Multiple Choice Questions.............................
Question 1: Which of the following reproduces only inside a host cell?
(a) Bacteria
(b) Virus
(c) Amoeba
(d) Fungus.
Solution 1: (b) Virus
The virus is known as a hybrid of living and non-living species. Outside of a host, the virus is dormant. Only when it is within a host cell can it carry out its life processes and replicate.
Question 2: A disease in human beings caused by a virus is _______.
(a) Typhoid
(b) Influenza
(c) Dysentery
(d) Cholera
Solution 2: (b) Influenza
Influenza is caused by virus; Typhoid is caused by bacteria. Dysentery is caused by an amoeba and due to vibrio cholera bacteria cholera is caused.
Question 3: Pathogenic micro-organisms present in host cells are killed by medicines called
(a) Pain killer
(b) Antibodies
(c) Antibiotics
(d) Vaccines
Solution 3: (b) Antibiotics destroy certain bacteria.
Question 4: The two micro-organisms which live in symbiotic association in lichens are
(a) Fungus and Protozoa
(b) Alga and Bacteria
(c) Bacteria and Protozoa
(d) Alga and Fungus
Solution 4: (d) Alga and Fungus
Alga and fungus are two micro-organisms which live in symbiotic association in lichens.
Question 5: The gas released during the preparation of bread is
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Sulphur dioxide
Solution 5: (b) Carbon dioxide
The fermentation process, which is carried out by yeast, produces carbon dioxide. CO2 allows the dough to rise, rendering the bread soft.
Question 6: The disease caused by a protozoan and spread by an insect is _________.
(a) Dengue
(b) Malaria
(c) Polio
(d) Measles
Solution 6: (b) Malaria
Malaria is caused by Plasmodium vivax, a protozoan spread by mosquito. Viral diseases are the other choices, but they are incorrect responses.
Question 7: Paheli dug two pits, A and B, in her garden. In-pit A, she put a polythene bag packed with some agricultural waste. In-pit B, she dumped the same kind of a waste but without packing it in a polythene bag. She then covered both the pits with soil. What did she observe after a month?
(a) Waste in pit A degraded faster than that in pit B.
(b) Waste in pit B degraded faster than that in pit A.
(c) Waste in both pits degraded almost equally.
(d) Waste in both pits did not degrade at all.
Solution 7: (b) Waste in pit B degraded faster than that in pit A.
Since the polythene in pit B is open and provides oxygen for composting, while the polythene in pit A is closed and species do not obtain oxygen to compost the waste material in the polythene container, waste in pit B degrades faster than waste in pit A.
Very Short Answer Questions.....................
Question 8: Unscramble the jumbled words underlined in the following statements.
(a) Cells of our body produce santiidobe to fight pathogens.
(b) curbossulite is an air-borne disease caused by a bacterium.
(c) Xanrhat is a dangerous bacterial disease.
(d) Yeasts are used in the wine industry because of their property of meronettinaf.
Solution 8:
(a) Antibodies
(b) Tuberculosis
(c) Anthrax
(d) Fermentation
Question 9: Suggest a suitable word for each of the following statements.
(a) Chemicals added to food to prevent the growth of microorganisms.
(b) Nitrogen-fixing microorganism present in the root nodules of legumes.
(c) The agent spreads pathogens from one place to another.
(d) Chemicals which kill or stop the growth of pathogens.
Solution 9:
(a) Chemicals added to food to prevent the growth of microorganisms- Preservatives
(b) Nitrogen-fixing microorganism present in the root nodules of legumes- Rhizobium
(c) The agent spreads pathogens from one place to another- Carrier/ vector
(d) Chemicals which kill or stop the growth of pathogens- Antibiotics
Question 10: Match the names of scientists given in Column A with the discovery made by them given in Column B.
Solution 10:
Question 11: Name one commercial use of yeast.
Solution 11: Yeast is used in the manufacture of bread and in the fermentation of alcohol.
Question 12: Name the process in yeast that converts sugars into alcohol.
Solution 12: Fermentation is the process in yeast that converts sugars into alcohol.
Question 13: In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?
Solution 13: Nitrogen is enriched by blue-green-algae in the soil.
Question 14: Why should we avoid standing close to a tuberculosis patient while he/she is coughing?
Solution 14: When an infected individual coughs, tuberculosis may spread through the air. As a result, we stop standing too close to a tuberculosis patient who is coughing.
Question 15: Polio drops are not given to children suffering from diarrhoea. Why?
Solution 15: If the children have diarrhoea, the oral polio drops will be excreted due to regular bowel movements. As a result, polio drops are not offered to children who have diarrhoea.
Question 16: Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?
Solution 16: Oils help to shield the pickle from bacteria, helping it to last longer.
Short Answer Questions.................
Question 17: Match the microorganisms given in Column A to the group to which they belong in Column B.
Solution 17:
Question 18: Classify the following into friendly and harmful microorganisms.
Yeast, malarial parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis
Solution 18:
Question 19: While returning from the school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?
Solution 19: The chaat may have been contaminated by pathogenic microbes due to unsanitary conditions near the store, or the serving utensil may have been contaminated. Food contamination by pathogenic microbes may be the cause. Contamination may be the result of unsanitary conditions near the shop or the chaat-serving utensil.
Question 20: What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?
Solution 20: Microbial activity causes pooris and unused kneaded flour to spoil. When food is left out in the open, it ferments and spoils.
Question 21:
(a) Name two diseases that are caused by the virus.
(b) Write one important characteristic of the virus.
Solution 21:
a. Diseases that are caused by the virus are Polio, HIV
b. Viruses don’t grow and divide infact new viral components are synthesized within the infected host cell.
Long Answer Questions....................
Question 22: Observe the Fig.2.1 and answer the questions that follow.
(a) Write the name of the disease.
(b) Name the causative agent of this disease?
(c) How does the disease spread from one plant to another?
(d) Name any two plant diseases and the microbes that cause them.
Solution 22:
(a) Yellow vein mosaic of lady’s finger/okra.
(b) Yellow vein mosaic virus is the virus that causes this disease.
(c) Insects transmit the disease from one plant to the next.
(d) (i) Bacteria causes citrus canker.
(ii) Wheat rust is caused by a fungus.
Question 23: How do vaccines work?
Solution 23: When a disease-carrying microbe infiltrates our bodies, antibodies are developed to combat the invader. If the microbe enters again, the body remembers how to combat it. When dead or damaged microbes are introduced into a healthy body, the body releases antibodies that fight and destroy the invading bacteria. Antibodies stay in the body permanently, shielding us from disease-causing microbes. A vaccine operates in this manner.
Question 24: Observe the set up given in Fig. 2.2 and answer the following questions.
(a) What happens to the sugar solution in A?
(b) Which gas is released in A?
(c) What changes will you observe in B when the released gas passes through it?
Solution 24:
a) Yeast ferments sugar, turning it to alcohol and releasing carbon dioxide.
b) Carbon-di-oxide from vessel A.
c) Limewater becomes milky when CO2 is added.
Question 25: Observe the Fig.2.3 and answer the following questions.
(a) Name the microorganism and the group to which it belongs.
(b) Name the food item on which the organism grows.
(c) Does it grow well in dry or in moist conditions?
(d) Is it safe to eat infected bread?
Solution 25:
a) This is an image of a bread mould. It's a form of fungus.
b) It thrives on stale, moist bread.
c) It thrives in damp environments.
d) No, eating contaminated bread is not healthy because the fungus produces a poisonous substance that spoils the food.
Question 26: Give reasons for the following.
(a) Fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling.
(b) Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.
(c) Farmers prefer to grow beans and peas in nitrogen-deficient soils.
(d) Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?
Solution 26:
(a) To destroy the harmful microorganisms in fresh milk, it is boiled. Since pasteurised milk is packaged, it does not need to be boiled.
(b) Microbes can easily infect raw vegetables. As a result, they are stored in the refrigerator because microorganisms cannot thrive at low temperatures. Sugar and salt, which serve as preservatives in jams and pickles, are present. As a result, they are immune to infection.
(c) Leguminous plants with Rhizobium in their root nodules include beans and peas. Rhizobium fixes atmospheric nitrogen, enriching the soil and increasing its fertility.
(d) Mosquitos, on the other hand, do not exist in water. However, they lay their eggs and raise their larvae in water. As a consequence, mosquitoes can be managed by preventing water stagnation.
Question 27: How can we prevent the following diseases?
(a) Cholera
(b) Typhoid
(c) Hepatitis A
Solution 27:
(a) Cholera can be avoided by practising proper personal hygiene and sanitation.
(b) Typhoid fever can be avoided by consuming properly cooked food, drinking boiled water, and having a typhoid vaccine.
(c) Drinking boiled water and having vaccinated are two ways to stop hepatitis.
Question 28: Complete the following cycle given as Fig. 2.4 by filling the blanks (a), (b), (c) (d)
Solution 28:
(a) Nitrogen is set by lightning.
(b) Blue-green algae and nitrogen-fixing bacteria fix nitrogen from the atmosphere.
(c) Excrement and death create nitrogenous waste.
(d) Bacteria convert nitrogen compounds into gaseous nitrogen.