Question 6. What is pulse rate? What does low heart beat indicates?
Answer:
Pulse rate is the heart rate, that is, the number of times the heart beats in one minute. In an adult at rest the normal rate is 60 to 100 beats per minute (bpm).
A low heart rate at rest indicates that the heart is working more efficiently.
In simple words: Pulse rate is heartbeats per minute; a lower rate at rest means a more efficient heart.

Teacher's Note:
1. Give the normal range of 60 to 100 bpm for an adult at rest.
2. Well-trained athletes can have a resting rate of 40 to 60 bpm.

Teacher's Note:
1. The membrane is the key difference between the two.
2. Osmosis is a special case of diffusion in which only water moves.

Question 8. What are xylem and phloem?
Answer:
Xylem and phloem are the specialized conducting tissues of a plant.
Xylem carries water and dissolved minerals from the roots (soil) to the aerial parts of the plant.
Phloem carries the food made by photosynthesis from the leaves to the various parts of the plant, even up to the root tip.
In simple words: Xylem is the water pipe and phloem is the food pipe of the plant.

Teacher's Note:
1. Mention the direction for each tissue.
2. Dead cells form most of the xylem, while phloem has living cells.

Question 9. How does open circulatory system differ from closed circulatory system? Give example for each.
Answer:
Open circulatory system: the blood is not carried through special tubes or vessels. The heart pumps it into the body cavities and the tissues lie in it. Example: insects.
Closed circulatory system: the blood flows through blood vessels such as arteries, veins and capillaries. Example: human beings.
In simple words: Open systems have no blood vessels; closed systems have them.

Teacher's Note:
1. The presence or absence of blood vessels is the one big difference.
2. Molluscs are another example of an open system.