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Page No 48:

Question 1:

Which of the following statements about the autotrophs is incorrect?
(a) They synthesise carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll
(b) They store carbohydrates in the form of starch
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight
(d) They constitute the first trophic level in food chains

Answer:

Autotrophs perform the process of photosynthesis which means the process of synthesising food in the presence of light. Carbohydrates are formed as the product of this process.

Hence, the correct answer is option C.

Page No 48:

Question 2:

In which of the following groups of organisms, food material is broken down outside the body and absorbed?
(a) Mushroom, green plants, Amoeba
(b) Yeast, mushroom, bread mould
(c) Paramecium, Amoeba, Cuscuta
(d) Cuscuta, lice, tapeworm

Answer:

Yeast, mushroom, and bread mould belong to the kingdom Fungi. These organisms release digestive juices outside the body which breakdown the food and then digested food is absorbed by the body.

Hence, the correct answer is option B.

Page No 48:

Question 3:

Select the correct statement
(a) Heterotrophs do not synthesise their own food
(b) Heterotrophs utilise solar energy for photosynthesis
(c) Heterotrophs synthesise their own food
(d) Heterotrophs are capable of converting carbon dioxide and water into carbohydrates

Answer:

Heterotrophs  cannot manufacture their food on their own. Hence, they are dependent on other organisms for their food.

Hence, the correct answer is option A.

Page No 48:

Question 4:

Which is the correct sequence of parts in human alimentary canal?
(a) Mouth → stomach → small intestine → oesophagus → large intestine
(b) Mouth →oesophagus → stomach → large intestine → small intestine
(c) Mouth → stomach → oesophagus → small intestine → large intestine
(d) Mouth → oesophagus → stomach → small intestine → large intestine

Answer:

The correct sequence for the propagation of food through alimentary canal is  Mouth → oesophagus → stomach → small intestine → large intestine.

 Hence, the correct answer is option D.



Page No 49:

Question 5:

If salivary amylase is lacking in the saliva, which of the following events in the mouth cavity will be affected?
(a) Proteins breaking down into amino acids
(b) Starch breaking down into sugars
(c) Fats breaking down into fatty acids and glycerol
(d) Absorption of vitamins

Answer:

Salivary amylase is an enzyme which helps in the breakdown of carbohydrate. As starch is a carbohydrate, lack of salivary amylase will affect the breakdown of it into sugar.

Hence,  the correct answer is option B.

Page No 49:

Question 6:

The inner lining of stomach is protected by one of the following from hydrochloric acid. Choose the correct one
(a) Pepsin
(b) Mucus
(c) Salivary amylase
(d) Bile

Answer:

Mucus protects the inner lining of stomach from hydrochloric acid.

Hence, the correct answer is option B.

Page No 49:

Question 7:

Which part of alimentary canal receives bile from the liver?
(a) Stomach
(b) Small intestine
(c) Large intestine
(d) Oesophagus

Answer:

Bile is produced in liver and then stored in gall bladder and then finally received by small intestines.

Hence, the correct answer is option B. 

Page No 49:

Question 8:

A few drops of iodine solution were added to rice water. The solution turned blue-black in colour. This indicates that rice water contains
(a) complex proteins
(b) simple proteins
(c) fats
(d) starch

Answer:

When iodine solution is added to starch solution, it turns the colour of the solution to blue-black colour. This indicates that rice water contains starch.

Hence, the correct answer is option D.

Page No 49:

Question 9:

In which part of the alimentary canal food is finally digested?
(a) Stomach
(b) Mouth cavity
(c) Large intestine
(d) Small intestine

Answer:

Food is finally digested into small intestines.

Hence, the correct answer is option D.

Page No 49:

Question 10:

Choose the function of the pancreatic juice from the following
(a) trypsin digests proteins and lipase carbohydrates
(b) trypsin digests emulsified fats and lipase proteins
(c) trypsin and lipase digest fats
(d) trypsin digests proteins and lipase emulsified fats

Answer:

Trypsin and lipase are released by pancreas. Trypsin digest proteins into small peptides which are further digested into amino acids and lipase helps in emulsification of  fats.

 Hence,  the correct answer is option D.

Page No 49:

Question 11:

When air is blown from mouth into a test-tube containing lime water, the lime water turned milky due to the presence of
(a) oxygen
(b) carbon dioxide
(c) nitrogen
(d) water vapour

Answer:

When air is blown from mouth into test-tube containing lime water, milky white colour appear in the solution due to presence of carbon dioxide in air blown. Carbon dioxide (CO2) turns lime water milky due to the formation of insoluble calcium carbonate. 

Hence, the correct answer is option B.



Page No 50:

Question 12:

The correct sequence of anaerobic reactions in yeast is

(a) Glucosecytoplasm Pyruvatemitochondria Ethanol + Carbondioxide

(b) Glucosecytoplasm PyruvatecytoplasmLactic acid

(c) Glucosecytoplasm PyruvatemitochondriaLactic acid

(d) Glucosecytoplasm Pyruvatecytoplasm Ethanol + Carbondioxide

Answer:

Correct sequence of anaerobic reactions in yeast is Glucosecytoplasm Pyruvatemitochondria Ethanol + Carbondioxide.

Hence, the correct answer is option A.   

Page No 50:

Question 13:

Which of the following is most appropriate for aerobic respiration?
(a) Glucosemitochondria Pyruvate cytoplasm CO2+H2O+Energy
(b) Glucose cytoplasm Pyruvate mitochondria CO2+H2O+Energy
(c) Glucose cytoplasm Pyruvate+Energy mitochondria CO2+H2O
(d) Glucose cytoplasm Pyruvate+Energy mitochondria CO2+H2O+Energy

Answer:

Most appropriate equation for aerobic respiration is Glucose cytoplasm Pyruvate mitochondria CO2+H2O+Energy.

Hence, the correct answer is option B.

Page No 50:

Question 14:

Which of the following statement(s) is (are) true about respiration?

  1. During inhalation, ribs move inward and diaphragm is raised
  2. In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air
  3. Haemoglobin has greater affinity for carbon dioxide than oxygen
  4. Alveoli increase surface area for exchange of gases
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer:

Alveoles act as site of  exchange of gases by diffusion and also they increase the surface area for the same.

Hence, the correct answer is option D.

Page No 50:

Question 15:

Which is the correct sequence of air passage during inhalation?
(a) Nostrils → larynx → pharynx → trachea → lungs
(b) Nasal passage → trachea → pharynx → larynx → alveoli
(c) larynx → nostrils → pharynx → lungs
(d) Nostrils → pharynx → larynx → trachea → alveoli

Answer:

During inhalation oxygen rich air is taken inside and it goes by following passage 
 Nostrils → pharynx → larynx → trachea → alveoli.

Hence, the correct answer is option D.

Page No 50:

Question 16:

During respiration exchange of gases take place in
(a) trachea and larynx
(b) alveoli of lungs
(c) alveoli and throat
(d) throat and larynx

Answer:

During the respiratory exchange of gases take place in the alveoli of the lungs. Alveoles are small, balloon like structures which increase the surface area inside the lungs for exchange of gases.

Hence, the correct answer is Option B.



Page No 51:

Question 17:

Which of the following statement (s) is (are) true about heart?
(i) Left atrium receives oxygenated blood from different parts of body while right atrium receives deoxygenated blood from lungs
(ii) Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs
(iii) Left atrium transfers oxygenated blood to right ventricle which sends it to different body parts
(iv) Right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body
(a) (i)
(b) (ii)
(c) (ii) and (iv)
(d) (i) and (iii)

Answer:

Left atrium of heart receives oxygenated blood from the lungs and pump it to rest body through left ventricle while right atrium receives deoxygenated blood from body and pump it to lungs through right ventricle. Statement (ii)and (iv) explains the same.
Image 

Hence, the correct answer is option C.

 

Page No 51:

Question 18:

What prevents backflow of blood inside the heart during contraction?
(a) Valves in heart
(b) Thick muscular walls of ventricles
(c) Thin walls of atria
(d) All of the above

Answer:

Preventing the backflow of blood during contraction of heart is function of valves in heart. Walls of atria and ventricles help in contractions of heart to pump blood.

Hence, the correct answer is option A.

Page No 51:

Question 19:

Single circulation i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by
(a) Labeo, Chameleon, Salamander
(b) Hippocampus, Exocoetus, Anabas
(c) Hyla, Rana, Draco
(d) Whale, Dolphin, Turtle

Answer:

Hippocampus, Exocoetus and Anabas are having blood flow through the heart only once.

Hence, the correct answer is option B.

Page No 51:

Question 20:

In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body?
(a) Pisces and amphibians
(b) Amphibians and reptiles
(c) Amphibians only
(d) Pisces only

Answer:

Pisces is the only class which have heart that doesn't pump oxygenated blood to different parts of the body.

Hence, the correct answer is option D.

Page No 51:

Question 21:

Choose the correct statement that describes arteries.

  1. They have thick elastic walls, blood flows under high pressure; collect blood from different organs and bring it back to the heart
  2. They have thin walls with valves inside, blood flows under low pressure and carry blood away from the heart to various organs of the body
  3. They have thick elastic walls, blood flows under low pressure; carry blood from the heart to various organs of the body
  4. They have thick elastic walls without valves inside, blood flows under high pressure and carry blood away from the heart to different parts of the body.

Answer:

Arteries have thick wall to manage blood pressure. They don't have valves and they carry blood from heart toward body tissues.

Hence, the correct answer is option D.



Page No 52:

Question 22:

The filtration units of kidneys are called
(a) ureter
(b) urethra
(c) neurons
(d) nephrons

Answer:

Structural and functional unit of kidney which help in filtration of blood is nephron.

Hence, the correct answer is option D.

Page No 52:

Question 23:

Oxygen liberated during photosynthesis comes from
(a) water
(b) chlorophyll
(c) carbon dioxide
(d) glucose

Answer:

Oxygen released during photosynthesis is released by water and carbon dioxide helps in formation of glucose. Chlorophyll absorbs sunlight for photosynthesis.

Hence, the correct answer is option A.

Page No 52:

Question 24:

The blood leaving the tissues becomes richer in
(a) carbon dioxide
(b) water
(c) heamoglobin
(d) oxygen

Answer:

Inside the tissue respiration takes place during which energy is produced, carbon dioxide is also produced as a byproduct which is released into the blood. Therefore, blood that leaves tissue is richer in carbon dioxide.

Hence, the correct answer is option A.

Page No 52:

Question 25:

Which of the following is an incorrect statement?
(a) Organisms grow with time
(b) Organisms must repair and maintain their structure
(c) Movement of molecules does not take place among cells
(d) Energy is essential for life processes

Answer:

The cell is a structural and functional unit of a living organisms and they are formed of molecules. Different metabolic reactions occur in cell and the molecules play fundamental role in these reactions.

Hence, the correct answer is option C.

Page No 52:

Question 26:

The internal (cellular) energy reserve in autotrophs is
(a) glycogen
(b) protein
(c) starch
(d) fatty acid

Answer:

Autotrophs use light as a source of energy, carbon dioxide as a carbon source and water plays an important role as electron donor which use atmospheric carbon dioxide into glucose. Chlorophyll absorbs the sunlight for light reaction which produce energy in the form of ATP and during the second phase of photosynthesis (dark reactions) carbohydrate.

Hence, the correct answer is option C.
 

Page No 52:

Question 27:

Which of the following equations is the summary of photosynthesis?
(a) 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
(b) 6CO2 + H2O + Sunlight→ C6H12O6 + O2 + 6H2O
(c) 6CO2 + 12H2O + Chlorophyll + Sunlight→ C6H12O6 + 6O2 + 6H2O
(d) 6CO2 + 12H2O + Chlorophyll + Sunlight→ C6H12O6 + 6CO2 + 6H2O

Answer:

The reaction for the process of photosynthesis is 6CO+ 12H2O + Chlorophyll + Sunlight→ C6H12O+ 6CO2 + 6H2O

Hence, the correct answer is option B.

Page No 52:

Question 28:

Choose the event that does not occur in photosynthesis
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy

Answer:

During photosynthesis light is used as a source of energy, carbon dioxide is the chief carbon source and water as electron donor which help in converting atmospheric carbon dioxide into glucose (carbohydrates).

The major photosynthetic pigment is  chlorophyll a and accessory pigments are chl b, chl c and carotenoids etc their function is to  trap sunlight  for light reactions of photosynthesis. During this phase, produced ATP and reducing agents which also serve as energy source to drive the second phase of photosynthesis (dark reactions) during which carbohydrate synthesis takes place.

Hence, the correct answer is option C.



Page No 53:

Question 29:

The opening and closing of the stomatal pore upon
(a) oxygen
(b) temperature
(c) water in guard cells
(d) concentration of CO2 in stomata

Answer:

Stomata are the tiny pores on the leaf surface, surrounded by two guard cells that regulate the opening and closing of the pores .When water enters in a guard cells, it becomes turgid and pores are opened. Removal of water makes them flaccid, resulting in closing of pores.

Hence, the correct answer is option C.
 

Page No 53:

Question 30:

Choose the forms in which most plants absorb nitrogen
(i) Proteins
(ii) Nitrates and Nitrites
(iii) Urea
(iv) Atmospheric nitrogen
(a) (i) and (ii) (b) (ii) and (iii)
(c) (iii) and (iv) (d) (i) and (iv)

Answer:

Plants absorb nitrogen from the soil in the form of nitrate (NO3) and nitrite (NO2). All other nitrogen sources (atmospheric nitrogen, proteins, urea etc.) must be broken down into either of these two forms to be absorbed by plants. 

Hence, the correct answer is option B.

Page No 53:

Question 31:

Which is the first enzyme to mix with food in the digestive tract?
(a) Pepsin
(b) Cellulase
(c) Amylase
(d) Trypsin

Answer:

Chemical digestion of food begins in the mouth, breakdown of starch into sugar  by salivary amylase takes place in the mouth. No digestion takes place in oesophagus, which follows mouth. In stomach gastric juice  digests the protein present in the food. Later, pancreatic amylase, trypsin and lipase as well as intestinal peptidases and maltase get mixed with the food  in the small intestine and the final digestion happens here.

Hence, the correct answer is option C.

Page No 53:

Question 32:

Which of the following statement(s) is (are) correct?
(i) Pyruvate can be converted into ethanol and carbon dioxide by yeast
(ii) Fermentation takes place in aerobic bacteria
(iii) Fermentation takes place in mitochondria
(iv) Fermentation is a form of anaerobic respiration
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (ii) and (iii)

Answer:

Yeast is a unicellular organism which carries out ethanol fermentation, which is anaerobic form of respiration During this reaction one glucose breaks into two pyruvate molecules which takes place in cytoplasm. Due to insufficiency of oxygen, pyruvate remains in cytoplasm where pyruvate decarboxylase and alcohol dehydrogenase enzymes carry out the second phase of anaerobic respiration and produce ethanol and carbon dioxide.

Hence, the correct answer is option C.

Page No 53:

Question 33:

Lack of oxygen in muscles often leads to cramps among cricketers. This results due to
(a) conversion of pyruvate to ethanol
(b) conversion of pyruvate to glucose
(c) non conversion of glucose to pyruvate
(d) conversion of pyruvate to lactic acid

Answer:

 In muscle cells, when there is a lack of oxygen, anaerobic respiration occurs where pyruvic acid is converted into lactic acid. This accumulation of lactic acid causes muscle cramps.

Hence, the correct answer is option D.

Page No 53:

Question 34:

Choose the correct path of urine in our body
(a) kidney → ureter → urethra → urinary bladder
(b) kidney → urinary bladder → urethra → ureter
(c) kidney → ureters → urinary bladder → urethra
(d) urinary bladder → kidney → ureter → urethra

Answer:

The urinary system or renal system consists of the organs, tubes, muscles, and nerves that work together to form, store, and carry urine. The renal system filters the plasma of blood and regulates blood volume by excreting excess water in the form of urine. Urine transport follows a path through the kidneys, ureters, bladder, and urethra, This path is collectively known as the urinary tract.

Hence, the correct answer is option C.



Page No 54:

Question 35:

During deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in the
(a) cytoplasm
(b) chloroplast
(c) mitochondria
(d) golgi body

Answer:

Pyruvic acid is not transported to the mitochondria. It remains in the cytoplasm. It is then broken down into waste products that can be removed from the cell. This entire process occurs in the absence of oxygen.

Hence, the correct answer is option A.


 

Page No 54:

Question 36:

Name the following
(a) The process in plants that links light energy with chemical energy
(b) Organisms that can prepare their own food
(c) The cell organelle where photosynthesis occurs
(d) Cells that surround a stomatal pore
(e) Organisms that cannot prepare their own food
(f) An enzyme secreted from gastric glands in stomach that acts on proteins.

Answer:

(a) The process in plants that links light energy with chemical energy is called photosynthesis.
(b) Organisms that can prepare their own food are known as autotrophs.
(c) The cell organelle where photosynthesis occurs is called chloroplast.
(d) Cells that surround a stomatal pore are called guard cells.
(e) Organisms that cannot prepare their own food are known as heterotrophs.
(f) An enzyme secreted from gastric glands in the stomach that act on proteins is pepsin.

Page No 54:

Question 37:

“All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.

Answer:

Yes, respiration takes place throughout the day and night but photosynthesis takes place only during day time. During day time, as the rate of photosynthesis is more than the rate of respiration, the net result is the release of oxygen. At night, there is no photosynthesis, so they give out carbon dioxide due to respiration.

Page No 54:

Question 38:

How do the guard cells regulate opening and closing of stomatal pores?

Answer:


The swelling of guard cells due to absorption of water causes the opening of stomatal pores while shrinking of guard cells closes the pores. Opening and closing of stomata occur due to turgor changes in guard cells. When guard cells are turgid, the stomatal pore is open while in flaccid conditions, the stomatal aperture closes.

Page No 54:

Question 39:

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.

Answer:

The plant which is kept in continuous light will live longer. This is because the light which is required by plants to perform photosynthesis is present for them. Photosynthesis is the process that is used by plants to make food and produce oxygen for respiration. The plant which is kept in dark would not be able to live due to lack of oxygen for respiration and light for photosynthesis. The plant kept in continuous light will live longer, as it will continue doing photosynthesis and will live longer.

Page No 54:

Question 40:

If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.

Answer:

During day time respiration and photosynthesis both occur. During photosynthesis, plant inhales carbon dioxide and exhales oxygen. At the same time during respiration plant inhales the oxygen in some amount (rest is diffused in the air) and exhales carbon dioxide which is again at the same time used up by the plants for photosynthesis.

Page No 54:

Question 41:

Why do fishes die when taken out of water?

Answer:

Fish takes the dissolved oxygen from the water for respiration. Fishes respire through their gills. The gill tissues allow the water to move in between the gill membrane and oxygen can diffuse into the fish’s bloodstream. So, there must be a constant flow of water over gills. If the fish are taken out of the water, it suffocates and dies due to insufficient oxygen. Without water, the gills dry and stick to each other, and gas exchange cannot take place.

Page No 54:

Question 42:

Differentiate between an autotroph and a heterotroph.

Answer:

Autotrophic Nutrition: The term ‘autotroph’ is derived from the Greek word ‘Auto’ meaning self and ‘trophos’ meaning nutrition.
In this mode of nutrition, organisms prepare or synthesize their own food with the help of inorganic raw materials in the presence of sunlight. These organisms are known as autotrophs. All green plants and some bacteria are autotrophs.

Heterotrophic Nutrition: The term ‘heterotroph’ is derived from the Greek words ‘Heteros’ meaning different or other, and ‘trophos’ meaning nutrition. In this mode of nutrition, organisms obtain energy from the intake of complex organic substances, generally from plant and animal sources. These organisms are known as heterotrophs. All fungi and animals and some bacteria are heterotrophs. 

Page No 54:

Question 43:

Is ‘nutrition’ a necessity for an organism? Discuss.

Answer:


Food is required to provide energy to do day-to -day activity and metabolic reactions. It  also helps in growth and replacement of cell and in fighting against germs and disease.
 

Page No 54:

Question 44:

What would happen if green plants disappear from earth?

Answer:

Green plants are producers and all organisms are dependent on them directly or indirectly. If all green plants disappear from the earth, all the herbivores will die due to starvation and so will the carnivores.

Page No 54:

Question 45:

Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.

Answer:

This plant will not remain healthy for a long time due to the following reasons-
(i) they will not get oxygen for respiration.
(ii) they will not get carbon dioxide for photosynthesis.
(iii) Upward movement of water and minerals would be hampered due to lack of transpiration.

Page No 54:

Question 46:

How does aerobic respiration differ from anaerobic respiration?

Answer:

Aerobic respiration

Anaerobic respiration

i.

It takes place in the presence of oxygen.

i.

It takes place in the absence of oxygen.

ii.

It occurs both in the cytoplasm and mitochondria.

ii.

It occurs only in the cytoplasm.

iii.

The energy yield is high.

iii.

The energy yield is comparatively low.

iv. End products are carbon dioxide and water. iv. End products are lactic acid or ethanol and carbon dioxide.



Page No 55:

Question 47:

Match the words of Column (A) with that of Column (B)
 

Column (A)
Column (B)
(a)
Phloem
(i)
Excretion
(b)
Nephron
(ii)
Translocation of food
(c)
Veins
(iii)
Clotting of blood
(d)
Platelets
(iv)
Deoxygenated blood

Answer:

(a) (ii), (b) (i),  (c) (iv), (d) (iii)

Page No 55:

Question 48:

Differentiate between an artery and a vein.

Answer:

-

Arteries

-

Veins

(i)

Arteries are tough, elastic and have thick walls.

(i)

Veins are thin-walled.

(ii)

They carry oxygenated blood from the heart to the other parts of the body. The pulmonary artery is an exception as it carries deoxygenated blood from the heart to the lungs.

(ii)

They carry deoxygenated blood from the body to the heart.  The pulmonary vein is an exception as it carries oxygenated blood from the heart to the lungs.

(iii) Blood flows under high pressure in the arteries. (iii) Veins bring back blood from the organs to the heart and blood is no longer under pressure.

Page No 55:

Question 49:

What are the adaptations of leaf for photosynthesis?

Answer:

 (i) Leaves are arranged at right angles to the light source in a way that causes overlapping.
(ii) Presence of a large number of stomata for gaseous exchange.
(iii) The extensive network of veins enables quick transport of substances to and from the mesophyll cells.
(iv) Leaves provide a large surface area for maximum light absorption.
(v) The chloroplasts are more in number on the upper surface of leaves as compared to lower surface.

Page No 55:

Question 50:

Why is small intestine in herbivores longer than in carnivores?

Answer:

The small intestine is larger in herbivores in animals than carnivores because they eat plants and the cell structure of plans is mainly made up of cellulose. So, breaking of cellulose food must stay in the small intestine for a longer duration of time. Hence, they have longer small intestine.

Page No 55:

Question 51:

What will happen if mucus is not secreted by the gastric glands?

Answer:

The mucus secreted by the gastric glands protect our stomach lining from the HCl in our stomach. If the mucus secretion stops, then the HCl will directly react with our stomach (we know that HCl is highly corrosive), causing acidity, burning pain, peptic ulcers etc.

Page No 55:

Question 52:

What is the significance of emulsification of fats?

Answer:

It is necessary as it is difficult for the enzymes (lipases) to act on large fat globules. Emulsion of fats increases the efficiency of enzyme action to break down fats into fatty acids and glycerol which are easily absorbed through small intestine.

Page No 55:

Question 53:

What causes movement of food inside the alimentary canal?

Answer:

  Peristalsis mainly causes the movement of food inside the alimentary canal. Rhythmic contraction and relaxation of these muscles help in propelling food through the alimentary canal.  

Page No 55:

Question 54:

Why does absorption of digested food occur mainly in the small intestine?

Answer:

The inner walls of the small intestine contain a number of finger-like projections called the villi. These villi help in the efficient absorption of food. Also, the wall of the intestine is richly supplied with blood vessels (which take the absorbed food to each and every cell of the body). Therefore, the absorption of digested food occurs mainly in the small intestine. 

Page No 55:

Question 55:

Match Group (A) with Group (B)
 

Group (A) Group (B)
 (a) Autotrophic nutrition  (i) Leech
 (b) Heterotrophic nutrition  (ii) Paramecium
 (c) Parasitic nutrition  (iii) Deer
 (d) Digestion in food vacuoles  (iv) Green plant

Answer:

 (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)

Page No 55:

Question 56:

Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

Answer:


Rate of breathing in aquatic organisms much faster than in terrestrial organisms because they have to take dissolved oxygen from water through gills. Amount of dissolved oxygen is less than that the oxygen available in the gaseous form to terrestrial animals.

Page No 55:

Question 57:

Why is blood circulation in human heart called double circulation?

Answer:


Double circulation means when blood passes heart twice in one cycle. In human heart, blood passes firstly from right side as deoxygenated blood and then it passes from left side as oxygenated blood.

Page No 55:

Question 58:

What is the advantage of having four chambered heart?

Answer:


The human heart is four-chambered, the left side of the heart is dedicated to carry oxygenated blood and the right side of the heart is dedicated to carry deoxygenated blood. The left half is completely separated from the right half by septa. This gives an efficient supply of oxygenated blood to the body parts and it helps animals to meet their high energy demand.

Page No 55:

Question 59:

Mention the major events during photosynthesis

Answer:

The major events during photosynthesis are as follows;
(a) reduction of CO2 to carbohydrates
(b) splitting of H2O into H2, O2, and e-
(c) conversion of light energy to chemical energy
(d) absorption of light energy by chlorophyll

Page No 55:

Question 60:

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 get blocked due to dust

Answer:

(a) In cloudy days, the rate of photosynthesis will decrease.
(b) If there is no rainfall in the area, the rate of photosynthesis will decrease.
(c) If there is good manuring in the area, the rate of photosynthesis will increase
(d)  If stomata get blocked due to dust, the rate of photosynthesis will decrease.

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Question 61:

Name the energy currency in the living organisms. When and where is it produced?

Answer:

Energy currency in the living organisms is Adenosine triphosphate (ATP) which is produced during respiration in living organisms. ATP is also during photosynthesis in plants.
 



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Question 62:

What is common for cuscuta, ticks and leeches?

Answer:

Cuscuta, ticks, and leeches are all Parasites. Parasites are organisms that feed on other living organisms called the host. The host may be plant or animal. A parasite receives its food from the host but gives no benefit to the host in return. 

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Question 63:

Explain the role of mouth in digestion of food.

Answer:

(i) In the buccal cavity, the food is crushed into small pieces by the teeth.
(ii) It mixes with saliva that contains the enzyme called salivary amylase and breaks down starch into sugars.
(iii) The tongue helps in the thorough mixing of food with saliva.

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Question 64:

What are the functions of gastric glands present in the wall of the stomach?

Answer:

The functions of gastric glands present in the wall of the stomach are as follows:
(a) It produces the enzyme called pepsin that digests proteins into peptones 
(b) It also secretes mucus which in turn protects the inner lining of the stomach from HCl.

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Question 65:

Match the terms in Column (A) with those in Column (B)
 

Group (A) Group (B)
 (a) Trypsin  (i) Pancreas
 (b) Amylase  (ii) Liver
 (c) Bile  (iii) Gastric glands
 (d) Pepsin  (iv) Saliva

Answer:

. (a)-i, (b)-iv, (c)-ii, (d) -iii 

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Question 66:

Name the correct substrates for the following enzymes
(a) Trypsin
(b) Amylase
(c) Pepsin
(d) Lipase

Answer:

(a)-Protein, (b)-Starch, (c)-Protein, (d)-Fats

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Question 67:

Why do veins have thin walls as compared to arteries?

Answer:

Arteries carry blood from the heart. The blood is pumped with pressure. So, to withstand the blood pressure, they have a thick wall. Veins carry the blood from all the parts of the body to the heart,  they have lower blood pressure. So, veins have thin walls as compared to arteries

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Question 68:

What will happen if platelets were absent in the blood?

Answer:

Platelets play a vital role in clotting of blood. So, in the absence of platelets, the process of clotting will be affected. 

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Question 69:

Plants have low energy needs as compared to animals. Explain.

Answer:


Plants are non-motile (i.e. do not move from one place to another). In a large plant body, there are many dead cells like sclerenchyma, as a result, it requires less energy as compared to animals.

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Question 70:

Why and how does water enter continuously into the root xylem?

Answer:

There is high tension and low pressure created in the root hair epidermis. This is because of the transpiration pull exerted by the loss of water by transpiration. This low pressure favors osmotic uptake of water and minerals from the soil into the root.

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Question 71:

Why is transpiration important for plants?

Answer:

Transpiration is important because
(a) It helps in absorption and upward movement of water and minerals from roots to leaves.
(b) It prevents the plant parts from heating up.

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Question 72:

How do leaves of plants help in excretion?

Answer:

Plants do not have specialized structures for the elimination of wastes like humans have kidneys, lungs, etc. Plants use a variety of techniques to remove waste materials. Oxygen, a by-product of photosynthesis is removed through stomata. The excess water absorbed from roots is also lost through stomata via transpiration. Cell vacuoles, gum, resin, etc. are stored in old xylem tissues. Waste products may be stored in leaves that fall. Plant roots also sometimes excrete wastes materials.

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Question 73:

Explain the process of nutrition in Amoeba.

Answer:

Amoeba shows the holozoic mode of nutrition and process by which it intakes the food is known as “phagocytosis ”.Amoeba can constantly change its shape. It forms finger-like projections called pseudopodia (meaning false feet). Pseudopodia help Amoeba in moving and capturing food.
When an Amoeba senses its prey, it pushes out its pseudopodia around its prey and engulfs it. The food thus gets trapped in the food vacuole. An Amoeba feeds on algae, rotifers, protozoans, and even other small Amoeba.

 

 








Digestive juices such as amylase and protease are secreted inside the food vacuole in Amoeba. These juices act on the food and break it down into smaller components. Amylase breaks down complex carbohydrates into simple sugars, while protease breaks down proteins to simpler substances. The digested food is later absorbed by Amoeba for growth, maintenance, and multiplication. The waste material or undigested food is then expelled out of the body using pseudopodia.

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Question 74:

Describe the alimentary canal of man.

Answer:

Human alimentary canal consists of various organs of digestion which are  in following sequence:

  • Mouth cavity: It is known as oral cavity or buccal cavity located inside mouth, it contains teeth, tongue and three pairs of salivary glands.
  • Pharynx: The oral cavity is followed by pharynx. It is  common pathway for food and wind pipe.
  • Oesophagus: It is a long muscular, tube that passes through thoracic cavity and diaphragm into abdominal cavity and carries the food down to the stomach by peristalsis.
  • Stomach: The stomach is J-shaped organ in the abdominal cavity and is continuous with the oesophagus above and the duodenum of the small intestine below.
  • Small intestine: Small intestine is tube like structure. It has three divisions, i.e., duodenum, jejunum and ileum.
  • Large intestine: Large intestine, which can be divided into two parts as  colon and rectum.
  • The rectum opens at the anus, which serves as site of defecation. 

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Question 75:

Explain the process of breathing in man.

Answer:

 

Breathing is the process of taking in oxygen-rich air and giving out carbon dioxide-rich air. Breathing in is 'Inspiration' and breathing out is 'Expiration'.

Breathing in humans is a physical change which involves inspiration and expiration that are explained below:

Inspiration involves bringing in air from outside the body into the lungs. When we breathe in, the size of our chest increases. This happens because when air enters, the lungs expand and the ribs move outwards. Simultaneously, the diaphragm contracts and becomes flat. Thus, the size of our chest increases.

Expiration involves the removal of CO2 from the body. When we breathe out, the size of our chest decreases. This happens because when air moves out of our lungs, the lungs contract, the ribs move back, and the diaphragm curves upwards into the chest decreasing the size of the chest.

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Question 76:

Explain the importance of soil for plant growth.

Answer:

Soil is the layer of earth that results from the degradation of the basement rock also known as bedrock due to certain physical, chemical and biological processes. It supports plant growth. It is a source for water and nutrients required by plants, An important constituent of soil is its organic component, comprising dead and decaying leaves and parts of plants and animals. This organic material decomposes to form humus, which in turn determines the structure and fertility of the soil( nutrient content). It is porous in nature and allows water and air to pass through.

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Question 77:

Draw the diagram of alimentary canal of man and label the following parts.
Mouth, Oesophagus, Stomach, Intestine

Answer:

              
                                  Human Alimentary Canal

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Question 78:

How do carbohydrates, proteins and fats get digested in human beings?

Answer:

When we eat something, the food is mixed with saliva inside the mouth cavity. Saliva contains enzyme amylase which partially digests carbohydrate and converts into maltose.
Saliva contains enzymes salivary amylase, lysozyme, and electrolytes. Salivary amylase basically helps in starch digestion up to 30%.


Then the food is swallowed down. Carbohydrate digestion does not take place in stomach as enzymes become inactive in presence of HCl. Again when the food pulp enters inside intestine, the intestinal juice and pancreatic juice contain amylase that again digests carbohydrate. Here, maltose gets converted into simplest form glucose.The small intestine is the site of complete digestion of carbohydrates, proteins and fats.

It receives secretion from liver and pancreas for this purpose. Bile juice makes the food alkaline due to the acidity of food coming from stomach. Bile also allows breaking of fats and enzyme action on food.The pancreatic juice from pancreas contains enzymes like trypsine, lipase and amylase for digesting proteins,fats and carbohydrates respectively.The walls of the intestine secretes intestinal juice converting carbohydrates to glucose,proteins to amino acid and fats to fatty acids and glycerol.

The digested food is taken by walls of the small intestine which contains numerous finger-like projections called villi and water is absorbed in large intestine. Excess waste materials is then finally thrown out via excretion.

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Question 79:

Explain the mechanism of photosynthesis.

Answer:

The process of photosynthesis takes place in the green leaves of a plant. The green leaves of a plant make food by combining carbon dioxide and water in the presence of sunlight and chlorophyll. The carbon dioxide is taken from the small pore-like structures called stomata from under the leaves, stem(pores in the bark are called lenticels) and roots. Water required for making food is taken from the soil. This water is transported through the leaves from the soil through the roots and stem. The sunlight provides the energy required to carry out the chemical reactions involved in the preparation of food. The green pigment called chlorophyll is present in green leaves helps in absorbing energy from the sunlight. Oxygen gas is produced as the by-product during the preparation of food by photosynthesis. plants also loose water through the process of transpiration. this food is called glucose. Extra glucose is changed to another food called starch, this is stored in the leaves of plants.

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Question 80:

Explain the three pathways of breakdown in living organisms.

Answer:

Breakdown of glucose occurs in two ways i.e aerobic breakdown (in presence of oxygen) or anaerobic breakdown (in absence of oxygen).

Aerobic breakdown involves the breakdown of glucose into pyruvic acid through glycolysis and then the breakdown of pyruvic acid into carbon dioxide and water with the release of energy through Kreb's cycle.

Anaerobic breakdown involves the breakdown of glucose into pyruvic acid through glycolysis and then the breakdown of pyruvic acid into carbon dioxide and alcohol in alcoholic fermentation, e.g, Yeast
It may also break down into carbon dioxide and lactic acid during lactic acid fermentation with the release of energy. E.g, Lactobacillus or muscle cells of humans.

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Question 81:

Describe the flow of blood through the heart of human beings.

Answer:

The heart is divided into four chambers − the right auricle, the right ventricle, the left auricle, and the left ventricle. The walls of these chambers are made up of a special muscle, called myocardium, which contracts and relaxes rhythmically to distribute blood to all the cells of the body. The passage of blood flow in the heart is as follows:

  • The superior and inferior vena cava carries deoxygenated blood from upper and lower regions of the body respectively and supplies this to the right auricle of the heart.

  • The right auricle then contracts and passes deoxygenated blood to the right ventricle. The right ventricle, in turn, contracts and passes deoxygenated blood into the two pulmonary arteries that pump it into the lungs. The purification of blood takes place in the lungs. From the lungs, the pulmonary veins transport oxygenated blood to the left atrium of the heart.
    Then, the left atrium contracts to pour the oxygenated blood into the left ventricle.

  • The left ventricle pushes the oxygenated blood into the aorta.

The aorta gives rise to many arteries that distribute oxygenated blood to all the regions of the body.

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Question 82:

Describe the process of urine formation in kidneys.

Answer:

All mammals including human beings are ureotelic animals since nitrogenous wastes in them are excreted chiefly in the form of urea.

In human beings, this function is performed by the excretory system consisting of a pair of kidneys, a pair of ureters, a urinary bladder, and urethra.

The urine is formed in kidneys and passes on to the urinary bladder via the ureters. The urinary bladder stores the urine until it is excreted through the urethra.

The kidney contains numerous filtration units called the nephrons. Nephron is the structural and functional unit of the kidney. The nephrons consist of a network of capillaries associated with a cup-shaped end of a tube in which the filtered urine is collected. When the blood passes through the tube, some substances such as glucose, amino acids, salts, and water are selectively reabsorbed. The final filtrate is collected in the collecting tubule and eventually enters the ureters.



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