Question

Brood parasitism is shown by:

• A. Cuckoo laying eggs in crow nest
• B. Orchid on tree
• C. Bacteria in gut
• D. Lichen

Hint:

"Brood" refers to the young of an animal. Brood parasitism = hijacking another organism's parental care.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Brood parasitism is a behavioral parasitism where one species (the parasite) tricks another species (the host) into raising its offspring.

Step 2: Detailed Explanation:
The classic example of brood parasitism is the relationship between the Cuckoo (Koel) and the Crow.
The Cuckoo does not build its own nest or incubate its eggs.
Instead, it lays its eggs in the nest of a host Crow.
The Cuckoo's eggs have evolved to look like the Crow's eggs to avoid detection.
The Crow spends its time and energy incubating the eggs and feeding the Cuckoo's hatchlings, often at the expense of its own chicks.
Evaluation of other options:
(B) Orchid on tree is Commensalism ($+$, $0$).
(C) Bacteria in gut is usually Mutualism ($+$, $+$).
(D) Lichen is an obligate Mutualism ($+$, $+$).

Step 3: Final Answer:
The interaction where a Cuckoo uses a Crow's nest for its offspring is the standard example of brood parasitism.

Answer 2

Classifying each option by what each party gains or loses in the relationship, and specifically whether reproduction or parental care is being exploited, shows which one qualifies as brood parasitism.

1. Cuckoo laying eggs in crow nest: The cuckoo gains free incubation and parental care while spending no energy on building a nest or raising young, and the crow bears a direct cost since its own chicks may be pushed out, starved of food, or reduced in number as a result. Because this exploitation is specifically targeted at another species' parental investment, and the cuckoo's eggs are known to closely resemble the host's own eggs to avoid detection, this is the defining case of brood parasitism.
2. Orchid on tree: The orchid gains physical support and better access to light while the tree is neither helped nor harmed, which describes commensalism. No reproductive exploitation or parental care is involved at all.
3. Bacteria in gut: The bacteria receive shelter and nutrients while the host benefits from digestion and vitamin production, so both parties gain, which is mutualism rather than any form of parasitism.
4. Lichen: The fungal partner provides structure and moisture while the algal partner supplies food through photosynthesis, and both benefit, again describing mutualism rather than exploitation of reproduction or parental care.

Only the cuckoo and crow relationship involves one species offloading its parental duties onto another at that species' expense, which is exactly what defines brood parasitism.

Hence, the correct answer is Cuckoo laying eggs in crow nest.