- Choose the correct option.
- Euglena is an example of
(i)Bacteria (ii) algae (iii)protozoa(iv)virus
Answer. Protozoa
b. Virus that infects bacteria are called as ____
(i) Tobacco Mosaic Virus (ii) influenza (iii) bacteriophages (iv)rhizobia
Answer. Bacteriophages
c. The bacterium that helps in the formation of curd is
(i)lactobacillus (ii) entamoeba histolytica (iii)Vibrio cholerae (iv)Streptococcus pneumoniae
Answer. Lactobacillus
d. Which of the following microorganism contains chlorophyll?
(i)Amoeba (ii) Fungus (iii)Virus (iv)Algae.
Answer. Algae
2. Assertion Reasoning questions.
For Question number (i) and (ii), two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, and Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.
(i) Assertion (A): Fungi are unable to make their own food.
Reason (R): Fungi lack chlorophyll.
Answer. Assertion (A): True (Fungi are heterotrophs).
Reason (R): True (No chlorophyll).
Answer: (a) (R correctly explains A).
(ii) Assertion (A). The replenishment of soil with nutrients is done by some microorganisms.
Reason (R). Fungi and bacteria are common decomposers.
Answer. Assertion (A): True (Microbes like Rhizobium enrich soil).
Reason (R): True (Decomposers recycle nutrients).
(b) (R is true but doesn’t directly explain A).
3. Answer the following questions in one sentence.
a. Name a multicellular filamentous alga.
Answer. Spirogyra is a multicellular filamentous alga with spiral chloroplasts.
- Mention any two skin diseases caused by fungi in humans.
Answer. Ringworm and athlete’s foot are fungal skin infections causing itching and rashes.
c. Name any two chemicals used to preserve food.
Answer. Sodium benzoate and vinegar are chemicals used to preserve food.
- What are vaccines?
Answer. Vaccines are biological preparations that provide immunity against specific diseases
4. Answer the following questions in 2-3 sentences.
a. Describe the process of milk preservation by pasteurisation.
Answer. Pasteurisation is a process in which milk is heated up to 72°C for 15 seconds, which helps to kill harmful bacteria while preserving nutrients, followed by rapid cooling to extend shelf life.
b. Write any two uses of microbes in agriculture.
Answer. Two uses of microbes in agriculture are mentioned below:
Fix nitrogen (Rhizobium in legumes).
Act as biopesticides (Bacillus thuringiensis).
5. Answer the following questions in 3-5 sentences.
a. What is food preservation? Explain in detail any four methods of food preservation.
Answer .Food preservation prevents spoilage by inhibiting microbial growth. Methods include:
- Refrigeration (slows bacteria).
- Canning (heat-sealed containers).
- Drying (removes moisture).
- Chemical preservatives (salt, vinegar).
b. List any three communicable diseases caused by microorganisms. Identify the pathogen and the means of transmission for each disease.
Answer. Communicable diseases:
- Malaria (Plasmodium/mosquitoes).
- Cholera (Vibrio cholerae/contaminated water).
- COVID-19 (SARS-CoV-2/airborne droplets).