Life Processes : Complete Set of Questions

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This set of questions contains all the possible concepts
which could be asked in the examination



Q.1 What is meant by life processes?

Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:

• Nutrition

• Respiration

• Transportation of substances

• Excretion

• Movement

• Reproduction

Q.2 What is meant by nutrition?

Nutrition is the process by which an organism obtains the food from its environment and utilizes it for various life processes like growth, replacement of tissues, energy etc.

Q.3 When we are asleep we are not performing any activity still our life processes are going on. Why?

The maintenance functions of living organisms must go on even when they are not doing anything particular. That is why the life processes are going on even while we are asleep or not performing any activity. 

Q.4 We say that movement is a characteristic of living organisms but we always don’t see visible movements in plants. Comment.

We always don’t see visible movements in plant s. It does not mean that they are not alive. Molecular movements take place in their body.




Q.5 What is the need for nutrition?

Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.

Q.6 What are nutrients?

Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.

Q.7 What are the types of nutrition?

Types of Nutrition:

Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.

Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition.

Q.8 What are the two types of heterotrophic nutrition?

Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.

Saprophytic Nutrition: In saprophytic nutrition, the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects like houseflies also follow this mode of nutrition.

Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.

Q.9 What are the differences between autotrophic and heterotrophic nutrition?

Q.10 Name any two autotrophic plants which also show heterotrophic mode of nutrition. Why do they need to do so?

All green plants are autotrophic but some of them also show heterotrophic nutrition like Venus fly trap and pitcher plant as their nutritional requirement is not fulfilled by photosynthesis like nitrogen and phosphorus as in some areas, the soil is deficient in nitrogen 

Q.11 What are the raw materials for photosynthesis?

The raw materials and other necessary items required for photosynthesis are Sunlight, Water, CO2 and Chlorophyll. 

Q.12 What is meant by photosynthesis?

It is the process by which autotrophs (green plants) make their own food from carbon dioxide and water which is converted into carbohydrates in the presence of sunlight and chlorophyll. During this process, oxygen gas is released.

Q.13 What are the important events that occur during the process of photosynthesis?

The following events occur during this process -

(i) Absorption of light energy by chlorophyll.

(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

(iii) Reduction of carbon dioxide to carbohydrates.

These steps need not take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

Q.14 How can you prove that chlorophyll is essential for photosynthesis?

Let us do an activity which demonstrates that chlorophyll is essential for photosynthesis

• We take a potted plant like croton whose leaves are partly green and partly white. The green part of the leaf has chlorophyll but the white part of the leaf does not have chlorophyll.

• Place this plant in a completely dark place for about three days to destarch its leaves.

• Take out the potted plant from the dark place and keep it in bright sunshine for three to four days.

• Pluck the variegated leaf from the plant, boil it in water for a few minutes and then remove its green colour 'chlorophyll' by boiling it in alcohol. The green parts of the leaf get decolourised. So, we get decolourised leaf.

• Wash the decolourised leaf with hot water to soften it and remove any chlorophyll which may be sticking to it.

• Pour iodine solution over the colourless leaf and observe the change in colour of the leaf.

• We will find that the outer part of leaf that was originally white (without chlorophyll) does not turn blue-black on adding iodine solution showing that no starch is present in this outer part of the leaf. From this observation we conclude that the photosynthesis to make starch does not take place without chlorophyll.

• The inner part of leaf which was originally green (contained chlorophyll) turns blue-black on adding iodine solution showing that starch is present in this inner part of the leaf. From this observation we conclude that the photosynthesis to make starch takes place in the presence of chlorophyll. In other words, chlorophyll is necessary for the process of photosynthesis to take place.

Q.15 How do plants obtain carbon-dioxide for photosynthesis?

Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis. These pores are surrounded by ‘guard cells’. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a function of the guard cells.

Q.16 How will you prove that sunlight is essential for photosynthesis and the food prepared by green plants using photosynthesis is starch?

Let us do an activity to prove that sunlight is necessary for photosynthesis-

• We take a potted plant having green leaves and place it in a completely dark place for about three days to destarch its leaves. So, in the beginning of the experiment, the leaves do not have any starch in them.

• Take a thin strip of aluminium foil (or black paper) and wrap it in the centre of one leaf on both the sides (while the leaf is still attached to the plant). The aluminium foil should be fixed tightly to the leaf by using paper clips so that sunlight may not enter it from the sides. The aluminium foil should cover only a small part of the leaf so that the remaining part of the leaf remains uncovered and exposed to sunlight. We have covered the centre part of the leaf with aluminium foil so that sunlight may not fall on this covered part of the leaf.

• Keep this potted plant (with partially covered leaf) in bright sunshine for three to four days.

• Pluck the partially covered leaf from the plant and remove its aluminium foil. Immerse this leaf in boiling water for a few minutes. This will break down the cell membranes of leaf cells and make the leaf more permeable to iodine solution (so that it may reach the starch present inside the leaf cells).This leaf is now to be tested for the presence of starch. But before testing for starch, chlorophyll has to be removed from the leaf. This is because chlorophyll interferes in the test for starch due to its green colour.

• Put the plucked leaf in a beaker containing some alcohol. Place the beaker containing alcohol and leaf in a water bath. A water bath is being used here for heating alcohol because alcohol is a highly inflammable liquid.

• Heat the water in the bigger beaker (or water bath). Now, the alcohol in the smaller beaker will also get heated and start boiling soon. This boiling alcohol will extract (or remove) chlorophyll from the green leaf.

• Boil the green leaf in alcohol till all its green pigment 'chlorophyll' is removed. The leaf will now become almost colourless or pale (and the alcohol will turn green).

• Remove the colourless leaf from alcohol and wash it thoroughly with hot water to soften it and remove any chlorophyll which may be sticking to it.

• Place the colourless leaf in a petri-dish. Drop iodine solution over the decolourised leaf with the help of a dropper. Observe the change in colour of leaf.

• The middle part of leaf which was covered with aluminium foil does not turn blue-black on adding iodine solution showing that no starch is present in this middle part of the leaf. This is because sunlight could not reach the covered 'middle part' of the leaf due to which the covered 'middle part' of leaf could not do photosynthesis to make starch.

• The uncovered part of leaf (on both sides of the aluminium foil) which was exposed to sunlight turns blue-black on adding iodine solution showing that starch is present in this part of leaf. This means that the part of leaf which was exposed to sunlight could do photosynthesis to make starch.

Since the part of leaf which was covered and hidden from sunlight does not contain starch but the part of leaf which was exposed to sunlight contains starch, therefore, we conclude that sunlight is necessary for photosynthesis (to make food like starch).

From the above experiment, we actually get two conclusions-

(i) Sunlight is necessary for the process of photosynthesis, and

(ii) Leaves make starch as food by photosynthesis.

Q.17 How do plants obtain nitrogen?

Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up in the form of inorganic nitrates or nitrites. Or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen. Atmospheric nitrogen is fixed by leguminous plants with the help of symbiotic bacteria present in the root nodules of these plants.

Q.18 How do the terrestrial plants get water for photosynthesis?

Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. It is transported to the leaves through the xylem tissues.

Q.19 Stomata remain closed in desert plants. How do they obtain carbon dioxide for photosynthesis?

In desert plants, stomata remain open at night and carbon-dioxide is absorbed at this time. It is stored in the form of an intermediate compound that can be utilised to form carbohydrates during daytime.

Q.20 How does amoeba obtain its food ? 

Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over the food particle forming a food-vacuole as shown in figure. Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.

Q.21 How does paramoecium obtain its food?

In Paramoecium, which is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. They have thousands of hair-like projections, called cilia, surrounding their bodies. Cilia beat back and forth and are what propel a paramecium through the water. They are also responsible for drawing food particles (yeast, algal cells) toward the mouth, which is known as an oral groove. When the food particle comes near the oral groove the cilia continue to beat and draw the food closer until it is engulfed by the paramecium. This process is known as endocytosis (literally, "inside the cell"). It is a little like the process of swallowing.

Q.22 Name the different parts of the alimentary canal?

Mouth, Oesophagus, stomach, small intestine, large intestine and anus.

Q.23 Name the digestive glands present in the body?

Salivary glands, gastric glands, pancreas, liver.

Q.24 Name the enzyme present in the saliva. What is its function?

The enzyme present in the saliva is Salivary Amylase. It helps in the digestion of starch to sugars.

Q.25 What is the role of teeth and tongue in digestion?

Teeth crush the food into small pieces for easy swallowing and digestive enzymes to act on it. Tongue mixes this food thoroughly with saliva and moves it around the mouth.

Q.26 What is peristaltic movement?

The rhythmic contradiction of muscles of the alimentary canal to push the food forward is known as peristaltic movement.

Q.27 What happens to the food in the stomach?

The hydrochloric acid present in our stomach dissolves bits of food and creates an acidic medium. In this acidic medium, enzyme pepsinogen is converted to pepsin, which is protein-digesting enzyme. The mucus protects the inner lining of the stomach from the action of acids.

Q.28 What causes acidity?

Imbalance in production of gastric juice causes acidity.

Q.29 Amylase is secreted by two different glands. Name them. What is the role of amylase in the digestion food?

Role of Amylase:

Amylase is a digestive enzyme that acts on starch in food, breaking it down into smaller carbohydrate molecules. The enzyme is made in two places.

(i) First, salivary glands in your mouth make salivary amylase, which begins the digestive process by breaking down starch when you chew your food, converting it into maltose, a smaller carbohydrate. 

(ii) Cells in your pancreas make another type of amylase, called pancreatic amylase, which passes through a duct to reach your small intestine. Pancreatic amylase completes digestion of carbohydrate, producing glucose, a small molecule that is absorbed into your blood and carried throughout your body. 

Q.30 What is the role of bile juice in digestion?

Bile is alkaline in nature and it is temporarily stored in gall bladder and helps in digestion of fats, it also helps in absorption fats. 

Q.31 What is the role of sphincter muscles in the stomach?

The exit of food from the stomach is regulated by the sphincter muscle. It releases food in small amounts into the small intestine.

Q.32 Why do carnivores have shorter intestine than herbivorous?

Herbivores eat grass which needs a longer small intestine to allow cellulose to get digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

Q.33 What is the function of digestive enzymes?

Digestive enzymes help in digestion of different food components like carbohydrates, proteins, fats etc. Different food components have specific enzymes that act on them. Enzymes are secreted from various parts of our digestive system like walls of stomach, liver, pancreas, salivary glands etc. Pepsin, amylase, lipase, protease, maltase etc are some examples of enzymes secreted by our body. They help in the breaking down of complex food particles into simple ones. These simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.

Q.34 What is the role of saliva in the digestion of food?

The salivary glands secrete the first of the digestive juices, the saliva. In the digestion process, the saliva helps the teeth and tongue to masticate and mix up the food thoroughly. Mucus in saliva helps in lubricating and adhering food particles into a bolus.  Then the bolus conveyed to pharynx for further digestion. Lysosomes present in saliva acts as an antibacterial agent that prevents infection.

Q.35 What is the role of pancreas in the process of digestion?

Pancreas produces pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down of emulsified fats.

Q.36 What are villi? What is their function?

Villi are finger-like projections on the inner lining of the small intestine. Villi absorb digested food. Surface area of absorption is increased by the numerous villi for proper absorption of the digested food.  Villi are richly supplied with blood vessels and lymph to absorb the food. Absorption takes place easily through the thin epithelium of villi.

Q.37 What happens to the absorbed food in the cells?

The absorbed food is supplied to different tissues of the body for building up new cells and tissues, for energy and for repair of old tissues.

Q.38 What are the end products of digestion of carbohydrates, proteins and fats?

Carbohydrates are digested to glucose. Proteins are digested to amino acids. Fats are digested into fatty acids and glycerol.

Q.39 Mucus is not used for churning the food or digesting it. Then why is it secreted in the stomach?

Mucus is secreted in the stomach to protect it s inner lining from being damaged by HCl. Excessive secretion of HCl can damage the lining and lead to peptic ulcer.

Q.40 Why are the leaves called the food factories of plants? Explain.

Leaves are called the food factories of plants due to following functions

• Green leaves have all the raw materials necessary to carry the process of photosynthesis.

• They have chlorophyll (green pigment) which captures the energy of sunlight.

• Leaves consist of tiny pores called stomata on their surface.

• Carbon dioxide from air is taken in through stomata.

• Water and minerals are absorbed by the roots from the soil and transported to the leaves by vessels.

Q.41 Distinguish between a parasite and a saprotrophs?


• A parasite takes readymade food from the organism on which it feeds.

• They feed on a living organism.

• The organism on which it feeds is called host.

• It deprives the host of valuable nutrients.


• They secrete the digestive juices on the matter they live and convert it into a solution and then absorb it.

• They feed on dead and decaying organism.

• They do not feed on a living organism.

• There is no host at all. 

Q.42 Why is the small intestine long in herbivores and short in carnivores?

Herbivores eat grasses, which contain mainly cellulose. They have long small intestine to allow digestion of cellulose. Carnivores eat smaller amount of food(flesh) compared to herbivores, and it is in the form of high energy molecules which are relatively easy to digest. Therefore, carnivores have a short small intestine 

Q.43 What is digestion?

The process of breaking down complex food substances into simple molecules is called as digestion.

Q.44 What does the human digestive tract consists of?

Digestive system in human beings consists of alimentary canal and digestive glands.

Alimentary canal is made up of mouth, buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and anus.

The digestive glands are the salivary glands, the gastric glands, the liver, the pancreas and the intestinal glands.

Q.45 What is the function of the small intestine?

The three main categories of nutrients that undergo digestion within the small intestine are proteins, lipids (fats) and carbohydrates. The small intestine is divided into duodenum, ileum and jejunum.

The intestinal enzymes such as invertase, maltase and lipase act upon partially digested proteins, carbohydrates and fats.

Proteins and peptides → amino acids

Lipids (fats) → fatty acids and glycerol 

Some carbohydrates → simple sugars, or monosaccharides  (e.g., glucose).

• Proteins, carbohydrates and fats are simplified into amino acids, glucose, fatty acids and glycerol in a liquid medium known as chyle.

• Specific structures called as villi in the small intestine increase its surface area to ensure efficient and rapid absorption of nutrients. Blood capillaries in the villi absorb nutrients and transport the food to all the cells in the body.

• Other carbohydrates pass undigested into the large intestine where they may, depending on their type, be broken-down by intestinal bacteria.

Q.46 What is the role of stomach in digestion?

The stomach is divided into three compartments namely cardiac, fundus and pylorus.  The junction of oesophagus and stomach is guarded by valve which does not allow the food to travel in backward direction.
• In the stomach, food is mixed with the gastric juices secreted by the gastric glands.
• Gastric juice is a combination of hydrochloric acid, enzymes like pepsin, lipase and mucous.
• Partially digested food in the stomach becomes acidic and is known as chyme.

Q.47 What is the role of liver in digestion?

The liver is the largest gland in the body. It secretes bile juice

• The acidic food coming from the stomach is made alkaline for pancreatic enzymes to act, by the bile juices.

• Bile brings about emulsification of fats which are later digested by intestinal lipases. It also aids in absorption of fat soluble vitamins like A, D E, K.

Q.48 What is the role of large intestine in digestion?

The large intestine comprises caecum, appendix, colon, rectum and anus. The large intestine absorbs water from undigested food and forms solid waste.

• The rectum stores the solid excreta until it is ready to be excreted from the digestive system through anus.

• The appendix is a small, hollow, finger-like pouch, which hangs at the end of the cecum. It does not have any function in the digestive system of humans. However, it is functional in herbivores such as cows

Q.49 How are water and minerals transport in plants?

The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the interconnected water-conducting channels.

Q.50 How is food transported in plants?

Food is transported in plants through phloem. The transport in phloem is an active process and involves use of energy. The energy in the form of ATP created osmotic gradient which results in transportation of food through phloem.

Q.51 What is trypsin? What is its function?

Trypsin is secreted by the duodenum of small intestine. When proteins are digested in the stomach the acidic medium is passed as such into the small intestine. The small intestine is incapable of handling such low pH and neither can its enzymes function. Hence Trypsin is released to neutralize the acidity.

Q.52 What is the role of acid in the stomach?

Hydrochloric acid is produced in the stomach by the gastric glands that are present in the walls of the stomach. Acid plays an important role in -

(a) Activating Pepsinogen to form the enzyme Pepsin, which digests proteins to smaller chains of amino acids.

(b) HCl also kills many bacteria and other microorganisms that enter along with the food.

(c) HCl denatures the proteins so that they can be easily digested.

Q.53 What is the function of digestive enzymes?

Digestive enzymes help in the chemically digestion of food. They break the bonds of bigger molecules such as proteins, fats, carbohydrates etc to release smaller molecules that can be easily absorbed by the small intestine. For example, Pepsin that is present in the gastric juice acts upon proteins to break them into smaller chains of amino acids, which are further, reduced to amino acids by other enzymes. The amino acids are absorbed into the small intestine and transported to the body cells for making proteins.

Q.54 How does each of the following factors affect the productivity in the process of photosynthesis?

(i) Temperature  

(ii) Water  

(iii) Carbon dioxide.

(i) Temperature : The higher the temperature then typically the greater the rate of photosynthesis, photosynthesis is a chemical reaction and the rate of most chemical reactions increases with temperature

(ii) Water : An increase in the amount of water leads to the increase in the amount of photosynthesis.

The amount of water available to the plant will affect the rate of photosynthesis. If the plant does not have enough water, the plant’s stomata will shut and the plant will be deprived of CO2, and thus lower photosynthesis rate .

(iii) Carbon dioxide : The concentration of carbon dioxide in the Earth’s atmosphere varies between 0.03% and 0.04%. An increase in the concentration of carbon dioxide gives an increase in the rate of photosynthesis.

Q.55 Give any 5 functions of bile?

Functions of Bile:

(i) Bile juice reduces the acid content of the chyme

(ii) It kills germs present in the food.

(iii) It emulsifies fat molecules

(iv) It helps in absorption of fat after digestion

(v) It helps in the excretion of bilirubin(byproduct of RBC) from the body




Q.56 What is respiration?

Respiration is the process of intake of intake of oxygen and using it for the breakdown of food materials to provide energy in the form of ATP.

Q.57 (i)How oxygen and carbon dioxide exchanged in our body during respiration?

(ii) Explain, how the air we breathe in gets cleaned while passing through the nasal passage.

(i) When the air enters into the lungs through nostrils, trachea and bronchi it enters into the bronchioles, from bronchioles it moves into thin walled alveolar sacs or alveoli. Alveoli are rich in blood capillaries, at this place oxygen from air diffuses into the blood and reaches to all the cells and tissues of body this oxygen now diffuses into the cell and is utilized for the oxidation of food and production of energy in mitochondria as a result of this carbon dioxide is produced in cells, due to this increased concentration of CO2, it diffuses into the blood and is brought back to alveoli and expelled out of the lungs through trachea and nostrils. 

(ii) Nasal passage: This passage is separated from oral cavity by means of a hard and bony palate. It is lined by ciliated columnar epithelial cells that are rich in mucus; it brings about warming, moistening and sterilization of air. It contains hair and mucus which entrap the dust particles.

Q.58 Write any three points of difference between respiration in plants and animals? 

Respiration in plants. 

(a)    In plants separate respiratory organs are absent

(b)    The rate of respiration is slow.

(c)    They lack respiratory surface 

Respiration in animals 

(a)    In animals respiratory organs are generally present

(b)    The rate of respiration is fast.

(c)    Respiratory surface is generally present. 

Q.59 Explain the process by which inhalation occurs during breathing in human beings?

The process by which oxygen rich air is taken up through the nostril into the body is known as inhalation. During inhalation, the chest cavity increases in size due to the downward movement of the diaphragm (dome shaped muscular sheet that separates chest from abdomen). As a result air from outside rushes into the lungs to fill the extra space.

Exhalation is the process by which carbon dioxide rich air comes out of the body. It occurs when the diaphragm moves up and the chest cavity becomes narrower. This creates a pressure on the air inside the lungs. As a result the air comes out of the lungs to the atmosphere due to lack of space inside. Both the process of inhalation and exhalation is commonly known as breathing.

Q.60 What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Oxygen is needed by the cells for aerobic respiration. A terrestrial organism living on land breathes in air, which contains a higher amount of oxygen (about 21 %). So it gets a higher amount of oxygen in each breath. On the other hand, an aquatic organism (like fish) has to breathe in water and take the oxygen that is dissolved in water. But, as the solubility of oxygen in water is very low the organism does not get sufficient oxygen in each breath. So it has to breathe faster in order to get sufficient oxygen.

Q.61 Explain different types of respiration?

Glucose is oxidized in two ways to provide energy-

(a) Anaerobic respiration-Partial oxidation of glucose in the absence of oxygen, resulting in release of some energy. Glucose is oxidized to pyruvate, which is then changed to ethyl alcohol or lactic acid. There is no role of mitochondria. Only two ATP molecules are gained by the oxidation of one glucose molecule. The breakdown of glucose to release energy from the cells in anaerobic conditions is fermentation.

(b) Aerobic respiration-Complete oxidation of glucose using oxygen to release high amount energy. Glucose is oxidized in the cytoplasm to pyruvate, which is then shifted to mitochondria for further breakdown. The pyruvate is oxidized to CO2 and water. 38 ATP molecules are formed by the oxidation of one molecule of glucose.

Q.62 How are lungs designed in human beings to maximize the area for exchange of gases?

The lungs are organs where gas exchange takes place between the blood and air. The blood gets re-oxygenated and carbon dioxide is released into the air.

Inside the lungs there are millions of air sacs called alveoli, which increase the surface area for exchange of gases.

The thin walls of alveoli are richly supplied with blood capillaries to carry blood for gas exchange. CO2 diffuses out from the blood into the air and the blood takes up fresh oxygen from the air.

Human beings have a thin layer of about 700 million alveoli within their lungs! This layer is very necessary in the process of gas exchange between air and blood. The subdivision of lung into millions of tiny air sacs provides a greater surface area for gas exchange to take place.

Q.63 How are Oxygen and Carbon dioxide transported in human beings?

Oxygen and Carbon dioxide are transported from in human beings by the blood. In the lungs, there is exchange of gases between the blood and air. Oxygen from air diffuses into the blood flowing in the thin walled blood capillaries. This oxygen is quickly taken up by haemoglobin in the RBCs. Thus, oxygen is mostly carried by the haemoglobin in the RBCs. Very little oxygen is carried in the dissolved form in the blood plasma. This is because solubility of oxygen in plasma (water) is very low.

Q.64 What is diffusion?

Diffusion is the movement of a substance from a region of higher concentration to a region of lower concentration.

Q.65 Explain the process of respiration in terrestrial forms?

Terrestrial animals have special organs for taking in oxygen from the atmosphere. For instance, cockroaches respire through the trachea, and scorpions through the book lungs.

Air enters a human body through the nostril, then the trachea. From the trachea, air enters the bronchi and then goes into the lungs. The bronchi form a network of bronchioles. Each bronchiole has alveoli at the end in the lungs. The thin membranes of alveoli allow the exchange of gases. Alveoli are richly supplied with blood vessels.

The diaphragm is a thin sheet of muscle separating the thorax and the abdomen, and helps in respiration.

The respiratory pigment, haemoglobin present in blood absorbs oxygen from the lungs and carries it to tissues all over the body.

Q.66 Explain the process of respiration in aquatic forms?

The rate of breathing in aquatic organisms is much faster than in terrestrial organisms.

Respiration in aquatic animals is performed by diffusion through body surface and special respiratory organs called as gills.

Fish take in water that has dissolved oxygen in it through the mouth. The dissolved oxygen diffuses into their blood. The water is then forced out through their gills

Q.67 Explain the process of respiration in plants?

In plants, carbon dioxide and oxygen are exchanged through the stomata by diffusion. Diffusion is the movement of a substance from a region of higher concentration to a region of lower concentration. Respiration takes place only during night in plants.

Q.68 Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Diffusion insufficient to meet the oxygen requirements of multicellular organism because-

• Multicellular organisms have different organs specialized for different functions.

• All the cells of the body are not in direct contact with the surrounding environment.

• Intake of oxygen takes place in one organ and is used in another organ.

Q.69 Why is the process of anaerobic respiration considered less efficient?

It is the process of incomplete oxidation of glucose and it releases less energy than aerobic respiration.

Q.70 Name two processes involved in the mechanism of respiration:

(i) Glycolysis

(ii )Kreb’s cycle

Q.71 Define glycolysis?

Glycolysis is the breakdown of a molecule of glucose(6-carbon molecule) into two molecules of pyruvate(3- carbon molecule). Glycolysis takes place in the cytoplasm.

Q.72 Define Kreb’s cycle?

Kreb’s cycle is the oxidation of pyruvate into carbon dioxide and water.

Q.73 When does anaerobic respiration take place in the muscles?

Anaerobic respiration take place in the muscles when there is no sufficient supply of oxygen.

Q.74 What is fermentation?

Fermentation is the conversion of organic materials in the surrounding medium into organic acids or alcohol by the action of bacteria or fungi like yeast.

Q.75 Respiration is a vital process for all organisms. Explain?

All organisms need energy for cell metabolism and physical activity. Respiration provides energy in the form of ATP, therefore, it is a vital process.

Q.76 Why should we always breathe through our nose?

Nasal cavities have ciliated epithelium with mucus secreting glands. Air gets filtered and moistened in the nasal passage. It removes bacteria and dust particles to save us from infections and allergy.

Q.77 Why is it not advisable to sleep under trees at night?

The air around the trees lack oxygen and contains more carbon dioxide as photosynthesis stops at night and respiration takes place. Consequently, plants also take in oxygen and give out carbon dioxide during respiration.

Q.78 How are gills and lungs designed for the exchange of gases?

Gills and lungs are specialised organs for the absorption of gases. They have-

(i) Extensive surface area in contact with oxygen rich environment.

(ii) Rich supply of blood through network of capillaries.

(iii) Fine and delicate surface for efficient diffusion of gases.

(iv) Mechanism for movement of air over lungs and water over gills.

Q.79 Describe the mechanism of breathing in human beings?

Mechanism of breathing involves 2 steps-

Inspiration- It is inhalation of air rich in oxygen. Inspiration occurs due to muscular movements of ribs and diaphragm. Contraction of rib muscles raises rib cage upward and contraction of diaphragm muscles cause flattening of diaphragm increasing the volume of the chest cavity. As a result, air is sucked into the lungs causing expansion of alveoli. Exchange of gases takes place between lung air and blood capillaries. Oxygen in the alveolar air is taken up by blood and carbon dioxide in the blood is released into the alveoli. Oxygen in the alveolar blood vessels is transported to all the cells in the body.

Expiration- It is the expulsion of air rich in carbon-dioxide and lacking in oxygen. It occurs passively when rib and diaphragm muscles relax, rib cage moves downwards and diaphragm moves upwards pushing the air out.

Q.80 Difference between aerobic and anaerobic respiration?

Q.81 What are the different ways in which glucose is oxidized to provide energy in various organism? 

At first glucose (6 carbon molecules) is broken in the cytoplasm of cells of all organisms. This process yields a compound with three carbon molecules is  called pyruvate.

Further break down of pyruvate takes place in different manners in different organisms.

Anaerobic Respiration

This process takes place in absence of oxygen, e.g. in yeast during fermentation. In this case pyruvate is converted into ethanol and carbon dioxide.

Aerobic Respiration

In aerobic respiration, breakdown of pyruvate takes place in presence of oxygen to give rise 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.

Lack of Oxygen

Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds). Formation of lactic acid in muscles causes cramp.

Q.82 Distinguish between lactic acid and alcoholic fermentation?

Lactic acid is a 3 carbon compound produced on oxidation of glucose anaerobically where as ethanol a 2 carbon compound is formed on anaerobic oxidation of glucose along with CO2.

Q.83 Give reasons of dental caries in people.

It is the tooth decay due to gradual softening of Enamel and Dentine. It take place when bacteria acting on sugar produce acids which softens the enamel.




Q.84 What is transportation?

Transportation is the life process by which substances absorbed or synthesised in one part of the body are carried to other parts where they are consumed.

• Animals have circulatory system for transportation of substances within the body

• Plants have specific tissues for transportation of materials within the plant body.

Q.85 Name the two components of blood?

The two components of blood are

• Fluid medium called plasma in

• The cells that are suspended in the plasma.

Q.86 Why is human circulatory system also called cardiovascular system?

Cardiovascular system means the system of heart and blood vessels of human body. The circulatory system is also known as the cardiovascular system, from the Greek word kardia , meaning "heart," and the Latin vasculum , meaning "small vessel."  So the name itself indicates that a cardiovascular system is the system of heart and blood vessels. The blood passes from the heart to the other parts of the body through tube- like structures therefore it is called vascular system.

Q.87 What is the function of heart valves?

Valves ensure that blood does not flow backwards during the contraction of auricles or ventricles.

Q.88 How does blood circulate between lungs and heart in human beings? Give two functions of lymph in human body.

At first the impure blood from all the body parts reach the right auricle and then into right ventricle. From right ventricle it is carried to lungs through Pulmonary arteries .In lungs, it gets purified [alveoli do the purification] and then it is send  to left auricle through Pulmonary Vein. From left auricle it flows into left ventricle and then to all the body parts through systemic aorta.

Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.

Q.89 Point out two differences between an artery and a vein.


• Vessels which carry blood from the heart to various body parts

• Arteries carry oxygenated blood from the heart except pulmonary artery


• Vessels which carry blood from the various body parts to the heart

• Veins carry deoxygenated blood from the various body parts except pulmonary vein 

Q.90 What do you mean by double circulation of blood?

In human beings (and other mammals), the circulatory system is designed in such a way that blood passes twice through the heart, which acts as a pumping organ. Double circulation has two components, pulmonary circulation and systemic circulation.

(i) Pulmonary Circulation: It is movement of blood from heart to the lungs and back. Deoxygenated blood of the body enters the right auricle, passes into right ventricle which pumps it into the lungs for oxygenation with the help of two separate pulmonary arteries. The oxygenated blood is brought back to the left atrium of the human heart through the pulmonary vein. From left atrium, the oxygenated blood is pushed into the left ventricle. The left ventricle pumps oxygenated blood into aorta for systemic circulation.

(ii) Systemic Circulation: It is the circulation of blood between heart and different parts of the body except lungs. Oxygenated blood received by left auricle passes in to left ventricle. The left ventricle pumps it into aorta for supply to different body parts including walls of the heart with the help of arteries. The deoxygenated blood is collected from the various body organs by the veins to pour into the vena cava and finally into the right atrium(auricle). Right atrium transfers this blood into the right ventricle.

This pure oxygenated blood returns back to the left side of the heart and the cycle is repeated again. This is known as double circulation.

Q.91 Name the constituents of blood. Why are WBC called ‘soldiers of the body’?

(a)The constituents of blood are

• Red blood cells or RBCs (erythrocytes)

• White blood cells or WBCs (leucocytes)

• Blood platelets (thrombocytes)

(b) WBC is called ‘soldiers of the body’ because

(i) White blood cells protect the body from infec on. If germs like bacteria or viruses enter the body, these cells surround the germs and destroy them by digesting.

(ii) They also produce antibodies (blood proteins) which kill the germs and foreign particles entering our body.

Q.92 What are the components of transport system in human beings?

The components of transport system in human beings are blood, blood vessels and lymph.

Q.93 What is blood?

(a) Blood-It is the fluid connective tissue that is responsible for transport of materials in human beings. It contains the fluid part called Plasma, which carries most of the materials in dissolved form. Plasma, which is basically water, carries materials such as minerals, amino acids, glucose, urea (as a waste), hormones, dissolved proteins etc.

In the blood plasma are also present the following cells-

(i) RBC-Red blood cells contain the pigment haemoglobin, which helps in carrying oxygen from the lungs to different tissue cells for respiration. This is because solubility of oxygen in the plasma is very low.

(ii) WBC-White blood cells are responsible for killing the microorganisms entering into the blood. Thus, WBCs play an important role in the immune system of the body.

(iii) Blood platelets- The blood plasma also contains blood platelets, which help in clotting of the blood during injury to prevent blood loss. 

Q.94 What are the various blood vessels?

Blood Vessels-These are Arteries, Veins and Blood capillaries.

(i) Arteries carry blood away from the heart. The three layered wall of arteries is thick to bear the pressure of blood that is pumped by the heart.

(ii) Veins carry blood towards the heart. The three layered wall of veins is thinner than arteries because it has to bear very low blood pressure. There are valves in the veins, which prevent back flow of the blood.

(iii) Blood Capillaries are the thinnest of the blood vessels. There is a wide network of blood capillaries in every organ of the body. The capillaries pass between the cells of the tissues. Oxygen, glucose, amino acids and other nutrients pass through the capillary walls and enter into the tissue fluid from where they are taken up by the surrounding cells.

Q.95 What are the function of lymph?

Lymph-The extra tissue fluid in the tissues enters the lymph capillaries. The lymph capillaries join up to form lymph vessels. The composition of lymph is almost similar to blood plasma but it contains less proteins. The lymph vessels join with veins and supply lymph into the blood.

Functions of Lymph are-

(a) Lymph that is basically the blood plasma that has come out of the blood capillaries into the intercellular spaces serves as a source of nutrients for the cells of the tissues. The cells take up many nutrients from the tissue fluid and release their wastes into the same

(b) Lymph helps in removing extra tissue fluid along with proteins from the body organs and returning them to the blood.

(c) Lymph contains specialized WBCs that play an important role in killing the microorganisms invading the body.

(d) Lymph plays an important role in the absorption of fats and fat soluble vitamins A, D,E and K in the small intestine.

Q.96 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Mammals and Birds are warm blooded animals and so to keep the body warm heat has to be continuously produced in the body. As a result, the rate of respiration is also higher in mammals and birds as compared to other animals. As the rate of respiration is high the demand for oxygen is also higher in mammals and birds as compared to other animals.

To supply sufficient oxygen to the body tissues and cells oxygenated blood should move separately to the body tissues and cells. It should not mix with the deoxygenated blood carrying carbon dioxide. Otherwise, it will not be able to carry sufficient oxygen to the body tissues. 

On cold blooded animals such fishes, amphibians and reptiles the rate of respiration is low. As a result their oxygen demand is also lower. In these animals there is partial mixing of oxygenated and deoxygenated blood. So the blood carries lesser oxygen to the body tissues. 

Q.97 What are the components of transport system in highly organized plants?

Highly organized plants have Vascular Tissues(also called complex tissues) for transport of materials. These tissues are like continuous tubes that conduct materials in dissolved form in water medium rapidly through the plant body. These tissues are-

(a) Xylem-It carries water and dissolved minerals from the plant roots to the leaves and other parts of the body. It has Vessels and Tracheids as the conducting elements to carry water and minerals.

(b) Phloem-Helps in translocation of food from leaves to other parts of the plant body and storage organs. It has sieve tubes as the conducting elements.

Q.98 Difference between Xylem and Phloem

Q.99 Name the two forces that are responsible for the movement of water in the xylem against gravity and how do they work?

There are mainly two forces that are responsible for the movement of water in the xylem against gravity. They are-

(a) Root pressure- At the roots, cells in contact with the soil actively (that is using energy from ATP) take up dissolved ions from the soil. As a result, the cytoplasm of root cells becomes hypertonic as compared to the water in the soil. Water therefore moves into the roots from the soil by endosmosis. This creates a column of water in the xylem that is pushed upwards. This upward push on the water is called Root pressure. It can push up water up to some height in the plants 

(b) Transpiration pull-Plant leaves lose water by the process of transpiration through stomata. To make up the water loss the leaf cells draw out water from the leaf xylem. As a result a suction pull is created on the water in the xylem tubes and the water rises up to great heights.

The transpiration pull is strong enough to draw up sufficient water to great heights. Transpiration pull generally operates during the day when the plants lose more water by transpiration due to sun’s heat. Root pressure mainly operates during night. Both of these forces together help in supplying water to great heights of big trees. 

Q.100 How are water and minerals transported in plants?

(a) Trachieds and vessels of xylem tissue carry water from roots to leaves.

(b) This tissue form a continuous system of water conducting channel reaching all plant parts.

(c) Root cell which are in contact with the soil actively takes up ion which creates a difference in the concentration of ions in soil and root cells.

(d) So, water moves into roots creating a column of water that is steadily pushed upward.

(e) Due to transpiration there is loss of water from the cells of leaf. It creates a suction which pulls water from xylem cells of roots.

So, transpiration helps in the absorption and the upward movement of water. 

Q.101 How is food transported in plants?

(a) Transport of soluble products of photosynthesis is called Translocation and it occurs in sieve tube and companion cells of phloem.

(b) These substances move from leaves to storage organs, growing organs etc. both in upward and downward direction.

(c) Photosynthetic product in the form of Sucrose is transferred from leaf cells to Phloem in expense of energy.

(d) This increases osmotic pressure of phloem tissue, so water moves into the tissue.

(e) The osmotic pressure moves the material in the phloem to tissues which is in less pressure according to the plants need. 

Q.102 What is the necessity or need for double circulation?

There is a partition between the right side and left side of the human heart which is particularly useful to prevent mixing of deoxygenated with oxygenated blood. This type of separation of deoxygenated and oxygenated blood ensures highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature.

Q.103 What is blood pressure and how is blood pressure measured?

The force that blood exerts against the wall of a vessel is called blood pressure. This pressure is much greater in arteries than in veins. The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure and pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

Blood pressure is measured with an instrument called sphygmomanometer.

Q.104 What is hypertension and what is its consequences?

High blood pressure is also called hypertension and is caused by the constriction of arterioles, which results in increased resistance to blood flow. It can lead to the rupture of an artery and internal bleeding.

Q.105 Why do ventricles have thicker muscular walls than the atria do?

Atria are the two upper chambers of the heart. They receive blood through veins in which blood does not flow at high pressure. Atria also forces blood into the ventricles, which are situated right below them. So, the Atria do not bear much blood pressure either while receiving or pushing out blood. So, they have thin walls.

On the other hand both the lower chambers i.e., ventricles have to force blood into the arteries, which carry it to long distances. So, Ventricles have thicker walls as compared to atria. Left Ventricle has the thickest walls with strong cardiac muscles because it has to force out blood into the main artery (Aorta), which supplies blood throughout the body at high pressure.

Q.106 Why do animals, like amphibians or many reptiles have three-chambered hearts?

Animals, like amphibians or many reptiles have three-chambered hearts and the supply of oxygen to the tissues is low as they are cold- blooded animals. They can also tolerate some mixing of the oxygenated and de-oxygenated blood streams as they do not use energy for to maintain their body temperature, as the body temperature of the cold- blooded animals depend on the temperature in the environment. 

Q.107 What is meant by transpiration? What is its use?

The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.

• Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves.

• It also helps in temperature regulation.

Q.108 What is meant by translocation and where does it occur?

Transport of soluble products of photosynthesis is called translocation and it occurs in sieve tube and companion cells of phloem.

Q.109 Why does haemoglobin molecule act as efficient carrier of oxygen than diffusion process?

Haemoglobin has high affinity for oxygen, so it carries the gas faster in blood where as diffusion is a slow process.

Q.110 Explain how exchange of materials takes place between Blood and Tissues.

Arteries supply fresh oxygenated blood to different body organs. Inside the body organ, the artery divides into smaller branches called arterioles. The arterioles further divide into extremely thin walled blood capillaries.

The blood capillaries form an extensive network inside the body organ. They make their way through the tissue cells. Blood plasma along with the dissolved materials comes out of the thin walls of the blood capillaries and collects into the tissue. It is then called tissue fluid, which acts as an intermediate medium between blood and tissue cells.

The tissue fluid contains different materials such as oxygen, amino acids, glucose, mineral ions, and proteins etc. which are needed by the body cells. The body cells take up the required materials from the tissue fluid and release their wastes such as CO2. CO2 enters through the blood capillary wall and dissolves into the blood plasma or enters into the red blood cells.

Q.111 Mention the functions of the blood?

Functions of Blood-

(a) Transport of Materials-The first and main function of blood is the transport of materials in the body. The blood plasma, which carries many materials in dissolved form, is the main transport medium in the body. It carries materials like glucose, proteins, amino acids, salts, water, hormones etc to different cells in the body.

(b) Osmoregulation-Blood helps in controlling the amount of water (fluid balance) in the body. It carries extra water to the kidneys where it is filtered out in the urine. When there is water scarcity in the body water is retained in the blood.

(c) Role in Immune system-The White Blood Cells protect the body from many invading microorganisms by killing them. In addition the blood plasma also carries special proteins, called antibodies which also kill the invading microorganisms.

(d) Role in Absorption of Digested Food in the intestine-Blood is richly supplied to the small intestine where it absorbs the nutrients from the digested food and supplies them to the different body organs.

(e) Role in Excretion of Wastes-Blood carries different wastes. CO2, which is produced as a waste during respiration is transported to the lungs for removal into the air. Urea that is produced in the liver is transported by the blood to the kidneys. Here urea along with other wastes is filtered out and released as urine.

(f) Role in Maintaining Proper Body Temperature-Blood helps in proper distribution of heat in the body. Plasma has high heat carrying capacity. It helps in normalizing the body temperature in extreme hot and cold conditions. 

Q.112 Name the respiratory pigment. Where is it found in the body?

Haemoglobin is basically an iron containing protein that is present in the Red Blood Cells. It acts as a respiratory pigment by carrying Oxygen and Carbon dioxide to and from the cells respectively.

(a) Haemoglobin carrying Oxygen-In the lungs, the oxygen gas that diffuses from air into the blood is taken up by the haemoglobin very rapidly. Every haemoglobin molecule can typically carry four oxygen molecules.

(b) Haemoglobin carrying Carbon dioxide-When the blood reaches into the tissues, by reverse reaction oxygen is released from the haemoglobin and diffuses out into the tissue fluid. The tissue cells take up this oxygen and in return release CO2 into the tissue fluid. Some of the CO2 coming into the tissue fluid is taken up by the haemoglobin in the red blood cells and carried to the lungs for removal. 

Q.113 How does transpiration help the ‘ascent of sap’ (water and dissolved minerals) in plants?

Evaporation of water molecules from the cells of the leaf creates a suction which pulls water from the xylem cells of roots. Thus transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to leaves.




Q.114 What is meant by excretion?

The process of removing harmful metabolic wastes such as urea, uric acid and salts from the body is called excretion.

Q.115 What is the basic reason of urine production?

Blood carries nitrogenous wastes in the form of urea or uric acid which needs to be removed. It is done by kidneys by filtering the blood and removing uric acid in the form of urine.

Q.116 State the role of kidney in human transport system:

(i) Remove or excrete nitrogenous wastes

(ii) Regulate water content of the body(osmo-regulation)

(iii) Maintain mineral balance in the blood.

Q.117 What are the methods used by plants to get rid of excretory products?

Plants do not have a well- developed system for excretion than those of animals. Plants use different methods for elimination of their waste products.

(a) Oxygen generated during photosynthesis diffuses out of the stomata.

(b) Excess water iss removed by transpiration.

(c) Some plant waste products are stored in cellular vacuoles.

(d) Some plant waste products are stored in leaves, which are removed from the plant when leaves fall off.

(e) Waste products resins and gums are stored in old xylem.

(f) They also release some waste substances into the soil around them.

Q.118 Explain the process of haemodialysis?

In case of kidney failure due to an infection, injury or restricted blood flow to kidneys, leading to the accumulation of poisonous wastes in the body, which can even lead to death.

An artificial kidney or dialyser is used to remove nitrogenous waste products from the blood through dialysis.

Artificial kidneys contain a number of tubes with a semi-permeable lining, suspended in a tank filled with dialysing fluid. This fluid has the same osmotic pressure as blood, except that it is devoid of nitrogenous wastes. The patient’s blood is passed through these tubes. During this passage, the waste products from the blood pass into dialysing fluid by diffusion. The purified blood is pumped back into the patient. This is similar to the function of the kidney, but it is different since there is no reabsorption involved.

Q.119 Briefly describe the mechanism of urine formation?

Steps in urine formation:

The kidney performs three functions as steps involved in urine formation - ultra-filtration, selective re-absorption and tubular secretion.

Filtration is a process which separates particles of different sizes, where as term ‘ultra-filtration’ is used when the particles being separated are very small i.e. molecules or ions. 


• Occurs in the Glomerulus of the Bowman’s capsule. Blood in the glomerulus is under high pressure. This forces substances that are small enough to get through the pores in the capillaries from the blood into Bowman’s capsule. The membrane lining the inner surface of thr Bowman’s capsule has small pores.

• The mixture of small molecules which forms inside the Bowman’s capsule is called Ultrafiltrate. The ultra-filtrate contains mainly water with dissolved amino acids, glucose, mineral salts, uric acid inorganic salts, pigments and urea. Red blood cells and large molecules such as blood proteins, Corpuscles (RBC and PATELETS), fat and other large molecules remain in the blood. Filtered fluid is called glomerular filtrate.

Selective re-absorption:

As the glomerular filtrate passes along each tubule, selective reabsorption takes place. This means that some substances pass back into the blood, while others remain in the glomerular filtrate.

• All the glucose, most of the mineral salts and usually about 70% of the water are reabsorbed. The urea, small amount of mineral salts and water remains are carried to the bladder as urine.

• Each part of the nephron is responsible for reabsorption of a particular substance from the glomerular filtrate.

• Loop of Henle’s helps in reabsorption of water from the ultrafiltrate.

Tubular secretion involves the secretion of substances not required by the body into the filtrate by the cells of the distal convoluted tubule before it leaves the kidney. The filtrate which drains into the collecting duct after Selective reabsorption and Tubular secretion is termed URINE.

Collecting duct   →     Pelvis   →      Ureters     →    Urinary bladder   →     urethra 

• Urine passes into the collecting ducts to the pelvis and through the ureters into the urinary bladder is due to ureteral peristalsis and gravity.

• Urine is expelled from the urinary bladder through the urethra is due to the relaxation of sphincter muscles located at the opening of the urinary bladder into the urethra.

• The expulsion of urine from the urinary bladder to the exterior through the urethra is called URINATION.

Q.120 What is meant by Diuretics?

Substances that increase the formation of urine are called DIURETICS (Liquid diet, Tea, Coffee, Alcohol etc.)

Q.121 Name the various parts of the nephrons and give its function:

Q.122 Name the organs that make up the excretory system in human beings:

The excretory system in human beings consists of:-

• A pair of kidneys

• A pair of ureters

• Urinary bladder

• Urethra

Q.123 Differentiate between osmoregulation and excretion?

Excretion is the elimination of metabolic waste products from the body.

Osmoregulation is regulating osmotic pressure of the body fluids by controlling the amount of water and salts in the body.

Q.124 Name the passage in sequence through which urine passes from kidneys to the outside in humans. How is urine prevented from flowing back into the ureters?

Kidney →  the urinary bladder → the urethra → outside [via vaginal opening in women or via the penis in man] 

There are valves present in ureters called as ureterovesical valves which prevent the backflow of urine.

Q.125 Explain the structure of the kidney:

Structure of human kidneys:- The human kidneys are reddish brown-paired structure, which lie along the posterior side of the abdominal wall on either side of the vertebral column. Each kidney is bean shaped and is enclosed in a thin, tough, fibrous, whitish capsule. The outer surface of each kidney is convex while the inner one is concave. The inner side of kidney is composed of two main regions, a dark outer region called cortex and a lighter inner zone called medulla.

The cortex contains uriniferous tubules or nephron, which manufactures the urine; the medulla contains conical projections called renal pyramids containing tubules, which carry urine from nephron to the pelvis of the kidney. From this region, the urine is taken to the urinary bladder through along tuber called ureters .




Q.1 Meena who is studying in Class-X gets tired very soon and her skin colour is turning pale,her haemoglobin content in the blood is also low. When her teacher comes to know about the problem faced by Meena, she advises her to have iron rich foods like clams, liver, sunflower seeds, nuts, beef, lamb, beans, whole grains, dark leafy greens (spinach), dark chocolate, and tofu. She is really confused about this situation.

(i) Which disease is she suffering from?

(ii) Where is haemoglobin found in the body?

(iii) What was the value shown by the teacher?

(i) Meena is suffering from Anaemia. Anaemia is usually defined as a decrease in the amount of red blood cells (RBCs) or the amount of haemoglobin in the blood. It can also be defined as a lowered ability of the blood to carry oxygen. 

(ii) Haemoglobin is basically an iron containing protein that is present in the Red Blood Cells. It acts as a respiratory pigment by carrying Oxygen and Carbon dioxide to and from the cells respectively. 

(iii) The teacher displays her concern for her students as well as her knowledge. 

Q.2 You were standing on the roadside, when you saw a family travelling in the car. An ambulance carrying a patient for dialysis was travelling behind the car. The driver of the car brought his car to one side of the road and allowed the ambulance to overtake.

(i) What was the value shown by the driver?

(ii) What is dialysis?

(iii) State the role of kidney in human transport system

(i) The driver shows concern for human life, sense of responsibility of every human being

(ii) Dialysis is a treatment that does some of the things done by healthy kidneys. It is needed when our own kidneys can no longer take care of our body's needs. Dialysis is the artificial process of eliminating waste (diffusion) and unwanted water (ultrafiltration) from the blood. An artificial kidney or dialyser is used to remove nitrogenous waste products from the blood through dialysis.

(iii) (a) Remove or excrete nitrogenous wastes

(b) Regulate water content of the body(osmo-regulation)

(c) Maintain mineral balance in the blood.


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