4.6 Eukaryotic Evolution and the Phylogeny of All Life - The Six Super Kingdoms: Chromalveolata - Martin V. Sørensen

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Do curso por University of Copenhagen

Origens - Formação do Universo, Sistema Solar, Terra e Vida

393 classificações

University of Copenhagen

Origens - Formação do Universo, Sistema Solar, Terra e Vida

393 classificações

O curso "Origens" traça a origem de todas as coisas - a partir do Big Bang até a origem do Sistema Solar e da Terra. O curso segue a Evolução da vida no nosso planeta desde os primórdios do tempo geológico até as formas de vida atuais.

Na lição

Transition from Microbial to Macrobial Life: Snowball Earth and the Ediacara Biota / Eukaryotic Evolution and the Phylogeny of All Life

In this module, we take a closer look at how the physical and biological conditions that made the Cambrian Explosion possible arose. In the first lectures Svend Stouge will tell you about the dramatic consequences of climate changes seen toward the end of the Precambrian. Geological evidence supports the idea that the Earth was completely covered in ice during periods that we, for obvious reasons, refer to as Snowball Earth. In the remaining lectures Martin Sørensen will tell you about one of the most significant building blocks of life on Earth – the cell – and how the early bacterial cells evolved and became capable of forming the huge variety of life that we see today. Martin Sørensen will also show how different evolutionary trends of cells resulted in six major organism groups, of which several gave rise to multicellular life.

4.1 Transition from microbial to macrobial life: Snowball Earth and the Ediacara Biota - Part 1 - Svend Stouge19:43

4.2 Transition from microbial to macrobial life: Snowball Earth and the Ediacara Biota - Part 2 - Svend Stouge13:47

4.3 Eukaryotic Evolution and the Phylogeny of All Life - The Transition from the Prokaryotic to the Eukaryotic Cell and the Endosymbiont Theory - Martin V. Sørensen11:48

4.4 Eukaryotic Evolution and the Phylogeny of All Life - The Eukaryotic Tree of Life and the Six Super Kingdoms: Archaeplastida - Martin V. Sørensen7:26

4.5 Eukaryotic Evolution and the Phylogeny of All Life - The Six Super Kingdoms: Excavata and Rhizaria - Martin V. Sørensen7:03

4.6 Eukaryotic Evolution and the Phylogeny of All Life - The Six Super Kingdoms: Chromalveolata - Martin V. Sørensen5:56

4.7 Eukaryotic Evolution and the Phylogeny of All Life - The Six Super Kingdoms: Amoebozoa and Opisthokonta - Martin V. Sørensen 7:06

Conheça os instrutores

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]

We have now moved to the beach because many of the most permanent members of

the next super kingdom live in the oceans.

The group we're going to talk about is called Chromalveolata, and

it's a group consisting of many different single-celled organisms.

But also large and multicellular ones such as the brown algae or kelp.

Again, the group is mainly supported by molecular data.

And the taxa in the group have no general morphological traits in common.

However, it seems like many of them have one thing in common.

Those that are able to make photosynthesis all developed their

plastids through secondary endosymbiosis.

And the eukaryotic cells were part of this endosymbiosis.

All seem to be red algae.

So, let's take a look at some of the members of the Chromalveolates.

We could, for instance, start with the multicellular ones and look for

some brown algae.

Let's see.

for instance,

we have this quite typical one in Danish water called the bladderwrack.

It's a brown algae, looking like this.

But we also have many other different kinds of brown algae, like, for

instance, the Laminaria that can reach gigantic sizes, for

instance, the big kelp forests that we have off the U.S. west coast.

If we take a look at the microscopic taxa of the group, we have several groups that

occur in very high abundances, and are important in the ecosystems.

One example is the dinoflagellates that exist in both freshwater and

marine waters.

They are interesting in many ways.

For instance, they have cyclomorphosis,

meaning that they can change shape over time.

If you look at this dinoflagellate on the photo you can see that it

has spines or spikes.

They will change in length and shape over the year depending on

the water temperature, which has to do with their ability to float in the water.

We all know that the water viscosity changes with the temperature, and

when the dinoflagellates change shape,

they are able to adapt to the changes in water viscosity.

Their changing spines can also be a reaction to predators.

Experiments have shown that if you add predators such as copepods or

maybe rotifers to a population of dinoflagellates, their spines will

get longer, which probably will make them more difficult to handle for the predator.

The dinoflagellates have this heavy armor as you see also.

It means that it fossilizes very well, and we have

a pretty rich fossil dinoflagellate fauna going all the way back to the Silurian.

Two other ecological important chromalveolate groups are the Diatoms and

the ciliates.

The diatoms have these two hard silicon shells, which

again mean that we have a very rich fossil record going back to the Jurassic.

So when dinosaurs started to develop on land,

these little organisms evolved in the lakes and the oceans.

They are very common and very important photoautotrophic organisms and

you find them in the plankton as well as in the benthic communities.

The ciliates are also very abundant aquatic organisms.

Opposed to the diatoms,

they are relatively soft and then they are often covered with cilia.

Despite the softness they are actually able to leave fossil traces, and

we have certain traces of ciliates from the Ordovician, and

it's not unlikely that they are much older and maybe even existed in the Ediacaran.

They can take many shapes, and as you see on the photo if you have been working

with aquatic plankton, you must have come across them, as they are very common.

But perhaps you also met them in the lab.

Many experiments about transport across membranes have for instance been

carried out on the ciliate Paramecium, the oval one that you see on the graphic.

The last chromalveolate groups I'm going to show you are some more algal groups,

namely the yellow algae and the golden algae.

Both are single celled organisms but they may form large colonies and

they may even occur in so high numbers that they'll color the water yellow.

For instance if any of you have visited the Yellowstone National Park in

Wyoming you probably know the amazing Morning Glory Pool.

Some of the fantastic coloring you see here is actually made by the yellow algae.

I said earlier that we have pretty good phylogenetic support for

our six Eukaryotic super kingdoms.

If we have one exception from this it might be the Chromalveolates.

We truly have molecular data that supports Chromalveolate monophyly,

but then again, other molecular data is conflicting and suggests that some

chromalveolates are actually more closely related with Rhizaria.

We are not still certain what's correct here but

until this has been clarified we operate with an alternative group

that tentatively is named the S-A-R or the SAR group.

The SAR group is an acronym for the groups Stramenopilis, which is kelp and

diatoms, Alveolates which are ciliates and dinoflagellates, and finally,

Rhizaria that's you'll remember was the super kingdom with the radiolarians and

the forams.

Hence if this alternative phylogeny is correct, the Chromalveolates would be

left with only yellow algae and golden algae and a few other minor groups.

But that is for the future to show us.

[MUSIC]

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