Plant Evolution 2

Exerpt 2   Algae to Organisms  from Science for the Gardener Book to be published 2017

First plant organisms

 

Cyanobacteria, a single bacteria cell, is believed to be the very first organism to emerge from the soup, using light to make the sugars needed for growth from carbon dioxide and water, and releasing oxygen into the air.  The oxygen needed to sustain human and animal life in the future.   It was several thousand million years before plants as we know them evolved to be able to make the sugars necessary for growth in this way, which is known as photosynthesis.

 

Fossilised remains of these first single cell bacterial organisms have been found around the world in Australia, Belize and the Bahamas.  Scientists have named these remains Stramatolites.

 

Over the next 50 million years these organisms started to multiply to produce what we now know as Green Algae.  Green Algae lived mostly in water – ponds, lakes and rivers or in the seas, attaching itself to the first rock formations.  Not terribly pleasant, rather slimy and not very welcome on our ponds today, but they were the ancestors of the first land plants.

 

Fast forward to 570 million years ago!  Plant evolution begins.  From Algae, very simple green and slimy, to Angiosperms, the myriad of beautiful flowering plants grown today.  Five different plant groups, all evolving with differing methods of reproduction – just as well we humans didn’t evolve in quite the same way.

 

The first land plants, with very simple branched stems, no leaves or roots evolved to live in drier conditions.  They were upright and developed a vascular system for drawing up water and nutrients and dispersed spores (a cell with a protective coating) from a sac at the tip of the stem in order to reproduce.  These first simple land plants have been given the name Cooksonia.  All these very early land plants are now extinct.