Plant Diversity

Before plants colonized land from the sea, the continents were barren. Now millions of species of microbes, plants, and animals live on land, and it was the evolution of land plants that made all of this possible. To understand this staggering transformation, we need to understand what exactly plants are and how they evolved to meet the challenges of life on land.

There are certain characteristics that all plants share, from the tallest trees to the smallest moss. First, all plants are multicellular eukaryotes. Second, plants produce the photosynthetic pigment chlorophyll in organelles called chloroplasts, enabling them to produce their own food using energy from the sun. Third, all plants have cells that are surrounded by walls made of cellulose. Lastly, all plants have a life cycle characterized by the alternation of generations, defined as the transition between haploid and diploid multicellular stages over the life cycle. Here, generations refers to two different multicellular phases in the life cycle. One phase is the haploid gametophyte. The gametophyte produces gametes by mitosis, which fuse during fertilization to form a diploid cell, which then undergoes mitosis to develop