Class 8 Science Chapter 1: Living World and Classification of Microbes
Complete Exercise Answers and Mind Maps
Mind Map: Whittaker's Five Kingdom Classification
Exercise 1: Use Whittaker method to classify bacteria, protozoa, fungi, algae, prokaryotic and eukaryotic microbes.
Classification of microbes according to Whittaker's method:
| Microbe Type | Kingdom | Cell Type | Characteristics | Examples |
|---|---|---|---|---|
| Bacteria | Monera | Prokaryotic | Unicellular, no true nucleus, no membrane-bound organelles | Lactobacillus, Escherichia coli, Bacillus |
| Protozoa | Protista | Eukaryotic | Unicellular, has true nucleus and membrane-bound organelles, heterotrophic | Amoeba, Paramecium, Euglena |
| Fungi | Fungi | Eukaryotic | Can be unicellular or multicellular, heterotrophic, chitin cell wall | Yeast, Candida, Aspergillus |
| Algae | Protista | Eukaryotic | Can be unicellular or multicellular, autotrophic (photosynthetic) | Chlorella, Spirogyra, Chlamydomonas |
Summary:
- Prokaryotic microbes: All bacteria (Kingdom Monera)
- Eukaryotic microbes: Protozoa, fungi, and algae (Kingdoms Protista and Fungi)
Note: Viruses are not included in Whittaker's five kingdom classification system as they are considered non-living outside their host cells.
Exercise 2: Complete the five kingdom method of classification using: living organism, prokaryotes, eukaryotes, multicellular, unicellular, protista, animals, plants, fungi.
Viruses and Their Hosts
Viruses are not classified in any of the five kingdoms as they exist at the boundary between living and non-living things.
| Host | Virus Examples |
|---|---|
| Human | Polio virus, Influenza virus, HIV-AIDS virus |
| Cattle | Picorna virus |
| Plants | Tobacco mosaic virus |
| Bacteria | Bacteriophage |
Internet My Friend
Collect pictures and characteristics of different microbes. Prepare a chart.
Suggested Research Topics:
- Common bacterial shapes (cocci, bacilli, spirilla)
- Structure of a bacteriophage
- Movement methods in protozoa
- Common fungal structures
Exercise 3: Find out my partner
| A | B |
|---|---|
| Fungi | Candida |
| Protozoa | Amoeba |
| Virus | Bacteriophage |
| Algae | Chlorella |
| Bacteria | Prokaryotic |
Exercise 4: State whether the following statements are true or false. Explain your statement.
a. Lactobacilli are harmful bacteria.
False
Explanation: Lactobacilli are beneficial bacteria that help in food digestion and absorption of nutrients. They are used in the production of fermented foods like yogurt, cheese, and pickles. They also maintain the pH balance in our body and prevent the growth of harmful microorganisms. Therefore, lactobacilli are helpful, not harmful bacteria.
b. Cell wall of fungi is made up of chitin.
True
Explanation: The cell wall of fungi is indeed made up of chitin, which is a nitrogen-containing polysaccharide. This is different from plant cell walls (made of cellulose) and bacterial cell walls (made of peptidoglycan). The presence of chitin gives fungi their characteristic rigidity and protection.
c. Organ of locomotion in amoeba is pseudopodia.
True
Explanation: Amoeba moves by extending temporary projections of its cytoplasm called pseudopodia (false feet). These pseudopodia help in locomotion and also in capturing food particles. The cytoplasm flows into these extensions, allowing the amoeba to change shape and move in various directions.
e. Tomato wilt is a viral disease.
False
Explanation: Tomato wilt is primarily caused by fungi (such as Fusarium oxysporum and Verticillium) or bacteria (like Ralstonia solanacearum), not viruses. These pathogens attack the vascular system of the plant, blocking water and nutrient transport, which causes wilting of the plant. There are viral diseases that affect tomato plants, but "tomato wilt" specifically refers to fungal or bacterial infections.
Exercise 5: Give answers.
a. State the merits of Whittaker's method of classification.
The merits of Whittaker's method of classification are:
- Comprehensive: It classifies all living organisms into five distinct kingdoms based on multiple criteria.
- Multiple criteria: Uses cell structure, mode of nutrition, and level of organization for classification, making it more systematic and accurate.
- Distinguishes prokaryotes and eukaryotes: Clearly separates primitive prokaryotic organisms (Kingdom Monera) from all other eukaryotic organisms.
- Recognizes fungi as separate: Acknowledges the unique characteristics of fungi, placing them in a separate kingdom rather than with plants.
- Evolutionary relationship: Reflects the evolutionary relationships among different groups of organisms.
- Simple and logical: Easy to understand and follow, making it widely accepted in biological studies.
b. Write the characteristics of viruses.
Characteristics of viruses:
- Non-cellular structure: Viruses are not made up of cells and do not have cellular organization.
- Size: They are extremely small (20-400 nanometers) and can only be seen under an electron microscope.
- Genetic material: Contain either DNA or RNA (not both) enclosed in a protein coat called capsid.
- Obligate parasites: They cannot reproduce on their own and need living host cells for replication.
- Host specificity: Most viruses infect specific types of cells or organisms (e.g., bacteriophages infect bacteria).
- Metabolism: They have no metabolic machinery and cannot produce their own energy.
- Crystalline state: Outside host cells, they exist as inert particles and can be crystallized.
- Boundary between living and non-living: They show characteristics of both living (reproduction inside host) and non-living things (inert outside host).
