Question

Ancestors of seed-bearing plants exhibit:

• A. Heterospory
• B. Heterotrichous thallus
• C. Homospory
• D. Alternation of generations

Answer 1

The correct option is A Heterospory

Gymnosperms and angiosperms are the seed-bearing group of plants.

Pteridophyte genera like Selaginella and Salvinia are heterosporous. They produce two kinds of spores and are considered to be the ancestors of seed-bearing plants.

• Small male microspores which geriminate to give rise to the female gametophyte.
• Large female macrospores which geriminate to give rise to the female gametophyte.
• The female gametophytes in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos take place within them. This event is a precursor to the seed habit considered an important step in evolution.

Plants that produce only one type of spore are said to be homosporous. Most pteridophyes exhibit homospory.

Alternation of generations between gamete producing haploid gametophyte and spore producing diploid sporophyte can be seen during the life cycle of all sexually reproducing plants.

Heterotrichous condition can be seen in many algae where the plant body show both well developed erect and prostrate forms of filament.