The Invisible Living World Beyond Our Naked Eye Class 8 Question Answer Science Chapter 2

Start by reviewing these Class 8 Science Curiosity Solutions Chapter 2 The Invisible Living World Beyond Our Naked Eye Question Answer to strengthen your knowledge.

Class 8 Science Curiosity Chapter 2 Question Answer

Class 8 Science Ch 2 The Invisible Living World Beyond Our Naked Eye Question Answer

Class 8 Science Chapter 2 The Invisible Living World Beyond Our Naked Eye Question Answer (InText)

Question 1.
Have you ever wondered what you might see if the invisible world around you became visible? (Page 8)
Answer:
If the invisible world became visible, it would show a wide variety of tiny living organisms present all around, in air, water, soil, and even on everyday objects. It would reveal how active and crowded the microscopic world is, even in places that seem clean or empty.

Question 2.
How do you think your observation of this hidden world might change the way you think about size, complexity, or even what counts as ‘living’? (Page 8)
Answer:
Observing the hidden world would help in understanding that even the smallest organisms can be highly complex and perform all the basic functions of life. It would also broaden the idea of what is considered ‘living’, showing that living beings can exist in many forms and sizes.

Question 3.
Have you thought how tiny living beings found in nature interact with each other? (Page 8)
Answer:
Tiny living beings interact in many ways. Some help each other grow, while others compete for food or space. These interactions play an important role in maintaining balance in natural systems such as soil, water bodies, and even the human body.

Question 4.
What is the smallest living organism that can be seen without using a microscope? How small can the human eye actually see? (Page 9)
Answer:
The smallest living organism visible to the naked eye is often a tiny insect or an organism like an ant or a mold spore. The human eye can generally see objects as small as about 0.1 millimetres. Anything smaller usually requires a microscope to be seen clearly.

Question 5.
You might have seen some people using reading glasses. How does it help them see better? Or what happens when we use a magnifying glass to observe something? (Page 9)
Answer:
Reading glasses or magnifying glasses bend light rays in a way that helps us see small or unclear objects more clearly. A magnifying glass enlarges the image of an object, making it easier to observe fine details. This is useful when looking at tiny organisms or small texts.

Question 6.
What do you observe when you look at letters through a water-filled flask? How does this compare to using a real magnifying glass to observe small organisms like an ant? (Page 9)
Answer:
When letters are viewed through a water-filled flask, they appear larger. This happens because the curved glass and water bend light, magnifying the image. Similarly, a real magnifying glass helps to see small organisms like an ant in greater detail by enlarging their appearance.

Question 7.
How was the invisible world of tiny living organisms discovered? What scientific invention made it possible to observe them for the first time? (Page 9)
Answer:
The invention of the microscope helped us see the invisible world of microorganisms for the first time. It allowed scientists to observe tiny life forms like bacteria and protozoa, which cannot be seen with the unaided eye. This discovery opened up a new world of study in science.

Question 8.
What are the similarities and differences you observe in onion peel cells and cheek cells? (Page 12)
Answer:
Both onion peel cells and cheek cells have a cell membrane, cytoplasm, and nucleus. However, onion cells also have a cell wall, while cheek cells do not. This is because onion cells are extracted from a plant, and plant cells have a cell wall that gives them shape and strength.

Question 9.
What is the role of the main parts of a cell i.e. the cell membrane, cytoplasm and nucleus? Why are these parts important for the functioning and survival of the cell? (Page 12)
Answer:
Each part of a cell performs a specific function. The cell membrane controls what enters and exits the cell. The cytoplasm holds the cell parts and helps in transporting materials. The nucleus controls the cell’s activities and carries instructions for its growth and reproduction. These structures are essential because they help the cell stay alive and carry out its functions properly.

Question 10.
Do different animal cells also vary in their shape and structure? Why do cells have different shapes and structures? How is the shape of a cell related to the function it performs? (Page 13)
Answer:
Yes, Cells differ in shape, size, and structure because each type of cell performs a specific function in the body. Some examples include

• Inner cheek cells are thin and flat, which helps them form a protective lining.
• Nerve cells have a long and branched shape that allows them to carry messages quickly to different parts of the body.
• In plants, cells can be rectangular, oval, elongated, or tube-like; some plant cells form long tubes that help in transporting water.
• In the digestive system, muscle cells in the food pipe are spindle-shaped and flexible, allowing them to push food downward.

Question 11.
Are the cells of microorganisms similar to plant and animal cells, or do they have a different structure? What do these tiny cells look like? (Page 15)
Answer:
Microorganisms have different kinds of cells. Some have simple cells without a clearly defined nucleus, while others have well-organised cells with a proper nucleus and other cell parts. Their cell structure is not always like that of plant or animal cells, but each is suited to carry out its own functions.

Question 12.
When food items like lemon, tomato, or orange are left outside and start to rot, a powdery or cotton-like growth appears on them. What causes this, and how do these microbes come in contact with the food? (Page 18)
Answer:
The powdery or cotton-like growth seen on rotting food is caused by microbes such as fungi. These microbes are present in the air around us. When food is left uncovered or in damp conditions, these airborne microbes settle on it, grow, and cause it to rot.

Question 13.
Why do microorganisms not infect pickels and murabbas? (Page 18)
Answer:
Microorganisms do not affect pickels and murabbas because various spices along with salt or sugar are added to these food, which act as preservative.

Question 14.
How does the diversity of microorganisms play a role in our daily life? How do they help clean the environment? (Page 18)
Answer:
Microorganisms show great diversity and are found all around us—in air, water, soil, and even inside our bodies. They play a vital role in our daily life

1. In Food Production: Some microorganisms are used in making curd, bread, and cheese. They help in fermentation, improving texture and taste.
2. In Cleaning the Environment: Certain microbes break down dead plants and animals into simpler substances. This process helps in the natural cleaning of our surroundings and recycling of nutrients.
3. In Decomposing Waste: Microorganisms act as natural decomposers. They break down organic waste and convert it into useful compost, making soil fertile.

Question 15.
How do fruit and vegetable peels turn into manure over time? (Page 19)
Answer:
When fruit and vegetable peels are left in a compost pit or open area, microorganisms such as bacteria and fungi start acting on them. These microbes break down the complex substances in the peels into simpler forms. Over time, this process of decomposition changes the waste into dark, nutrient-rich manure that can be used to enrich the soil and help plants grow better.

The Invisible Living World Beyond Our Naked Eye Class 8 Questions and Answers (Exercise)

Question 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

Answer:

Question 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 testtube B was inflated. What can be a possible explanation for this?
(a) Water evaporated in test tube Band 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?
Answer:
(i) (c)Yeast converted sugar into gas, which inflated the balloon. Yeast ferments sugar and releases carbon dioxide gas, which fills and inflates the balloon.

(ii) Aanandi wanted to test whether the gas collected in the balloon is carbon dioxide. When the balloon is shaken with time water, if the time water turns milky, it confirms the presence of carbon dioxide gas.

Question 3.
A farmer was planting wheat crops in his field. He added nitrogen-rich fertilizer 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 fertilizer to get healthy crops. Can you think of the reasons?
Answer:
The second farmer did not add nitrogen fertilizer because bean plants are legumes. They have root nodules containing nitrogen-fixing bacteria called Rhizobium. These bacteria convert atmospheric nitrogen into usable forms for the plant. Hence, bean crops can grow well without adding nitrogen-rich fertilizers.

Question 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?
Answer:
Snehal is trying to test the role of dried leaves in the process of composting. By comparing the two pits, she wants to observe whether mixing fruit and vegetable peels with dried leaves helps in faster and better formation of compost.

Question 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.
Answer:
(i) The microorganism that lives in every kind of environment, including the human gut, is bacteria.
(ii) The microorganism that makes bread and cakes soft and fluffy is yeast.
(iii) The microorganism that lives in the roots of pulse crops and provides nutrients for their growth is Rhizobium.

Question 6.
Devise an experiment to test that microorganisms need optimal temperature air, and moisture for their growth.
Answer:
Aim To test that microorganisms need optimal temperature, air, and moisture for their growth, you can perform the following experiment.
Materials required 4 slices of bread, water, 4 zip-lock bags or airtight containers, labels, refrigerator, warm place (like a cupboard)

Procedure

1. Label the zip-lock bags as A, B, C, and D.
2. Place a dry bread slice in bag A and store it in a warm place.
3. Slightly moisten the bread slice in bag B with water and place it in a warm place.
4. Slightly moisten the bread slice in bag C with water and place it in the refrigerator.
5. Place a dry bread slice in bag D and keep it in the refrigerator.
6. Seal all the bags properly and observe them for a week.

Observation
After a few days, bag B will show the most fungal growth because it had warmth and moisture. Bag A may show less growth due to dryness. Bags C and D will show little or no growth due to cold temperature, even if moisture is present.

Conclusion
Microorganisms grow best when temperature, air, and moisture are available in optimal conditions.

Question 7.
Take 2 slices of bread. Place one slice in a plate near the sink. Place the other slice in the refrigerator. Compare after three days. Note your observations. Give reasons for your observations.
Answer:
The bread slice kept near the sink showed fungal growth, whereas the slice kept in the refrigerator remained unchanged. As the microorganisms grow well in warm and moist places and the cold temperature in the refrigerator inhibits their growth.

Question 8.
A student observed that when curd is left out for a day, it becomes more sour. What can be two possible explanations for this?
Answer:
Two possible explanations for this are as follows:

• Lactobacillus bacteria multiply over time, producing more lactic acid, which increases sourness.
• Warm temperature encourages bacterial growth, making the curd sour faster.

Question 9.
Observe the setup given in figure 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 do you think this happened?
(iii) What would happen if yeast was not added in flask A?
Answer:
(i) The sugar solution in flask A gets fermented by the yeast.
(ii) The lime water in test tube B turns milky. This happens because carbon dioxide gas is released during fermentation by the yeast, which reacts with lime water.
(iii) Fermentation would not take place and lime water would remain clear.

Class 8 Science Chapter 2 Question Answer (Activities)

Activity 1 (Page 9)

Aim
To observe how a flask filled with water can magnify objects and understand how magnification helps to see small details.
Materials Required Round-bottom glass flask, clean water, cork or stopper, open book, magnifying glass small organism like an ant.

Procedure

1. Fill the round-bottom flask with water.
2. Seal it with a cork or stopper.
3. Place the flask on top of an open book.
4. Look at the printed letters through the water-filled flask.
5. Now use a magnifying glass to observe a small organism, such as an ant.
6. Observe whether you can see more details of its body.

Observation: The letters appear larger through the water-filled flask, and the magnifying glass shows more details of the ant’s body.
Conclusion: Water and curved surfaces can magnify objects. Magnifying tools help us explore what we cannot see with the naked eye.

Viva Questions

1. What type of flask is used in this activity?
2. Can a flask filled with air instead of water magnify letters?
3. What is the purpose of using a magnifying glass in this activity?

Activity 2 (Page 11)

Aim
To observe the structure of onion peel cells under a microscope or foldscope.

Materials Required
Onion bulb, knife, forceps, thin brush, two petri dishes, safranin stain (red), water, glycerin, glass slide, coverslip, needle, blotting paper, microscope or foldscope

Procedure

1. Wash the onion bulb thoroughly with water.
2. Cut it vertically into pieces.
3. Take one piece and peel off the thin transparent layer (onion peel) using forceps.
4. Place the peel in a petri dish with a few drops of safranin for 30 seconds to stain the cells.
5. Rinse the peel in another petri dish containing water using a thin brush.
6. Place the stained peel gently on a glass slide without folding or tearing it.
7. Add a drop of glycerin to the peel to prevent drying and improve clarity.
8. Using a needle, slowly lower a coverslip over the peel to avoid air bubbles.
9. Use blotting paper to remove any extra glycerin around the coverslip.
10. Observe the slide under a microscope or foldscope.

Mounting the onion peel in glycerin using needle

Observation
Rectangular structures, closely packed together without any gaps can be seen. These are onion peel cells.

Conclusion
Onion peels, like other plant tissues, are made up of cells that are similar in structure.

Viva Questions

1. What were shape are the onion peel cells that you observed?
2. Why was safranin used in this activity?
3. What is the function of glycerin in the slide preparation?

Activity 3 (Page 12)

Aim
To observe the structure of human cheek cells under a microscope.
Materials Required: Clean glass slide, toothpick, methylene blue stain, glycerin, clean water, coverslip, blotting paper, microscope or foldscope.

Procedure

1. Rinse your mouth thoroughly with clean water.
2. Gently scrape the inside of your cheek using the blunt end of a clean toothpick.
3. Place the scraped material in a drop of water on a clean glass slide and spread it evenly.
4. Add a drop of methylene blue stain to increase the contrast of the cells.
5. Wait for one minute, then add a drop of glycerin to prevent drying.
6. Carefully place a clean coverslip on the material and use blotting paper to remove extra glycerin.
7. Observe the slide under a microscope.
8. Draw your observation in your notebook.

Observation
Polygon-shaped cheek cells can be seen, with a visible nucleus and cytoplasm enclosed by a thin cell membrane.

Conclusion
The cheek cells are animal cells. They do not have a cell wall like onion cells but share common features like the cell membrane, cytoplasm, and nucleus.

Viva Questions

1. What is the shape of the cheek cells observed under the microscope?
2. Which cell parts were visible in the cheek cells?
3. Why is methylene blue stain used in this activity?

Activity 4 (Page 15)

Aim
To observe microorganisms present in pond or stagnant water using a microscope or foldscope.

Materials Required
Container, dropper, microscope or foldscope, slide, coverslip, pond/stagnant water sample.

Procedure

1. With the help of a teacher or elder, collect pond or stagnant water in a clean container.
2. Using a dropper, place one drop of the water sample onto a microscope or foldscope slide.
3. Gently place a coverslip over the drop of water.
4. Observe the slide under a microscope or foldscope.

Observation
Tiny organisms moving in the water sample will be observed. These are microorganisms that are not visible to the naked eye.

Conclusion
Pond or stagnant water contains many microorganisms. These tiny living beings are called microbes and are present even when we cannot see them.

Viva Questions

1. What can be seen in pond water when viewed under the microscope?
2. Why can’t we see these microorganisms with our naked eye?

Activity 5 (Pages 15 and 16)

Aim
To observe microorganisms present in a soil suspension using a microscope.

Materials Required
Beaker, moist soil, glass rod, spoon or gloves, water, dropper, microscope slide, coverslip, microscope or foldscope.

Procedure

1. Take a beaker and collect some moist soil from a nearby garden or field using a spoon or while wearing gloves. Do not use bare hands.
2. Pour some water into the beaker and stir it with a glass rod.
3. Let the mixture settle for some time so that soil particles can sink and the suspension forms.
4. Using a dropper, take a drop of water from the top layer of the suspension.
5. Place the drop on a microscope slide and cover it gently with a coverslip.
6. Observe the slide under a microscope.

Observation
Small moving organisms may be seen in the soil suspension.

Conclusion
Soil contains a variety of microorganisms that are too small to be seen without a microscope.

Viva Questions

1. What do you observe in the drop of soil suspension?
2. What does your observation tell you about the presence of microorganisms in the soil?
3. Name one common place where microorganisms can be found beside soil.

Activity 6 (Pages 18 and 19)

Aim
To observe how fruit arid vegetable peels decompose into manure with the help of microorganisms.

Materials Required
Empty container, garden soil, fruit peels, vegetable peels.

Procedure

1. Take an empty container and fill it halfway with garden soil.
2. Add fruit and vegetable peels to the soil.
3. Cover the peels with another layer of soil.
4. Leave the container undisturbed in a corner for 2 – 3 weeks.
5. After the waiting period, observe the contents of the container carefully.

Observation
The fruit and vegetable peels appear to have broken down and turned into a dark-colored manure

Conclusion
The peels are converted into manure through the action of microorganisms like fungi and bacteria. This nutrient-rich material improves soil fertility and supports plant growth.

Viva Questions

1. What change did you observe in the contents of the container after 2 – 3 weeks?
2. Which organisms are responsible for the formation of manure from plant waste?

Activity 7 (Page 20)

Aim
To observe the effect of yeast on dough formation and understand its role in fermentation.

Materials Required
Two bowls (A and B), 200 grams flour (atta or maida) for each bowl, sugar, yeast powder, warm water, spoon, damp cloth.

Procedure

1. Take 200 grams of flour and a pinch of sugar in both bowls A and B.
2. Add a small amount of yeast powder to bowl A. Do not add yeast to bowl B.
3. Mix both bowls well.
4. Knead both mixtures using warm water to form a soft dough.
5. Cover both bowls with a damp cloth and place them in a warm area.
6. Observe the dough after 4 – 5 hours.

Observation

• Dough in bowl A rises, becomes fluffy, and gives off a fermented smell.
• Dough in bowl B shows little or no change.

Conclusion
Yeast, a type of fungus, respires and produces carbon dioxide. The gas makes the dough rise and become soft. Warm water and sugar support yeast growth.

Viva Questions

1. What change did you notice in the dough with yeast after a few hours?
2. Why was sugar added to the dough?
3. Why does yeast work better in warm conditions?

Activity 8 (Page 21)

Aim
To study how temperature affects the formation of curd from milk.

Materials Required
Two small glass bowls (A and B), lukewarm milk, cold milk, curd, spoon, covers.

Procedure

1. Pour lukewarm milk in bowl A and cold milk in bowl B.
2. Add a small spoonful of curd to each bowl and stir gently.
3. Cover both bowls.
4. Place bowl A in a warm place and bowl B in a cool place (like a refrigerator).
5. Leave them undisturbed for a few hours or overnight.
6. Observe the changes and note them down in the observation table.

Observation

Conclusion
Lactobacillus bacteria present in curd multiply faster in warm conditions and convert milk into curd.

Viva Questions

1. In which bowl did curd form faster and why?
2. What role does temperature play in curd formation?