The process of plant evolution

It is said that plants appeared on the earth during the time between the Ordovician period and the Silurian period of the Paleozoic era, some four hundred million years ago. The first plants that appeared on land may have been Pteridopytes or Bryophytes, and it is Pteridopytes that had become large-sized on land and markedly expanded their habitat by Carboniferous period of the Paleozoic era. Although unlike plants living in water, Pteridopytes cannot absorb water and nutrients from the whole plant body, they developed the tube system called vascular bundles, which enabled the plants to absorb water and nutrients at one part of the plant body and transport them to the other parts. In addition, after developing stomata on the surface of leaves, they are able to prevent water loss and lower the leaf temperature by opening and closing stomata. Thanks to these changes Pteridopytes adapted themselves to dry land conditions to some extent. Pteridopytes, however, need external water at the time of reproduction and their habitats were limited to areas not too dry, such as river coasts.

It is Spermatophytes that have evolved from Pteridopytes. Spermatophytes can tolerate dry conditions more pronouncedly. Because Spermatophytes do not need external water at the time of reproduction, they were suitable to life under dry inland conditions. Spermatophytes developed cuticle layers on the surface of the whole plant body, which effectively prevent water loss from the surface of the plant body, Spermatophytes include Gymnosperms and Angiosperms, and in the flower former ovules are exposed, whereas in the flower of the latter ovules are covered by ovaries. Gymnosperms appeared in the late Devonian period of the Paleozoic era and prospered during the time from the Carboniferous period to the Permian period. Angiosperms appeared during the time from the Jurassic period to the Cretaceous period of the Mesozoic era, and diversified during the period from then to the Cenozoic era. Angiosperms further differentiated into Monocotyledons and Dicotyledons.

At end of the process of plant evolution, crops appeared after the appearance of human beings, very recently in the history of the earth. Crops may have evolved from ancestral wild plant species by artificial selection. They can be distinguished from wild plants by many characteristics. One of them is the non-dormant characteristics of the seeds, by which crops germinate uniformly when planted. Crops do not contain toxic substances n store organs like fruits. The seeds or fruits of wild plants generally are detached from the plant body when mature, whereas the seed or fruits of crops are not and efficient harvest is possible. In crops, harvested organs, such as the grains of cereal crops, the fruits or fruit vegetables and the corms or tuberous roots in root crops, are enlarged abnormally.

2 Response to "The process of plant evolution"

  1. panjjj says:

    nice post. Actually, I have a question related to this post, did the historical plants have done pollination between each other? if so, what were their mediums?
    by the way, I am PERTAMAX gan.

    generally, the historical plants have done pollination because whitout pollination, plants can't multiply, then it will extinct. pteridophytes need water as a medium.however, after it evolved to spermatophytes, it didn't need just done directly

Post a Comment

Powered by Blogger