The diagram shows a typical bacterial cell - Leaving Cert Biology - Question 13 - 2007
Question 13
The diagram shows a typical bacterial cell.
(i) Some bacteria have a layer outside the cell wall (labelled A in diagram). Name this layer and state its function.
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Worked Solution & Example Answer:The diagram shows a typical bacterial cell - Leaving Cert Biology - Question 13 - 2007
Step 1
What is this layer and its function?
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Answer
The layer labelled A is the capsule or slime layer. Its function is to provide protection to the bacterial cell, helping it evade the immune response and adhere to surfaces.
Step 2
Name a structure not found in all bacteria.
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Answer
A structure, other than A, that is not found in all bacteria is the flagellum. This structure is responsible for motility in some bacterial species but is absent in others.
Step 3
Distinguish between autotrophic and heterotrophic nutrition.
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Autotrophic nutrition is when organisms make their own food using light or chemical energy, while heterotrophic nutrition involves organisms that consume organic matter produced by other organisms.
Step 4
What is saprophytic nutrition?
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Saprophytic nutrition is the process by which certain organisms, particularly certain bacteria and fungi, feed on dead organic matter, breaking it down to recycle nutrients back into the ecosystem.
Step 5
Why are saprophytic bacteria important in nature?
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Saprophytic bacteria play a crucial role in decomposition. They break down dead plants and animals, releasing nutrients back into the soil, which supports new plant growth and maintains ecosystem balance.
Step 6
Briefly explain chemosynthesis.
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Chemosynthesis is the process by which certain organisms obtain energy by oxidizing inorganic substances rather than relying on sunlight, thus enabling them to generate organic matter from carbon dioxide.
Step 7
What term is used for the organism from which a parasite obtains its food?
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The term used for the organism from which a parasite obtains its food is the host.
Step 8
Give examples of two harmful bacteria.
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Examples of harmful bacteria include Staphylococcus aureus, which can cause skin infections, and Escherichia coli O157:H7, known for causing foodborne illness.
Step 9
Draw a labelled diagram to show the structure of Rhizopus.
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Answer
A diagram showing Rhizopus should include: the stolon, rhizoid, and sporangiophore, each clearly labelled.
Step 10
Give a brief account of its asexual reproduction.
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Rhizopus asexual reproduction occurs through the formation of sporangia. In this process, sporangiospores are released from sporangium when it bursts, allowing them to disperse and germinate into new fungal individuals.
Step 11
Name the parts labelled A and B.
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In the diagrams showing the sexual reproduction of Rhizopus, part A is the zygosporangium (the thick-walled structure containing zygotes) and part B is the zygospores (the spores that develop after fertilization).
Step 12
What is the function of B?
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The function of B (the zygospore) is to provide protection and to ensure the survival of the fungal species during unfavorable conditions, allowing it to remain dormant until conditions are suitable for growth.
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