Question

Student to attempt either option (A) or (B):
(A) How is the interaction between Ophrys and its specific bee pollinator one of the best examples of co-evolution? Explain. 
OR 
(B) Arrange the given important steps of decomposition in their correct order of occurrence in the breakdown of complex organic matter and explain the fourth step in the process.

Hint:

Ophrys-bee pollination is a classic example of species-specific co-evolution. In decomposition, humification forms stable humus essential for fertile soil.

Answer 1

(A) Step 1: Co-evolution is a process where two or more species reciprocally affect each other’s evolution.
Step 2: In the case of Ophrys, the orchid flower mimics the female bee in appearance and scent. 
Step 3: This mimicry attracts the male bee for mating, during which pollination occurs. 
Step 4: The specific bee species and Ophrys have co-evolved to maintain this highly specialized pollination strategy. 
Conclusion: This precise and exclusive interaction is one of the best examples of co-evolution. 
OR 
(B) Step 1: Correct order of decomposition steps:

1. Fragmentation
2. Leaching
3. Catabolism
4. Humification
5. Mineralisation

Step 2: Explanation of the fourth step — Humification:

• Humification leads to the formation of a dark-colored, amorphous substance called humus.
• Humus is highly resistant to microbial action and hence persists in the soil for a long time.
• It plays a key role in soil fertility by improving its texture and water-holding capacity.