Here's why:

* Two distinct phases: Plants have two distinct multicellular phases in their life cycle:

* Sporophyte: The diploid phase that produces spores through meiosis.

* Gametophyte: The haploid phase that produces gametes (sperm and egg) through mitosis.

* Alternation: These two phases alternate with each other, meaning the sporophyte generation gives rise to the gametophyte generation, which in turn gives rise to the sporophyte generation.

This cycle is different from animals, which only have a diploid phase (zygote to adult).