The Invisible Living World: Beyond our Naked Eye Class 8 (Curiosity)

Q 1
Question
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
Nucleoid
Cell
Membrane
Chloroplast
Cytoplasm
Nucleus
Cell Wall
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Q 2
Question
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 hours? 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?
Test Tube A
Test Tube B
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Q 3
Question
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?
Wheat Crops
Pea Crops
Nitrogen - rich
fertilizer used
No Nitrogen - rich
fertilizer used
Rhizobium
Bacteria
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Q 4
Question
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?
Pit A
Pit B
Fruit and vegetable peels
mixed with
dried leaves
Fruit and vegetable peels
without mixing with
dried leaves
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Q 5
Question
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.
I live in
every kind of
environment,
and inside your
gut
I live in the
roots of
pulse crops
and provide
nutrients
for their growth
I make
Bread and cakes
soft and fluffy
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Q 6
Question
Design an experiment to test that microorganisms need optimal temperature, air, and moisture for their growth.
Bread in warm
and moist (air)
- Ideal Condition
Bread in Fridge
(Cold)
- To test Temperature
Bread in Dry
Place
- To test Moisture
Bread sealed
in airtight container
- To test Air
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Q 8
Question
A student observes that when curd is left out for a day, it becomes more sour. What can be two possible explanations for this observation?
Fresh
Curd
Older
Sour Curd
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Q 9
Question
Observe the set-up given in Fig. 2.15 and answer the following questions.
(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?
Flask A
Test Tube B
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Project 1
Task
India has a long history of biogas production. One of our oldest biogas plant was set up in late 1850s. Find out about the Biogas Program initiated by the Ministry of New and Renewable Energy, Government of India.
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Sample Answer
How does waste become biogas?
Cattle dung and waste
Plant and animal waste, or household wastewater
↓
Bacteria, without oxygen
They decompose the waste in an oxygen-free tank
↓
Biogas is released
Mostly methane, with carbon dioxide
↓
Fuel for cooking, heating, electricity and vehicles
Biogas is made when microbes break down animal and plant waste without oxygen.
It is mostly methane and carbon dioxide, and is used for cooking, heating, and electricity.
The government's programme helps villages set up biogas plants from cattle dung and waste.
This gives clean fuel and good manure, and reduces waste.

Project 2
Task
Fermented food items like fermented soya bean and fermented bamboo shoots are consumed as traditional food in some parts of India. With the help of your parents and teachers, list some traditional food items from your area that utilise the process of fermentation. Investigate the ingredients used in the preparation of these fermented food items; the method of preparing them; the microorganism responsible for the fermentation of the food, and the cultural and nutritional importance of the fermented food.
Fermentation makes food softer , tastier and easier to digest.
Idli and dosa batter is fermented by bacteria Lactobacillus and by Yeast.
Examples include idli, dosa, dhokla, curd and pickles.
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Sample Answer
Food
Microorganism
What it does
Idli and dosa batter
Lactobacillus
and yeast
Softens and sours the batter
Curd
Lactobacillus
Ferments milk and sets it into curd
Bread and
bhatura
Yeast
Releases carbon dioxide, makes it fluffy
Fermented soya bean, bamboo shoots
Bacteria
Preserves the food and adds flavour
Examples include idli, dosa, dhokla, curd, and pickles.
Idli and dosa batter is fermented by bacteria like
Lactobacillus
and by yeast.
Fermentation makes food softer, tastier, and easier to digest.
Many fermented foods are an important part of local food culture.

Project 3
Task
Study the different parts of a macro fungus mushroom using a magnifying glass and microscope. Take the help of students from senior classes and explore the internal structure of different parts of mushrooms under the microscope in your school laboratory.
Under the microscope, you can see
fine thread - like filaments and tiny pores.
A Mushroom has a cap, gills underneath and a stalk.
Students observing Mushroom.
Cap
Gills
Stalk
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Sample Answer
Which parts of a mushroom can you see?
Mushroom
A macro fungus
Visible with the eye
Cap, gills, stalk
Example:
Cap
Gills
Stalk
Seen under a microscope
Threads and spores
Example:
Thread-like filaments
Spores
A mushroom has a cap, gills underneath, and a stalk.
Under the microscope, you can see fine thread-like filaments and tiny spores.
Mushrooms are fungi, so they have a cell wall but no chloroplasts.
They cannot make their own food, so they grow on decaying matter.

Project 4
Task
Interact with an entrepreneur and learn the steps for cultivation of mushroom.
Mushrooms are grown on a moist mixture of straw or compost.
Mushroom spores (spawn) are added to this material.
They are kept in a cool, dark, and humid place to grow.
In a few weeks, the mushrooms grow and can be harvested.
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Sample Answer
How is a mushroom grown?
Straw or compost
The bed the mushroom will feed on
↓
Add spawn
The spores from which the mushroom grows
↓
Keep it cool, dark and humid
Fungi need moisture and no direct sunlight
↓
Mushrooms are harvested in a few weeks
Mushrooms are grown on a moist mixture of straw or compost.
Mushroom spores (spawn) are added to this material.
They are kept in a cool, dark, and humid place to grow.
In a few weeks, the mushrooms grow and can be harvested.