YRS : DAV | Class - 7 | Science | Chapter - 2 | Solutions - Nutrition in Living Organisms Animals and Humans/Man

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DAV Class 7 Science Chapter 2: Nutrition in Living Organisms Animals and Humans/Man

Complete Question Answers

Introduction

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In this chapter, we learn about nutrition in animals and humans. We will study different modes of nutrition, the human digestive system, types of teeth, digestion and absorption of food, nutrition in ruminants, and how Amoeba takes in and digests food.

In this chapter, we learn about:

• Different modes of nutrition
• Holozoic nutrition
• Human digestive system
• Types of teeth
• Digestion and absorption of food
• Nutrition in ruminants
• Rumination
• Nutrition in Amoeba
• Pseudopodia
• Importance of teamwork

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A. Fill in the Blanks

1. The digestion of food in humans starts in the __________ and is completed in the __________.

Answer: Mouth, small intestine

Explanation:

Digestion begins in the mouth when food mixes with saliva. The process of digestion is completed mainly in the small intestine.

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2. __________ present in the stomach, kills bacteria.

Answer: Hydrochloric acid

Explanation:

Hydrochloric acid is present in the stomach. It helps kill harmful bacteria and provides the acidic medium needed for the proper action of digestive enzymes.

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3. The largest gland in the human body is the __________.

Answer: Liver

Explanation:

The liver is the largest gland in the human body. It produces bile juice, which helps in the digestion of fats.

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4. Partially digested food, that is chewed again by grass-eating animals, is called the __________.

Answer: Cud

Explanation:

Grass-eating animals such as cows bring partially digested food back into their mouth and chew it again. This partially digested food is called cud.

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5. Amoeba uses __________ for locomotion and for capturing its food.

Answer: Pseudopodia

Explanation:

Pseudopodia are temporary finger-like projections used by Amoeba for movement and capturing food. The word pseudopodia means false feet.

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B. Match the Following

Column A	Column B
1. Gall bladder	a) Bile juice
2. Proteins	e) Amino acids
3. Intestinal wall	c) Absorption
4. Rumen	b) Cow
5. Pseudopodia	d) False feet

Answers

1. Gall bladder — Bile juice
2. Proteins — Amino acids
3. Intestinal wall — Absorption
4. Rumen — Cow
5. Pseudopodia — False feet

Explanation

Gall bladder → Bile juice:

The gall bladder stores bile juice.

Proteins → Amino acids:

During digestion, proteins are broken down into simpler substances called amino acids.

Intestinal wall → Absorption:

The wall of the small intestine absorbs digested nutrients.

Rumen → Cow:

The rumen is the first chamber of the stomach of a cow and other ruminants.

Pseudopodia → False feet:

Amoeba uses pseudopodia for movement and capturing food. They are also called false feet.

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C. Tick (✓) the Correct Option

1. Organisms that can synthesise their own food are—

(a) Heterotrophs

(b) Parasites

(c) Autotrophs ✓

(d) Saprotrophs

Answer: (c) Autotrophs

Explanation:

Organisms that can synthesise or prepare their own food are called autotrophs.

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2. Cow is a/an—

(a) Saprotroph

(b) Parasite

(c) Autotroph

(d) Heterotroph ✓

Answer: (d) Heterotroph

Explanation:

A cow cannot prepare its own food. It depends on plants for food. Therefore, it is a heterotroph.

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3. Animals eating both plant materials and animals are—

(a) Herbivores

(b) Omnivores ✓

(c) Carnivores

(d) Ruminants

Answer: (b) Omnivores

Explanation:

Animals that eat both plant materials and other animals are called omnivores.

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4. Which of the following is not a part of the alimentary canal?

(a) Stomach

(b) Anus

(c) Liver ✓

(d) Large intestine

Answer: (c) Liver

Explanation:

The liver is an important digestive gland, but it is not a part of the alimentary canal. The alimentary canal is the tube through which food passes.

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5. Bile juice is released by—

(a) Salivary glands

(b) Pancreas

(c) Liver ✓

(d) Large intestine

Answer: (c) Liver

Explanation:

Bile juice is produced by the liver. It helps in the digestion of fats and provides suitable conditions for digestive enzymes.

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D. Answer the Following Questions in Brief

1. Define the following:

(a) Holozoic Nutrition

Answer:

Holozoic nutrition is a mode of nutrition in which an animal takes in food and digests it inside its body.

Explanation:

In holozoic nutrition, an organism takes food into its body and digests it internally. The useful nutrients are then absorbed and used by the body.

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(b) Alimentary Canal

Answer:

The alimentary canal is a hollow tube through which food passes from the mouth to the anus.

Explanation:

Food enters the body through the mouth and passes through different organs of the digestive system before the undigested matter is removed through the anus.

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2. What do you mean by the following?

(a) Assimilation

Answer:

Assimilation is the process by which the body uses the absorbed nutrients for growth, repair and other activities.

Explanation:

After digested food is absorbed into the blood, the body uses these nutrients for energy, growth, repair and other activities. This process is called assimilation.

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(b) Rumination

Answer:

Rumination is the process of bringing partially digested food, called cud, back into the mouth and chewing it again.

Explanation:

Grass-eating animals such as cows first swallow grass quickly. Later, the partially digested food is brought back into the mouth and chewed again. This process is called rumination.

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3. Name the organs that make up the human alimentary canal.

Answer:

The organs of the human alimentary canal are:

1. Mouth
2. Oesophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum
7. Anus

Food pathway:

Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

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4. Give two differences between milk teeth and permanent teeth.

Milk Teeth	Permanent Teeth
They fall out during childhood.	They normally do not fall out naturally.
They are fewer in number.	They are more numerous.

Explanation:

Milk teeth are the first set of teeth in children. They are temporary and are replaced by permanent teeth.

Permanent teeth replace the milk teeth and normally remain throughout life.

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5. Name the four types of teeth found in humans.

Answer:

The four types of teeth found in humans are:

1. Incisors
2. Canines
3. Premolars
4. Molars

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6. State the functions of incisors and premolars.

Answer:

• Incisors: They cut and bite food.
• Premolars: They crush and grind food.

Remember:

Incisors → Cut and bite

Premolars → Crush and grind

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7. What is the role of acid in the stomach?

Answer:

Hydrochloric acid in the stomach helps to kill harmful germs and provides the acidic medium needed for the proper action of digestive enzymes.

Explanation:

The stomach contains hydrochloric acid. It helps protect the body from harmful microorganisms present in food and creates the conditions needed for digestion.

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8. State the functions of bile juice and pancreatic juice.

Answer:

Bile Juice:

It helps in the digestion of fats and provides suitable conditions for digestive enzymes.

Pancreatic Juice:

It contains digestive enzymes that help digest different components of food.

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E. Answer the Following Questions

1. Draw a neat and labelled diagram of the human digestive system.

Answer:

Draw and label the following parts:

Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

Also show:

• Liver
• Gall bladder
• Pancreas

Easy way to remember the food pathway:

Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

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2. Justify the following statements.

(a) Crow is an omnivore.

Answer:

A crow eats both plant materials and animals. Therefore, it is an omnivore.

Explanation:

Omnivores are animals that consume both plant and animal food. Since a crow eats both types of food, it is classified as an omnivore.

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(b) Nutrition in humans and Amoeba is similar.

Answer:

Both humans and Amoeba show holozoic nutrition. They take in food, digest it inside their bodies, absorb the useful nutrients and remove the undigested matter.

Explanation:

Although humans and Amoeba are very different organisms, both follow the basic process of holozoic nutrition.

Both show:

Ingestion → Digestion → Absorption → Assimilation → Removal of undigested matter

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3. Give reasons for the following.

(a) It is difficult to ingest food without teeth.

Answer:

Teeth cut, tear and grind food into smaller pieces. This makes food easier to chew and swallow.

Explanation:

Teeth perform important mechanical functions during eating. They break food into smaller pieces so that it can be swallowed and digested more easily.

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(b) Rice or bread tastes sweet after being chewed for some time.

Answer:

Saliva contains an enzyme that acts on starch present in rice and bread and changes it into sugar. Therefore, the food starts tasting sweet.

Explanation:

Rice and bread contain starch. When they are chewed, they mix with saliva. The enzyme present in saliva acts on starch and changes it into simpler sugars, giving a sweet taste.

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(c) Bacteria are present in the rumen.

Answer:

The rumen contains bacteria that help in the digestion of plant material in grass-eating animals.

Explanation:

Grass contains plant material that is difficult to digest. Bacteria present in the rumen help grass-eating animals digest this plant material.

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4. How is digested food absorbed into the body?

Answer:

The wall of the small intestine absorbs the digested food. The absorbed nutrients then enter the blood and are carried to different parts of the body.

Explanation:

The small intestine plays an important role in absorption. After digestion, nutrients pass through the intestinal wall and enter the blood. The blood then transports them to different parts of the body.

Remember:

Digested food → Small intestine → Blood → Body cells

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5. Explain nutrition in ruminants.

Answer:

Grass-eating animals such as cows quickly swallow grass into the rumen. The food is partially digested there. It is later brought back into the mouth as cud. The animal chews the cud again and swallows it. The food then passes through the remaining parts of the digestive system for further digestion and absorption.

In simple steps:

Grass → Rumen → Partially digested food → Cud → Chewing again → Further digestion → Absorption

Explanation:

Ruminants are grass-eating animals. They have a special digestive system that allows them to first swallow food quickly and later chew the partially digested food again.

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6. How does Amoeba ingest its food?

Answer:

Amoeba uses its pseudopodia to surround and capture a food particle. The food is enclosed inside a food vacuole, where it is digested.

Explanation:

Amoeba is a single-celled organism. It extends pseudopodia around a food particle and encloses it. A food vacuole is formed, where the food is digested.

Remember:

Pseudopodia → Capture food → Food vacuole → Digestion

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Value-Based Questions

1. Which two values did the teacher want the students to develop?

Answer:

The two important values are:

1. Teamwork
2. Selfless attitude

Explanation:

Working together helps people complete a common task successfully. A selfless attitude encourages people to support others and contribute towards a common goal.

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2. Name the eleven teams involved in the process of digestion.

Answer:

1. Mouth
2. Oesophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Teeth
7. Tongue
8. Salivary glands
9. Liver
10. Pancreas
11. Gall bladder

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3. Why is teamwork important?

Answer:

Teamwork helps people work together towards a common goal. When everyone performs their role properly and supports others, the work becomes easier and more successful.

Remember:

Teamwork → Cooperation → Common Goal → Success

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Something to Do

1. Prepare a PPT on different ways in which animals ingest food.

Some examples are:

Type of Feeding	Example
Herbivores	Cow
Carnivores	Lion
Blood suckers	Leech
Fruit eaters	Birds
Fluid feeders	Butterflies and moths
Insectivores	Frog

Activity: Prepare a PPT using suitable examples and pictures.

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2. Collect information about milk teeth.

Collect information from the parents of five classmates and prepare a table with the following headings:

Name	Age when first tooth fell	Age when last tooth fell	Number of teeth lost	Number of teeth replaced

Then calculate the average age at which the teeth were lost.

Activity: Do it yourself.

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3. Make a model of the human digestive system.

Use clay or plasticine to make the different digestive organs. Use rubber pipes or ribbons to represent the food pipe and small intestine.

Activity: Do it yourself.

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4. Enact the role of digestive organs.

Divide the students into groups. Assign each student an organ of the digestive system.

Each student should explain the:

• Structure
• Function
• Importance
• Significance

of the assigned organ.

Activity: Do it yourself.

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⭐ Important Points to Remember

1. Animals generally depend on other organisms for food.
2. Holozoic nutrition involves taking in and digesting food inside the body.
3. The human digestive system begins at the mouth and ends at the anus.
4. Teeth help in cutting, tearing, crushing and grinding food.
5. The four types of teeth are:
   • Incisors
   • Canines
   • Premolars
   • Molars
6. The stomach contains hydrochloric acid.
7. The liver is the largest gland in the human body.
8. The liver produces bile juice.
9. The small intestine is the main site for absorption of digested food.
10. Grass-eating animals such as cows chew their cud.
11. Amoeba uses pseudopodia to capture food.
12. Teamwork is important for completing tasks successfully.

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🌟 Super Easy Chapter Revision

Nutrition

Food → Digestion → Absorption → Assimilation

Human Digestive System

Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

Teeth

Incisors → Cut and bite

Canines → Tear

Premolars → Crush

Molars → Grind

Important Digestive Organs

Liver → Produces bile juice

Gall bladder → Stores bile juice

Pancreas → Produces pancreatic juice

Stomach → Contains hydrochloric acid

Small intestine → Absorption

Ruminants

Cow → Rumen → Cud → Rumination

Amoeba

Pseudopodia → Capture food → Food vacuole → Digestion

Food Types

Herbivore → Plants

Carnivore → Animals

Omnivore → Plants + Animals

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Conclusion

In this chapter, we learned about nutrition in animals and humans. We studied holozoic nutrition, the human digestive system, types and functions of teeth, digestion and absorption, nutrition in ruminants and food intake in Amoeba.

Understanding these processes helps us learn how animals obtain and use food for energy, growth and repair.

The main concepts to remember are:

Nutrition → Digestion → Absorption → Assimilation

Humans → Holozoic nutrition

Cow → Ruminant

Cud → Partially digested food

Amoeba → Pseudopodia

Small intestine → Absorption

Liver → Bile juice

Stomach → Hydrochloric acid

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📚 YRS YASRAJ STUDIES

DAV Class 7 Science | Chapter 2 | Nutrition in Living Organisms

Complete question answers, explanations, activities and revision notes for students.