7.3 Origin and early development of plants: Conifers - Vivi Vajda

Loading...

From the course by University of Copenhagen

Origins - Formation of the Universe, Solar System, Earth and Life

379 ratings

Explore Related Videos

At Coursera, you will find the best lectures in the world. Here are some of our personalized recommendations for you

University of Copenhagen

Origins - Formation of the Universe, Solar System, Earth and Life

379 ratings

The Origins course tracks the origin of all things – from the Big Bang to the origin of the Solar System and the Earth. The course follows the evolution of life on our planet through deep geological time to present life forms.

From the lesson

Origins and Early Development of Plants / The Origin and Diversification of Flowering Plants

In module 7, we will have a closer look at the biggest source of oxygen – the plants. Up till now we have heard a lot about the evolution of higher life forms in the oceans. While evolution took a giant step forward in the oceans, the continents remained totally barren for another approx. 100 million years. Vivi Vajda from the Lund University in Sweden and Gitte Petersen will tell you how the plants began to inhabit the terrestrial environment, thus paving the way for other life forms living on land. Land plants have managed to adapt to a very different environment, with new challenges and possibilities. Some of the early plants have survived as fossils – whereas others are still alive. Some of these living fossils will be presented in the videos. We will also have a close look at the biggest group of plants – which has evolved in close collaboration with insects, birds and even some mammals – the flowering plants.

7.1 Origins and early development of plants: Evolution of plants - Vivi Vajda 13:19

7.2 Origin and early development of plants: Ferns - Vivi Vajda6:09

7.3 Origin and early development of plants: Conifers - Vivi Vajda6:34

7.4 The origin and diversification of flowering plants: The Origin - Gitte Petersen15:13

7.5 The origin and diversification of flowering plants: Diversification of Flowering Plants - Gitte Petersen 16:32

7.6 The origin and diversification of flowering plants: The Impact of Flowering Plants on Earth - Gitte Petersen 11:56

Meet the Instructors

Henning Haack
Associate Professor
Natural History Museum
James Connelly
Professor
Natural History Museum of Denmark
Vivi Vajda
Professor
Department of Geology, Lund University
Jon Fjeldså
Professor, Curator
Thomas Gilbert
Professor
Michael Houmark-Nielsen
Associate Professor
Natural History Museum of Denmark
Bent Erik Kramer Lindow
Curator
Natural History Museum of Denmark
Gilles Guy Roger Cuny
Associate Professor
Natural History Museum of Denmark
Ole Seberg
Associate Professor
Natural History Museum of Denmark
Gitte Petersen
Associate Professor
Natural History Museum of Denmark
Tais Wittchen Dahl
Assistant Professor of Geobiology
Arne Thorshøj Nielsen
Associate Professor
Natural History Museum of Copenhagen
Martin Vinther Sørensen
Associate Professor, Curator
Natural History Museum of Denmark
Svend Stouge
Associate Professor
Natural History Museum of Denmark
Danny Eibye Jacobsen
Associate Professor, Curator
Natural History Museum of Denmark
Jan Audun Rasmussen
Associate Professor
Natural History Museum of Denmark
Emily Catherine Pope
Assistant professor
Natural History Museum of Denmark

[MUSIC]

The conifers are seed producing plants that protect their developing seeds

within cones.

The conifers are very succesful and although their present total number of

species is relatively small, reaching about 600,

they are of major ecological and economical importance.

They particularly dominate the vast boreal forests of Siberia,

Scandinavia, and Canada.

The male cones produce pollen, and these are wind-pollinated.

An example of conifer,

considered to be a living fossil, is the Wollemia that you see here.

Wollemia nobilis is the only living species within this genus, and

it's as close as you can come to a living fossil.

The oldest fossil of the Wollemias here, has been dated to around 80 million years.

And Wollemia pollen are relatively abundant in Cretaceous deposits,

showing that it was an important part of the Mesozoic ecosystems in

the Southern Hemisphere.

Based on the distribution of fossils,

it was assumed that these plants progressively declined

and died out about two million years ago.

But, one day in 1994, so not so long ago,

several strange looking trees were found, in a region

in a national park just 150 kilometers northwest of Sydney in Australia.

The natural population consists of just a handful of

individuals clinging to life in a protected ravine.

Since their discovery they have been cloned commercially, and the clones have

been sold to botanical gardens and to private collectors worldwide.

And here is one example and a really nice one.

The Wollemia is a conifer within the family Araucariaceae, the monkey puzzle

tree family. Wollemia novialis is the sole survivor of its genus.

It's an evergreen tree reaching up to 40 meters in height and

the bark is very distinctive, dark brown and bubbly.

After a few years, some branches terminate in a cone and

they have both female and male cones growing on the same trees.

The seed cones, the female cones are green.

And when they mature, they fall apart and drop their seeds.

The more slender and reddish male cones all tend to

grow on lower branches under the seed cones, thus avoiding self-pollination.

The Wollemia however, also commonly has a growing habit called coppicing

which means that the stem grows from the base of the original tree and

each stem represents a clone.

The leaves are flat and linear, and about three to eight centimeters long and

about two to five millimeters broad.

They are arranged spirally on the shoot, but twisted at the base.

So, they look quite different to other conifers.

The young leaves are first light green, by turn dark when they mature.

Metasequoias, belonging to the redwood family,

are another excellent example of a living fossil.

They are large trees and they're well represented in the fossil record

in the Cretaceous to Miocene deposits, so 100 to 20 million-year-old deposits.

So Metasequoias were once thought to have become extinct during the Miocene.

But in 1944, a population of previously unknown trees

were found in Eastern China in the wetlands of the Hubei Province.

Due to the war though, they were not described until 1948.

And then identified as Metasequoia, the dawn redwood, and

they were then classified as living fossils.

There is only one living species in the genus, and

that is Metasequoia glyptostroboides.

It's the smallest of the redwood trees, but

still it reaches at least 60 meters, so it's still a huge tree.

Metasequoias are deciduous which means that they shed their leaves every autumn,

which is actually an unusual habit within the conifers.

The dawn redwood trees have leaves that are so-called oppositely arranged.

And the individual leaves are about one to three centimeters long and

bright green turning red-brown during the autumn.

The pollen cones are small, at least reaching only one centimeter and

they're produced in the spring.

But can only grow in environments where the

summers are really hot.

The seed cones reach a size of 2 cm and

these mature in nine months after pollination.

This Metasequoia you see here is morphologically identical,

meaning that it looks the same as the ancestor that lived 66 million years ago

at the end of the Cretaceous.

We have not talked about the real winners in the evolution of the land plants,

the plant group that highly dominates with over 300,000 species,

and which, without, we would not survive.

Those are the flowering plants, the angiosperms.

The first record of these is from early Cretaceous deposits, but

their evolution was fast.

And by the end of the Cretaceous they had out-competed most other plant groups.

[MUSIC]

Explore our Catalog

Join for free and get personalized recommendations, updates and offers.

Coursera provides universal access to the world’s best education, partnering with top universities and organizations to offer courses online.

© 2019 Coursera Inc. All rights reserved.

Download on the App Store

Get it on Google Play