Life processes

Why is energy required by an organism even during sleep?

This is because even when an organism is asleep, various biological processes keep on occurring in its body which requires energy.

Give the energy transformation that takes place in the process of photosynthesis.

Solar energy is converted into chemical energy during photosynthesis.

What is chlorophyll?

Chlorophyll is a green coloured pigment found in the green leaves or green parts of the plant which traps solar energy for photosynthesis. Chlorophyll is present in cell organelles called chloroplasts.

Name the various factors which affect the rate of photosynthesis.

The factors which affect the rate of photosynthesis are light, water, temperature and carbon dioxide.

Define photolysis.

The phenomenon of breaking down of water molecule using solar energy absorbed by chlorophyll molecules is known as photolysis.

Define light reaction.

A chemical reaction, which take place only in the presence of light, is called light reaction or light dependent reaction. It takes place in grana of chloroplast.

Define dark reaction.

A chemical reaction, which can take place even in the absence of light, is called a dark reaction or light independent reaction. It takes place in stroma of chloroplast.

What are peristaltic movements?

The contraction and expansion movements of the walls of food pipe are called peristaltic movements. This movement pushes the food in forward direction in the alimentary canal.

Which is the largest gland in the human body?

Liver

Give an example of an organism whose digestion is intracellular.

Amoeba

Name the various cells through which water moves upward to reach the leaves.

Water absorbed by root hairs moves through epidermis → root cortex → endodermis → root xylem (i.e., tracheids and vessels) → stem xylem → xylem in the leaf.

What will happen to a plant if its xylem is removed?

[CBSE Delhi 2009]

The xylem tissue transports water and minerals from the soil to the leaves of a plant for photosynthesis. If xylem is removed, upward movement of water will stop leading to wilting of leaves and ultimately causes death of a plant.

In which chamber of heart is oxygenated and deoxygenated blood found?

Oxygenated blood: It is found in left auricle and left ventricle.

Deoxygenated blood: It is found in right auricle and right ventricle.

What makes red blood corpuscles red?

Haemoglobin

What will happen if platelets were absent in the blood?

[NCERT Exemplar]

In the absence of platelets, the process of clotting will be affected.

What is the main function of kidneys in humans?

Kidneys excrete water and dissolve metabolic wastes, e.g., urea and other dissolved solids like uric acid, creatinine and inorganic salts.

In which part of nephron is water reabsorbed?

Proximal and distal convoluted tubules.

In which region of kidney Malpighian corpuscles are found?

In the outer part i.e., cortex of kidney.

What process in plants is known as transpiration?

The release of water vapours in the atmosphere through the pores present on plant leaves, i.e., stomata, is called transpiration.

What is urethra?

It is a muscular tube through which the collected urine passes into the urinary bladder.

Which is the major nitrogenous waste product in human beings? How is it removed from the body?

The major nitrogenous waste product in human beings is urea. Urea is removed/ eliminated from the body through urine.

Name the membrane covering the lungs.

Pleura

What is osmoregulation?

Osmoregulation is the maintenance of optimum concentration of water and salts in the body fluids.

In which form

oxygen is carried to the tissues?

Oxyhaemoglobin

CO2 moves out of the blood?

Carboxyhaemoglobin and as carbonic acid (CO2 dissolved in blood plasma).

Why do the walls of trachea not collapse when there is less air in it?

Tracheal walls do not collapse when there is less air in it because it is supported by rings of cartilage.

Which part of root is involved in the exchange of respiratory gases in plants?

Root hairs are involved in the exchange of respiratory gases in plants.

Name two organisms in which food material is broken down outside the body and absorbed.

Yeast, mushroom.

What prevents backflow of blood inside the heart during contraction?

Valves in heart prevent backflow of blood inside the heart during contraction.

Which is the first enzyme to mix with food in the digestive system?

Salivary amylase

Why does lack of oxygen in muscles often lead to cramps among cricketers?

This is due to the conversion of pyruvate to lactic acid in the absence of oxygen.

Where is pyruvic acid converted into lactic acid during deficiency of oxygen in tissues of human beings?

Golgi body

Where does the oxygen come from when it is liberated during photosynthesis?

Oxygen liberated during photosynthesis comes from water.

What is the internal (cellular) energy reserve in autotrophs?

Starch

In which forms do most plants absorb nitrogen?

Nitrates and nitrites

What is common for Cuscuta, ticks and leeches?

All are parasites. They derive their nutrition from plants or animals without killing them.

If salivary amylase is lacking in the saliva, which event in the mouth cavity will be affected?

Starch breaking down into sugars.

What protects the inner lining of stomach from hydrochloric acid?

The inner lining of stomach is protected from hydrochloric acid by mucus.

What is chyme?

The slightly digested food, enters into the stomach through the alimentary canal. In the stomach, this food is churned along with gastric juices converting this food into a semi-solid paste called chyme.

Name the enzyme which is present in infants but may be absent in adults.

Renin