Welcome to the eighth post in the series we’re calling Mother Earth
Today we’ll be going a slightly different route. We’re going to forget animals for the most part and talk about another Kingdom that shaped the face of the Earth.
Kingdom Plantae, or the plant kingdom, will be the focus of our article today. While animals usually get more attention, plants have had an arguably greater impact on the world in which we live. The first plants are closely linked to some of the creatures we discussed in earlier articles, in particular cyanobacteria and green algae. They share a very important characteristic with these early species, namely photosynthesis.
Plants evolved chloroplasts, the organelles that conduct photosynthesis in plants, from earlier symbiotic relationships between cyanobacteria and small single celled organisms. All members of the plant kingdom display photosynthesis. For those of you who have forgotten your childhood science lessons, photosynthesis is the process by which plants convert carbon dioxide, water, and the sun’s energy into chemical energy for the plant and an oxygen byproduct. They get glucose to power them, we get fresh air.
The earliest plants were tiny water based organisms. These were found during the Cambrian period, and were closely related to algae. Soon after the Cambrian period, however, plants started to creep up on to the land. Starting around 450 million years ago, the planet started going green.
The Plants Begin to Spread
A fern fossil
One of the major steps in plant evolution, one that allowed them to spread on land effectively, was the widespread occurrence of spores as a form of plant reproduction. These spores often had hard shells, which has enabled us to find them in the fossil record quite easily. Due to the nature of the plants at the time, plant species were restricted to waterlogged environments. Because they did not have any tissue that conducted water very well, they had to stay close to it to obtain the water they needed for photosynthesis. These spores could travel until they reached a suitably wet environment in which to grow, helping the plants spread all over their chosen environment.
More complex plant forms began to occur during the time known as the Silurian period. The Silurian period (circa 450 to 410 million years ago) also marked the first appearance of plants with vascular systems. These are essentially plant veins that carry around water, chemicals, minerals, et cetera within the plant. Shortly after this time period, we start seeing some familiar faces. The ferns made their appearance on the stage. During the late Devonian period, (385 to 359 million years ago) we started seeing plants that worked a lot like plants do today. We started getting larger plants, and we started seeing plants that had root systems and leaves for the first time.
The Forests and the Grass
A conifer fossil
Some of the world’s most majestic and massive trees appeared after this. In the Permian period, conifers appeared and they thrived. The conifers are cone bearing seed plants, mostly trees. The conifer family includes pines, cedars, cypress, and the massive redwoods, among others.
Conifers became the most dominant plant family in the world during the Mesozoic era. This was also the era of the dinosaurs. While T-Rex was tearing up his meaty brethren, the conifer family spread until massive conifer forests covered most of the planet. The fern was also quite abundant during this period, as it grew well in the undergrowth of these forests.
By the end of the Mesozoic, we see some of the more popular plant species come to be. The angiosperms, or flowering plants, came into existence. By the end of the period, they were the predominant species, although not without a little help. The predominance of angiosperms is closely related to the evolution of certain insects, most notably the bee. The fates of the two organisms were closely linked, and they coevolved for some time.
About 35 million years ago, the first grasses began to evolve from these angiosperms, and we began to see landscape similar to today’s savannahs start to dominate the landscape. These grasses became very important to our own evolution. About 10,000 years ago, human beings figured out how to domesticate these grasses, resulting in the beginning of agriculture. From there, we begin to see the beginnings of civilization.
Join us next time on Mother Earth when we discuss how fish began to walk. The easiest way of keeping up with the rest of the series is probably by subscribing to our RSS feed… and if you do that we’ll also give you a free album! What a bargain.