From pre-historic Charophytes to Angiosperms.A crash course in the evolution of terrestrial 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

The end of the Mesozoic era 140 million years ago not only led to the mass extinction of dinosaurs, the once dominant gymnosperms which covered the earths landscape would also diminish. Perhaps the most important evolutionary event within the kingdom Plantae at the time, was the evolution of seeded flowering plants, angiosperms (Rost 1998). 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). Much like gymnosperms, angiosperms also produce seeds, however, many characteristics of their life cycles differ greatly. The ovaries of angiosperms are enclosed within the carpel and ovules have two layers of protective integument, whereas gymnosperms have a single integument (Rost 1998). Comparison of gymnosperm and angiosperm integument layers Angiosp

There are several phyla which became extinct towards the end of the Mesozoic era 65 million years ago, such as the Pteridospermales and Cordaitales, however, this blog will focus on the 4 extant phyla, Coniferophyta (conifers), Cycadophyta (cycads), Ginkgophyta (ginkgo) and Gnetophyta (gnetophytes) (Evert and Eichhorn 2013). The most abundant of all gymnosperms, with approximately 630 species, are the conifers, Coniferophyta (Evert and Eichhorn 2013). These include some of the more commonly known like red woods, pines, firs and cypresses, and others less familiar such as larches, bristlecones, junipers, yews and plum yews (Rost 1998). Not all conifers are cone bearers as the phylum name suggests. Junipers, yews and plum yews are unique in that they lack woody cones.  Giant Sequoia pinecones They have seeds which are surrounded by a fleshy, berry like tissue, called an aril, and are fruit like in appearance (Rost 1998). There are other unique features within the conif