{"id":154390,"date":"2024-01-11T16:46:03","date_gmt":"2024-01-11T11:16:03","guid":{"rendered":"https:\/\/icsesolutions.com\/?p=154390"},"modified":"2024-01-12T09:30:13","modified_gmt":"2024-01-12T04:00:13","slug":"living-science-biology-class-7-icse-solutions-chapter-9","status":"publish","type":"post","link":"https:\/\/icsesolutions.com\/living-science-biology-class-7-icse-solutions-chapter-9\/","title":{"rendered":"Living Science Biology Class 7 ICSE Solutions Chapter 9 Life Under a Microscope"},"content":{"rendered":"

ICSE Living Science Biology for Class 7 Solutions Chapter 9 Life Under a Microscope<\/h2>\n

Check Your Progress<\/span><\/p>\n

Fill in the blanks.<\/p>\n

Question 1.
\n………….. are spherical-shaped bacteria.
\nAnswer:
\nCocci are spherical-shaped bacteria.<\/p>\n

Question 2.
\n……….. algae contain brown pigments along with chlorophyll.
\nAnswer:
\nBrown algae contain brown pigments along with chlorophyll.<\/p>\n

Question 3.
\nKelps contain a gummy substance called ………..
\nAnswer:
\nKelps contain a gummy substance called algin.<\/p>\n

Question 4.
\nAn important product called ………….. is obtained from red algae.
\nAnswer:
\nAn important product called agar is obtained from tion<\/p>\n

Question 5.
\n…………. are extensively used in making metal polish, toothpaste and porcelain.
\nAnswer:
\nDiatoms are extensively used in making metal polish. toothpaste and porcelain.<\/p>\n

Practice Question 1.
\nA …………… colony is a hollow sphere made of many identical cells.
\nAnswer:
\nA Volvox colony is a hollow sphere made of many identical cells.<\/p>\n

Check Your Progress<\/span><\/p>\n

Question 1.
\nBacteria are used in …………. of leather and …. ……..of fibres.
\nAnswer:
\nBacteria are used in tanning of leather and retting of fibres.<\/p>\n

Question 2
\n…………… is prepared by fermentation of …………. by yeast.
\nAnswer:
\nAlcohol is prepared by fermentation of cereals by yeast.<\/p>\n

Question 3.
\n………… is a fungus used in the baking industry.
\nAnswer:
\nYeast is a fungus used in the baking industry.<\/p>\n

Question 4.
\n…………. is used for the fermentation of sugar to manufacture alcohol.
\nAnswer:
\nYeast is used for the fermentation of sugar to manufacture alcohol.<\/p>\n

Question 5.
\nTwo diseases caused by viruses are ………….. and ………….
\nAnswer:
\nTwo diseases caused by viruses are polio and AIDS.<\/p>\n

Question 6.
\nImporperly canned food can cause a dangerous disease called …………..
\nAnswer:
\nImporperly canned food can cause a dangerous disease called botulism.<\/p>\n

A. Tick the most appropriate answer.<\/span><\/p>\n

Question 1.
\nWhat is the shape of vibrios bacteria ?
\na. Rod-shaped bacteria
\nb. Spherical bacteria
\nc. Comma-shaped bacteria
\nd. Triangular bacteria
\nAnswer:
\nc. Comma-shaped bacteria<\/p>\n

Question 2.
\nWhich type of bacteria can grow in the absence of oxygen ?
\na. Saprophytic bacteria
\nb. Parasitic bacteria
\nc. Anaerobic bacteria
\nd. Aerobic bacteria
\nAnswer:
\nc. Anaerobic bacteria<\/p>\n

Question 3.
\nWhich of these is a colonial alga ?
\na. Chlamydomonas
\nb. Chlorella
\nc. Diatoms
\nd. Volvox
\nAnswer:
\nd. Volvox<\/p>\n

Question 4.
\nLaminaria and Fucus are examples of
\na. red aglae
\nb. green algae
\nc. brown algae
\nd. blue-green algae
\nAnswer:
\nc. brown algae<\/p>\n

Question 5.
\nAll organisms belonging to the group protozoa are –
\na. unicellular
\nb. multicellular
\nc. colonial
\nd. filamentous
\nAnswer:
\na. unicellular<\/p>\n

Question 6.
\nPneumonia is caused by –
\na. virus
\nb. Amoeba
\nc. bacteria
\nd. paramecium
\nAnswer:
\nc. bacteria<\/p>\n

Question 7.
\nMalaria is caused by –
\na. Amoeba
\nb. Entamoeba
\nc. Plasmodium
\nd. giardia
\nAnswer:
\nc. Plasmodium<\/p>\n

Question 8.
\nBotulism and Tuberculosis are caused by –
\na. bacteria
\nb. protozoa
\nc. fungi
\nd. viruses
\nAnswer:
\na. bacteria<\/p>\n

B. Fill in the blanks.<\/span><\/p>\n

Question 1.
\nThe bacteria that need oxygen to grow are called ………………. bacteria.
\nAnswer:
\nThe bacteria that need oxygen to grow are called aerobic bacteria.<\/p>\n

Question 2.
\n…………. are the simplest green plants that contain chlorophyll and usually live in water.
\nAnswer:
\nAlgae are the simplest green plants that contain chlorophyll and usually live in water.<\/p>\n

Question 3
\n………….. are on the borderline of the living and non – living worlds.
\nAnswer:
\nViruses are on the borderline of the living and non-living worlds.<\/p>\n

Question 4
\n…………… are the microrganisms without chlorophyll.
\nAnswer:
\nBacteria are the microrganisms without chlorophyll.<\/p>\n

Question 5.
\n…………… is a bread mould.
\nAnswer:
\nRhizopus is a bread mould.<\/p>\n

Question 6.
\n…………… is also used to ferment skimmed milk to butter milk.
\nAnswer:
\nLactobacillus (bacteria) is also used to ferment skimmed milk to butter milk.<\/p>\n

Question 7.
\nThe process of treating animal skin to produce leather is called ………….
\nAnswer:
\nThe process of treating animal skin to produce leather is called tanning.<\/p>\n

C. State if the following statements are true or false. Correct the statement if it is false.<\/span><\/p>\n

Question 1.
\nMicroorganisms live in extremely dry conditions.
\nAnswer:
\nFalse. Microorganisms live in warm and humid weather.<\/p>\n

Question 2.
\nThe mushrooms that we eat are a type of bacteria.
\nAnswer:
\nFalse. The mushrooms that we eat are a type of fungus.<\/p>\n

Question 3.
\nRed algae do not have chlorophyll
\nAnswer:
\nFalse. Red algae contain chlorophyll as well as red and blue pigments.<\/p>\n

Question 4.
\nAlgae are nature\u2019s scavengers.
\nAnswer:
\nFalse. Saprophytic bacteria are nature\u2019s scavengers.<\/p>\n

Question 5.
\nA spore-forming organism that lacks chlorophyll and absorbs food substances made by other organisms is an alga.
\nAnswer:
\nFalse. A spore forming organism that lacks chlorophyll and absorbs food substances made by other organisms is a bacteria.<\/p>\n

Match the following :<\/p>\n\n\n\n\n\n\n\n
Column A<\/td>\nColumn B<\/td>\n<\/tr>\n
1. typhoid<\/td>\na. virus<\/td>\n<\/tr>\n
2. polio<\/td>\nb. bacteria<\/td>\n<\/tr>\n
3. ringworm<\/td>\nc. protozoa<\/td>\n<\/tr>\n
4. diarrhoea<\/td>\nd. fungus<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Answer:<\/p>\n\n\n\n\n\n\n\n
Column A<\/td>\nColumn B<\/td>\n<\/tr>\n
1. typhoid<\/td>\nb. bacteria<\/td>\n<\/tr>\n
2. polio<\/td>\na. virus<\/td>\n<\/tr>\n
3. ringworm<\/td>\nd. fungus<\/td>\n<\/tr>\n
4. diarrhoea<\/td>\nc. protozoa<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

E. Find the odd one out. Give reasons.<\/span><\/p>\n

    \n
  1. Clilamydomonas, Spirogyra, Volvox, Mucor<\/li>\n
  2. Spirogyra, Ulothrix, Volvox<\/li>\n
  3. Amoeba, Chlamydomonas, Paramecium, Euglena<\/li>\n
  4. Giardia, mushroom, bread mould, Penicillium<\/li>\n<\/ol>\n

    Answer:<\/p>\n

      \n
    1. Mucor – It is a fungus while rest all are types of algae.<\/li>\n
    2. Volvox – It is a colonial alga while the rest two are filamentous algae.<\/li>\n
    3. Chlamydomonas – It is an alga while the rest all are protozoa.<\/li>\n
    4. Giardia – It is a protozoa while rest all are fungi.<\/li>\n<\/ol>\n

      F. Answer the following in short.<\/span><\/p>\n

      Question 1.
      \nWrite two examples of filamentous algae.
      \nAnswer:
      \nSpirogyra and Ulothrix.<\/p>\n

      Question 2.
      \nWhat are bacteriophages ?
      \nAnswer:
      \nViruses which attack bacteria and infect bacterial cells are known as bacteriophages.<\/p>\n

      Question 3.
      \nName the bacterium which causes cholera in human beings.
      \nAnswer:
      \nVibrio cholerae causes cholera in human beings.<\/p>\n

      Question 4.
      \nWhy are bacteria and fungi called nature\u2019s scavengers?
      \nAnswer:
      \nBacteria and fungi are called nature\u2019s scavengers because they help in cleaning the earth. They decompose excretory products and dead remains of plants and animals into simple substances. Thus, they clear the earth of all the wastes.<\/p>\n

      Question 5.
      \nWhat is retting of fibres ?
      \nAnswer:
      \nSeparation of fibres from the long lasting line stem of fibre plants, such as flax and jute is called retting of fibres. This is brought about by the action of bacteria on plant parts submerged in water.<\/p>\n

      Question 6.
      \nName the bacteria that helps in the formation of curd.
      \nAnswer:
      \nLactobacillus<\/p>\n

      H. Answer the following in detail.<\/span><\/p>\n

      Question 1.
      \nWhat are the conditions that facilitate the growth of bacteria ?
      \nAnswer:
      \nConditions which facilitate the growth of bacteria are :
      \na. Most bacteria grow best in the range of temperature between 25\u00b0C to 40\u00b0C. Some bacteria can grow at a very high or low temperature.
      \nb. Bacteria grow best in darkness. Sunlight kills many kinds of bacteria. ,
      \nc. They become active in moisture otherwise become inactive.
      \nd. Most of the bacteria can survive under extreme harsh conditions due to formation of hard protective covering around them called a cyst or a spore. They remain inactive in the cyst during unfavourable conditions.
      \ne. They are also affected by the presence or absence of oxygen.<\/p>\n

      Question 2.
      \nHow do bacteria obtain their nutrition ? How do bacteria survive harsh conditions ?
      \nAnswer:
      \nBacteria lack chlorophyll and hence cannot prepare their own food. They depend on other sources for their food. They may be saprophytes i.e. derive their food from dead and decaying matter or they may be parasites i.e. obtain their food by living on or inside the body of other organisms. Thus most of the bacteria are heterotrophs. However, there are some bacteria which are autotrophic and are able to synthesise their own food.<\/p>\n

      Bacteria can survive under harsh conditions due to the formation of a hard protective covering around them called a cyst or a spore. They remain inactive in the cyst during unfavourable conditions. The hard protective covering protect it from the unfavourable conditions and it becomes active during favourable conditions by breaking the cyst wall.<\/p>\n

      Question 3.
      \nName the three groups of algae. How are they different from each other ?
      \nAnswer:
      \nThe three groups of algae are :
      \n(i) Red algae
      \n(ii) Green algae
      \n(iii) Brown algae
      \n\"Living<\/p>\n

      Question 4.
      \nList five ways in which algae are useful.
      \nAnswer:
      \nAlgae are useful in the following ways :<\/p>\n