5. Give answers.

a. State the merits of Whittaker’s method of classification.

Ans: Merits of Whittaker’s classification:

(i) It is the most widely accepted system of classification as it considers the phylogenetic placing of different groups of living organisms.

(ii) Separation of Monera (Prokaryotes) as an independent kingdom is justified as they differ from all other organisms in cellular, genetic, reproductive and physiological organization.

(iii) Unicellular eukaryotes are the intermediate forms of prokaryotes and eukaryotes. They have characteristics of both plants and animals. Separation of unicellular eukaryotes into kingdom Protista is one of the highlights of this system of classification.

(iv) Kingdom Animalia became more homogeneous due to separation of protozoans.

(v) Earlier classification systems included bacteria, blue green algae, fungi, mosses, ferns, gymnosperms and the angiosperms under plants. The common characteristic that unified the entire kingdom was the presence of a cell wall. Green plants have cellulose cell walls whereas fungi have chitin in their cell walls and they lack chloroplast. When such characteristics were considered, fungi were separated into the kingdom Fungi.

(vi) It has tried to establish phylogenetic relationships even amongst the primitive forms.

b. Write the characteristics of viruses.

Ans: 

(i) Viruses are said to be the organisms at the edge of living and nonliving. Generally viruses are not considered as living organisms.

(ii) Size of viruses ranges from approximately 10 nm to 100 nm. They can be seen only with an electron microscope. Viruses are 10 to 100 times smaller than bacteria.

(iii) Viruses are independent particles made up of a long molecule of DNA (DeoxyriboNucleic Acid) or RNA (Ribonucleic acid) covered by a protein coat.

(iv) Viruses infect only living plant or animal cells and produce their own proteins with the help of the host cell and replicate inside the host cell. After this, they destroy the host cell and further infect new cells.

(v) Viruses cause many diseases to plants and animals.

e.g. In plants – Tomato spotted wilt virus, Tobacco mosaic virus; In humans – Polio virus, Influenza virus, HIV; In cattles Picornavirus; In bacteria – Bacteriophages.

c. Explain the nutrition in fungi.

Ans: 

(i) Fungi are non-green, heterotrophic organisms. Due to the absence of chlorophyll they cannot synthesize their own food by photosynthesis.

(ii) They rely solely on nutrients obtained from other organisms for their nutrition.

(iii) They secrete enzymes at the surface to which they are attached. These enzymes help in digestion of food into simpler molecules that can be absorbed as nutrients by the fungal cells.

(iv) Fungi feed on dead decaying organic matter and absorb nutrients thus, have a saprotrophic mode of nutrition.

d. Which living organisms are included in the kingdom monera?

Ans: 

(i) Organisms included in kingdom Monera are unicellular and microscopic prokaryotes. 

(ii) They include all types of bacteria and blue green algae.

(iii) For example: Streptococcus pneumoniae, Clostridium tetani, Treponema pallidum, Vibrio cholerae, Legionella pneumophila, Salmonella typhi, Clostridium botulinum, Staphylococcus, aureus, etc.