Science [5 marks Questions]

1. (i) Organism A is a green plant, (ii) Food B is glucose and (iii) Food H is starch.
2. C is carbon-dioxide and D is water.
3. (i) The green coloured substance E is chlorophy ll and (ii) Organ F is a leaf.
4. The process G is photosynthesis.

1. Organism B is undergoing aerobic respiration.
2. Organism A is undergoing anaerobic respiration.
3. In anaerobic respiration, glucose breaks down to form alcohol and carbon dioxide with the release of small amount of energy. Hence, organism A can convert glucose into alcohol.
4. Yeast behaves like organism A.
5. Humans and dogs behave like organism B.

Thevarious methods used by the plants to get rid of their waste products are:

1. The plants get rid of gaseous waste products through stomata in leaves and lenticels in stems.
2. They get rid of solid and liquid waste by shedding off leaves, peeling of bark and falling of fruits.
3. Secreting gums and resins.
4. Plants excrete some waste substances into the soil around them.

1.  

1. The process by which water and dissolved minerals get into the root hair of a plant is known as diffusion. Hence, A is diffusion.
2. The water and dissolved minerals are absorbed by the cells of the root hair, which enter the conducting tissue known as xylem. Hence, B is xylem.
3. Transpiration helps in transporting water and dissolved minerals to move up through the xylem tissue (B) in the roots and the stem, and reach the leaves of a plant. Hence, C is transpiration.
4. In leaves, the food is prepared by a process known as photosynthesis. Hence, the process D is photosynthesis.
5. The food synthesised by the leaves of a plant is transported to all the parts of a plant through tissue phloem (E). Hence, E is phloem.
6. The process of distributing (or transporting) food made in the leaves to all the parts of the plant is called translocation. Hence, F is translocation.

2. B represents xylem, while E represents phloem. Out of these, phloem (E) is made of living cells.
3. E (phloem) contains sieve tubes.
4. B (xylem) contains tracheids.

1. Organism B refers to an omnivore, Organism D refers to a herbivore and Organism A refers to a carnivore.
2. Organism C is an autotroph.
3. The organisms A, B and D are heterotrophs as they obtain food from other organisms and cannot synthesise their own food.
4. Organism C can be a producer as it is an autotroph.
5. The organisms A, B and D are consumers as they all are heterotrophs.
6. The examples of organisms A, B, C and D are lion, crow, green plants (like mango) and cow, respectively.

Aerobic respiration:

1. Aerobic respiration takes place in the presence of oxygen.
2. Complete breakdown of food occurs in aerobic respiration.
3. The end products in aerobic respiration are carbon-dioxide and water.
4. Aerobic respiration produces a considerable amount of energy.

Example: Human Beings.
Anaerobic respiration:

1. Anaerobic respiration takes place in the absence of oxygen.
2. Partial breakdown of food occurs in anaerobic respiration.
3. The end products in anaerobic respiration are ethanol and carbon-dioxide (in yeast) and lactic acid (in animal muscles).
4. Much less energy is produced in anaerobic respiration.

Example: Yeast.

1. Organ A is kidney. Complete damage of the kidney (organ A) can lead to the accumulation of waste material B, i.e. urea, in the blood.
2. The waste substance B is urea.
3. (i) In dialysis, the blood from a convenient artery is pumped into the dialyser of a dialysing machine. The dialyser contains a coiled cellophane tube made of substance E, called cellulose. It is surrounded by the dialysing solution (F). Hence, E represents cellulose. (ii) F represents the dialysing solution.
4. The dialysing solution contains water (G), glucose (H) and salts (I), which is similar in concentration to those in normal blood.
5. The process of removing waste substances like urea from the blood using a kidney machine is known as dialysis.

There are mainly two modes of nutrition:
Autotrophic: Autotrophic nutrition is that mode of nutrition in which an organism makes its own food from the simple inorganic materials like carbon-dioxide and water present in the surroundings (with the help of sunlight energy).
Example: Green plants obtain food by autotrophic nutrition.
Heterotrophic: Heterotrophic nutrition is that mode of nutrition in which an organism cannot make its own food from simple inorganic materials like carbon-dioxide and water, and depends on other organisms for its food.
Example: All animals obtain food by heterotrophic nutrition.

1.  

1. Organism A has parasitic mode of nutrition.
2. Organism B has holozoic mode of nutrition.
3. Organism C has saprophytic mode of nutrition.

2. The organisms like D are called hosts.
3. The process E is egestion.
4. The example of organisms like

1. A is Cuscuta.
2. B is cow.
3. C is mushroom.

5. The general name of the three modes of nutrition exhibited by organism A, B and C are parasitic nutrition, holozoic nutrition and saprophytic nutrition, respectively.

1. Lymph (X) is a light yellow colour (Y) liquid that circulates in the human body. It circulates from the body tissues to the heart. Hence, (i) the liquid X is lymph., (ii) The colour Y is light yellow.
2. The liquid X (lymph) is cleaned of germs and dead cells by a special type of white blood cells called lymphocytes (Z). Lymphocyte helps in fighting infections and diseases. Thus, Z represents lymphocytes.
3. The liquid X, i.e. lymph, is somewhat similar to plasma.
4. The liquid X, i.e. lymph, is not red because it does not contain red blood cells that have red colour pigment called haemoglobin.

1. W is the dental plaque.
2.  

1. X refers to the saliva.
2. Y refers to the salivary glands.

3. Organisms Z are bacteria.
4. Layer of W, i.e. dental plaque, can be removed by regular brushing of teeth.

Lymphatic system: A system of tiny tubes called lymph vessels (lymphatics) and lymph nodes (lymph glands) in the human body which transports the liquid called lymph from the body tissues to the blood circulatory system is called lymphatic system. Functions of lymphatic system:

1. It takes part in the nutritive process of the body.
2. It protects the body by killing the germs drained out of the body tissues with the help of lymphocytes contained in the lymph nodes, by making antibodies.
3. It helps in removing the waste products like fragments of dead cells etc.

The main components of blood are:

1. Plasma: It carries all the dissolved substances such as proteins, digested food, common salt etc from one part to another part of the body.
2. Red blood corpuscles (RBC): It carries oxygen from the lungs to all the cells of the body.
3. White blood corpuscles (WBC): It fights infection and protects us from diseases.
4. Platelets: It helps in the coagulation of blood in a cut or wound.

During the process of ‘breathing in’ the air sacs or alveoli of the lungs get filled with air containing oxygen. The alveoli are surrounded by capillaries carrying blood so the oxygen of air diffuses from the alveoli walls into the blood from where it is carried to all the parts of the body.As the blood passes through the tissues of the body, the oxygen present in it diffuses into the cells. This oxygen combines with the digested food to release energy. Carbon-dioxide gas is produced as a waste product during respiration in the cells of the body tissues which diffuses into the blood. Blood carries the carbon-dioxide back to the lungs where it diffuses into the alveoli.

Pancreatic juice contains digestive enzymes? Pancreatic Amylase, trypsin and lipase.Functions:
Pancreatic amylase: The enzyme amylase breaks down the starch. Trypsin: Trypsin digests the proteins. Lipase: Lipase breaks down the emulsified fats.

1.  

1. X is yeast.
2. Y is ethanol.
3. Z is carbon-dioxide.

2. Fermentation is the process of converting sugar into substance Y by the action of X.
3. Anaerobic respiration is exhibited by X in the above process.

1. Animals like X are known as carnivores.
2. Animals like Y are known as herbivores.
3. Animals like X have longer small intestine as they are grass eating animals and they need long intestine to digest the cellulose present in the grass.
4. Lion is a carnivore.
5. Cow is an herbivore.

1.  

1. Gland A is salivary gland.
2. Substance B is saliva.
3. Enzyme C is salivary amylase.

2. Tube D is oesophagus.
3. The movement E is known as peristaltic movement.
4. (i) F is hydrochloric acid, G is mucus and H is pepsin.

1.  

1. Organism A is bacteria.
2. Substance B is acid.

2.  

1. Part C is the tooth enamel.
2. part D is the dentine of the tooth.

3. The small holes, E, are known as cavities.
4. F is the pulp of the tooth.
5. When a bacterium (organism A) reaches the pulp (part F) of the tooth, it irritates the nerve endings and causes toothache.

The tooth has hard outer covering called enamel. The part of tooth below enamel is called dentine inside which is the pulp cavity. The pulp cavity contains nerves and blood vessels.

1. The unicellular animal P is Amoeba.
2. Q is pseudopodia and R is the food vacuole.
3. Chemical S is the digestive enzyme and Process T is diffusion.
4. Organelle U is cell membrane and Process V is egestion.

The raw materials for photosynthesis are carbon-dioxide and water. The green plants take carbon-dioxide from air for photosynthesis. The carbon-dioxide gas enters the leaves of the plants through the stomata present on their surface. The water required by the plants for photosynthesis is absorbed by the roots of the plants from the soil through the process of osmosis. The water absorbed by the roots is transported upwards through the xylem vessels to the leaves where it reaches the photosynthetic cells and utilized in photosynthesis.

Principle of Dialysis: The blood from an artery in the patients arm is made to flow into the dialyser of a dialysis machine made of long tubes of selective permeable membrane (like cellulose) which are coiled in a tank containing dialysing Solution. The dialysing Solution contains water, glucose and salts in similar concentrations to those in normal blood. As the patient’s blood passes through the dialysing Solution most of the waste like urea present in it pass through the selectively permeable cellulose tubes into the dialysing Solution. The clean blood is pumped back into a vein of the patients arm.

The process of photosynthesis takes place in the green leaves of a plant. The carbon-dioxide gas required for making food is taken by the plant leaves from the air which enters the leaves through tiny pores called stomata. Water required for making food is taken from the soil which is transported to the leaves from the soil through the roots and the stem. The sunlight provides energy required to carry out the chemical reactions involved in the preparation of food. The green pigment called chlorophyll absorbs sunlight energy.
The photosynthesis takes place in three steps:

1. Absorption of sunlight energy by chlorophyll.
2. Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen by light energy.
3. Reduction of carbon dioxide by hydrogen to form carbohydrates like glucose by utilising the chemical energy.

​​​​​​​

Lion	Carnivore
Man	Omnivore
Dog	Omnivore
Goat	Herbivore
Crow	Omnivore
Elephant	Herbivore
Snake	Carnivore
Hawk	Carnivore
Rabbit	Herbivore
Deer	Herbivore

1. Heart is the organ in the human body that acts as a double pump. Hence, organ A represents the heart.
2.  

1. The oxygenated blood from the lungs enters the left atrium (chamber C) via the blood vessel called pulmonary vein (B). Hence, B is pulmonary vein.
2. The contraction of left ventricle (chamber D) forces the blood into the blood vessel called aorta (E), which supplies the oxygenated blood to the organs of the body, except the lungs. Hence, E is aorta.
3. From the body tissues, the deoxygenated blood is transported back to the heart into the right upper chamber called right atrium (G), by the vena cava (F). Hence, F is vena cava.
4. Contraction of chamber G (right atrium) forces the deoxygenated blood into the lower right chamber called right ventricle (H). Finally, the contraction of H (right ventricle), sends the deoxygenated blood into the lungs through the blood vessel called pulmonary artery (I). Hence, I represent pulmonary artery.

3.  

1. The chamber C represents left atrium.
2. The chamber D represents left ventricle.

4.  

1. The chamber G represents right atrium.
2. The chamber H represents right ventricle.

1.  

1. Blood is the liquid connective tissue that circulates in our body continuously without stopping. Hence, A is blood.
2. Our blood contains a pigment called haemoglobin, which imparts it a red colour. Hence, pigment B is haemoglobin and colour C is red.
3. Our blood contains a pigment called haemoglobin, which imparts it a red colour. Hence, pigment B is haemoglobin and colour C is red.

2.  

1. White blood cells, fight infection and protect us from diseases. Hence, D refers to white blood cells.
2. Platelets are the component of blood, which help in the clotting of blood (A). Hence, E refers to platelets.
3. Plasma is a liquid, which consists mainly of water with many substances dissolved in it. Hence, F refers to plasma.
4. Red blood cells carry oxygen from the lungs to all the parts of the body. Hence, G refers to red blood cells.

3. Blood also carries the digested food from the small intestine to all other parts of the body.
4. E (platelets) and G (Red blood cells) are the cells without nucleus.
5. Amoeba and grasshopper do not have blood (A) like liquid in their body.

1. Yeast shows anaerobic respiration.
2. Humans show aerobic respiration.
3. In humans beings, during high muscular activity, the respiration represented by equation (iii) occurs. It occurs in the muscle tissue.
4. Equation (ii) represents aerobic respiration.
5. Equation (i) represents anaerobic respiration.
6. Aerobic respiration, i.e. the reaction represented by equation (ii), produces maximum amount of energy.

1.  

1. Kidneys are bean shaped organs in the human body, towards the back of the body, just above the waist. Hence, organs P are kidneys.
2. Urea is the waste product that is formed by the decomposition of unused proteins in the liver. Hence, the waste substance Q represents urea.

2.  

1. Urea (substance Q) is brought into kidney (organ P) through blood by an artery called renal artery. Hence, R represents renal artery.
2. The numerous tiny filters called nephrons (S) present in the kidneys (organ P), clean the dirty blood by removing the waste product Q (urea). The clean blood then goes into circulation through T, i.e. renal vein. Hence, vein T represents the renal vein.
3. The tiny filters S are known as nephrons.
4. The waste substance Q (urea), other waste salts and excess water form yellowish liquid called urine (U). Urine goes from organ P (kidney) into a bag-like structure V, i.e. urinary bladder, through two tubes W, called ureters. This urine is then thrown out of the body through tube X, called urethra.
   Hence, (i) the liquid U is urine, (ii) structure V is urinary bladder, (iii) tubes W is ureters, and (iv) tube X is the urethra.

1. During daytime when photosynthesis occurs, oxygen is produced. The leaves use some of this oxygen for respiration and the rest of oxygen diffuses out into the air. Carbon-dioxide produced by respiration is all used up in photosynthesis by leaves during the daytime. Even more carbon-dioxide is taken in from air. Thus, the net gas exchange in leaves during daytime is: Oxygen diffuses out Carbon-dioxide diffuses in.
2. At night time, when no photosynthesis occurs and hence no oxygen is produced, oxygen from air diffuses in leaves to carry out respiration. Carbon dioxide produced by respiration diffuses out into air. So, the net gas exchange in leaves at night is: Oxygen diffuses in Carbon-dioxide diffuses out.

1. The organ A is small intestine.
2. Liquid B is bile and Organ C is gall bladder.
3. The digestive enzymes D, E and F are Amylase, Trypsin and Lipase, respectively.
4. The projections G are villi that are present on the inner wall of organ A.
5. Tube H is the large intestine, Part I is the rectum, Opening J is the anus and The process K is egestion or defecation.

1. T is Amoeba.
2. Q is frog.
3. P is fish.
4. S is grasshopper.
5. R is earthworm.

1. Organism X could be a human being. The breathing organs A are lungs.
2. Organism Y could be a fish. The breathing organs B are gills.
3. Organism Z could be a frog. The breathing organ C is skin and D are lungs.
4.  

1. Z is an amphibian.
2. Y is an aquatic organism.
3. X is a terrestrial organism.

1.  

1. Organism A is yeast.
2. AmoebaOrganism B is .
3. C is mosquito.Organism.

2.  

1. P is alcohol.
2. breathes through the cell membrane.Amoeba Q is the cell membrane because
3. R is spiracle.
4. S is tracheae.

3.  

1. Organisms B and C undergo aerobic respiration.
2. Organism A, i.e. yeast, undergoes anaerobic respiration.

Digestion of food in human beings: Digestion of food begins in the mouth. The mouth cavity contains teeth, tongue and salivary glands. The teeth cut the food into small pieces, chew and grind it. This is called physical digestion. Salivary glands produce saliva which mixes with the food. This involves chemical digestion of food. The saliva contains an enzyme called salivary amylase which digests the starch and converts it into maltose sugar. Mouth opens into a small funnel shaped area called pharynx which leads to a long tube called oesophagus. It carries the food down into the stomach.
The wall of oesophagus is muscular. When the slightly digested food enters the food pipe, the walls of the oesophagus starts contraction and expansion movements called peristaltic movements which push the food into the stomach. Digestion does not take place in the oesophagus. The glands present on the walls of the stomach secrete gastric juice that contains hydrochloric acid, the enzyme pepsin and mucus. A small amount of gastric lipase is also present that breaks down the fats present in the food. Gastric juice is acidic due to the presence of HCl which is necessary for the pepsin to become active and converts the proteins into peptones.
The mucus protects the stomach walls from HCl. From the stomach, the partially digested food goes into the small intestine through sphincter muscle. Small intestine is divided into two parts: Duodenum and Ileum.
Duodenum receives the secretions of two glands, liver and pancreas through a common duct. Liver secretes bile which is alkaline and contains salts to emulsify the fats (or lipids). The bile secreted by the liver is stored in the gall bladder. Pancreas secretes pancreatic juice which contains trypsin, lipase and pancreatic amylase. Trypsin digests the proteins, lipase emulsifies the fats and pancreatic amylase breaks down the starch. Thus, small intestine is the site of complete digestion of carbohydrates, proteins and fats. The walls of ileum secrete succus entericus which completes the digestion process.

Urine formation: The dirty blood containing waste like urea enters the glomerulus which filters the blood. During filtration, the substance like glucose, amino acids, salts, water, urea etc present in the blood pass into Bowman’s capsule and then enter the tubule of nephron. When the filtrate containing useful substances as well as the waste substances passes through the tubule, the useful substances like glucose, amino acids, most salts and water are reabsorbed into the blood through blood capillaries surrounding the tubule. Only the waste substances like urea, some unwanted salts and excess water remains behind in the tubule. This yellowish liquid is called urine.

Working of Human blood circulatory system takes place in the steps below:

1. When the muscles of all the four chambers are relaxed, the pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart.
2. When the left atrium contracts, the oxygenated blood is pushed into the left ventricle through valve V .
3. When the left ventricle contracts, the oxygenated blood enters the main artery called aorta from which it goes to the different body organs through small branches called arterioles and capillaries.
4. The main artery carries the blood to all the organs of the body head, arms etc except the lungs. The oxygenated blood gives off oxygen, digested food and dissolved materials to the body cells. The carbon-dioxide produced in the cells enters the blood. The deoxygenated blood enters main vein called vena cava which carried it to the right atrium of the heart.
5. When the right atrium contracts, the deoxygenated blood enters right ventricle through valve V .
6. When the right ventricle contracts, the deoxygenated blood enters the lungs through pulmonary artery and releases carbon-dioxide and absorbs fresh oxygen from air. The blood becomes oxygenated again and is sent to the left atrium of heart by pulmonary vein for circulation in the body. This whole process is repeated continuously.

​​​​​​​

Nutrition in amoeba: Nutrition in amoeba involves the following steps

1. Ingestion? Amoeba has no mouth for ingestion of food. It ingests the food by using its pseudopodia. The food is engulfed with little water to form a food vacuole.
2. Digestion? The food is digested by digestive enzymes present in the cytoplasm which breaks the food into small soluble molecules by chemical reactions.
3. Absorption? The digested food is absorbed directly into the cytoplasm by diffusion. The digested food spreads out from the food vacuole into the whole cell and after absorption the food vacuole disappears.
4. Assimilation? Food is used to obtain energy through respiration and the remaining part of the food is used for growth.
5. Egestion? The undigested food collects inside the cell and the cell membrane ruptures. Through this, the undigested food is thrown out of the body.

1. Carbohydrates: The digestion of carbohydrates begins in the mouth. The human saliva contains an enzyme called salivary amylase which digests the starch present in the food into maltose sugar. The slightly digested carbohydrates when reaches the small intestine, pancreatic amylase present in the pancreatic juice breaks down the starch. The intestinal juice of the small intestine completes the digestion of carbohydrates and finally coverts it into glucose.
2. Fats: The process of digestion of fats begins in the stomach. The glands of stomach secrete a small amount of gastric lipase that breaks down the fats present in the food. From the stomach the partially digested food goes into small intestine where the pancreatic lipase breaks down the emulsified fats. The walls of small intestine secrete intestinal juice which converts the fats into fatty acids and glycerol.
3. Proteins: The digestion of proteins begins in the stomach. The glands of the stomach secrete gastric juice which contains an enzyme called pepsin. Pepsin converts the proteins into peptones. Pancreatic juice contains trypsin which digests the proteins into peptides and the intestinal juice completes the process of digestion of proteins thus converting it into amino acids.