Double fertilisation is a unique features of

Step 1: Analyze the question The question asks which group of plants shows double fertilisation as a unique feature.

Step 2: Explain the concept Double fertilisation is a process in which two fertilisation events happen in the embryo sac of the ovule. It occurs only in flowering plants (angiosperms).

• A pollen grain lands on the stigma and grows a pollen tube down the style.
• The pollen grain's generative nucleus divides to give two male gametes (sperm nuclei).
• The pollen tube enters the ovule through the micropyle and releases both male nuclei into the embryo sac.

Step 3: Show the solution

1. First fertilisation: One male nucleus (n) fuses with the egg cell (n) to form the zygote (2n), which develops into the embryo.
2. Second fertilisation: The other male nucleus (n) fuses with the two polar nuclei (n + n) to form the triploid (3n) endosperm nucleus. This develops into the endosperm, the food store for the embryo.

Now check the other options:

• Bryophytes (mosses and liverworts): The sperm swims in water to the egg. There is only one fertilisation, so no double fertilisation.
• Pteridophytes (ferns): These also have swimming sperm and a single fertilisation.
• Algae: Fertilisation is single, and there are no flowers or embryo sacs.

Only angiosperms have an embryo sac with polar nuclei and two male gametes delivered by a pollen tube.

Step 4: Answer The correct option is A. Angiosperms.

Step 5: Exam tip Remember "Double fertilisation = Dual product (zygote + endosperm) = Angiosperms only." Also, the triploid endosperm (3n) is a favourite JAMB follow-up question, so keep that in mind.