Download CHAPTER-6 NCERT SOLUTIONS

CHAPTER-6 NCERT SOLUTIONS
Q1: Name an organ which is part of two body systems.
Answer: Pancreas which if part of


Endocrine System
Digestive System
Q2: Why do raw bread taste sweeter on mastication?
Answer: It is because salivary glands secrete Salivary Amylase which converts starch into sugars.
Q3: How are fats digested in our bodies? Where does this process take place?
Answer: The small intestine is the site of the complete digestion of fats. Fats are present in the
intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile juice
from the liver accomplishes this. Bile salts emulsify these large globules of fats and break them down
into smaller globules increasing the efficiency of enzyme action. The pancreas secretes pancreatic
juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down
emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The
enzymes present in it finally convert the fats into fatty acids and glycerol.
Q4: What is the role of saliva in the digestion of food?
Answer: Saliva is a fluid which is secreted by the salivary glands. It helps in digestion of food by
following ways:
1. Saliva contains a digestive enzyme called salivary amylase, which breaks down starch into
sugars (maltose).
2. It cleans the mouth cavity and tends to destroy germs that cause teeth decay. It contains
lysozymes which help in destroying the bacteria.
3. It moistens and lubricates food which again helps in swallowing.
4. It acts as solvent, dissolving some food particles to stimulate taste buds of the tongue.
Q5: Why will simple diffusion not meet the requirement of human beings?
Answer: All cells of body are not in direct contact with the environment. In humans the energy
requirements are high. Waste produced is more due to active metabolism. Therefore simple diffusion
does not meet the oxygen requirement of human beings.
Q6: What criteria do we use to decide whether something is alive?
Answer: Following criteria may be used to define whether something is alive:
1. It is an organized system of molecules that captures energy and nutrients to grow by
molecular movements,
2. It has the ability to reproduce at some point in its life cycle, and
3. It has the potential to evolve in response to changes in the environment.
Q7: After long running, you may experience cramps in your leg muscles. Whats the reason
behind this?
Answer: It is due to sudden build up of lactic acid (because of lack of oxygen) in our muscles after
long exercise. It causes muscular cramps in our leg muscles.
Q8: What processes would you consider essential for maintaining life?
Answer: Various life processes are essential for maintaining life. Some are:



Nutrition
Respiration
Excretion

Transportation
Q9: How do villi enhance absorption of food in the intestine?
Answer:


Increased surface area
Highly vascular
Q10: Why bile juice is considered important even though it does not contain any digestive
enzymes?
Answer: Bile juice is important for the following reasons:
1. It contains bile salts and bile pigments that emulsify fats.
2. Contains NaHCO3 that neutralizes the acidic medium of the food in small intestine.
Q11: Which organs secrete the following enzymes:
(i) Trypsin
(ii) Pepsin
Answer: (i) Trypsin - Pancreas (ii) Pepsin - Gastric lining of Stomach
Q12: Name the factors that affect photosynthesis.
Answer:





Light Intensity, its quality and duration.
Temperature
Water Availability
CO3 availability
Other Factors like age and histology of leaf, amount of chlorophyll present
Q13: Name the vestigeal part of human alimentary canal?
Answer: vermiform appendix or caecal
Q14: What is the name given to rhythmic wave like manner occurring in alimentary canal?
Answer: Peristalsis or Peristaltic movements
Q15: The bark of woody plants is dead but the inner layers inside the bark are living. How do
they get oxygen and release carbon dioxide?
Answer: Through lenticels
Q16: What are lenticels?
Answer: Lenticels are portions of the periderm (bark) with numerous intercellular spaces. Their
purpose is to allow gas exchange through the compactly arranged cork cells of the bark, which
otherwise presents an impermeable barrier to the passage of water and gases.
Q17: How does photosynthesis occur?
Answer: The process of photosynthesis is completed in two steps:
1. light reaction
2. dark reaction
i) Light reaction: The first step of photosynthesis occurs in the presence of light. During this step,
chlorophyll contained in the chloroplast of plant cells absorbs light energy. This energy is converted
into another form, which can be supplied for the completion of the dark reaction.
ii) Dark reaction: This second step of photosynthesis does not require light, and is called dark
reaction. It can also carry on in the presence of light. During this step, energy generated during light
reaction is used to combine carbon dioxide and water molecules to form energy rich compounds,
such as glucose. Oxygen is also released in this process.
The following equation summarizes the raw materials and products of photosynthetic process:
RAW MATERIALS PRODUCTS
sunlight
6CO2 + 12H2O ----------------> C6H12O6 + 6H2O + 6O2
carbon water chlorophyll glucose water oxygen
dioxide
Q18: Name the mode of nutrition in an organism that uses simple substances like CO2 and
water to prepare food inside its body?
Answer: Autotrophic mode of nutrition.
Q19: What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
Autotrophic
Nutrition
Hetrotrophic
Nutrition
Green plants are self-dependent, because they
synthesize their own food materials by photosynthesis.
1
Such mode of nutrition is
described as autotrophic nutrition.
Organisms which depend upon plants or other
organisms for their nutrition.
2 Green Plants (producers) are autotrophs.
Non-Green Plants, Animals, Parasites are
hetrotrophs (consumers).
Q20: Read following statements from A to E and identify the relevant life process from the
following word list.
growth, transport, synthesis, regulation, nutrition
A. A butterfly sucking the nectar from the flowers in a garden.
B. A boy shouts with excitement when his school team wins the match on the last ball.
C. After finishing lunch, Mohan's blood distributes the food molecules to different cells of his body.
D. Green plants prepares starch (complex substance) from simpler chemicals.
E. Radha finds her height has increased by 4 cm since her last birthday.
Answer:
A-nutrition
B- regulation
C- transport
D- synthesis
E- growth
Q21: What is osmoregulation?
Answer: The regulation of the water content of the cell is called osmoregulation.
Q22: What are the different ways in which glucose is oxidized to provide energy in various
organisms?
Answer: Breaking down of glucouse involves two step process. In the first step, it is broken into three
carbon molecule called pyruvate. The pyruvate is further broken down into energy in following
different ways in various organisms:
1. Aerobic Respiration: In this case, pyruvate is broken down into water and carbon dioxide
along with release of energy. It commonly occurs in mitochondria of cells.
2. Anaerobic Respiration in Yeast: In yeast cells during fermentation pyruvate is converted into
ethanol and carbon dioxide in the absence of oxygen.
3. Anaerobic Respiration in Muscles: Due to lack of oxygen, e.g. during vigorous running or
exercise, in human muscles, pyruvate is converted into lactic acid.
Q23: Which organ of the plant body helps in osmo-regulation?
Answer: Leaves
Q24: Which organelle of the cell in animals helps in osmo-regulation?
Answer: Contractile Vacuole.
Q25: If kidney fails to reabsorb water, the tissues would
(a) remain unaffected
(b) shrink to shrivel
(c) absorb water from blood
(d) take more oxygen from blood
Answer: (c) absorb water from blood. This condition is called Oedma or Dropsy
Q26: How does transpiration pull help in ascent of sap?
Answer: Water column builds up as a result of cohesion and adhesion forces. The negative pressure
in the upper tissues results in upward pull of water.
Q27: In what form excretion takes place in plants?
Answer: Plants produce secondary metabolites like organic acids, tannin, resins, latex, gums etc.
Q28: What are the components of the transport system in highly organised plants?
Answer: The transport system of organised plants consist of xylem and phloem. Xylem which have
vessels and tracheids which transport water and minerals from root to other parts of the plant. Phloem
which consists of sieve tubes, sieve cells and companion cells transport food from leaves to storage
organs and other parts of the plant. In xylem, the transport is unidirectional i.e. from root upward while
in phloem, it is bidirectional.
Q28: What is meant by double circulation? Mention its advantages.
Answer: In human beings and other vertegrates, the blood goes through heart twice during each
cycle. This process is known as double circulation. Deoxygenated blood enters through right auricle
and then it enters right ventricle from where it is pumped to lungs for oxygenation. From lungs after
oxygenation it comes to left auricle and enters left ventricle from where it is pumped to various parts
of body.
Advantages:
1. It helps in keeping oxygenated and De-oxygenated blood completely separated.
2. It increases the efficiency of oxygen in the body.
Q29: Who has longer small intestine tiger or cow?
Answer: Cow because it has to digest cellulose requiring an elaborate digestion. Most of the plant
eaters (ruminants) have to undergo additional process of digestion i.e. break the cellulose wall and
digest it.
Q30: Leaves of a healthy potted plant are coated with Vaseline to block the stomata. Will this
plant remain healthy for long? State three reasons to support your answer.
Answer: No the plant will not remain healthy because no exchange of gases are taking place. It will
lead to:
1. low respiration
2. no photosynthesis occur
3. no transpiration.
Hence plant will not remain healthy and may die eventually.
Q31: Outline inhalation-exhalation cycle.
Answer:
1. Inhalation: Lowering of diaphragm → rising of rib cage → Gas (O2) passes to Alveoli
2. Exhalation: Air is forced out → Rising of diaphragm → lowering of ribcage
Q32 : Haemoglobin is a type of
(a) Carbohydrate
(b) Skin Pigment
(c) Vitamin
(d) Respiratory Pigment
Answer: (d) Respiratory Pigment
Q33: What are the components of the transport system in human beings? What are the
functions of these components?
Answer: The main components of the transport system in human beings are:



heart,
blood, and
blood vessels.
❶ Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from
various parts of the body and transports this impure blood to the lungs for oxygenation.
❷Blood is a fluid connective tissue and it helps in the transport of oxygen, nutrients, CO , and
2
nitrogenous wastes.
❸The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to
various organs or from various organs back to the heart.
It is a double circulatory system in human body.
Q34: Why is it necessary to separate oxygenated and deoxygenated blood in mammals and
birds?
Answer: Warm-blooded animals like birds and mammals maintain a constant body temperature under
different temperature conditions. They cool themselves in a hotter environment and warm their bodies
in a cooler environment. Therefore, these animals need more energy to maintain their body
temperature. This requires more cellular respiration which means more oxygen (O 2). Therefore it is
more efficient if mammals and birds keep separate oxygenated and deoxygenated blood.
Q35: Why is there extra air in our lungs after exhaling?
Answer: This extra air is called residual volume of air. During the breathing cycle, when air is taken
in and let out, the lungs always contain a residual volume of air so that there is sufficient time for
oxygen to be absorbed and for the carbon dioxide to be released. Also we need to do extra work to
empty and refill the lungs, if there is no residual volume of air inside the lungs.
Q36: Which cell are the site of exchange of gases?
Answer: Alveoli
Q37: How are the lungs designed in human beings to maximize the area for exchange of
gases?
Answer:
1. Inside the lungs, the blood capillaries surround the alveoli. The exchange of gases takes
place between the blood of the capillaries and the gases present in the alveoli. Thus alveoli
are the site for exchange of gases.
2. During the process of inhalation, the lungs get filled up with air as ribs are lifted up and
diaphragm is flattened.
3. Air is sucked into the lungs and fills the expanded alveoli. Each lung contains 300-400 million
alveoli. These numerous alveoli increase the surface area for gaseous exchange making the
process of respiration more efficient.
4. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the
oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported
to all the cells in the body.
Q38: Why blood is necessary for oxygen delivery to all parts of the body in larger animals?
Answer:
1. Since the body size of animals is large, the diffusion pressure alone cannot take care of
oxygen delivery to all parts of the body.
2. Instead, respiratory pigments take up oxygen from the air in the lungs and carry it to tissues
which are deficient in oxygen before releasing it. In human beings, the respiratory pigment is
haemoglobin which has a very high affinity for oxygen.
3. This pigment is present in the red blood corpuscles. Carbon dioxide is more soluble in water
than oxygen is and hence is mostly transported in the dissolved form in our blood.
Q39: Define homeostasis.
Answer: The series of physical and chemical processes that work to maintain an internal equilibrium
is called homeostasis.
Q40: Name the organ systems that help us maintain homeostasis.
Answer: Circulatory System and Excretory System.
Q41: Wastes concentrated in the tubules of Bowman’s capsule are called ____.
(a) salts.
(b) juices
(c) urine
(d) amino acids
Answer: (c) urine.
Q42: What in kidneys is analogous to alveloli in lungs?
Answer: Nephrons.
Q43: State the role and function of lymph in human transport system.
Answer: Lymph (like blood) is a circulatory fluid. It flows in the lymph vessels.
1.
2.
3.
4.
5.
Lymph (also called tissue fluid) is colourless.
It consists of lymphocytes which kills germs and protect the human body from infections.
Lymph carries digested and absorbed fat from intestine.
It drains excess fluid from extra cellular space back into the blood.
Its flow is unidirectional i.e. from tissues → lymph capillaries → veins → heart.
Q44: What is the basic reason of urine production?
Answer: Blood carries nitrogenous waste in the form of urea or uric acid which needs to be removed.
It is done by kidneys by filtering the blood and removing uric acid in the form of urine.
Q45: State the role of kidneys in human transport system.
Answer:
1. Remove or excrete nitrogenous wastes
2. Regulate water content of the body (osmo-regulation).
3. Maintain mineral balance in blood.
Q46: Who discovered systemic blood circulation system in human body?
Answer: William Harvey in 1628
Before that people believe, it is the same tubes carry the blood and blood is formed in liver.
Q47: What is pulmonary circulation and systemic circulation?
Answer: Humans have a double circulatory system. The right side of the four chambered heart pumps
blood to the lungs only and is called the pulmonary circulation.
The left side of the heart pumps blood to the rest of the body is called the systemic circulation.
Q48: Which fluid is also know as tissue fluid?
Answer: Lymph
Q49: What is sphygmomanometer?
Answer: In layman terms it is called blood pressure apparatus which is used to measure blood
pressure of humans.
Q50: What is the function of ureter?
Answer: Transports urine from kidneys to bladder.
Q51: Assertion and Reason Type
Assertion: Bile is essential for fat digestion
Reason: Fats cannot be digested without emulsification
Use the following Key to choose the appropriate answer.
(a) Both Assertion & Reason are True & Reason is a correct explanation of the Assertion.
(b) If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
(c) If Assertion is True but the Reason is False.
(d) If both Assertion and Reason are False
Answer: (a) Both Assertion & Reason are True & Reason is a correct explanation of the Assertion.
Q52: Chyme is ____.
(a) Digestive enzyme secreted by stomach.
(b) Hormone secreted by islets of Pancreas
(c) food which enters into intestine from stomach.
(d) Part of bile juice which stores in gall bladder.
Answer: (c) food which enters into intestine from stomach.
Q53: What is the nature of Chyme? Acidic or Basic or Neutral?
Answer: Acidic.
Q54: During daytime transpiration and photosynthesis are interlinked. What do you mean by
this statement?
Answer: During daytime, stomata is open to diffuse in Carbon Oxide gas for photosynthesis. In
parallel, it also facilitates transpiration. Therefore, during daytime the process of transpiration and
photosynthesis are interlinked.
Q55: 'Sweating in animals' is equivalent to what in plants?
Answer: Transpiration.
Q56: What factor contribute to rate of transpiration?
Answer:
1.
2.
3.
4.
5.
6.
Number of leaves
Number of stomata
Temperature of Surroundings
Wind
Water supply
Amount of Light
Q57: How does transpiration help plants?
Answer:
1. During transpiration the evaporating water carries away heat energy. Thus it cools the
temperature of plants.
2. Due to water loss, the osmotic pressure inside leaves decreases. Due to which water and
other mineral is able to reach leaves from roots and stem.
Following you tube video gives detailed explanation about Urinary System (Credits: Introductory B.
Timby and N. Smith)
Q58: Name the mineral required for healthy growth of teeth.
Answer: Calcium
Q59: Name the chemical used to detect presence of starch.
Answer: Iodine
Q60: What is the function of mucus secreted in stomach during digestion?
Answer: Mucus does not participate directly in digestion. However, it protects the inner lining of the
stomach due to HCl secretion.
Q61: What is the optimum temperature for photosynthesis?
Answer: 25° C is considered as optimum temperature for photosynthesis.
Q62: Differentiate between Blood and Lymph
Answer:
Blood
Lymph
Blood
Lymph
1. Reddish in Colour
2. RBCs present
3. Flow is rapid
4. Bidirectional Flow
5. Leucocyte count is relatively less.
6. Platelests present
1. Pale Yellow in colour
2. No RBCs
3.Flow is slow
4. Unidirectional
5. High leucocyte count.
6. Platelets absent
Q63: How does diaphragm help in inhalation?
Answer: It flattens during inhalation, thus increasing the volume of the thoracic cavity.