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Life Processes - Class 10 Science Textbook Solutions

 Life Processes
 Life Processes Class 10 Extra s with Answers Science Chapter 6

 1. Why is energy required by an organism even during sleep?
This is because even when an organism is asleep, various biological processes keep on occurring in its body which requires energy.
2.Give the energy transformation that takes place in the process of photo synthesis.
Solar energy is converted into chemical energy during photosynthesis.

3.What is chlorophyll?
Chlorophyll is a green coloured pigment found in the green leaves or green parts of the plant which traps solar energy for photosynthesis. Chlorophyll is present in cell organelles called chloroplasts.
4. Name the various factors which affect the rate of photosynthesis.
The factors which affect the rate of photosynthesis are light, water, temperature and carbon dioxide.
5. Define photolysis.
The phenomenon of breaking down of water molecule using solar energy absorbed by chlorophyll molecules is known as photolysis.
6. Define light reaction.
A chemical reaction, which take place only in the presence of light, is called light reaction or light dependent reaction. It takes place in grana of chloroplast. 
7. Define dark reaction.
A chemical reaction, which can take place even in the absence of light, is called a dark reaction or light independent reaction. It takes place in stroma of chloroplast.
8. what are peristalic movements?
The contraction and expansion movements of the walls of food pipe are called peristaltic movements. This movement pushes the food in forward direction in the alimentary canal.
9. Which is the largest gland in the human body?
10. Give an example of an organism whose digestion is intracellular.
11. Name the various cells through which water moves upward to react the leaves.
Water absorbed by root hairs moves through epidermis root cortex -endodermis → root xylem (i.e., tracheids and vessels) → stem xylem + xylem in the leaf.
12. What will happen to a plant if its xylem is removed?
The xylem tissue transports water and minerals from the soil to the leaves of a plant for photosynthesis. If xylem is removed, upward movement of water will stop leading to wilting of leaves and ultimately causes death of a plant.
13.In which chamber of heart is oxygenated and deoxygenated blood found?
Oxygenated blood: It is found in left auricle and left ventricle. Deoxygenated blood: It is found in right auricle and right ventricle.
14. What makes red blood corpuscles red?
15. What will happen if platelets were absent in the blood?
In the absence of platelets, the process of clotting will be affected.
16. What is the main function of kidneys in humans?
Kidneys excrete water and dissolve metabolic wastes, e.g., urea and other dissolved solids like uric acid, creatinine and inorganic salts.
17. In which part of nephron is water reabsorbed?
Proximal and distal convoluted tubules.
18. In which region of kidney Malpighian corpuscles are found?
In the outer part i.e., cortex of kidney. 
19. What process in plants is known as transpiration?
The release of water vapours in the atmosphere through the pores present on plant leaves, i.e., stomata, is called transpiration.
20. What is urethra?
It is muscular tube through which the collected urine passes into the urinary bladder.
21. Which is the major nitrogenous waste product in human beings? How is it removed from the body?
The major nitrogenous waste product in human beings is urea. Urea is removed/eliminated from the body through urine.
22. Name the membrane covering the lungs.

23. What is osmoregulation?
Osmoregulation is the maintenance of optimum concentration of water and salts in the body fluids. 
24. In which form
(i) oxygen is carried to the tissues
(ii) CO2 moves out of the blood?
(i) Oxyhaemoglobin
(ii) Carboxyhaemoglobin and as carbonic acid (CO2 dissolved in blood plasma). 
25. Why do the walls of trachea not collapse when there is less air in it?
Tracheal walls do not collapse when there is less air in it because it is supported by rings of cartilage.
26. Which part of root is involved in the exchange of respiratory gases in plants? 
Answer:Root hairs are involved in the exchange of respiratory gases in plants.
27. Name two organisms in which food material is broken down outside the body and absorbed.
Yeast, mushroom.
28. What prevents backflow of blood inside the heart during contraction?

Valves in heart prevent backflow of blood inside the heart during contraction.  
29. Wich is the first enzyme to mix with food in the digestive system?

Salivary amylase.
30. Why does lack of oxygen in muscles often lead to cramps among cricketers?

This is due to the conversion of pyruvate to lactic acid in the absence of oxygen. 
31.Where is pyruvic acid converted into lactic acid during deficiency of oxygen in tissues of human beings?
Golgi body.
32. Where does the oxygen come from when it is liberated during photosynthesis?
Oxygen liberated during photosynthesis comes from water. 
33. What is the internal (cellular) energy reserve in autotrophs?
34. In which forms do most plants absorb nitrogen?
Nitrates and nitrites.
35. What is common for Cuscuta, ticks and leeches?
All are parasites. They derive their nutrition from plants or animals without killing them.
36. Write the name of enzyme present in saliva and tell what function it has
Salivary amylase (ptyalin). It converts starch into sugar at pH of 7.
37. What protects the inner lining of stomach from hydrochloric acid?
The inner lining of stomach is protected from hydrochloric acid by mucus.
38. What is chyme?
The slightly digested food, enters into the stomach through the alimentary canal. In the stomach, this food is churned along with gastric juices converting this food into a semi-solid paste called chyme.
39. Name the enzyme which is present in infants but may be absent in adults.
40. Write the name and functions of two digestive enzymes secreted by pancreas.
Pancreas secretes pancreatic juice which contains enzymes like amylase, trypsin and lipase.Amylase helps in breakdown of carbohydrates. Lipase helps in breakdown of complex fat molecules.
41. Where is haemoglobin found? Write its main function.
Haemoglobin is a red coloured pigment found in red blood cells.
Its main function is to transport the respiratory gases like oxygen due to increased affinity towards oxygen.

Life Processes Extra s Short Answer Type
1. What is compensation point?
When the rate of photosynthesis is equal to rate of respiration, it is called as compensation point. The rate of liberation of O2 during photosynthesis is equal to the rate of liberation of CO2 during respiration. Thus, there is no net uptake of gases from the environment. Compensation point is usually reached at dusk and dawn and on a cloudly day.
2. What happens to visible light of the sun when it falls on chlorophyll?
Visible light of the sun consists of seven colours-violet, indigo, blue, green, yellow, orange and red. Out of these lights of different wavelengths, chlorophyll absorbs mainly blue, violet, red and orange lights but does not absorb the green light. It is due to the reflection of green light by chlorophyll of the plants that the plants look green in colour.
3. “All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.

During day time, as the rate of photosynthesis is more than the rate of respiration, the net result is evolution of oxygen. At night there is no photosynthesis, so they give out carbon dioxide due to respiration.
4. How does water affect the rate of photosynthesis in plants?
Water controls the opening and closing of stomata. The deficiency of water causes stomata to open very little or it may even remain closed. Therefore, it (required as a raw material for photosynthesis) cannot enter into the leaves and thus lack of water slows down the rate of photosynthesis.
5. What is peptic ulcer? How is peptic ulcer caused?
An ulcer on the inner membrane lining of the stomach is called peptic ulcer. Peptic ulcer is caused by the high acidity of gastric juice secretions. 
6. How does respiration occur in the leaves?
Leaves have tiny opening on their lower surface called stomata. The exchange of gases takes place through the stomata by the process of diffusion. 
7. What is ascent of sap?
Absorbed water from the soil also contains dissolved minerals (nitrates, phosphates, etc.) and hence it is called sap. This sap moves upwards due to the ‘transpiration pull’ developed in the xylem elements. Thus, transportation of sap from roots to the leaves at the top is called ascent of sap.
 8. What is transpiration pull?
Water in the mesophyll cells of leaves (cells located below the stomata) is in contact with water or sap in xylem of leaf petiole, stem and root. This water evaporates by the process of transpiration. Thus, due to transpiration water is pulled upward which creates an upward suction force called ‘transpiration pull’. 
9. Plants have low energy needs as compared to animals. Explain.
Plants do not move. In a large plant body there are many dead cells like schlerenchyma which provide strength to the plant but do not perform any cellular function. As a result they requires less energy. Animals, on the other hand, need energy for different activities like movement or search of food. SO2 they require more energy.
10. What is root pressure?
It is a pressure developed in the xylem due to metabolic activity of the root cells. It is a hydrostatic pressure developed in the root system that pumps the water or sap in the root xylem.
11. How do leaves of plants help in excretion?
Many plants store waste materials in the vacuoles of mesophyll cells and epidermal cells. When old leaves fall, the waste materials are excreted along with the leaves.
12. What is the role of intercostal muscles in respiration and where are these found?
Intercostal muscles are found in between the ribs. Their contraction and relaxation changes the volume of thoracic cavity so that air can enter and leave the lungs.
13. State the function of Bowman’s capsule and glomerulus.
Bowman’s capsule and glomerulus have semipermeable walls. The glomerulus, is a tuft of capillaries contained in Bowman’s capsule. The water and dissolved substances (wastes and useful) are filtered into the Bowman’s capsule and from here they are filtered into the tubule. Thus, both the structures act as filtering apparatus.
14. What causes movement of food inside the alimentary canal?
The wall of alimentary canal contains muscle layers. Rhythmic contraction and relaxation of these muscles pushes the food forward. This is called peristalsis, which occurs all along the gut.
15. What happens to glucose which enters the nephron along with the filtrate?
Glucose along with filtrate runs down through the long renal tubule by the action of cilia. Glucose, amino acids, salts, etc., are reabsorbed by the tubular cells and then secreted into the capillary blood cells by diffusion.
16. Name the correct substrates for the following enzymes:
1.    Trypsin
2.    Amylase
3.    Pepsin
4.    Lipase

1.    Protien
2.    Starch
3.    Protein
4.    Fats
17. Write down the functions of lymph nodes.
Functions of lymph nodes are:
•    Lymph nodes produce and maintain the lymphocytes of blood. These are only found in the mammals.
•    Lymph nodes filter the blood and remove poisonous and foreign substances, e.g., bacteria, debris, etc.
18. Name the organs of excretory system in human. Show them with the help of a labelled diagrams.


Excretion in Human Beings: The main function of human excretory system is to re move nitrogenous wastes such as urea from the body. It includes a pair of kidneys, a pair of ureters, a urinary bladdes and a urethra. Kindneys are located in the abdomen one on either side of Right Kidney the back bone. 
19. State the function of epiglottis.
At the top of the trachea (or wind pipe) there is a flap of cartilage called epiglottis. The function of epiglottis is to cover the mouth of trachea (or wind pipe) when we swallow food so that the food may not enter the trachea (or wind pipe).
20. Why are white blood corpuscles called soldiers of the body?
White blood corpuscles engulf (phagocytose) the foreign matter (bacteria, dust and other foreign material) entering the body, and are hence called soldiers. They produce antibodies against antigens, and antitoxins against toxins. 
21. Describe the importance of stomata in plant.
Plants release gaseous wastes such as CO2 produced during respiration at night and O2 produced during photosynthesis in daytime through stomata on leaves and lenticels found on stems.
22. What happens to the rate of breathing during vigorous exercise and why?
During vigorous exercise, our body requires more energy and for this purpose more oxygen is needed, so the rate of breathing is increased. Oxygen intake rate increases by about 20 to 25 times.
23. How do the guard cells regulate opening and closing of stomatal pores?
The swelling of guard cells due to absorption of water causes opening of stomatal pores while shrinking of guard cells closes the pores. Opening and closing of stomata occurs due to turgor changes in guard cells. When guard cells are turgid, stomatal pore is open while in flaccid conditions, the stomatal aperture closes. 
24. Two green plants are kept separately in oxygen-free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons.
Plant kept in continuous light will live longer. Because it will be able to produce oxygen required for its respiration by the process of photosynthesis.
25. In each of the following situations what happens to the rate of photo synthesis?
1.    Cloudy days
2.    No rainfall in the area
3.    Good manuring in the area
4.    Stomata get blocked due to dust.

1.    Decreases
2.    Decreases
3.    Increases
4.    Decreases.
26. Name the energy currency in the living organisms. When and where is it produced?
Adenosine triphosphate (ATP) is the energy currency in the living organisms. It is produced in the mitochondria during respiration in living organisms and also during photosynthesis in plants.
27. Explain the role of mouth in digestion of food.

1.    Food is crushed into small pieces by the teeth.
2.    It mixes with saliva and the enzyme amylase (found in saliva) breaks down starch into sugars.
3.    Tongue helps in thorough mixing of food with saliva.
28. Explain the statement, ‘Bile does not contain any enzyme but it is essential for digestion.’
Bile does not contain any enyzme but it is essential for digestion because bile is alkaline and contain salts which helps to emulsify the fat present in the food. SO2 the bile perform two functions:
•    The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act.
•    The bile salts breakdown the fat present in the food into smaller globules. This increases the efficiency of enzymes in the small intestine to digest the food effectively.
29. Why is blood circulation in human heart called double circulation?
The blood circualtion in human heart is called double circulation because the blood passes through the heart twice in one complete cycle of the body i.e., once through the right half in the form of deoxygenated blood and once through the left half in the form of oxygenated blood. 
30. What are the adaptations of leaf for photosynthesis?

1.    Leaves provide large surface area for maximum light absorption.
2.    Leaves are arranged at right angles to the light source in a way that causes overlapping.
3.    The extensive network of veins enables quick transport of substances to and from the mesophyll cells.
4.    Presence of numerous stomata for gaseous exchange.
5.    The chloroplasts are more in number on the upper surface of leaves.
31. Study the given diagram: Name the parts ‘A’ and ‘B’ and state one function of each.

A → Stomatal pore
Function: Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpsoe of photosynthesis.
B → Guard cell.
Function: The opening and closing of the stomatal pore is a function of the guard cell. 
32. Why does absorption of digested food occur mainly in the small intestine?
Maximum absorption occurs in small intestine because:
1.    digestion is completed in small intestine.
2.    inner lining of small intestine is provided with villi which increases the surface area for absorption.
3.    wall of intestine is richly supplied with blood vessels which take the absorbed food to each and every cell of the body.
33. What substances are contained in the gastric juice? What are their functions? 
Answer:Gastric juice contains three substances: hydrochloric acid, enzyme pepsin and mucus. Their functions are:
1.    Hydrochloric acid in the stomach is used to make the medium acidic to facilitate the action of the enzyme pepsin and to kill germs if any.
2.    Enzyme pepsin digests proteins to convert them into peptones.
3.    The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid. 
34. What are the various processes that take place in the duodenum?
Processes that take place in the duodenum are:
1.    Bile emulsifies the fat molecules present in the food into small globules.
2.    The pancreatic enzyme trypsin starts digesting the proteins and the pancreatic amylase breaks down the starch.
3.    Bile juice secreted by the liver and bicarbonate ions secreted by the duodenal wall makes the medium alkaline.
35. How does respiration occur in the roots of the plant?
Air is present in between the particles of the soil. The roots take the oxygen by the. process of diffusion. Oxygen first diffuses into the root hairs and reaches all other cells of the root for respiration. CO2 produced in the cells moves out through the root hairs, by the process of diffusion. For respiration, in older roots, where root hair is not present, the exchange of gases takes place through lenticels (tiny openings in the protective layer) by the process of diffusion. 
(i) Explain why the rate of photosynthesis in plants is low both at lower and higher temperatures.
(ii) Is green light most or least useful in photosynthesis and why?
(i) Photosynthesis is an enzymatic process. The enzymes function within an optimum range of temperature which is neither very low nor very high. At low temperature the activity of enzymes is lowered due to which the rate of photosynthesis is also low. Again when the temperature is very high, the activity of enzymes decreases which leads to low rate of photosynthesis.
(ii) Green light is least useful in photosynthesis, because chlorophyll does not absorb green light.
37. Though what conduction of water in plants takes place? Explain its mechanism.
Transport of water in plants: The transport or movement of soluble products (sugar) of photosynthesis from leaves to other parts of the plant is known as translocation. It occurs is the part of vascular tissue known as pheloem. Besides the product of photosynthesis, phloem also transports amino acids and other substances (such as plant harmones).
These substances are especially delivered to storage organs of roots, fruits, seeds and growing organs.
38. How does respiration occur in the stem of the plant?
In the stem of herbaceous plants, stomatas are present. SO2 the exchange of gases takes place through stomata by the process of diffusion. In the woody and hard stems of big plants, the exchange of gases takes place through lenticels which are present on the bark of the stem.
39. State the functions of the following components of transport system:
(i) Blood
(ii) Lymph.
(i) The following are the important functions of blood:
(a) It transports the digestive component of food to all the body cells.
(b) It also transports respiratory gases to body cells.
(c) It carries waste product for excretion.
(d) It acts as carrier of hormones.
(ii) Lymph contains lymphocyte cells which fight against infection and it also carries digested fat.

40. What is the advantage of having four chambered heart?
In four chambered heart, left half is completely separated from right half by septa. This prevents oxygenated and deoxygenated blood from mixing. This allows a highly efficient supply of oxygenated blood to all parts of the body. This is useful in animals that have high energy needs, such as birds and mammals.
41. State differences between artery, vein and capillary.
Differentiate between an artery and a vein.

42. What is autotrophic nutrition? Explain in brief with example.
Autotrophic Nutrition: Some organisms use simple food materials obtained from inorganic sources in the form of carbon dioxide and water. These organisms are called autotrophs.
Ex. Green plants and some bacteria. This mode of nutrition is called autotrophic nutrition.
43. Write differences between respiration and combustion.
Difference between Respiration and Combustion

44. What type of blood flows in pulmonary vein?
Following differences are there in arteries and veins:
In pulmonary vein, oxygenated blood from lungs is transported to left atrium of the heart. 

45. What is transpiration? Write down four factors affecting transpiration process.
Transpiration: Water loss from the aerial parts of the plant is called transpiration. Following factors are there to influence the process of transpiration.
(i) Humidity: There is an increase in transpiration when atmospheric humidity decreases, while transpiration decreases with increase in humidity.
(ii) Speed of Air: High speed of air causes higher rate of transpiration. But when the air speed is high, stomata get closed and causes a decrease in transpiration.
(iii) Temperature: Increased atmospheric temperature causes decrease in humidity of air. This causes increase in transpiration. When temperature decreases, decrease in transpiration takes place.
(iv) Light Intensity: When intensity of light increases it causes increase in temperature and decrease in atmospheric humidity which causes increased rate of transpiration.

Life Processes Extra s Long Answer Type 
1. What are the differences between autotrophic nutrition and hetrotrophic nutrition?


2. What are the common features between all the respiratory organs? Explain the mechanism of gaseous exchange between tissues and blood.
Common features between all the respiratory organs are:
1.    All the respiratory organs have large surface areas to get enough oxygen.
2.    All the respiratory organs are thin-walled for easy diffusion of gases and substances.
3.    All the respiratory organs (like skin, lungs, gills) have a rich supply of blood for transporting respiratory gases.
The mechanism of gaseous exchange between tissues and blood is as follows:
1.    The blood reaching the tissues has higher concentration of oxygen than in the cells so it gets diffused into the cells.
2.    the carbon dioxide, which is formed in the cells, gets accumulated in higher concentration as compared in the blood, so it easily diffuses into the blood.
3.    The blood with CO2 takes this gas to the lungs, from where it is expelled out during exhalation. 
3. Explain the nutrition process in an Amoeba.


The mode of nutrition in Amoeba is holOzoic. The various steps involved in the process of nutrition are:
(i) Ingestion: Amoeba ingests food with the help of its finger-like extensions, called pseudopodia. When a food particle approaches Amoeba, it forms pseudopodia around it and forms a food vacuole inside the Amoeba.
(ii) Digestion: Various enzymes from the cytoplasm enter into the food vacuole and break them down into simple soluble molecules.
(iii) Absorption: The simple soluble food is absorbed by cytoplasm of Amoeba from food vacuoles through the process of diffusion.
(iv) Assimilation: Amoeba cell obtains energy from the absorbed
Food vacuole food through respiration. This energy is utilised by Amoeba for its growth and repair of the body.
(v) Egestion: When a considerable amount of undigested food gets collected inside Amoeba, its cell membrane ruptures and throws out the undigested food. 
4. Give the role of liver in the human beings.

Liver is the largest gland in human beings. Its main functions are as follows:
1.    It secretes bile juice which makes the medium of the food alkaline Amoeba and also emulsifies fat.
2.    It stores the excess of glucose in the form of glycogen.
3.    Old worn-out RBC’s are broken down in liver cells. Their haemoglobin is changed into bile pigments.
4.    The ammonia is produced as a result of metabolism of amino acids. It is highly toxic. The ammonia combines with CO2 and is converted into urea (less toxic).
5.    It stores vitamins, iron and copper.
6.    It produces fibrinogen and helps in blood-clotting.
7.    It produces heparin which does not allow the clotting of blood inside the blood vessels.
8.    It regulates the volume of blood to some extent.
9.    RBCs are produced at the foetal stage by the liver.
(i) Describe aerobic respiration.
(ii) Describe the process of anaerobic respiration. Or
What is A.T.P.? How is it formed? What is the use of it?
(i) The respiration which needs oxygen or occurs in the presence of oxygen is called aerobic respiration. During this type of respiration, glucose is broken down into carbon dioxide and water with the release of considerable amount of energy. The energy is stored in the form of ATP.
It consists of two steps:
(a) Glycolysis: The conversion of glucose into pyruvate (or pyruvic acid) is called glycolysis. It occurs in the cytoplasm.
(b) Kreb’s Cycle: It is the process of converting pyruvate into CO2 and H,O along with the release of considerable amount of energy. It occurs in the mitochondria. One molecule of glucose liberates 38 ATP of energy during aerobic respiration.

(ii) The respiration which takes place in the absence of oxygen is called anaerobic respiration. During this respiration glucose is broken down into ethyl alcohol and CO2 with the release of very small amount of energy. In anaerobic respiration, one molecule of oxygen produces only 2ATP of energy. This type of respiration occurs in microscopic organisms like yeast, etc.

In human beings, the energy is obtained by aerobic respiration but sometimes anaerobic respiration occurs in muscles during vigorous exercise when oxygen gets consumed faster than its supply by the blood. During the anaerobic respiration in the muscles the glucose is converted into lactic acid with the release of 2 ATP of energy.
Anaerobic respiration in human beings:

6. Distinguish between breathing and respiration.

7. Explain process of breathing in man.
Where does exchange of oxygen and carbon dioxide occur in human? Describe its function with diagram.

Human respiratory system: The human respiratory system begins from nose cavities called nostrils. The air from cavity enters into the pharynx and then into the trachea (or wind pipe). The trachea runs down the neck and divides into two tubes called bronchi. Each bronchi is connected to a lung. In the lungs each bronchi divides into a large number of thin tubes called bronchioles. The bronchioles have a tiny air sac at their ends called alveoli. It is in the alveoli where exchange of gases takes place.
Mechanism of breathing:
(i) When we breathe in air, the diaphragm contracts which results in the increase in volume of chest cavity. Due to this expansion of chest cavity, the air pressure in the lungs decreases. Thus, air from outside rushes into the lungs through nostrils, trachea and bronchi. Therefore, air sacs of lungs get filled with air when we breathe in. The exchange of gases between alveoli and blood takes place by the process of diffusion.
(ii) Human respiratory system: Now, the air present in air sacs of the lungs in rich in CO2. When we breathe out air, the diaphragm relaxes which results in the decrease in volume of chest cavity. This contraction pushes the air from the lungs into the trachea, nostrils and then out of the body into air. Breathing in air is called inhalation and breathing out air is called exhalation.
Mechanism of gaseous exchange during respiration: The oxygen is carried by blood to all the parts of the body. As the blood passes through the tissues of the body, the oxygen from the blood diffuses into the cell, whereas the CO2 which is produced during respiration diffuses into the blood and is carried to the lungs. 
8. Describe the structure of human kidney.

Kidneys are bean-shaped and located at the back of abdomen, one on either side of backbone. Its inner concave surface has a depression called hilum through which renal artery enters and renal vein leaves the kidney. Kidney has two regions: outer cortex and inner medulla. Each kidney has a large number of filtering units called nephrons.
9. Describe the process of digestion of food in human beings.
Draw the diagram of alimentary canal of man and label the following parts: Mouth, Oesophagus, Stomach, Intestine
How do carbohydrates, proteins and fats get digested in human beings?
Draw a well labelled diagram of human digestive system and explain the diges tive process.

The various processes involved in the digestion of human beings are:
(i) Ingestion: Through the help of mouth human beigns ingest food.
(ii) Digestion: The teeth helps in physical digestion of food. In mouth there are salivary glands, which secretes saliva, in which salivary amylase enzyme is present which digest the starch present in food into maltose sugar, i.e., the digestion of carbohydrate starts from mouth itself. Mouth opens into a small funnel-shaped area called pharynx which leads to a long tube called oesophagus, whose wall is highly muscular.
When the slightly digested food enters into oesophagus the contraction and expansion movement of its wall, takes place, which is known as peristaltic movement. This movement helps the food to move towards the stomach. Usually, in oesophagus there is no digestion of food. From the oesophagus the food enters into the stomach.
In the stomach there is secretion of gastric juices which is a mixture of hydrochloric acid, pepsin (protein Colon digesting enzyme) and mucus. Now, the partially digested food enters from stomach into the small intestine’s wider part which is known as duodenum and the remaining part of the small intestine is termed as ileum.
The duodenum, receives secretions of two glands, i.e., liver and pancreas. Liver secretes bile pigments and pancreas secretes pancreatic juice which digestes the proteins, carbohydrates and emulsified fats. Here the digestive enzymes are amylase, maltose and invertase for digesting the carbohydrates, trypsin for proteins and lipase for fats.
Thus, food is completely digested in ileum part of small intestine.
(iii) Absorption: Now, the food enters from duodenum into ileum part of small intesntine where millions of finger-like projections known as villi are present which absorb the food.
(iv) Assimilation: The blood carries the digested and dissolved food to all parts of the body, where it is assimilated into the cells which is used for obtaining energy as well as for growth and repair of the body.
(v) Egestion: The undigested food enters into the large intestine’s wider part, where water is absorbed from the undigested food and the food becomes solid. Now, this solid undigested food enters the last part of large intestine known as rectum through which it moves out from the body.
10. Differentiate between blood and lymph.

11. Define the terms, ‘nutrition’ and ‘nutrients’. List two differences between ‘holozoic nutrition’ and ‘saprophytic nutrition’. Give two examples of each of these two types of nutrition.

Nutrition: The process by which the living organisms receive and utilise the food materials necessary for their survival, growth and repair of worn-out tissues is called nutrition.
Nutrients: Those substances which supply nourishment to living organisms from its surroundings and use it as an energy source or for biosynthesis of body constituents.

12. Describe internal structure of a human heart.
Describe the flow of blood through the heart of human beings.

The two auricles or atria are thin-walled and are separated from each other by a thin inter-atrial septum. The right atrium receives venous (deoxygenated blood having very little O2) from the entire body through a superior and inferior vena cava. The left smaller atrium receives oxygenated blood from the lungs through four pulmonary veins.
The two auricles (atria) are separated from the ventricles by two apertures guarded by membranous valves. The valve separating right atrium from right ventricle is called right atrio-ventricular valve or tricuspid valve made up of three flaps. The valve separating left atrium from left ventricle is called left atrio-ventricular valve or mitral valve, formed of two flaps. These valves are attached with fine cords with the papillary muscles of the ventricular wall.
These valves only allow blood flow from auricles into ventricles and not in opposite direction. Both the ventricles are separated from each other by a thick inter-ventricular septum. The wall of left ventricle is much thicker than that of right ventricle. The left ventricle pushes blood into aorta which supplies blood to entire body. The opening of aorta is also guarded by a valve formed of 3 semilunar flaps.
The right ventricle pumps venous blood into lungs by a pulmonary aorta. Its opening is also guarded by a valve, having 3 semilunar flaps. These valves allow the flow of blood from ventricles into the aorta and not back. Heart is formed of cardiac muscle fibres, which rhythmically contract the heart without feeling fatigue.

13. Write a brief account on composition and functions of human blood.
It is slightly thicker than water and is slightly basic with a pH 7.3-7.4. Two main components of blood are:
(i) Plasma: It forms about 55% of the blood which have 90% water and 10% complex organic and inorganic compounds. It is called inanimate part of blood because it lacks blood corpuscles. Organic compounds in plasma include antibodies, glucose, amino acids, hormones, enzymes, fatty acids, vitamins and proteins (i.e., albumin, globulin, prothrombin, fibrinogen, heparin).
Heparin acts as anticoagulant in blood. It prevents clotting of blood in blood vessels. On the contrary, prothrombin and fibrinogen help in formation of clot during an injury. Inorganic compounds include potassium, sodium, calcium, magnesium and their compounds in the wound form of phosphate, biocarbonate, sulphate, chloride, etc.
(ii) Blood Corpusscles: They form about 45% of the blood composition. (See Fast Track Revision):
Function of Blood
Transport of Gases: Blood transports gases like bind O2 and CO2. RBCs present in blood have haemoglobin which bind with O2 and form oxyhaemoglobin. This oxyhaemoglobin breaks down into O2 and haemoglobin in tissues. O2 is absorbed by tissues, while haemoglobin and bicarbonates help in CO2 transport. Transport of Nutritive Materials: Nutritive materials absorbed by intestine transported to tissues by plasma.
Transport of Excretory Materials: In body, by metabolic process many excretory products such as urea, etc., are formed. This is transported to liver and then to kidney. Regulation of Body Temperature: Blood maintains temperature of all body parts and also helps in transport of hormones.

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