Alternation of generations is a type of life cycle in which a diploid sporophytic spore producing phase is alternating with a haploid gametophytic gamete producing generation.

Lets take the example of fern life cycle for better understanding.

Ferns (Pteris: most common fern) belongs to pteridophytes

What is Alternation of Generation in Plants? Difference between Gametophyte and Sporophyte with example

Lets us explain in simplified steps (Figure)

  • Here the fern plant that we see is the sporophytic diploid plant; the dominant phase in the life cycle.
  • This sporophytic plant produces haploid spores by meiosis.
  • These spores germinate to form minute heart shaped haploid gametophyte (also called as prothallus)
  • Gametophytic plant produces male (antheridium) and female sex organs (archegonium) finally forming male gamete and female gamete (egg) by mitosis
  • The haploid gametes fuse to form diploid zygote (2n). Zygote germinate to form the sporophyte again. Thus the gametophytic phase is alternating with the sporophytic phase in the life cycle; therefore called as alternation of generation.

This type of life cycle occurs in plants and some algae

 Now let us see the difference between gametophyte and sporophyte.

Sporophyte (2n)

Gametophyte (1n)

Diploid plant with two sets of chromosome (2n)

Haploid plant with a single set of chromosome in the cells(1n)

Reproduce asexually or asexual generation that produces asexual spores

Reproduce sexually or sexual generation as it bears the sex organs

Sporophyte forms spores inside sporangia

Gametophyte forms gametes inside gametangium or sex organs

Spore mother cell; a diploid cell undergo meiosis forming haploid spores

Gametes (1n) are produced by mitosis inside sex organs (1n)

Spores produced germinate to form gametophyte

Gametes fuses to form zygote which germinates to form the sporophyte

Sporophytic phase is dominant in higher vascular plants like pteridophytes, gymnosperms and angiosperms

Gametophytic phase is dominant in bryophytes and some algae

Thank you so much.

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