10/1

Viridiplantae:

  1. Green Algae

  2. Land plants

Green Algae

The first green plants in the fossil record are green algae, found in rocks from 725-1000 million years ago (Precambrian!)

Biologists are still investigating which group of green algae is most closely related to land plants, but we know that it’s a green algae

Land plants:

Nonvascular land plants: liverworts, mosses, hornworts

The first land fossil plants are found in rocks around 475 million years ago, along will animals and fungi

These plants would have been quite small with low, sprawling habits. They lacked rigidity and would have had to obtain water via pores. Kinda look like moss.

Life out of water was hard, so the oldest land plants adapted:

Adaptations of nonvascular land plants:

Sporopollenin: a very durable biopolymer that encases spores and prevents dying

Cuticle and UV-absorbing compounds that acted as sunscreen

Land plants exhibit alternation of generations. Nonvascular land plants are gametophyte (haploid) dominant.

Sperm need to swim in the water to get to the archegonia

Vascular Land Plants

Ferns and friends

First vascular plants show up in the fossil record around 420 million years ago

Ferns and friends undergo adaptive radiation around 360 million years ago

Adaptations:

  • The evolution of lignin and secondary cell walls facilitated the evolution of vascular systems in land plants

  • Primary cell wall of cellulose and secondary cell wall of lignin

  • Vascularity gives them rigidity

Still needs water for the sperm to swim in