Life process

CHAPTER6

Life Processes

1. Nutrition
   
2. Transportation
   
3. Metabolism
   
4. Respiration
   
5. Reproduction
   
6. Excretion.
   

2.1    Nutrition: Nutrition is defined as (a) The process by which a living organism assimilates food and uses it for growth and for replacement of tissues. (b) The science or study that deals with food and nourishment, specially in human. (c) The process of nourishing or being nourished for animal and plant.

2.2    The general requirement for energy and material in common in all organisms, but it is fulfilled in different ways. Some organisms use simple food material obtained from inorganic sources in the form of carbon dioxide and water. Such organisms are called Autotrophs. Example: Green plants and some bacteria. Other organisms utilize complex substances. These complex substances have to be broken down into simpler one before they can be used for upkeep and growth of the body. As a result it can be said that the Hetrotrophs survival depends directly or indirectly on Autotrophs. Hetrotrophs organisms include animal and fungi.

2.3    Autotrophic Nutrition: The process by which organisms prepare their food from the simple inorganic materials like mineral salts, Carbon dioxide and water in the presence of sunlight. Mostly all green plants have an autotrophic mode of nutrition.

The energy requirements of the autotrophic organism are fulfilled by the process of photosynthesis. Photosynthesis is the process by which autotrophs take in substances from the outside and convert them into stored form of energy. This material is taken in the form of Carbon dioxide and water and the same are converted into Carbohydrates in the presence of sunlight and Chlorophyll. Carbohydrates are utilized for providing energy to plants. Amount of carbohydrates which are not used immediately are stored in the form of starch.
Process to gain Carbon dioxide for photosynthesis: Carbon dioxide is obtained by plant through tiny pores present on the surface of leaves called Stomata.  Large amount of water can also be lost through these stomata. Plants close stomata when they don’t need Carbon dioxide for photosynthesis. The opening and closing of stomata is controlled by ‘guard cell’.

2.4    Heterotrophic Nutrition: Heterotrophic nutrition is a type of nutrition in which organisms depend upon other organisms for food to survive.  All animals, fungi and non-photosynthesizing plants are heterotrophic.

2.5    Nutrition in uni-cellular organisms: (a) Amoeba takes in food using temporary finger like extensions of the cell surface which fuse over the food particles forming a food-vacuole. 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. (b) In Paramoecium which is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

2.6    Nutrition in Human beings: Nutrition in human being is carried out in different five stages – (a) Ingestion (b) Digestion (c) Absorption (d) Assimilation (e) Egestion.

2.7    Alimentary canal: The human digestive system which is also called alimentary canal is a muscular tube which extends from the mouth to the anus. Alimentary canal includes – mouth, oral cavity, teeth, esophagus, pharynx, stomach, small intestine, large intestine and anus.

All these stages are carried out in digestive system called Alimentary canal which extends from mouth to the anus.

1. (a) Ingestion: The process of taking food, drink or another substance into the body by swallowing, chewing or absorbing (through cell membrane) is called ingestion.
   (b) Digestion: It is the process of breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream.
   (c) Absorption: Absorption is a complex process in which nutrients from digested food are harvested.
   (d) Assimilation: The process of absorbing nutrients during digestion and distrusting them to the body for growth and repair. The small intestine uses microvilli to absorb nutrients. The large intestine observes water by osmosis (The gradual passing of a liquid through a thin layer/membrane) to the blood. by which taking food and absorbing takes place.                                                                                                                    (e) Egestion: The process of discharging undigested food or water material from cell or organism is called egestion.                                                                                                          Questions (Page – 105)

Q-1: What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans: The differences between Autotrophic Nutrition & Heterotrophic Nutrition are as follows:

Q-2: Where do plants get each of the raw materials required for photosynthesis?

Ans: The raw materials required for photosynthesis by plants and their sources are given below:

1. CO₂ is obtained from atmosphere through stomata.
   
2. Water is absorbed by plant roots from the soil.
   
3. Sunlight is an essential raw material for Photosynthesis.
   
4. Nutrients are obtained by soil by plant roots.
   

Q-3: What is the role of the acid in our stomach?

Ans: Acid like HCl present in the stomach dissolves food particles and creates an acidic medium. In acidic environment protein digesting enzymes pepsinogen is converted into pepsin. HCl in the stomach also acts as protective barrier against many disease causing pathogens.

Q-4: What is the function of digestive enzymes?

Ans: Digestive enzymes break the complex food molecules into simpler ones. This will make the food absorption process very easy and effective. Absorbed food is transported to all parts of the body by blood.

Q-5: How is the small intestine designed to absorb digested food?

Ans: Small intestine has small projections called ‘micro villi‘ which increases the surface volume which make absorption more effective. Within the villi there are numerous blood vessels that absorb digested food and carry it to blood stream. Blood transports food to each part of body.

3.1    Transportation: Transportation in living organism is a process by which food, Oxygen & waste materials etc. are transported in the entire body. The process of transportation in animals specially in human beings and plants are different. Hence, it is necessary to discuss the transport system in both categories of living organisms separately.

3.2    Transportation in Human beings: In human beings, blood plays the most important role as blood consists of a fluid medium called ‘plasma’ in which the cells are suspended. Plasma transports- food, Carbon dioxide and Nitrogenous wastes in dissolved form. Oxygen is carried by the Red Blood Corpuscles (RBC and due to which, the colour of blood is red). Many other substances like salts etc. are also transported by blood. Therefore, a pumping organ is required to push blood around the body. 

(a) Pumping organ the Heart: In human beings, heart is a muscular organ. Both Oxygen and Carbon dioxide have to be transported by blood. Heart has different chambers to prevent the Oxygen-rich blood from mixing with the blood containing Carbon dioxide. The Carbon dioxide-rich blood has to reach to lungs for the removal of Carbon dioxide and the Oxygenated blood from the lungs is again brought back to the heart and this Oxygen-rich blood is then pumped to the rest of the body. Oxygen-rich blood from lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle relaxes, so that the blood is transferred to it. When the muscular left ‘ventricle’ contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it relaxes. As the right atrium contracts, the corresponding lower chamber, the right ‘ventricle’ dilates. This transfers blood to the right ‘ventricle’ which in turn pumps it to the lungs for oxygenation. Since, ‘entricles’ have to pump blood into various organs, they have thicker muscular walls than that of ‘atria’. Valves ensure that blood does not flow backwards when the ‘atria’ or ‘ventricles’ contract.

(b) Lung: The most important function of the lungs is to take oxygen from the environment and transfer it to the bloodstream. Taking more than 6 million breaths per year, the lungs affect every aspect of human bodies and health.

Location & size: The lungs are located in the chest, behind the rib cage on either side of the heart. They are roughly conical in shape with a rounded point at their apex and a flatter base where they meet the diaphragm. Although they are a pair, the lungs are not equal in size and shape. The left lung has an indentation bordering where the heart resides, called the cardiac notch. The right lung is shorter to allow space for the liver below. Overall, the left lung has a slightly smaller weight and capacity than the right. The lungs are surrounded by two membranes, known as the pulmonary pleurae. The inner layer directly lines the outer surface of the lungs, and the outer layer is attached to the inner wall of the rib cage.

The space between the two membranes is filled with pleural fluid.

Function: The lungs’ main role is to bring in air from the atmosphere and pass oxygen into the bloodstream. From there, it circulates to the rest of the body. Necessary help is required from structures outside of the lungs in order to breathe properly. To breathe, human use the muscle of the diaphragm, the intercostal muscles (between the ribs), the muscles of the abdomen, and sometimes even muscles in the neck. The diaphragm is a muscle that is domed at the top and sits below the lungs. It powers most of the work involved in breathing.

As it contracts, it moves down, allowing more space in the chest cavity and increasing the lungs’ capacity to expand. As the chest cavity volume increases, the pressure inside goes down, and air is sucked in through the nose or mouth and down into the lungs.

As the diaphragm relaxes and returns to its resting position, the lung volume decreases because the pressure inside the chest cavity goes up, and the lungs expel the air.

The lungs are like bellows. As they expand, air is sucked in for oxygen. As they compress, the exchanged carbon dioxide waste is pushed back out during exhalation.

When air enters the nose or mouth, it travels down the trachea, also called the windpipe. After this, it reaches a section called the carina. At the carina, the windpipe splits into two, creating two main stem bronchi. One leads to the left lung and the other to the right lung. From there, like branches on a tree, the pipe-like bronchi split again into smaller bronchi and then even smaller bronchioles. This ever-decreasing pipework eventually terminates in the alveoli, which are little air sac endings.

(c) Blood vessels: The transportation of blood in human body is carried out by two blood vessels – (i) Artery- The vessels which carry blood away from the heart to various

organs of the body. Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls & (ii) Vein – The vessles which collect the blood from different organs and bring it back to the heart. Veins do not need thick walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows only in one direction.

(d) Platelets: Platelets play a very vital role in conservation of blood as they minimize the loss of blood due to injury, wound, accident etc. In addition, leakage would lead to a loss of pressure which would reduce the efficiency of the pumping system. To avoid this, the blood has ‘platelet’ cells which circulate around the body and plug these leaks by helping to clot the blood at the points of injury.

(e) Lymph: There is another type of fluid which is also involved in transportation in human body, this is called ‘lymph’ or ’tissue fluid’. Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into larger veins.

3.3    Importance of Blood Pressure (BP):     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.

3.4    Transportation in Plants: In plants, a proper system of transportation is essential as plants absorb several raw materials like Nitrogen (N), Phosphorous(P) and other materials. The absorption of such materials/substances occurs through root which is in contact with the soil. If the distance between soil and contacting organ of plant and chlorophyll is small then the energy can easily be diffuse to all parts of the plant body. On the contrary, if such distance is large due to changes in plant body design etc. then the process of diffusion will not be sufficient to provide raw materials in leaves and energy in roots. Therefore, a proper system of transportation is essentially required for plants.

    The need of energy differs among different body designs. Plants do not move, and plant bodies have a large proportion of dead cells in may tissues. As a result, plants have low energy needs and can use relatively slow transport systems. Plant transport system move energy stores from leaves and raw materials from roots. These two pathways are constructed as independently organized conducting tubes. These are ‘Xylem’ & ‘Phloem’. Xylem transports water and minerals obtained from the soil and phloem transports products of photosynthesis from the leaves.

3.5    Transportation of water: Xylem is a plant tissue in which vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. Roots are connected to soil, actively takes up ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference. Means to say that there is steady movement of water into root xylem, creating a column of water that is steadily pushed upwards.

However, this pressure by itself is unlikely to be enough to move water over the heights that we commonly see in plants. Plants use another strategy to move water in the xylem upwards to the highest points of the plant body provided that the plant has an adequate supply of water, the water which is lost through the stomata is replaced by water from the xylem vessels in the leaf. In fact, evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration. Hence, 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. The effect of root pressure in transport of water is more important at night. During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.

3.6    Transport of food and other substances: Water, minerals and food with other substances are required for growth of a plant. The products of metabolic processes, particularly photosynthesis (where they are formed), are transported from leaves to other parts of the plant. This transport of soluble products of photosynthesis is called ‘translocation’ and it occurs in the part of the vascular tissue known as ‘phloem’. Besides the products of photosynthesis, the phloem transports Amino acids and other substances. These substances are especially delivered to the storage organs of roots, fruits and seeds and to growing organs. The translocation of food and other substances takes place in the ‘sieve tubes’ with the help of adjacent companion cells both in upward and downward directions. The translocation in phloem is achieved by utilizing energy. Material like sucrose is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure. This allows the phloem to move material according to the plant’s needs.

Questions (Page – 110)

Q-1: What are the components of the transport system in human beings? What are the functions of these components? 

Ans: Heart, blood and blood vessels (arteries and veins ) are the main components of transport system in human beings.

Functions of these components are as follows:

Heart: Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.

Blood: Blood transports Oxygen, nutrients, CO₂, and Nitrogenous wastes.

Blood vessels: Blood vessels such as arteries and veins transports blood to all parts of body.

Q-2: Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Ans: Mammals and birds are warm blooded animals which keep their body temperature constant irrespective of the environment they leave. This process require lot of oxygen for more cellular respiration so that warm blooded animals produce more energy to balance their body temperature. Hence, it is very important for warm blooded animals to separate oxygenated and deoxygenated blood to keep their circulatory system efficient.

Q-3: What are the components of the transport system in highly organized plants?

Ans: There are two types of conducting tissues in highly organized plants that carry out transport system (1) Xylem (2) Phloem. Xylem conduct water and minerals from roots to rest of the plant parts. Similarly, Phloem transports food materials from leaf to other parts of the plant.

Q-4: How are water and minerals transported in plants?

Ans: Xylems parts 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 which forces water into xylem cells of roots. After this, there will be a steady movement of water from the root xylem to all parts of the plant connected through conducting interconnected water-conducting channels.

Q-5: How is food transported in plants?

Ans: Food is transported in plants by a special organ called as phloem. Phloem transports food materials from leaf to different parts of a plant. Transportation of food in phloem is achieved by the expenditure of ATP (energy). This increases osmotic pressure in the tissue causing water to move. This pressure moves material in the Phloem to the tissues with less pressure. This is helping in transportation of food material as per the needs. Ex: Sucrose

4.1    Metabolism: Metabolism is a process in plants and animals by which food is changed into energy to help them grow.

5.1    Respiration: Respiration is the biological process in which the cells of an organism obtain energy by combining oxygen and glucose resulting in the release of Carbon dioxide, water and ATP. This process differs in different organisms like plants and animals.

5.2    Respiration in plant: The method by which cells get chemical energy by the consumption of Oxygen (O) and liberate of Carbon dioxide (CO₂ ). In this process, plants require Oxygen (O) and dispose Carbon dioxide () like animals. In plants, every their parts viz. root, stem execute the process of respiration as plants do not have specific developed organs for the same. The method of respiration may be written as follows:

Oxygen (O) + Glucose = Water + Carbon dioxide (CO₂) with energy.

    Plants do not have any specific developed organ to respirate that’s why plants don’t breath but they respire.

1. Respiration in root: In plants, respiration occurs with the help of roots as oxygenated air is present in soil. Roots absorb oxygen from soil with the help of their root hair and then Oxygen is transported to all parts of root for respiration. During respiration, Oxygen is transformed into Carbon dioxide which is released in the opposite direction to soil.
   
2. Respiration in stem: The stems of plants are hard and woody that’s why the exchange of gases take place through ‘lenticels’. Lenticels are generally loosely packed dead cells whch are present in the form of tiny pores on the back of woody plants. These allow Oxygen (O) to pass to intercellular spaces of the inside of tissues and Carbon dioxide to be liberated into the atmosphere by diffusion and hence process of respiration is completed.
   

   In case of ‘herbaceous stem’, exchange of gases takes place through stomata .
   

3. Respiration by leaves: In leaves, the exchange of gases (respiratory) takes place through stomata which is in the form of very small pores available in big numbers on the lower side of leaves. Every stomata has a tiny pore at it’s center which is enclosed and regulated by two kidney shaped cells called ‘guard cell’. The opening and closing of stomata is controlled by ‘guard cell’. When stomata opens the exchange of gases takes place between the atmosphere and interior of the leaf by diffusion and hence the process of respiration through leaves is completed.
   

5.3    The rate of respiration differs in plant with the change of temperature like human. When a sprinter is running he/she respirates more frequently in compare to a person in rest. Owing to increase in the rate of respiration, the temperature of the running person increases and vis-versa. Similarly, in plants increase in temperature enhances the rate of cellular respiration and decreases when temperature dips down.

    Plants emit Carbon dioxide (CO₂) in day and night times but in day time the amount of Carbon dioxide (CO₂) released as a result of photosynthesis is very large. At night the process of photosynthesis does not takes place due to absence of the sunlight. Hence, at night plants only emit Carbon dioxide (CO₂). Therefore, it is advised to avoid sleeping under a tree in night.

5.4    Respiration in human: In human, it is done by inhaling Oxygen (O) and releasing

Carbon dioxide (CO₂). Two lungs are the primary organs of the respiratory system. Other components of the respiratory system conduct air to the lungs, such as the ‘Trachea (windpipe) which branches into smaller structures called ‘Bronchi’.

The process of respiration in human being is discussed as follows:

Air is taken into the body through the nostrils. The air passing through the nostrils is filtered by fine hairs that line the passage. The passage is also lined with mucus which helps in this process. From here, the air passes through the throat and into the lungs. Rings of cartilage are present in the throat. These ensure that the air-passage does not collapse.

Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli (singular–alveolus). The alveoli provide a surface where the exchange of gases can takes place. The walls of the alveoli contain an extensive network of blood-vessels. As it is experienced in earlier years, when air is inhaled , ribs of human are lifted and flatten the diaphragm, and the chest cavity becomes larger as a result. Owing to this, air is sucked into the lungs and fills the expanded alveoli. The blood brings Carbon dioxide from the rest of the body for release into the alveoli, and the Oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

When the body size of animals is large, the diffusion pressure alone cannot take care of Oxygen delivery to all parts of the body. Instead, respiratory pigments take up Oxygen from the air in the lungs and carry it to tissues which are deficient in oxygen before releasing it. In human beings, the respiratory pigment is hemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles. Carbon dioxide is more soluble in water than Oxygen is and hence is mostly transported in the dissolved form in human blood.

5.5    Respiration in unicellur organism: In such organisms, Oxygen enters into the body through cell membrane through the process of diffusion. Such organisms are so small that they don’t have any specific developed organ to carry out respiration.

6.1    Reproduction: It is discussed in Chapter – 8 named How do Organisms reproduce?

7.1    Excretion: The biological process involved in the removal of harmful metabolic wastes from the body is called excretion.

Different organism use various strategies to do this process. Many unicellular organisms remove these wastes by simple diffusion from the body surface into the surrounding water.

7.2    Excretion in human beings: The process of excretion in human beings is carried out be excretory system which includes pair of Kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen, one on either side of the backbone. Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.

    The purpose of making urine is to filter out waste products from the blood. As CO2 is removed from the blood in the lungs, Nitrogenous waste such as Urea or Uric acid are removed from blood in the Kidneys. The basic filtration unit in the kidney like in the lungs is a cluster of very thin-walled blood capillaries. Each capillary cluster in the Kidney is associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate. Each Kidney has large number s of these filtration units called nephrons packed close together. Some substance in the initial filtrate, such as glucose amino acids, salts and a major amount of water are selectively re-absorbed as the urine flows along the tube. The amount of water re-absorbed depends on the amount of excess water there in the body, and the amount of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connect the Kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra.

7.3    Artificial kidney Hemodialysis: When Kidney reduces it’s activity due to infections, injury or restricted blood flow to Kidneys then this leads to accumulation of poisonous wastes in the body, which can even lead to death. In case of Kidney failure, an artificial kidney can be used. An artificial Kidney is a device to remove Nitrogenous waste products from the blood through the process of dialysis.

    Artificial kidney contains a number of tubes with a semi-permeable lining, suspended in a tank filled with dialyzing fluid. This fluid has the same osmotic pressure as blood, except that it is devoid of Nitrogenous waste. The patient’s blood is passed though these tubes. During this passage, the waste products from the blood pass into dialyzing 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. Normally, in a healthy adult, the initial filtrate in the Kidneys is about 180 L in a day. However, the volume actually excreted is only a liter or two a day because the remaining filtrate is reabsorbed in the kidney tubules.

7.4    Excretion in plants: Plants have completely different system of excretion than those of animals. It is known that Oxygen (O) is excreted through the process of photosynthesis. Plants excrete excess water by means of transpiration. For other wastes, plants even excrete by losing their parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, specially in old xylem. Plants also excrete some waste substances into the soil around them.       

                                         Questions (Page – 112)

Q-1: Describe the structure and functioning of nephrons

Ans: Nephrons are the filtration units of the kidney which are large in numbers. Some substances in the initial filtrate, such as Glucose, Amino acids, Salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube.

The main components of Nephrons are as – (a) Glomerulus (b) Bowman’s capsule (c) Long renal Tube (d) Structure of Nephron.

Structure of nephron: The structure of nephron is given above at para 7.2

Functioning of Nephron is as follows:

Q-2: What are the methods used by plants to get rid of excretory products?

Ans: Plants can get rid of excess water by transpiration.

For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off.

Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete some waste substances into the soil around them.

3. How is the amount of urine produced regulated?

Amount of urine produced depends on the amount of excess water and dissolved waste present in the body. Other factors may be environment and ADH hormone which regulates the production of urine.

Exercise (Page – 113 )

 Q-1: The kidneys in human beings are a part of the system for

(a) nutrition

(b) respiration.

(c) excretion.

(d) transportation

Ans: The correct answer is D excretion.

The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Kidneys are located in the abdomen, one on either side of the backbone. Urine produced in the kidneys passes through the ureters into the urinary bladder where it is stored until it is released through the urethra.

Q-2: 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: In plants Xylem is responsible for transport of water hence the correct answer is (a)

Q-3: The autotrophic mode of nutrition requires

(a) carbon dioxide and water.

(b) chlorophyll.

(c) sunlight.

(d) all of the above.

Ans: Autotrophic mode of nutrition requires carob-di-oxide, water, chlorophyll and sunlight from the preparation of food hence the correct answer is (d).

Q-4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.

(b) mitochondria.

(c) chloroplast.

(d) nucleus

Ans: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria. Hence the correct answer is (b) mitochondria

Q-5: How are fats digested in our bodies? Where does this process take place?

Ans: The process of fat digestion is mentioned as follows:

• The small intestine is the place for complete digestion of carbohydrates, fats and proteins. It receives the secretions of the liver and pancreas for this purpose.
  
• The food coming from the stomach is usually acidic in nature and it has to be made alkaline so that pancreatic enzymes can act on it. Bile juice produced in the liver accomplish this process.
  
• Fats are usually present in the intestine in the form of larger globules, which makes it difficult for enzymes to act on them. The bile salts helps in breaking down larger globules into smaller globules. The pancreas helps in secreting pancreatic juice, which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.
  
• The walls of the small intestine contains glands, which secretes intestinal juice. The enzymes present in it finally converts the proteins to amino acids, complex carbohydrates into glucose and finally fats into fatty acids and glycerol.
  

Q-6: What is the role of saliva in the digestion of food?

Ans: Food we intake is complex in nature, if it is to be absorbed from the alimentary canal then it has to be broken into smaller molecules. This process is mainly done with the help of biological catalysts called enzymes. The saliva contains an enzyme called salivary amylase that breaks down starch, which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing the muscular tongue. Hence saliva plays a pivotal in digestion and absorption of food.

Q-7: What are the necessary conditions for autotrophic nutrition and what are its byproducts?

Ans: Autotrophic nutrition is the mode of nutrition in which the organisms prepare their own food with the help of certain conditions. The necessary condition for autotrophic nutrition are:

(i) Carbon dioxide: The plants take the carbon dioxide released by the animals. The carbon dioxide gets reduced to carbohydrates and hence, it is necessary for autotrophic nutrition.

(ii) Water: The plants get water from the roots. Water is necessary to provide hydrogen and oxygen for photosynthesis. Hence, water is necessary for autotrophic nutrition.

(iii) Sunlight: Plants absorbs light energy from the sun and this light energy is converted to chemical energy for the breakdown of water into hydrogen and oxygen. Hence, sunlight is important for autotrophic nutrition.

(iv) Chlorophyll: The chlorophyll is present in the chloroplast and it helps in the absorption of light energy which is useful for photosynthesis.

Byproducts: The byproducts of autotrophic nutrition are food in the form of Carbohydrate and Oxygen.

Q-8: What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration?

Ans: The difference between aerobic and anaerobic respiration are give as:

Aerobic respiration –

• The process takes place in the presence of free Oxygen
  
• The products of aerobic respiration are CO_2, water and energy.
  
• The first step of aerobic respiration (glycolysis) takes place in cytoplasm while the next step takes place in mitochondria.
  
• The process of aerobic respiration takes place in all higher organisms.
  
• In this process complete oxidation of glucose takes place.
  

Anaerobic respiration –

• The process takes place in the absence of the free oxygen.
  
• The products of anaerobic respiration are ethyl alcohol, CO₂ and a little energy.
  
• Even in anaerobic respiration, the first step takes place in cytoplasm while the next step takes place in mitochondria.
  
• In this process the glucose molecules is incompletely broken down.
  
• The process of anaerobic respiration takes place in lower organism like yeast, some species of bacteria and parasites like tapeworm.
  

Q-9: How are the alveoli designed to maximize the exchange of gases?

Ans: Alveoli is designed to maximize the exchanges of gases in the following ways:

• The lung is an important part of the body. The passage inside the lungs divides into smaller and smaller tubes, which finally terminate in balloon-like structures, called as alveoli.
  
• The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli usually contains an extensive network of blood vessels. We know that, when we breathe in, we lift our ribs, flatten our diaphragm and chest cavity becomes larger.
  
• Because of this action, air is sucked into the lungs and fills the expanded alveoli.
  
• The blood brings the essential carbon dioxide from rest of the body and supply it to alveoli; the oxygen in the alveolar air is taken up by the blood in the alveolar blood vessels to be transported to the all other cells of the body. During normal breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and carbon dioxide to be released.
  

Q-10: What would be the consequences of a deficiency of haemoglobin in our bodies?

Ans: Haemoglobin is a protein which is responsible for transportation of oxygen from hurt to all parts of the body cells for cellular respiration. Any deficiency of Haemoglobin can affect the Oxygen carrying capacity of RBC’S. This lead to lack of Oxygen in our body cells. Haemoglobin deficiency leads to a disease called as Anaemia.

Q-11: Describe double circulation of blood in human beings. Why is it necessary?

Ans: Double circulation means, in a single cycle blood goes twice in the heart. The process helps in separating oxygenated and deoxygenated blood to maintain a constant body temperature.

The double circulatory system of blood includes

• Pulmonary circulation
  
• Systemic circulation.
  

Pulmonary circulation: The right ventricle pumps deoxygenated blood into the lungs where it is oxygenated. The oxygenated blood is brought back to the left atrium from there, it is pumped into the left ventricle and finally blood goes into the aorta for systemic circulation.

Systemic circulation: The oxygenated blood is pumped to various parts of the body from the left ventricle. The deoxygenated blood from different parts of the body passes through vena cava to reach right atrium. The right atrium transfers the blood into right ventricle.

Q-12: What are the differences between the transport of materials in xylem and phloem

Ans: The difference between Xylem & Phloem are given below:

Q-13: Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Ans: The required comparison is as follows:

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