Q. The autotrophic mode of nutrition requires :

  • (a) carbon dioxide and water
  • (b) chlorophyll
  • (c) sunlight
  • (d) all of the above
  • Ans. (d) all of the above
 Explanation :

In the autotropic mode of nutrition, the plants can prepare their own food in the presence of sunlight, carbon dioxide, water and chlorophyll present in the leaves of the plants.

Q. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in :

(a) Cytoplasm

(b) Mitochondria

(c) Chloroplast

(d) Nucleus

Ans. (b) Mitochondria

 Explanation :

Aerobic respiration is the process of breaking down pyruvate into carbon dioxide, energy, and water in the presence of oxygen. This process takes place in the mitochondria of the cell.

Q. When air is blown from mouth into a test tube containing lime water, the lime water turns milky due to the presence of :

(c) Chloroplast

(d) Nucleus

(a) Oxygen

(b) Nitrogen

Ans. (c) Carbon dioxide

 Explanation :

Calcium hydroxide solution is the lime water. When it reacts with carbon dioxide, it forms insoluble calcium carbonate, which remains suspended in water and gives it a milky white colour.

Q. During deficiency of oxygen in tissues of human beings pyruvic acid is converted into lactic acid in :

(a) Cytoplasm

(b) Chloroplast

(c) Mitochondria

(d) Golgi body

Ans. (a) Cytoplasm

 Explanation :

The pyruvate produced during glycolysis usually enters the Kreb’s cycle as acetyl coenzyme A in the mitochondrial matrix, where it provides a reservoir of chemical energy (ATP, NADH and FADH2). Pyruvic acid can be transformed to lactic acid as one of its potential fates in cellular respiration. Under stressful conditions, this often occurs in the cytoplasm of muscle tissue.

Q. During respiration exchange of gases takes place in :

  • (a) Trachea and larynx
  • (b) Alveoli of lungs
  • (c) Alveoli and throat
  • (d) Throat and larynx

Ans. (b) Alveoli of lungs

 Explanation :

The air sacs in lungs are known as alveoli. The alveoli are the sites where exchange of the gases takes place. The concentration of oxygen gas in the alveoli is higher than that in the blood during inhalation, therefore it diffuses into the blood. Concentration of carbon dioxide is more in the blood than that in the alveoli during exhalation, thus it diffuses into the alveoli.

Q. The xylem in plants are responsible for : 

  • (a) transport of water
  • (b) transport of food
  • (c) transport of amino acids
  • (d) transport of oxygen

Ans. (a) transport of water

 Explanation :

In vascular plants, xylem is a type of tissue that transports water and some nutrients from the roots to the leaves. The other type of transport tissue is phloem, which is responsible for transporting sucrose and other nutrients throughout the plant. The xylem acts as a conducting tissue to transport water and some soluble nutrients such as minerals and inorganic ions from the roots to the rest of the plant.

Q. The kidneys in human beings are a part of the system for :

(a) Nutrition

(b) Respiration

(c) Excretion

(d) Transportation

Ans. (c) Excretion

 Explanation :

Kidneys are the bean shaped reddish brown paired organs in human beings. These are a part of excretory system that helps in the process of urine formation. Thus kidneys help in excretion.

Q.The correct path of urine flow in our body is :

  • (a) Kidney → Ureter → Urethra → Urinary bladder
  • (b) Kidney → Urinary bladder → Urethra → Ureter
  • (c) Kidney → Ureter → Urinary bladder → Urethra
  • (d) Urinary bladder → Kidney → Ureter → Urethra

Ans. (c) Kidney → Ureter → Urinary bladder → Urethra

 Explanation :

Urine from the nephron is transported to the collecting duct, where it enters the ureters. Ureters

Q. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Ans. Unicellular organisms have only one cell and they do not have any specific organs for diffusion of gases. The cell itself is in direct contact with the environment so they can get oxygen easily by simple diffusion process. But in multicellular organisms large number of cells, tissues and organs are present which are not in direct contact with the environment. So, the requirement of oxygen by each and every cell cannot be fulfilled by simple diffusion process quickly. It has been estimated that in human beings a period of three years is needed to carry a molecule of oxygen from head to toe, if oxygen moves from one cell to another through diffusion process.

Q. Why is it necessary to separate oxygenated and de-oxygenated blood in mammals and birds?

Ans. Mammals and birds are warm blooded animals so they need to maintain their constant body temperature and they need more energy to maintain their body temperature. The separation of oxygenated and deoxygenated blood allows highly efficient supply of oxygen to the body thus they get more energy which helps them in maintaining their body temperature.

Q. What criteria do we use to decide whether some-thing is alive?

  • Ans. The following criteria decides whether something is alive:
  • 1. Movement and growth: All living organisms show movement like running, walking. They also show growth. They require energy for cell repair and replacement.
  • 2. Nutrition: They require food to derive energy in order to carry out their metabolic activities.
  • 3. Respiration: They inhale oxygen to break down glucose to release energy. During this process they exhale carbon dioxide.
  • 4. Reproduction: They reproduce to give birth to their new ones.
  • 5. Excretion: They eliminate waste products in the form of urine, faeces, etc., from their body.

Q. What process would you consider essential for maintaining life?

Ans. Processes like nutrition, respiration, transportation, excretion, control and coordination, reproduction, etc., are considered essential for maintaining life.

Q. What are the necessary conditions for autotrophic nutrition and what are its byproducts?

Ans. The necessary conditions for autotrophic nutrition are carbon dioxide, water, sunlight energy, chlorophyll. The byproducts are water and oxygen.

Q. What are outside raw materials used by an organism?

  • Ans. The important outside raw materials used by an organism are:
  • 1. Carbon dioxide, water and mineral nutrients are needed by autotrophic plants.
  • 2. Organic nutrients are required by heterotrophic organisms.
  • 3. Oxygen is used for respiration by both autotrophs and heterotrophs for oxidation of glucose to release chemical energy in the form of ATP.

Q. What is the role of the acid in our stomach?

  • Ans. Hydrochloric acid which is secreted in our stomach has following functions:
  • 1. It makes the medium acidic so that the enzyme pepsin gets activated and acts upon proteins to convert them into peptones and proteases.
  • 2. It also kills the bacteria that might have entered to our body along with the food we eat.

Q. What is the function of digestive enzymes?

  • Ans. Digestive enzymes are the biocatalysts which catalyse the biochemical reactions. They help in breaking down larger, insoluble molecules like carbohydrates, fats, proteins into simpler and soluble forms. For example – Lipases act upon fats to convert them into fatty acids and glycerol. Amylases convert carbohydrates to simple sugars. Protein digesting enzymes like pepsin, trypsin convert proteins to smaller peptides and amino acids etc.

Q. How is the small intestine designed to absorb digested food?

  • Ans. Small intestine is the part in which maximum absorption of digested food occurs. It has numerous tiny finger like projections called villi which increase the surface area for maximum absorption of nutrients. The villi are richly supplied with blood vessels where nutrients are absorbed by the process of diffusion into the blood stream.

Q. How are fats digested in our bodies? Where does this process take place?

  • Ans.The complete digestion of fats occurs in small intestine. Bile juice secreted by liver acts upon large fats to convert them into small globules by the process of emulsification. Lipase enzyme secreted by pancreas acts upon lipids to convert them into fatty acids and glycerol.

Q. What is the role of saliva in the digestion of food?

  • Ans. Saliva is secreted by salivary glands. It contains enzyme ptyalin which acts upon starch to convert them into maltose. This action of ptyalin upon starch occurs in mouth.

Q. What are the different ways in which glucose is oxidised to provide energy in various organisms?

  • Ans. Glucose is oxidised in the following ways to provide energy:
  • 1. In cytoplasm glucose is oxidised to pyruvate and it releases energy .
  • 2. In mitochondria [aerobic respiration] pyruvate breaks down to form carbon dioxide and water to releases energy in the form of ATP.
  • 3. In muscles of humans i.e., under anaerobic conditions pyruvate breaks down to lactic acid and releases energy
  • 4. In yeast i.e., during fermentation process pyruvate converts to ethanol, carbon dioxide, along with it releases certain amount of energy.

Q. What advantage over an aquatic organism does a terrestrial organism have with regards to obtaining oxygen for respiration?

  • Ans.Aquatic organisms like fishes take oxygen which is dissolved in water but terrestrial organisms take oxygen directly from air. The amount of oxygen dissolved in water is fairly low as compared to the amount of oxygen present in air. So the rate of breathing in aquatic organisms is much faster as compared to terrestrial organisms.

Q. How are the lungs designed in human beings to maximise the area for exchange of gases?

  • Ans. Lungs are elastic, spongy, moist sacs like structures. Gaseous exchange occurs between alveoli and the blood vessels surrounding alveoli. Alveoli are tiny sacs like structures present in lungs which increase the surface area for gaseous exchange and lungs contain about 300-350 million alveoli. They have very thin walls making the diffusion of gases more convenient. They are surrounded by numerous tiny blood capillaries which facilitate for efficient gaseous exchange. During inhalation the ribs move outward and diaphragm moves downwards so the space inside the thoracic cavity increases letting more amount of oxygen to diffuse inside.

Q. How is oxygen and carbon dioxide transported in human beings?

Ans. Oxygen from air enters through nostrils, nasal passage, pharynx, larynx, trachea, bronchi, bronchioles and finally to alveoli during inhalation. Alveoli are surrounded with blood vessels where gaseous exchange occurs i.e., oxygen diffuses inside the blood vessels and carbon dioxide diffuses out from the blood vessels into alveoli. Oxygen then combines with haemoglobin present in blood to form oxyhaemoglobin and is carried to heart by pulmonary veins and then it is transported to the rest parts of the body.
Carbon dio xide is transported mainly in dissolved form in the blood stream given out by tissues during cellular respiration and is carried to the alveoli present in lungs where it diffuses out to the alveoli from blood stream and is exhaled out through the nostrils.

Q. What would be the consequences of deficiency of haemoglobin in the body?

Haemoglobin is the respiratory pigment found in RBCs of blood which carries oxygen in the form of oxyhaemoglobin to different parts of the body. If there is deficiency of haemoglobin, the oxygen that is required by our body cannot be supplied i.e., there would be less supply of oxygen to the body. So person will tired, feel weak, tired, look pale and cannot do heavy work. This condition of person is called anemia.

Q. Describe double circulation in human beings? Why is it necessary?

Ans. In human beings, the blood passes through our heart twice so this type of circulation is called double circulation. It consists of:


1. Pulmonary circulation: Here deoxygenated blood from whole parts of body through venacavas comes to right atrium. Then it passes to right ventricle. Pulmonary artery carries this blood to lungs for oxygenation. Then pulmonary veins carry oxygenated blood back to left atrium of heart from lungs. This is called pulmonary circulation.

2. Systemic circulation: Here oxygenated blood from left atrium moves to left ventricle and finally by aorta gets distributed to whole parts of the body. This is called systemic circulation.
It is necessary because both oxygenated and deoxygenated blood are separated from each other. This makes the circulatory system more efficient which provides more energy that is required to maintain constant body temperature.

Q. What are the components of the transport system in human beings? What are the functions of these components?

  • The components of the transport system in human beings are:
  • 1. Heart: It is the central pumping organ which pumps blood to various parts of the body.
  • 2. Blood: It is a mobile, red coloured fluid that circulates within the blood vessels in the body. It supplies nutrients and oxygen to all the living
  • 3. Some wastes are stored in dried leaves which eventually fall.
  • 4. Some wastes are stored in barks of stem which are removed periodically.

Q. How is the amount of urine produced regulated?

  • Ans. The amount of urine produced depends upon the amount of excess water and dissolved wastes present in the body. If the amount of excess water and wastes is more urine produced will be more and vice-versa. The hormone ADH secreted by posterior pituitary gland also regulates the amount of urine produced.

Q. How are water and minerals transported in plants?

Ans. Water and minerals are transported in plants by xylem. Water containing minerals is called sap which is carried by xylem vessels to all parts of the plant from the roots. Root hairs absorb water from the soil by the process of osmosis whereas mineral salts are absorbed from the soil by the process of active transport. Water and minerals absorbed by the root hairs pass from cell to cell through epidermis, root cortex, endodermis and root xylem. The xylem vessels of the root of the plant are connected to xylem vessels of the stem so water pass from root to stem and finally to leaves. Water is used up for photosynthesis and some of water is also lost through leaves by the process of transpiration. The pressure at the xylem vessels of leaves is reduced due to transpiration so it creates a suction force and water rises from xylem vessels of stems and roots thus forming a continuous flow of water and mineral salts.

Q. How is food transported in plants?


Ans. The transport of food from the leaves to the other parts of the plant is called translocation. Food is transported in plants through phloem. Phloem has sieve tubes which are the living cells. Sieve tubes are connected to each other by sieve plates which have small holes in them and which allows the food in solution form to pass through them. Interconnected phloem tubes are present in all parts of the plant so food is carried from leaves to all the parts of the plant. The translocation process requires energy in the form of ATP. The glucose which is made in leaves is loaded into sieve tubes of phloem tissue by using ATP, water enters into this tissue by osmosis now high pressure is created which helps in movement of food to low pressure region.

Q.Describe the structure and functioning of nephrons?

  • Ans. Nephron is the structural and functional unit of life. It has the following parts:
  • 1. Bowman’s capsule: It is a thin walled cup like structure which contains a knot like mass of blood capillaries called glomerulus. Both Bowman’s capsule and glomerulus are together called Malpighian capsule.
  • 2. Proximal Convoluted Tubule (PTC): It is a convoluted region found near Bowman’s capsule.
  • 3. Loop of Henle: It lies next to Proximal Convoluted Tubule which is U shaped structure.
  • 4. Distal convoluted tubule: It is the end part of the nephron which opens to collecting duct.

Functions of nephron: The formation of urine occurs in three steps:

1. Ultrafiltration: Blood flows under high pressure in glomerulus and the liquid portion of the blood filter out from glomerulus and passes to the cup shaped cavity of Bowman’s capsule and this process is called ultrafiltration.


2. Selective reabsorption: It is the process of selective absorption of useful substances like glucose, water, some salts etc., from glomerular filtrate which is obtained from ultrafiltration by different parts of nephron.

3. Tubular secretion: Some harmful substances like chemicals, drugs like penicillin, potassium ions etc., are released by renal tubule to the forming urine called tubular secretion.

Q. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration?

Aerobic Respiration Anaerobic Respiration
This process occurs in presence of oxygen. This process occurs in absence of oxygen.
During this process glucose is completely oxidised to release carbon dioxide and water. Glucose is incompletely oxidised. In yeast the products are ethanol and carbon dioxide. In human beings under anaerobic conditions the products are lactic acid and carbon dioxide.
More amount of energy is released during this process. Less amount of energy is released during this process.
It takes place in mitochondria. It takes place in cytoplasm.

Some organisms that use the anaerobic mode of respiration are yeast, some bacteria, some parasitic wor ms, etc.

Q.What are the differences between transport of materials through xylem and phloem?

Transport in Xylem Transport in Phloem
It transports water and mineral salts. It transports manufactured food from leaves.
Mainly the transport is unidirectional. The transport is in different directions.
Transport occurs by tracheids and vessels. Transport occurs in sieve tubes with help of companion cells.
It does not require energy. ATP is required for this transport.
Transport by xylem mainly occurs by transpiration pull. It is also called ascent of sap. Transportation of phloem occurs by the process known as translocation.

Q. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning?

Alveoli in Lungs Nephrons in Kidneys
Alveoli are tiny sacs like structures having thin walls present in lungs. Nephrons are long tubules like structures present in kidneys.
Alveoli are surrounded by blood capillaries. Nephrons have a knot of blood capillaries in Bowman’s capsule called glomerulus and a network of capillaries surround the tubule called vasa recta.
They provide large surface area for exchange of gases inside lungs. In nephrons urine formation occurs by three steps i.e., ultrafiltration, selective reabsorption, tubular secretion.
They are the site for gaseous exchange. They serve as filtration unit of waste materials from the body.