Ques. 1AIPMT 2011 (Mains)
Selaginella and Salvinia are considered to represent a significant step toward evolution of seed habit because
- female gametophyte is free and gets dispersed like seeds.
- female gametophyte lacks archegonia.
- megaspores possess endosperm and embryo surrounded by seed coat.
- embryo develops in female gametophyte which is retained on parent sporophyte.
Answer
(4) embryo develops in female gametophyte which is retained on parent sporophyte.
Solution
As per NCERT, Selaginella and Salvinia are heterosporous pteridophytes producing microspores and megaspores.
∵ The megaspores germinate into female gametophytes which are retained on the parent sporophyte for variable periods,
⇒ the zygote develops into a young embryo within the female gametophyte.
∴ This event is a precursor to the seed habit – an important step in evolution.
Answer: (4)