Question

Heterospory is found in some members of ______ and all members of ______.
A. Bryophyta, Pteridophyta.
B. Pteridophyte, bryophyta.
C. Bryophyta, gymnosperms.
D. Pteridophyte, spermatophyte.

Answer 1

Hint: Heterospory is found in some members of cryptogams and all members of seed producing plants. Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. Heterospory is evolved from homospory as a part of the process of evolution.

Complete answer:
> The phenomenon of the production of spores of two different sizes and sexes by the sporophytes of land plants is called heterospory.
> The spores produced by males are called microspores which are small in size and the spores produced by the females are called megaspores which are bigger in size.
> Microspore- Microspores are haploid spores that contain the male gametophyte which is carried to the megaspores by wind, water currents, or animal vectors. Microspores are nearly all non flagellated and are therefore not capable of active movement.
> Megaspores- Megaspores comprise of the female gametophytes. They consist of archegonia that produce egg cells. The egg cells are fertilized by sperm of the male gametophyte produced from the microspore. This fertilization results in the formation of a diploid zygote that further develops into the sporophyte embryo.
> The phenomenon of heterospory was first found in pteridophytes.
> Examples of plants showing heterospory are selaginella, Salvinia and marsilea, etc.

The correct answer for the above question is option ( D ) i.e. pteridophyta and spermatophyta.

Note: The advantages of heterospory are
> Seed development.
> The retaining and germination of the egg, and embryo formation which is still within the germinating megaspore.
> There is an extreme reduction in the male and female gametophytes.
> The differentiation of sexes can be guessed at the stage of spore.