In one of our (upcoming) podcasts, Ivonne wanders through the Evolution of Land Plants dell in Bristol. After coming home, she refreshed her knowledge of plant evolution.
What are plant evolution highlights? This is an overview for the very keen and eager to learn plant enthousiasts 😉 Footnotes explain some common plant names in Dutch.
Precambrian and Cambrian (487+ million years ago)
During the Precambrian period, the very first life forms evolved, but their world was inhospitable.
In the Cambrian, many animal groups appear to have evolved in a very short time.
In the seas, algae1 were developing increasingly complex forms. Algae is an informal term for any organisms of a large and diverse group of photosynthetic creatures. This evolution of algae would eventually lead to the evolution of land plants. So, land plants had aquatic ancestors.
Ordovician period (487-443 million years ago)
Algae transitioned to life on land. They left fossilised spores behind. Early land plants are thought to have resembled living mosses (Bryophyta), liverworts (Marchantiophyta) or hornworts (Anthocerotophyta).2 These plants require damp habitats.
Silurian (443-419 million years ago)
In this Silurian period, the non-vascular plants were very small. They had no leaves. Their only source of food came from their photosynthetic stems.
Then came the appearance of vascular plants. First fossils of land plants have been found, such as fossils from Cooksonia, depicted in the top part of this blog. Cooksonia was a group of small vascular plants without leaves.
Devonian period (419-359 million years ago)
The flora diversified very quickly in the Devonian period. Diverse, expansive forests were developing.
Two important innovations made it easier for land plants to survive and spread:
- leaves
- seeds
Carboniferous period (359-299 million years ago)
During the Carboniferous periode, plants were abundant and diverse. Imagine dense forests of plants, including giant horsetails3 (Equisetum), early seed plants and tree ferns.4
There were high levels of oxygen. This meant bigger animals could live on earth. But it also meant there were devastating wildfires.
Tree fern
Tree ferns are living representatives of ancient forest plants. They are tree-like ferns that grow with a trunk elevating the fronds above ground level, making them trees.
There must have been hundreds of species. Many may have become extinct in the last century as a result of human intervention.
Many surviving tree ferns are members of one and the same order (Cyatheales). It is estimated that this order originated in the early Jurassic.
Depicted is a specimen in a London park.
Permian period (299-252 million years ago)
In the Permian period, a global climate change occured. Forests were largely replaced by arid desert environments. Plants were more drought tolerant. Seed coats enabled seed plants to colonise seasonally dry environments. Spore producing plants could not do this succesfully. Ginkgos were an important plant of the flora.
Maidenhair tree
The well-known living fossil maidenhair tree5 (Ginkgo biloba) is the last living species in its order (Ginkgoales), which first appeared over 290 million years ago. Some specimens are claimed to be more than 2,500 years old.
Fossils very similar to the living species, belonging to the genus Ginkgo, extend back to approximately 170 million years ago.
Maidenhair trees are very durable. Why is that? They have:
- a high resistance to disease
- insect-resistant wood
- the ability to form aerial roots and sprouts
Triassic period (252-201 million years ago)
At the end of the Permian, 85% of animal species had died out.
However, the existing trends in plant evolution continued.
The climate remained hot and arid.
Monkey puzzle
Conifers like the well-known monkey puzzle6 (Araucaria araucana, depicted) dominated forest landscapes.
Logging, forest fires, and grazing caused its population to dwindle.
The International Union for Conservation of Nature changed its conservation status to ‘endangered’ in 2013.
Wollemi pine
Wollemi pine7 (Wollemia nobilis, depicted) is another living fossil from the Triassic period.
It’s not a pine!
In fact this tree is closely related to the monkey puzzle.
The living plant was accidentally discovered in Australia in 1994!
Jurassic period (201-143 million years ago)
In the Jurassic period, much of the world experienced wetter, temperate conditions. Lush vegetation returned, feeding dinosaurs.
Conifers such as cypress (Cupressus) and yew8 (Taxus) continued to diversify. Ginkgos remained common in the northern hemisphere, including the UK.
Seed ferns dominated the flora. A specific group of them, now extinct, were common and may have been ancestors of flowering plants.
Around 140 million years ago, the first flowering plants appeared.
Cretaceous period (143-66 million years ago)
The Cretaceous period saw diversification and spread of flowering plants. Conifers and ginkgos remained common. Early flowering plants are thought to have resembled magnolias. There was an evolution of bees, ants, butterflies, and other pollinators.
Magnolias: nice to know fact
The magnolia-like plants of the Cretaceous period were most likely pollinated by primitive wingless beetles. The magnolia flower reflects this with a hardened carpel to protect it from mandible damage. It has no nectar, as beetles were just interested in pollen.
Magnolia used to be prevalent in Europe before the Ice Age restricted it to South East Asia and North America where we see their native range today.
Source: March of the Magnolias, in The Garden Blog of the botanical garden
Cenozoic era (66 million years ago – now)
Our current era, the Cenozoic, knew huge changes in animal life after an asteroid impact at the end of the Cretaceous period. Remarkably, plant life remained largely unchanged.
Climates began to become more arid, with more seasonal variability. Grasses thrived, and giant grazing mammals appeared.
Common plant names in Dutch
- algae = algen ↩︎
- living mosses = bladmossen, liverworts = levermossen, hornworts = hauwmossen ↩︎
- horsetail = paardenstaart
Field horsetail = heermoes (Equisetum arvense) can be a real nuisance in the garden ↩︎ - tree fern = boomvaren ↩︎
- maidenhair tree= Japanse notenboom, ginkgo ↩︎
- monkey puzzle = slangenden, apenboom ↩︎
- wollemia pine = wollemia ↩︎
- yew = taxus, venijnboom ↩︎
Where?
Do you want to enjoy the journey through time yourself?
Visit the University of Bristol Botanic Garden!
