NCERT Solutions for Class 8 Science Chapter 2 – The Invisible Living World: Beyond Our Naked Eye

NCERT Solutions for Class 8 Science Chapter 2 – The Invisible Living World: Beyond Our Naked Eye help students understand the vast world of microscopic living organisms that cannot be seen without the help of scientific instruments. This chapter introduces students to microorganisms, their characteristics, and their significance in daily life.

Chapter 2 explains how invisible organisms play both beneficial and harmful roles in nature and human life. By studying this chapter, students develop an understanding of how microorganisms affect health, the environment, food production, and medicine.

1.0NCERT Solutions for Class 8 Science Chapter 2 PDF Download

This section provides students with direct access to the PDF version of The Invisible Living World: Beyond Our Naked Eye Class 8 solutions, enabling them to study and review more easily.

The NCERT Solutions for Class 8 Science Chapter 2 PDFs are prepared to ensure 100% accuracy and to cover all topics in the NCERT syllabus. The solutions support students in the following areas:

 1) Prepare efficiently for tests by helping them review.  

2) Support them to be more confident during the examination process.

2.0NCERT Questions with Solutions Class 8 Science Chapter 2 Detailed Solutions

1. Various parts of a cell are given below. Write them in the appropriate places in the following diagram.

Nucleus, Cytoplasm, Chloroplast, Cell wall, Cell membrane, Nucleoid, Centriole

Ans.

2. Aanandi took two test tubes and marked them A and B. She put two spoonfuls of sugar solution in each of the test tubes. In test tube B, she added a spoonful of yeast. Then she attached two incompletely inflated balloons to the mouth of each test tube. She kept the set-up in a warm place, away from sunlight.

(i) What do you predict will happen after 3–4 days?

She observed that the balloon attached to test tube B was inflated. What can be a possible explanation for this?

(a) Water evaporated in test tube B and filled the balloon with the water vapour.
(b) The warm atmosphere expanded the air inside the test tube B, which inflated the balloon.
(c) Yeast produced a gas inside the test tube B which inflated the balloon.
(d) Sugar reacted with warm air, which produced gas, eventually inflating the balloon.

(ii) She took another test tube, 1/4 filled with lime water.

She removed the balloon from test tube B in such a manner that the gas inside the balloon did not escape. She attached the balloon to the test tube with lime water and shook it well. What do you think she wants to find out?

Ans.

(i) Prediction: After 3–4 days, the balloon on test tube B will become inflated, while the balloon on test tube A will remain mostly the same.

The balloon attached to test tube B will become inflated because yeast in that test tube ferments the sugar solution, producing carbon dioxide gas (CO₂). This gas collects and inflates the balloon.
So, the answer is option (c) — Yeast produced a gas inside the test tube B which inflated the balloon.

(ii) Aanandi wants to find out which gas was collected in the balloon by using lime water. The gas present in the balloon was produced by the yeast in test tube B. If the lime water turns milky, it shows that carbon dioxide is present. This is a common test used to check for carbon dioxide and helps prove that yeast ferments sugar to produce carbon dioxide gas.

3. A farmer was planting wheat crops in his field. He added nitrogen-rich fertiliser to the soil to get a good yield of crops. In the neighbouring field, another farmer was growing bean crops, but she preferred not to add nitrogen fertiliser to get healthy crops. Can you think of the reasons?

Ans. Yes, there is a clear reason for the difference in their approach.

Bean plants are a type of legume, just like peas and lentils. These leguminous plants have special bacteria called Rhizobium in their root nodules.

Rhizobium is in symbiotic association with leguminous plants. It converts atmospheric nitrogen into a form that plants can absorb, and this process is known as nitrogen fixation. Because of this natural process, the farmer growing beans didn’t need to add nitrogen fertiliser.

On the other hand, wheat plants do not have these bacteria, so the farmer growing wheat needs to add nitrogen fertiliser to ensure healthy growth and good yield.

4. Snehal dug two pits, A and B, in her garden. In pit A, she put fruit and vegetable peels and mixed it with dried leaves. In pit B, she dumped the same kind of waste without mixing it with dried leaves. She covered both the pits with soil and observed after 3 weeks. What is she trying to test?

Ans. Snehal is trying to find out how dried leaves help in the process of decomposition and manure formation. She put the same kitchen waste in both pits, but in pit A, she mixed dried leaves, while in pit B she did not.

Dried leaves are rich in carbon and help balance the carbon–nitrogen ratio, which is important for decomposition. They also improve airflow in the pit and create a better environment for microorganisms. This speeds up decomposition and results in better manure formation.

5. Identify the following microorganisms:

(i) I live in every kind of environment, and inside your gut.

(ii) I make bread and cakes soft and fluffy.

 (iii) I live in the roots of pulse crops and provide nutrients for their growth.

Ans.
(i) Bacteria
(ii) Yeast
(iii) Rhizobium

6. Devise an experiment to test that microorganisms need optimal temperature, air, and moisture for their growth.

Ans.

(i) Take three slices of bread and keep them in different conditions.

(ii) Keep the first slice in a warm place with moisture and air.

(iii) Keep the second slice in the refrigerator.

(iv) Keep the third slice inside an airtight container.

(v) Observe after 3–4 days.

Observation:
• Bread in warm and moist conditions shows fungal growth.
• Bread in the refrigerator shows little or no growth.
• Bread in airtight container shows little or no growth.

Conclusion: Microorganisms require optimal temperature, moisture, and air for growth.

7. Take two slices of bread. Place one slice near the sink and the other in the refrigerator. Compare after three days.

Ans. Observation: The bread near the sink develops mould, while the refrigerated bread shows little or no growth.

Reason: Warm and moist conditions favour microbial growth, while cold temperature slows it down.

8. A student observes that when curd is left out for a day, it becomes more sour. What can be two possible explanations?

Ans.

• Lactic acid bacteria continue to ferment lactose into lactic acid.
• Warm temperature helps bacteria grow faster, increasing sourness.

9. Observe the set-up and answer the following:

(i) What happens to the sugar solution in flask A?

(ii) What do you observe in test tube B after four hours? Why?

(iii) What would happen if yeast was not added in flask A?

Ans. (i) Yeast ferments the sugar solution in flask A producing alcohol and carbon dioxide. This process is called fermentation.

(ii) Lime water in test tube B turns milky because carbon dioxide reacts with it to form calcium carbonate.

(iii) Without yeast, fermentation would not occur, no carbon dioxide would be produced, and the lime water would remain clear.

3.0Key Topics Covered in Class 8 Science Chapter 2 – The Invisible Living World

• The discovery of microscopes and the development of lenses were the first steps to allow humans to see a vast array of living organisms that we could not ordinarily see. This began with Robert Hooke, who discovered "cells" when he examined cork, followed by Antonie van Leeuwenhoek ("Father of Microbiology") with his discoveries of bacteria and protozoa.
• Cells are the building blocks of all living organisms and, therefore, contain three basic components: the cell membrane (outer covering of a cell), the cytoplasm, which is a jelly-like substance, and the nucleus, which is the cell's control structure.
• Both plant and animal cells contain the same three components. However, plant cells have more structural characteristics than animal cells, such as a rigid cell wall that provides support for the plant cell and chloroplasts (which contain chlorophyll) that allow the plant cell to produce food.
• All living organisms are organized in hierarchical structures, starting with cells that make up tissues that make up organs that make up organ systems that make up an entire organism.
• Microorganisms (commonly referred to as "microbes") are the smallest lifeforms that can be classified as either unicellular (consist of only one cell), as in the case of bacteria and Amoeba, or multicellular (such as some fungi and algae), and are found in diverse environments on earth.
• This chapter identifies the major types of microbes, including bacteria, fungi (such as yeast and bread mould), protozoa (such as Paramecium), and algae.
• Unlike cellular organisms, viruses are highly specialized and composed of acellular components that can only replicate inside the cells of a host organism.

4.0Benefits of Studying This Chapter

• Learning About Living Organisms: The cell is the smallest unit of life; therefore, it underlies all life functions. The importance of bacteria in environmental cleanup is stressed when they degrade waste products into organic compost and fertilizes assist as an element of sustainability.
• Knowledge of Health and Nutrition: It presents how common methods used to create curds (using Lactobacillus) and also creating yeast dough are part of the everyday biological process.
• Knowledge of Agricultural Systems: It demonstrates how various forms of bacteria are beneficial in providing nitrogen to the soil by forming a bond with it (known as nitrogen-fixing bacteria), which decreases the need to use chemical fertilizers in agricultural production.