Bacteria and Viruses Worksheets - 15 Worksheets Library - Free Printable

Problem Analysis and Solutions:

#### Q.10. Which of the following statements about bacteria is incorrect?

Options:
- a) Bacterial cells require living host cells to reproduce.
- b) Some bacteria fix nitrogen.
- c) Bacteria can be found almost everywhere.
- d) All bacteria are prokaryotes.

Solution:
- Option (a): Bacterial cells require living host cells to reproduce.
- This statement is incorrect. Most bacteria are free-living and do not require a host cell to reproduce. They can replicate independently through binary fission. Only certain types of bacteria, such as obligate intracellular parasites (e.g., Chlamydia), require a host cell for reproduction.

- Option (b): Some bacteria fix nitrogen.
- This statement is correct. Nitrogen-fixing bacteria, such as *Rhizobium* and *Azotobacter*, play a crucial role in converting atmospheric nitrogen into ammonia, which is usable by plants.

- Option (c): Bacteria can be found almost everywhere.
- This statement is correct. Bacteria are ubiquitous and can be found in various environments, including soil, water, air, and even extreme conditions like hot springs and deep-sea vents.

- Option (d): All bacteria are prokaryotes.
- This statement is correct. Bacteria are single-celled microorganisms that lack a nucleus and membrane-bound organelles, making them prokaryotic.

Final Answer for Q.10:
$$
\boxed{a}
$$

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#### Q.11. Which of the following microorganisms make their own food from sunlight and carbon dioxide?

Options:
- a) Pathogenic bacteria
- b) Viruses
- c) Bacteriophage
- d) Cyanobacteria

Solution:
- Option (a): Pathogenic bacteria
- Pathogenic bacteria cause diseases but do not perform photosynthesis. They obtain energy through other metabolic processes.

- Option (b): Viruses
- Viruses are not capable of producing their own food. They are obligate parasites that rely on host cells for replication and energy.

- Option (c): Bacteriophage
- Bacteriophages are viruses that infect bacteria. They do not perform photosynthesis.

- Option (d): Cyanobacteria
- Cyanobacteria are photosynthetic bacteria. They contain chlorophyll and can convert sunlight, water, and carbon dioxide into glucose and oxygen through photosynthesis.

Final Answer for Q.11:
$$
\boxed{d}
$$

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#### Q.12. Label the diagram of bacteriophage.

The provided diagram shows the structure of a bacteriophage, which is a virus that infects bacteria. The parts of the bacteriophage need to be labeled based on the given options:
- Tail Sheath
- Baseplate
- Tail Fiber
- Capsid Head
- Collar
- Nucleic acid (DNA)

Diagram Analysis:
1. Capsid Head: This is the topmost part of the bacteriophage, which contains the viral DNA.
2. Collar: This is the ring-like structure just below the capsid head.
3. Tail Sheath: This is the elongated tube-like structure that connects the collar to the baseplate.
4. Baseplate: This is the plate-like structure at the end of the tail sheath.
5. Tail Fiber: These are the thin, hair-like structures extending from the baseplate.

Labeling the Diagram:
- Top left: Capsid Head
- Middle left: Collar
- Bottom left: Tail Sheath
- Bottom right: Baseplate
- Right side (attached to baseplate): Tail Fiber
- Inside the capsid head: Nucleic acid (DNA)

Final Answer for Q.12:
$$
\boxed{\text{Labels as described above}}
$$

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Summary of Answers:

1. Q.10: $\boxed{a}$
2. Q.11: $\boxed{d}$
3. Q.12: Labels as described in the solution.