The on going evolution of plants.


Over the past 10 weeks we have embarked on a journey from 1.2 billion years ago to the present. This final blog is a summary of my previous posts on the evolution of plants. The transition of aquatic plant life to terra-firma during the mid-Paleozoic era enabled the commencement of terrestrial life. Phylogenetic studies linked the ancestral origin of land plants to a charophycean green algae (Crane & Kenrick 1997).

During the Upper Ordovician period 475 million years ago, the terrestrialization of charophycean algae led to the evolution of the first permanent land-dwelling plants, the bryophytes (Willis & McElwain 2014). We learnt that bryophyte is used to describe plants with no vascular or specialised transportation system such as liverworts, mosses and hornworts.

 The evolution of seedless vascular plants towards the end of the Silurian period, 425 million years ago, allowed for the re-transformation of the pre-historic landscape filled with lycophytes (quillworts) and monilophytes (ferns) (Evert, Raven & Eichhorn 2013).



A change in prehistoric global climate during the Mesozoic era, brought a transformation of the landscape. The arrival of gymnosperms. The evolution of the ovule, the seed, and pollination allowed for the successful radiation of gymnosperms, such as cycads and conifers throughout the Mesozoic era and into our current period (Evert & Eichhorn 2013).

The end of the Mesozoic era 140 million years ago not only led to the mass extinction of dinosaurs, gymnosperms which covered the earths landscape also diminished. Perhaps the most important evolutionary event within the kingdom Plantae at the time, was the evolution of seeded flowering plants, angiosperms (Rost 1998).

We learnt angiosperms are all grouped within the phylum, Anthophyta. Angiosperms, meaning “seed within a vessel”, make up 90% of all plants we see today, between 300-450 000 species, making them by far the largest phylum of photosynthetic organisms (Evert and Eichhorn 2013). We also learnt that as plants have evolved, the once large and dominant gametophyte generations, over time were reduced, and sporophyte generations now dominant the lifecycles.



The amazing, ongoing evolution of plants, particularly angiosperms, allows for continued domination, diversification and radiation of plant life in all climatic conditions.



References
Crane, P.R. & Kenrick, P. 1997, "The origin and early evolution of plants on land", Nature, vol. 389, no. 6646, pp. 33-39.

Evert, R.F., Raven, P.H. & Eichhorn, S.E. 2013, Biology of plants, Eighth edn, W.H. Freeman and Company Publishers, New York.

Rost, T.L. 1998, Plant biology, Wadsworth, Belmont, Calif.

Willis, K.J. & McElwain, J.C. 2014, The evolution of plants, Second edn, Oxford University Press, Oxford.

Pinterest,  Date unknown, Plant evolution timeline, image, viewed May 2018, < https://www.pinterest.com.au/pin/366339750913786669/>.

Nicer web, 2018, Gametophyte and sporophyte lifecycle, image, viewed May 2018, < http://bio1151b.nicerweb.net/Locked/media/ch30/>.

Comments

  1. Tasmin19 May 2018 at 19:19

    Thank you for an interesting and enjoyable blog.

    ReplyDelete

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