If intelligent extraterrestrials visited Earth 475 million years ago, and then again 300 million years ago (at the close of the Carboniferous period), what trends would they have noticed in Earth's terrestrial vegetation over this period? 1. a trend from dominant gametophytes to dominant sporophytes 2.a trend from sporangia borne on modified leaves (sporophylls) to sporangia borne on stalks (seta) 3.a trend from no true leaves, to microphylls, to megaphylls 4.a trend from soil-surface-hugging plants to 'overtopping' plants 5.a trend toward increased lignification of conducting systems

The Kingdom Plantae first appeared about 410 million years ago when green algae transitioned from water to land. The differences between land and sea posed a challenge to early colonizing species, which prompted many new adaptations. These adaptations have resulted in the wide variety of plant forms observed today.

There are an estimated 250,000 species, with the greatest diversity in the moist tropics.