Science Textbook Solutions for Class 8 Science Chapter 1 – Living World and Classification of Microbes

Important points to remember :

  1. The process of dividing  living  organism into groups and subgroups is called  Biological classification. 
  2. Carl Linnaeus in 1735 divided living world in 2 kingdoms Vegetabilia and  Animalia. 
  3. Haeckel in 1866 considered 3 kingdoms- Protista, Plants and Animals. 
  4. In 1925 – Chatton created two groups Prokaryotes and Eukaryotes. 
  5. In 1938 Kopland divided living organisms into 4 kingdoms- Monera,  Protista,  Plants  and Animals. 
  6. Robert Harding Whittaker  (1920-1980) was an American Ecologist.  In 1969 he divided living organisms into 5 groups. 
  7. Human – polio virus, Influenza virus, HIV  – AIDS  virus etc. 
  8. Cattle- picorna virus Plants- Tomato- Wilt virus,  Tobacco mosaic virus etc. 
  9. Bacteria- Bacteriophage (viruses attack bacteria).

Question 1: Use Whittakar method to classify bacteria, protozoa, fungi, algae, prokaryotic and eukaryaotic microbes.

Answer :The characteristic features of each of the five kingdoms classified by Whittaker are:
Kingdom Monera

  1. Absence of a well-defined nucleus or membrane-bound organelles
  2. all are unicellular
  3. Cell wall may be Present or absent.
  4. Autotrophic or heterotrophic mode of nutrition

Kingdom Protista

  1. They are unicellular, eukaryotic organisms.
  2. They can be autotrophic or heterotrophic.
  3. Some members have cilia or flagella, which helps in locomotion.

Kingdom Fungi

  1. They may be unicellular or multicellular, eukaryotic organisms.
  2. Their body consists of mycelium, which is made up of multicellular filamentous hyphae.
  3. Their cell walls are made up of tough, complex sugar called chitin.
  4. They are saprophytes, which feed on dead organic material.

Kingdom Plantae

  1. They are multicellular, eukaryotic organisms.
  2. Cell wall is made up of cellulose and not chitin unlike that of fungi.
  3. Most plant cells contain chlorophyll pigments. Hence, they are autotrophic.
  4. They are non-motile.

Kingdom Animalia

  1. They are multicellular eukaryotes.
  2. Cell wall is absent in them.
  3. Chloroplast is absent in animal cells. Hence, they have a heterotrophic mode of nutrition.

Question 2: Complete the five kingdom method of classification using living organism prokaryotes, eukaryotes, multicellular,  unicellular, protista, animals, plants, fungi.

Answer : 

Question 3: Find out my partner
 A.                    B
1.Fungi .            Chlorella

2.Protozoa .      Bacteriophage

3.Virus              Candida

4.Algae             Amoeba

5.Bacteria        Prokaryotic

Answer :
1.Fungi Candida
2.Protozoa Amoeba
3.Virus   Bacteriophage
4.Algae Chlorella
5.Bacteria Prokaryotic

Question 4: State whether the following statements are true or false. Explain your statement.

a. Lactobacilli are harmful bacteria.
Answer : False
Lactobacilli are not harmful bacteria, infact they are found in gastrointestinal tracts of animals and humans. They are also an important part of dairy products such as milk, yogurt etc.

b. Cell wall of fungi is made up of chitin. Answer : True

c. Organ of locomotion in amoeba is pseudopodia.
Answer : True

d. Tomato wilt is viral disease.
Answer  : True

Question 5: Give answers.
a. State the merits of whitetaker’s method of classification.
Answer : Merits of R. H. Whittaker 5 Kingdom Classification

  1. This system of classification looks more scientific and natural because of the following considerations:
  2. It is largely the most accepted system of modern classification mainly because of the phylogenetic placing of different groups of living organisms
  3. Separation of prokaryotes into an independent kingdom is justifiable because they differ from all other organisms in their general organization. 
  4. Grouping of all unicellular eukaryotes under the kingdom Protista has solved many problems, particularly related to the position of organisms like Euglena.
  5. Elevation of the group fungi to the status of a kingdom is justifiable since fungi totally differ from other primitive eukaryotes like algae and protozoans. 
  6. The kingdoms plantae and animalia are now more homogeneous groups than they were in the two kingdom classification as it shows the phylogeny of different life styles. 
  7. The five-kingdom classification gives a clear indication of cellular organization and modes of nutrition, the characters which appeared very early in the evolution of life.

Demerits of R. H. Whittaker 5 Kingdom Classification

  1. The five-kingdom classification has certain drawbacks also, particularly with reference to the lower forms of life.
  2. The kingdoms Monera and Protista include diverse, heterogeneous forms of life. In both the kingdoms there are photosynthetic (autotrophic) as well as non-photosynthetic (heterotrophic) organisms. Both the kingdoms include organisms which have cells with cell wall as well as without cell wall.
  3. None of the three higher kingdoms include a single ancestor of all its forms.
  4. Multicellular lines have originated from protistans several times.
  5. Unicellular green algae like Volvox and Chlamydomonas have not been included under Protista because of their resemblance to other green algae. 
  6. Slime moulds differ totally from other members of Protista in their general organization.
  7. Viruses have not been given proper place in this system of classification

b. Write the characteristics of viruses.
Answer :

  1. They can mutate.
  2. They are acellular, obligatory parasites that is, they contain no cytoplasm or cellular organelles.
  3. They carry out no metabolism on their own and must replicate using the host cell’s metabolic machinery. 
  4. In other words, viruses don’t grow and divide.
  5. The vast majority of viruses possess either DNA or RNA but not both.

c. Explain the nutrition in fungi.
Answer : Fungi get their nutrition by absorbing organic compounds from the environment. They decompose dead organic matter. A saprotroph is an organism that obtains its nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds.

d. Which living organisms are included in the kingdom monera ?
Answer : Kingdom Monera includes living organisms that are single celled, such as bacteria. They neither have a nucleus nor cell membrane. The organisms that are included in this kingdom are prokaryotes. Kingdom Monera is divided into two groups i.e. archaebacteria and eubacteria.

Question 6: Who am I ?

A. I don’t have true nucleus, cell organelles or plasma membrance. – Monera

B. I have nucleus and membrane bound cell orgenelles. – Protozoa

C. I live on decaying organic matter. – Fungi

D. I reproduce mainly by cell division.- Bacteria

E. I Can produce my replica. – Viruses

F. I am green, but don’t have organs. – Algae

Question 7: Draw neat and labelled diagrams.
A. Different types of bacteria.

Fig : different shapes of bacteria.

B. Paramoecium

Fig : Paramoecium

C. Bacteriophage.

Fig : bacteriophage

Question 8: Arrange the follwing in ascending order of size Bacteria, Fungi, Viruses, Algade.
Answer : Viruses →Bacteria →Fungi→Algae

# can you tell 
1.  What is the hierarchy for classification of living organisms? 
Answer : A hierarchical system is used for classifying organisms to the species level. This system is called taxonomic classification. The broadest classifications are by domain and kingdom; the most specific classification is by genus and species. The hierarchical groupings in between include phylum, class, family, and order.

2. Who invented ‘bionomial system’ of nomenclature? 
Answer : The adoption by biologists of a system of strictly binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more commonly known by his Latinized name Carl Linnaeus (1707–1778).

3. Which  levels  of hierarchy  are considered  while  writing  the  name in binomial nomenclature?
Answer : Binomial nomenclature follows certain rules and is a formal way of naming the living organisms. The first part is always the generic name and it always italicized and starts with a capital letter. The second part is the species name and is italicized. So, Generic name followed by specific name is the hierarchy.

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