Problem 4

Plants have two different stages in their lifetime, in other words, two distinct multicellular body types, 1. A diploid sporophyte producing spores, 2. A haploid gametophyte producing gametes. 

Alternation of generation is the transition of plant life between sporophytic and gametophytic stages alternatively.

Based on the duration of each stage, plants can have three types of life cycles:

1. Haplontic lifecycle - the haploid gametophytic stage is dominant and long-lasting, while the diploid sporophytic stage is short. Ex: green algae.

2. Diplontic lifecycle - the diploid sporophytic stage is dominant and long-lasting, while the haploid gametophytic stage is short. Ex: Gymnosperms, angiosperms.

3. Haplodiplontic lifecycle - both haploid and diploid stages dominate the lifecycle almost equally. Ex: bryophytes, pteridophytes.