Solutions-Class-10-CBSE-NCERT-Science-Chapter-5-Life Processes

In multicellular organisms like humans, all the body cells are not in direct contact with the surrounding environment. Thus, every cell of the body will not get sufficient oxygen as per need by the process of diffusion from the environment. So, complex multicellular organisms need specialised tissues, organs and organ system to take in oxygen.

All live or living organisms respire. Also some movements either visible like locomotion from one place to another and growth related movements or invisible movement such as movement of molecules are the criteria to decide whether something is alive or not.

Raw materials are the substances which can not be directly utilized by the organisms. These are to be processed inside the body like photosynthesis in plants and digestion in man. Raw materials taken by plants from outside are carbon dioxide, water and sunlight. Animals take various materials from outside which are:

• Food: To supply energy, materials like carbohydrates, fats, proteins, minerals, vitamins etc., for working and maintenance of cells/tissues.
• Water: To provide medium in the cells of body and to carry out all the metabolic reactions necessary for life.
• Oxygen: To break down food so as to release energy.

Processes essential for maintaining life :

• Nutrition: It provides energy and materials (nutrients) required to sustain life.
• Respiration: It breaks down food (especially glucose) in the cells of organisms to release energy in the presence or absence of oxygen.
• Transportation: It is the process for carrying food and oxygen from one place to another in the body. Also it transports Wastes from body cells to excretory tissues.
• Excretion: It is the process to remove the by-products produced during other life processes.

Plants require carbon dioxide, water, sunlight and chlorophyll for photosynthesis.

• Carbon dioxide: Plants get carbon dioxide from the environment/atmosphere through stomata.
• Water: Plants (land plants) absorb water from the soil through roots and transport to leaves.
• Sunlight: Plants get it from the sun.
• Chlorophyll is present in chloroplast which is found in the cells of green leaves and green parts of plants.

Role of the hydrochloric acid released by the gastric glands in the stomach is

• to create acidic medium which is necessary for the activation of the enzyme pepsin.
• to kill the germs which food may contain.

The function of digestive enzymes: The food that we eat is complex in nature i.e., it contains complex molecules. Digestive enzymes break down these complex molecules into soluble smaller molecules so that they can be absorbed by the walls of the intestine.

• The small intestine is the site where digestion of food components is almost completed.
• It is also the place where digested food is absorbed into the blood to transport it to each and every cell of the body.
• The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body.
• For this, the inner lining of the small intestine has numerous finger like projections called villi.
• The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

• The organisms that live in water use oxygen dissolved in surrounding water.
• Since concentration of dissolved oxygen in water is fairly low, the aquatic organisms have much faster rate of breathing.
• Terrestrial organisms take oxygen from the oxygen-rich atmosphere, through respiratory organs.
• As there is sufficient amount of oxygen present in atmosphere so terrestrial organisms have much less breathing rate than aquatic organisms.

Different ways in which glucose is oxidised to provide energy in various organisms:

• First step of breakdown of glucose (6 carbon molecule) takes place in the cytoplasm of cells of all organisms. This process yields a three carbon molecule compound called Pyruvate or pyruvic acid.

Further breakdown of pyruvate takes place in different ways in different organisms.

(i) Anaerobic respiration: This process takes place in the absence of oxygen. In

this case pyruvate is converted into ethanol and carbon dioxide. This type of respiration is observed in yeast. Less amount of energy is released during Anaerobic respiration.

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

(ii) Aerobic respiration: In aerobic respiration breakdown of pyruvate takes place in the presence of oxygen to give rise to carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.

• Transport of oxygen: In human beings, the respiratory pigment, called haemoglobin present in the red blood corpuscles carry oxygen to different tissues of the body. The respiratory pigment present in the blood takes up the oxygen from the air in the lungs and carry it to tissues which are deficient in oxygen.
• Transport of carbon dioxide: Carbon dioxide is more soluble in water. Therefore it is mostly transported in dissolved form through blood plasma. Blood plasma transports carbon dioxide from the tissues to the lungs.

• In the lungs, the air passage (wind pipe) divides into smaller tubes, called bronchi which in turn form bronchioles.
• The bronchioles terminate in balloon-like structures, called alveoli.
• The alveoli present in the lungs provide maximum surface for exchange of gases.
• The alveoli have very thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.

The transport system (called circulatory system) in human beings consists of heart, blood and blood vessels.

Functions of components of circulatory system:

• Blood: Blood is a fluid connective tissue, it consists of a fluid medium known as plasma in which different types of cells such as white blood cells and red blood cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes (urea and uric acid) in dissolved form. Red blood cells transport oxygen. Blood also transports many other substances like hormones, salts, etc. Platelets present in the blood stop bleeding by forming blood clots.
• Heart: The heart is a muscular organ which is as big as our fist. Heart is a pumping organ to push blood around the body. It receives deoxygenated blood from the body parts and pumps it to lungs for its oxygenation. It receives purified blood from lungs and pumps it around the body.
• Blood vessels: Blood vessels form a closed network of tubes to reach all the tissues. Thus, the blood pushed by the heart flows in the blood vessels (arteries) and also comes back to the heart in the blood vessels (veins).

• Separation of oxygenated and deoxygenated blood allows a highly efficient supply of oxygen to the body. This system is useful in animals that have high energy need.
• Mammals and birds constantly need oxygen to obtain energy to maintain a constant body temperature.
• The heart in these organisms is 4-chambered and there is separation of left side and right side which is useful for birds and mammals by not allowing mixing of oxygenated and deoxygenated blood.

The transport system in highly organised plants consists of two components- xylem and phloem.

• Xylem: It consists of vessels, tracheids, xylem parenchyma and xylem fibres. The interconnected vessels and tracheids form a continuous system of water conducting channels reaching all parts of the plant. Xylem conducts water and dissolved minerals absorbed from the soil.
• Phloem: It consists sieve tubes, companion cells, phloem parenchyma and phloem fibres. The sieve tubes of phloem with the help of companion cells conduct soluble products of photosynthesis from leaves to different parts of the plant. The transportation of materials through phloem is called translocation.

• Water and dissolved minerals are transported through xylem tissue.
• Xylem vessels and tracheids of roots, stem and leaves are interconnected to form a continuous system of water conducting channels reaching all the parts of the plant.
• The root cells in contact with the soil actively take up ions from the soil.
• This creates a difference in the concentration of these ions between the root and the soil.
• Water therefore moves into roots from the soil to eliminate this difference. This results in continuous movement of water into the xylem. It forms a column of water that is steadily pushed upwards.
• There is continuous loss of water through stomata of the leaves in the form of water vapours. This process is called transpiration.
• Transpiration creates a suction pressure which pulls water from the xylem cells of root. As a result, there is enhanced absorption and upward movement of water and dissolved minerals from roots to the leaves.

Plants transport products of photosynthesis, amino acids and other substances in soluble form through phloem to storage organs of roots, fruits and seeds and also to growing organs. This transport of different materials in soluble form through phloem is known as translocation.

Translocation takes place in phloem by sieve tubes with the help of companion cells both in upward and downward directions.

Mechanism of translocation:

• Translocation is an active process and utilizes energy. Materials like sucrose is transferred from leaf cells or from the site of storage into phloem tissue.
• This process requires energy which is provided by ATP (adenosine triphosphate) molecules.
• Entry of sucrose into phloem tissue causes increase in osmotic pressure. As a result, water from outside moves into phloem.
• This pressure moves the dissolved materials in the phloem to tissues which have less pressure.

Structure and functioning of nephrons :

Structure of Nephron:

• Nephron is the filtration unit of kidney.
• It consists of a tubule which is connected with collecting duct at one end and a cup-shaped structure at the other end.
• This cup-shaped structure is called Bowman’s capsule.
• Every Bowman’s Capsule contains a cluster of capillaries, called Glomerulus.
• The blood enters into glomerulus through afferent arteriole of renal artery and leaves it through efferent arteriole.

Functioning of nephron: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.

Reabsorption:

• As the filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule.
• The amount of water reabsorbed depends on the need of the body and also on the amount of wastes to be excreted.
• The filtrate which remained after reabsorption is called urine.
• Urine contains dissolved nitrogenous wastes i.e., urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting duct to carry it to the ureter.

To get rid of excretory products, plants use the following ways:

• In many plants, waste products are stored in vacuoles of the cells.
• Some waste products are stored in the leaves. They are removed as the leaves fall off.
• Some waste products such as resins and gums are stored, especially in non-functional mature secondary xylem.
• Some waste products such as tannins, resins, gums are stored in bark, which is removed by peeling off the bark.
• Plants also excrete some waste substances through roots into the soil around them.

The amount of urine produced depends on the amount of water reabsorbed

which in turn depends on

• amount of water present in the body.
• amount of nitrogenous wastes present in the body.

The amount of urine produced is regulated by certain hormones like Antidiuretic hormone (ADH) or vassopressin hormone of the posterior lobe of master gland (pituitary) of the body which controls the movement of water and Na+ ions into and out of the nephrons.

(c) excretion.

(a) transport of water.

(d) all of the above.

(b) mitochondria.

Digestion of fats takes place in the small intestine.

Digestion of Fat:

• The fats are present in the form of large globules in the small intestine.
• Fat digesting enzymes are not able to act upon large globules efficiently.
• Bile juice secreted by the liver is poured in the intestine along with pancreatic juice. The bile salts present in the bile juice emulsify the large globules of fats. So, by emulsification large globules breakdown into fine globules to provide larger surface area for the proper action of enzyme.
• Lipase enzyme present in the pancreatic juice causes breakdown of emulsified fats.
• Glands present in the wall of small intestine secrete intestinal juice which has a fat digesting enzyme that converts fats into fatty acids and glycerol.
• Small intestine is the region of digestion of fats.

• The saliva contains salivary amylase that breaks down starch to sugar maltose.
• The saliva moisten the food that helps in chewing and breaking down the big pieces of food into smaller ones. So, that salivary amylase can digest the starch efficiently.

• Chlorophyll, carbon dioxide, water, sunlight and appropriate temperature are the necessary conditions for autotrophic nutrition.
• Molecular oxygen is the by-product of autotrophic nutrition.

Some organisms that use the anaerobic mode of respiration are yeast and bacteria.

• The alveoli are thin-walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air present in alveoli.
• Alveoli are balloon shaped which provide maximum surface for exchange of gases.

• The average haemoglobin content of blood, is 13-18 g per 100 ml in human males and 12-16 g per 100 ml in human females.
• If haemoglobin content decreases in blood, its oxygen carrying capacity will decrease and it will lead to a disease called anaemia.
• An anaemic person gets tired easily and loses weight.

Double circulation: In human beings, the blood goes through the heart twice

during each cycle. This is called double circulation of blood.

The double circulation of blood includes (i) Systemic circulation and (ii) Pulmonary circulation.

• Systemic circulation: It supplies oxygenated blood from left auricle (atrium) to left ventricle which is pumped to various body parts. The deoxygenated blood is collected from the various body organs by the veins to pour into vena cava and finally into right atrium (auricle). Right atrium transfers the blood into the right ventricle.
• Pulmonary circulation: The deoxygenated blood is pushed by the right ventricle into the lungs for oxygenation. The oxygenated blood is brought back to left atrium of the human heart from lungs. The oxygenated blood is pushed into the left ventricle. The left ventricle pumps oxygenated blood into aorta for systemic circulation.

Necessity of double circulation:

• The separation of the right side and the left side of the human heart is useful to keep deoxygenated and oxygenated blood from mixing.
• This type of separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body.
• This is useful in case of humans which constantly require energy to maintain their body temperature.