1 Nutrition in Plants

ANSWERS
MAIN COURSEBOOK
ORAL QUESTIONS (PAGE 8)
1. The new organism will be classified as an autotroph. This is because only green plants or
autotrophs can make food from simple non-living substances, that are carbon dioxide and water.
2. The absence of oxygen will not affect photosynthesis. In photosynthesis, carbon dioxide and
water combine in the presence of chlorophyll and sunlight to form glucose (food) and oxygen.
So, oxygen is released in the process and hence not needed in photosynthesis.
3. Yes, the intensity of light will affect the rate of photosynthesis.

ORAL QUESTIONS (PAGE 11)

1. No, the statement is not true. A tiger does not eat plants but it does depend on plants for
food. A tiger eat herbivores which in turn eat plants. Thus, a tiger indirectly depends on food
prepared by plants.
2. All plants are not autotrophic. Non-green plants cannot prepare their own food as they do not
have chlorophyll.
3. No, I do not agree with this statement that after sometime the nutrient level of the soil in a
forest becomes so low that growth of trees will suffer. Because, in a forest the nutrients in the
soil get naturally replenished by decaying of dead plants and animals.
4. No, the plants cannot absorb nitrogen from the atmosphere. They get it in a soluble form from
the soil.

EXERCISES
A. 1. c 2. b 3. d 4. a 5. c 6. d 7. a 8. b
B. 1. heterotrophs 2. chloroplasts 3. light 4. Rhizobium
5. parasitic plant 6. symbiosis 7. saprotrophs, for example, fungi
8. blue-black 9. sun or solar energy 10. false
11. true 12. guard cells
C. 1. The process of taking in food by an organism and its utilization by the body is called
nutrition.
2. Stomata are tiny pores through which leaves take in carbon dioxide from the air. Stomata are
found on the underside of the leaves.
3. Carbon dioxide + Water  Sunlight
Chlorophyll
 Glucose + Oxygen
4. Water, carbon dioxide, chlorophyll and sunlight are essential for photosynthesis to take place.
In photosynthesis, carbon dioxide and water combine in the presence of chlorophyll and
sunlight to form glucose and oxygen.
LIVING SCIENCE 7  ANSWERS 3
 5. The cells of an insectivorous plant secrete digestive juices to absorb nutrients from an insect
trapped by it.
6. Nitrogenous fertilizer is not added in soil in which leguminous plants are grown. This is so
because farmers know that leguminous plants like gram, peas contain Rhizobium bacteria
in their roots which convert atmospheric nitrogen into a soluble form that the plants can
absorb.
7. Saprophyte like a mushroom secretes digestive juice on the dead and decaying matter. This
juice converts the solid matter into a liquid. The saprophyte then absorbs the nutrients from
this liquid.
D. 1. Autotrophs: The organisms which can make their food from simple non-living substances are
called autotrophs. Examples: green plants.
Heterotrophs: The organisms which can not make their own food, and depend on green
plants for their nutrition directly or indirectly are called heterotrophs. Examples: animals and
non-green plants.
2. To test a leaf for starch: Pluck a leaf from a plant that has been exposed to sunlight. Boil
it for about five minutes in water to soften it. Place it in a test tube containing alcohol
and indirectly boil it in a water-filled beaker or water-trough. The alcohol will dissolve the
chlorophyll and the leaf will lose its green colour. Wash the leaf in warm water to remove
the alcohol. Now spread the leaf out flat on a tile and pour iodine solution on it. Remove the
leaf from the iodine and wash it with water. Hold it up against the light. You will observe that
parts of the leaf become blue-black which proves the presence of starch in it.
Precaution: The water in the beaker should not be allowed to boil.
3. Plants get nitrogen to synthesize proteins in two ways:
a. Soil contains certain bacteria called Rhizobium that can convert atmospheric nitrogen into
water-soluble compounds. Plants absorb these compounds along with water to get nitrogen.
b. Farmers add fertilizers rich in nitrogen to the soil. These are absorbed by plants.
4. All animals whether herbivores, carnivores or omnivores can not prepare their own food.
They are known as heterotrophs. They depend directly or indirectly on green plants for their
nutrition. Herbivores depend directly on plants for their food. Carnivores depend on other
animals, which in turn depend on plants. Omnivores depend both on plants and herbivores
for their food.
5. a. Parasitic nutrition: The mode of nutrition in which organisms live in or on other living
organisms (hosts) to derive their food from them is known as parasitic nutrition. Example:
dodder
b. Symbiosis: The mode of nutrition where two different organisms work together for their
mutual benefit is called symbiosis. Example: Rhizobium and leguminous plants. Rhizobium
converts atmospheric nitrogen to soluble nitrogen for the host plant and the host plant in
turn supplies food and shelter to Rhizobium.
c. Saprotrophic nutrition: The mode of nutrition in which organisms live on dead and decaying
matter (plants and animals) to derive their food from them is known as saprotrophic
nutrition. Example: mushroom
4 LIVING SCIENCE 7  ANSWERS
 Plants absorb nutrients from the soil. Therefore, the amount of nutrients in the soil goes on
6.
decreasing. In a farm these nutrients have to be added to the soil in the form of manure and
fertilizers. They contain plant nutrients such as nitrogen, potassium and phosphorus.
7. Parasites: Some non-green plants live in or on other living organisms to derive their food
from them. These plants are known as parasites. Example: dodder.
Partial parasites: Some parasitic plants growing on other trees have green leaves and can
synthesize their food. They take water and minerals from the host plants. Such plants are
known as partial parasites. Example: mistletoe plant grows on mango tree.
HOTS QUESTIONS
1. Green plants are autotrophs because they synthesize their own food from simple non-living raw
materials – carbon dioxide and water. We cannot be called autotrophs because the food we
make in the kitchen comes directly or indirectly from the food made by plants.
2. Animals cannot make food from carbon dioxide, water and sunlight like plants do because
photosynthesis requires chlorophyll which animals do not have.
3. Pitcher plant and Venus flytrap plant grow in soil that is not so rich in nutrients. They need to
feed on insects to use the nutrition obtained from insects to supplement the food they prepare
by photosynthesis.
4. Plants do not need a digestive system because they do not consume complex food like us. They
prepare their own simple food (glucose) which can be directly used by the plant without the
need to digest it first.
BE A SCIENTIST
1. By measuring the volume of oxygen given off in a certain time.
2. By bubbling carbon dioxide through the water (carbon dioxide is soluble in water to some
extent). A more accurate method will be to add sodium hydrogen carbonate to water, about
0.1 g at a time.
3. The amount of light falling on the plant should also be kept constant.
4. As the carbon dioxide supply increases, the rate of photosynthesis also increases initially.
5. The rate of photosynthesis ultimately levels off because of some other limiting factor
(for example, the amount of light available).
ASSERTION—REASON TYPE QUESTIONS
1. a 2. c
CASE-BASED QUESTIONS
1. Two factors that are contributing to increased levels of carbon dioxide in the atmosphere are
burning of fossil fuels and deforestation.
2. Two ways in which increasing carbon dioxide levels is expected to be beneficial are:
i. Increase in plant photosynthesis which results in more growth in some plants and hence
increase in yields in some plants.
ii. Reducing the release of water by plants to the atmosphere thus keeping more on land.
3. Increasing carbon dioxide levels is also impacting other factors critical to plants’ growth, such as
nutrients, temperature, and water. This can limit the benefits of increasing carbon dioxide levels.

LIVING SCIENCE 7  ANSWERS 5

 WORKSHEET
A. 1. b 2. c 3. c 4. c
B. 1. chlorophyll
2. photosynthesis
3. Rhizobium
4. sun
5. mistletoe
6. fungi
C. 1. false 2. false 3. true 4. false 5. true
D. 1. autotrophic, heterotrophic
2. guard
3. glucose, starch
4. carbon, hydrogen, oxygen
5. host
E. 1. The process of taking in food by an organism and its utilization by the body is called
nutrition.
2. Nutrition and respiration are the two processes that help in obtaining energy from food.
3. The chemical reaction that takes place in green parts of a plant during photosynthesis is as
follows:
sunlight
carbon dioxide + water glucose + oxygen
chlorophyll

Plants get nitrogen from the air in two ways:

4.
a. Soil contains certain bacteria called Rhizobium that can convert atmospheric nitrogen
into water-soluble compounds. Plants absorb these compounds along with water to get
nitrogen.
b. Farmers add fertilizers rich in nitrogen to the soil. These are absorbed by plants.
5. The mode of nutrition where green plants make food themselves from simple substances is
called autotrophic nutrition.
Animals and non-green plants, such as fungi and bacteria, cannot prepare their own food.
They depend directly or indirectly on green plants for their nutrition. This mode of
nutrition is called heterotrophic nutrition.
6. Some parasitic plants which grow on other trees such as mango or mahua, have green leaves
and can synthesize their food. They take water and minerals from the host plants. They are
known as partial parasites. Example: mistletoe plant
7. The Venus flytrap and pitcher plant are two insectivorous plants. They grow in soil that is not
so rich.
8. Symbiosis is a close relationship between two or more different organisms. In this mode
of nutrition, two different kinds of organisms work together for their mutual benefit. For
example, alga, which is an autotroph, and fungus, which is a saprophyte, live together
in lichen. The fungus supplies water and minerals to the cells of the alga, while the alga

6 LIVING SCIENCE 7  ANSWERS

 supplies food to the fungus.
9. The method of getting nutrients from dead and decaying matter in the form of a liquid is
known as saprotrophic nutrition. Examples are fungi and bacteria.
10. Saprotrophs secrete digestive juices on the dead and decaying matter. This converts the solid
matter into a liquid. They then absorb the nutrients from this liquid.
11. The three plant nutrients are nitrogen, potassium and phosphorus.
12. Rhizobium can take atmospheric nitrogen and convert it into a soluble form that the
plants can absorb. Rhizobium cannot make its own food. It therefore lives in the roots of
leguminous plants like gram, peas and moong where it gets food and shelter. In turn, it
provides them with nitrogen. It thus has a symbiotic relationship with leguminous plants.

LIVING SCIENCE 7  ANSWERS 7

 2 Nutrition in Animals

ANSWERS
MAIN COURSEBOOK
ORAL QUESTIONS (PAGE 18)
1. Food needs to be digested because the food we eat is not in a form that can instantly provide
us with nutrients. Food has to be broken down to a simple, soluble form which the body cells
can absorb.
2. No, digestion of food does not occur inside the body in all animals. For example, the digestion
of a spider’s food takes place outside the spider’s body.
3. Mosquito, housefly

ORAL QUESTIONS (PAGE 22)

1. Stomach, small intestine
2. No, absorption of the digested food occurs in the small intestine.
3. No, I do not agree. Some digestive juices are also secreted by the liver and pancreas. The liver
secretes bile juice and the pancreas secretes the pancreatic juice.
4. The food after it is digested, and absorbed by the blood is transported to different parts of the
body. This is used to provide energy and materials for growth and repair of body tissue.
5. In a cow, the stomach is of four chambers.

EXERCISES
A. 1. d 2. d 3. b 4. d 5. c 6. b 7. b 8. d 9. a 10. b
B. 1. soluble 2. assimilation 3. food vacuole 4. false 5. false 6. stomach 7. enamel
8. large intestine 9. cud 10. false
C. 1. A frog uses its long sticky tongue to catch its prey.
2. A spider injects digestive juices into the body of the insect caught in a sticky web formed
by the spider. This digests the body parts of the insect and the spider then sucks up the
digested food.
3. The organs that make up the human alimentary canal are
i. mouth, ii. food pipe or oesophagus, iii. stomach,
iv. small intestine, v. large intestine, vi. rectum, and
vii. anus.
4. Differences between milk teeth and permanent teeth are as follows.
Milk teeth: The first set of teeth, 20 in number, grown in a child are milk teeth.
Permanent teeth: Milk teeth fall off by the age of ten and are replaced by larger permanent
teeth, 32 in number.
5. Saliva is a digestive juice. It is produced by three pairs of salivary glands in our mouth.
8 LIVING SCIENCE 7  ANSWERS
 6.Taste buds detect all tastes – sweet, salty, sour and bitter.
7. Food stays in the stomach from a few minutes to a few hours depending on the type of food eaten.
8. The acid in the stomach kills bacteria present in the food and also helps in digestion of proteins.
D. 1. The various processes involved in nutrition in animals are as follows:
i. Ingestion: It is the process of taking in food through the mouth and eating it.
ii. Digestion: It is the process of breaking down of food into a simple, soluble form with the
help of digestive juices in the body.
iii. Absorption: It is the process by which the food in the soluble form passes into the body
fluids such as blood.
iv. Assimilation: It is the process of using the absorbed food to produce energy and for growth.
v. Egestion: It is the process of elimination of undigested solid parts of the food.
2. a. Amoeba engulfs tiny particles of food by throwing its false feet, known as pseudopodia
around it. The pseudopodia join together to form a small cavity known as a food vacuole.

b. Hydra has a number of tentacles around its mouth, which are used for ingestion of food.
The tentacles entangle small aquatic animals and kill them with their stinging cells. They
then push them into the mouth.

The four types of teeth in our mouth and their functions are:
3.
i. Incisors (or biting teeth): are used for biting and cutting.
ii. Canines (or tearing teeth): are used for tearing pieces of food such as meat.
iii. Premolars (or crushing teeth): are used for crushing food like nuts.
iv. Molars (or grinding teeth): are used for grinding and chewing food.
4. The muscular movement of contraction and expansion to push food down in our oesophagus
to our stomach in a wave-like action is called peristalsis.

LIVING SCIENCE 7  ANSWERS 9

 5. a. The function of saliva: (i) It helps to break down starch of the food into sugars that are easier
to digest. (ii) It also makes food softer and easier to swallow by making it wet and slippery.
b. The function of bile juice: The bile breaks up fats into tiny droplets that can be digested
and absorbed more easily.
c. The function of pancreatic juice: Pancreatic juice changes starch into simple sugars in small
intestine and proteins into simpler compounds called amino acids.
6. a. Food in stomach: Stomach secretes mucous, hydrochloric acid and digestive juices. The
acid kills bacteria that enter alongwith food and also helps in digestion of proteins. The
digestive juices break down proteins to simpler substances. Thus, food gets partly digested
in the stomach.
b. Food in small intestine: The muscles in the small intestine mix food with more digestive
juices from its wall, some from liver (bile juice) and some from pancreas (pancreatic juice).
Bile and digestive juice from intestinal wall together act on fats and break it into simplest
form as fatty acids and glycerol. Pancreatic juice changes starch into simple sugars and
proteins into simpler compounds called amino acids. Thus, digestion completes in small
intestine and then it is absorbed by the intestinal wall.
7. The digested food is absorbed into thousands of small finger-like projections in the inner
walls of small intestine. These projections called villi increase the surface area of absorption
of digested food. Each villus has a network of fine blood capillaries close to the surface. So
the food absorbed on the surface of the villus passes into the blood in the capillaries.
8. Process of digestion in ruminants: Ruminants have stomachs consisting of four chambers.
Food that is swallowed goes into the first chamber called the rumen. Here it is partially
digested and is called cud. Then it goes to the second chamber from where it is returned
to the mouth for thorough chewing. This process is called rumination. After chewing, the
food is swallowed for a second time and then digested further in the remaining chambers.
Absorption of the nutrients is done in small intestine.
HOTS QUESTIONS
1. Sugar is a simpler food than proteins and carbohydrates (present in beans). Therefore sugar will
be digested faster than beans.
2. Digestion needs the help of the respiratory and circulatory systems to get energy from food.
The circulatory system takes the digested food to the cells of the body. The respiratory system
provides the oxygen required to convert the food into energy.
3. If we eat food while hanging upside down it will still go through the alimentary canal because
of peristaltic movement of the oesophagus and the alimentary canal.
BE A SCIENTIST
Animals in their natural habitat have to constantly move around and put in a lot of effort to find
food. They do not have a sedentary lifestyle like many overweight humans. However, pets do tend
to become overweight as they get food easily and may not get enough exercise.
ASSERTION—REASON TYPE QUESTIONS
1. c 2. b

10 LIVING SCIENCE 7  ANSWERS

DIAGRAM-BASED QUESTIONS
1. c 2. b 3. c

WORKSHEET
A. b
1. 2. d 3. b 4. c 5. b 6. b
B. 1. pseudopodia 2. spider 3. enamel 4. 10 5. small intestine 6. liver
C. 1. false 2. true 3. true 4. false 5. true
D. 1. pseudopodia 2. saliva 3. mucous, hydrochloric acid, digestive juices
4. stomach 5. starch
E. 1. The various processes involved in nutrition in animals are as follows:
Ingestion: It involves taking in the food through the mouth.
Digestion: It is the breakdown of food into a simple, soluble form with the help of digestive
juices made in the body.
Absorption: It is the process by which the food in the soluble form passes into the body
fluids such as blood.
Assimilation: It is the process of using the absorbed food for producing energy and for growth.
Egestion: It is the process of elimination of undigested solid parts of the food.
2. A spider weaves a sticky web in which small insects get stuck. It then injects digestive juices
into the body of the insect, which digest the body parts of the insect. The spider then sucks
up the digested food.
3. The butterfly uses its proboscis to suck nectar from flowers.
4. Hydra has a number of tentacles around its mouth, which are used for ingestion of food.
The tentacles entangle small aquatic animals and kill them with their stinging cells. They
then push them into the mouth. Inside the body cavity the digestive juices secreted by the
surrounding cells help to digest the food. This is then absorbed through the cavity walls and
assimilated in the cells.
5. The various parts of the alimentary canal in a human body are: the mouth; food pipe or
oesophagus; stomach; small intestine; large intestine ending in the rectum; and anus.
6. Some organs that secrete digestive juices in our body are salivary glands, stomach, small
intestine, liver and pancreas.
7. Digestion begins inside our mouth when we chew the food. Chewing breaks down the food
into small pieces and mixes it with saliva. This process is called mastication.
8. The tongue is a muscular organ that helps us to eat food. It pushes food towards our teeth.
It also helps to mix the food with saliva and then enables us to swallow it. The tongue also
helps us to speak.
9. Taste buds are small structures spread across the surface of the tongue.
Taste buds help us to detect all tastes—sweet, salty, sour and bitter.
Scientists earlier thought that the taste buds that detect different kinds of tastes are located
in specific areas of the tongue. Now it is proved that each taste bud can detect all tastes.
10. After the food is swallowed, it slides down the pharynx into the oesophagus. The oesophagus

LIVING SCIENCE 7  ANSWERS 11

 is made up of muscles. These muscles gently push food down to the stomach in a wave-like
action. This is called peristalsis.
This movement takes place throughout the alimentary canal to push the food forward.
11. The hydrochloric acid kills bacteria that enter along with food and also helps in digestion of
proteins.
12. The pancreatic juice in our body changes starch into simple sugars, and proteins into simpler
compounds called amino acids.
13. Absorption of food occurs through thousands of small finger-like projections known as villi.
The villi are present in the inner walls of the small intestine. These villi increase the surface
area of absorption of digested food. Each villus has a network of fine blood capillaries close
to the surface. The food absorbed on the surface of the villus passes into the blood in the
capillaries.
14. The food absorbed into the blood is transported to different parts of the body. It is used to
provide energy and materials for growth and repair of body tissues. This is the final stage in
the process of digestion and is known as assimilation. Glucose is broken down in the cells
with the help of oxygen into carbon dioxide and water, to provide energy. Amino acids are
used for building and repairing of body parts. Fatty acids and glycerol are stored under the
skin and act as energy reserves.
15. The last step of digestion takes place in the small intestine. The muscles in the small intestine
mix food with more digestive juices. Some juices are secreted by the cells of the small
intestine itself. Others come from the liver and the pancreas that is located just below the
stomach. The liver secretes bile juice which is stored in the gall bladder. The bile breaks up
fats into tiny droplets that can be digested and absorbed more easily. The digestive juices
then act on these tiny droplets to form simpler compounds known as fatty acids and glycerol.
The pancreas secretes the pancreatic juice that changes starch into simple sugars, and
proteins into simpler compounds called amino acids.
16. Ruminants are hooved, plant-eating animals that digest their food in two steps. They have
complicated stomachs consisting of four chambers. Some examples are cows, buffaloes, goats,
sheep and bison.

12 LIVING SCIENCE 7  ANSWERS