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Class 8 MAHARASHTRA STATE TEXTBOOK BUREAU Solutions Science Chapter 1: Living World and Classification of Microbes

Living World and Classification of Microbes Exercise Exercise

Solution 1

The criteria used by R. H. Whittaker for five-kingdom classification were cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships.

Based on these criteria, R. H. Whittaker categorized organisms into five kingdoms - Monera, Protista, Fungi, Plantae and Animalia.

  • Bacteria: Kingdom Monera
  • Protozoa: Kingdom Protista
  • Fungi: Kingdom Fungi
  • Algae: If unicellular, Kingdom Protista. If multicellular, Kingdom Plantae
  • Prokaryotic microbes: Kingdom Monera
  • Eukaryotic microbes: Any kingdom other than Monera.

Solution 2

Solution 3

Solution 4

  1. False. Lactobacilli are useful bacteria. They are used for curdling of milk. They are also used for preparing variety of milk products such as yoghurt.
  2. True. The cell wall of plants is made up of cellulose while the cell wall of fungi is made of a complex sugar called chitin. 
  3. True. Amoeba is a protozoan, primitive organism which possesses pseudopodia as the organ for locomotion.
  4. True. A wilt disease affects the vascular system of plants.

Solution 5.a

Merits of Whittaker's Five-Kingdom classification:

  • The classification system of Whittaker is totally based on scientific foundation where the cell structure, organisation of cell, mode of nutrition, lifestyle and phylogenetic relationship are taken into consideration.
  • It is more natural than two-kingdom classification.
  • Prokaryotes are placed under separate category of Monera.
  • Unicellular and multicellular organisms are kept under separate categories.
  • All unicellular eukaryotic organisms are clubbed together in one kingdom named, Protista. This has helped to solve the placement of Euglena.
  • A separate kingdom is assigned to fungi because of its saprophytic mode of nutrition.
  • Autotrophs and heterotrophs are placed in separate groups.

Solution 5.b

Characteristics of viruses:

  • Extremely minute, seen only using an electron microscope.
  • Found in the form of independent particles.
  • Contain DNA or RNA as the genetic material, which is covered with a protein coat.
  • Survive only in living plant or animal cells.
  • Produce their own proteins within the host cell and create their numerous replicas.
  • After replication, they destroy the host cell and become free; these free viruses again infect new cells.
  • Cause diseases in plants, animals and human beings.

Solution 5.c

The mode of nutrition in fungi is saprophytic and they are called saprophytes. It is a mode of nutrition in which an organism obtains its nutrients from dead and decaying organic matter.

Solution 5.d

  • All living organisms belonging to Kingdom Monera are unicellular.
  • Their mode of nutrition is either autotrophic or heterotrophic.
  • These are prokaryotic and thus, do not have a well-defined nucleus. They lack nuclear membrane and cell organelles.
  • Kingdom Monera consists of different types of bacteria and blue-green algae.
  • Examples: Streptococcus pneumoniae, Treponema pallidum.

Solution 6

a. Monera

b. Eukaryotic cell

c. Fungi

d. Bacteria, some Protozoa

e. Virus

f. Algae

Solution 7.a

Different types of bacteria

Solution 7.b

Paramoecium

Solution 7.c

Bacteriophage

Solution 8

Viruses → Bacteria → Fungi → Algae

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