CBSE Class 10 Science HOTs Life Processes Set 05

Question. Why does absorption of digested food occur mainly in the small intestine?
Answer: Absorption of digested food occur mainly in the small intestine because:
(i) Digestion of food is completed in small intestine.
(ii) Inner lining of small intestine bears a number of finger-like projections called villi, which increases the surface area for absorption.
(iii) Wall of intestine has blood vessels for carrying the absorbed food to different parts of the body.

Question. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Answer: The rate of breathing in aquatic organisms is much faster than in terrestrial organisms because the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air. Aquatic animals take in water through their mouths and pass it to the gills where the dissolved oxygen is taken up by blood.

Question. What is the advantage of having four chambered heart?
Answer: The advantage of having four chambered heart is that it prevents oxygenated and deoxygenated blood from mixing, as the left half of the four chambered heart is completely separated from right half by septum. This mechanism is useful to animals with high energy needs such as birds and mammals. In this way, highly efficient supply of oxygenated blood is passed to all parts of the body.

Question. In each of the following situations what happens to the rate of photosynthesis?
(a) Cloudy days
(b) No rainfall in the area
(c) Good manuring in the area
(d) Stomata gets blocked due to dust.
Answer: (a) In cloudy days, photosynthesis is reduced due to low light intensity. (b) In case of no rainfall in the area, rate of photosynthesis decreases. (c) With good manuring in the area, rate of photosynthesis increases, it increases soil fertility. (d) When stomata gets blocked due to dust, photosynthesis decreases by reducing gaseous exchange.

Question. Name the energy currency in the living organisms. When and where is it produced?
Answer: Adenosine triphosphate (ATP) is the energy currency of the living organisms. It is produced during respiration in living organisms and also during photosynthesis in plants.

Question. What is common for cuscuta, ticks and leeches?
Answer: All are parasites and they derive their nutrition from their hosts directly without killing them.

Question. What are the functions of gastric glands present in the wall of the stomach?
Answer: Functions of the gastric glands present in the wall of the stomach are as follows:
(i) Secretion of mucus for protection of inner lining of stomach.
(ii) Secretion of \( HCl \) which makes the food soft and acidified for pepsin to act upon food.
(iii) Secretion of pepsin enzyme that digests proteins.

Question. Plants have low energy needs as compared to animals. Explain.
Answer: Plants have low energy needs as compared to animals because plants do not move and most of their body is made up of dead cells like sclerenchyma. But animals move about in search of food, mate and shelter.

Question. Why and how does water enter continuously into the root xylem?
Answer: Cells of root are in close contact with soil and so actively take up ions. Ions pass inward increasing osmotic concentration of xylem. Because of it water from the soil continuously pass into the root xylem.

Question. How do leaves of plants help in excretion?
Answer: (a) In leaves, the waste materials are stored in the vacuoles of mesophyll and epidermal cells. When old leaves fall, the waste materials are excreted along with the leaves. (b) Transpiration of gases via stomata helps in removal of gaseous waste of respiration and photosynthesis.

Question. Explain the importance of soil for plant growth.
Answer: Importance of soil for plant growth:
(i) It anchors the plant.
(ii) It is the source of water and minerals.
(iii) It helps in symbiotic association with microbes.
(iv) It helps for respiration of root cells due to availability of oxygen of food material.

Question. Describe the alimentary canal of man.
Answer: Alimentary canal in man is 9 metres long and consists of the following parts:
(i) Mouth. It leads into buccal cavity. The floor of the buccal cavity has a tongue bearing taste buds. Man possess teeth on both the jaws. There are 32 teeth of four different types, namely incisors, canines, premolars and molars.
(ii) Pharynx. It is a short, conical region that lies after the mouth cavity.
(iii) Oesophagus. It is a long, narrow, muscular tube which leads to the stomach.
(iv) Stomach. It lies below the diaphragm on the left side of abdominal cavity and is J-shaped. The food is stored and partly digested in the stomach.
(v) Small Intestine. It is a convoluted tube and differentiated into three regions, viz., duodenum, which is the first part of small intestine and is curved C-shaped; jejunum, comparatively longer and more coiled, and ileum, which is the last part of small intestine whose inner surface is folded to form villi, which absorbs the products of digestion.
(vi) Large Intestine. It is much shorter and wider than small intestine and is differentiated into three regions viz., caecum, which is small rounded blind sac from which vermiform appendix arises; colon is the inverted U-shaped tube and the rectum opens to exterior through anus.

Question. Formation of urine involves the following processes in order:
(a) Filtration, secretion, reabsorption
(b) Secretion, absorption, filtration
(c) Glomerular filtration, reabsorption, tubular secretion
(d) Reabsorption, filtration, secretion
Answer: (c) Glomerular filtration, reabsorption, tubular secretion

Question. Urea is transported by:
(a) Plasma
(b) RBC
(c) WBC
(d) All of the options
Answer: (a) Plasma

Question. Which of the following contributes most to transport water from the ground to the leaves of a tall tree?
(a) Breakdown of ATP
(b) Root Pressure
(c) Capillary rise of water in xulem
(d) Cohesion of water and transpiration pull
Answer: (d) Cohesion of water and transpiration pull

Question. Arteries carry oxygenated blood except
(a) Pulmonary artery
(b) Coronary artery
(c) Hepatic artery
(d) Systemic artery
Answer: (a) Pulmonary artery

Question. Assertion: All proteins in our food are digested in small intestine only.
Reason: The protein digesting enzymes are released in small intestine and stomach.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) Both the Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Aerobic respiration require less energy as compared to anaerobic respiration.
Reason: Mitochondria is the power house of the cell.
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) Both the Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Explain the mechanism of gaseous exchange in tissues and blood.
Answer: Gaseous exchange between blood and tissues occurs through diffusion. Blood arriving at tissues has a high partial pressure of oxygen and low partial pressure of carbon dioxide. Tissues, having used oxygen for respiration, have a high partial pressure of carbon dioxide and low partial pressure of oxygen. Thus, oxygen diffuses from blood into the tissues, and carbon dioxide diffuses from the tissues into the blood.

Question. Why is there no mixing of deoxygenated and oxygenated blood in human heart normally?
Answer: Normally, there is no mixing of deoxygenated and oxygenated blood in the human heart because the heart is divided into four chambers. The left side (atrium and ventricle) is completely separated from the right side by a muscular wall called the septum. This separation ensures an efficient supply of oxygen to the body.

Question. What are the components of the transport system in highly organised plants? What are the functions of these components?
Answer: The components of the transport system in highly organised plants are Xylem and Phloem.
Functions:
1. Xylem: Transports water and minerals from the roots to the other parts of the plant.
2. Phloem: Translocates food (products of photosynthesis) from the leaves to the storage organs and growing parts of the plant.

Question. Describe the mechanism of breathing in human being.
Answer: Breathing involves two phases: Inhalation and Exhalation. During inhalation, the diaphragm contracts and flattens, and the ribs move upwards and outwards. This increases the space in the chest cavity, lowering air pressure and drawing air into the lungs. During exhalation, the diaphragm and rib muscles relax, reducing the space in the chest cavity, which increases air pressure and forces air out of the lungs.

The maintenance of living organisms continue even when they do not do anything particular. The maintenance processes are needed to prevent damage or breakdown, for which energy is needed. The energy comes from outside the body of the organism, which is called food. There is a process to transfer energy from outside the body to inside the body of the organism. Depending on the complexity of the food, different organisms use different kind of nutritional processes to transfer energy.

Question. State one difference between autotrophic and heterotrophic mode of nutrition.
Answer: Autotrophic nutrition involves the synthesis of food from simple inorganic materials like \( CO_2 \) and water using light energy, whereas heterotrophic nutrition involves obtaining food from other organisms as they cannot synthesise their own food.

Question. How do organisms like bread mould and mushrooms obtain their food?
Answer: These organisms follow saprophytic nutrition. They break down the complex organic matter of dead and decaying organisms outside their body and then absorb the simpler molecules.

Question. What is the function of digestive enzyme? Or What is the role of acid in our stomach?
Answer: Digestive enzymes break down large, complex food molecules into smaller, soluble molecules that can be absorbed by the body. Alternatively, the acid (\( HCl \)) in the stomach kills bacteria swallowed with food and provides an acidic medium necessary for the enzyme pepsin to begin protein digestion.