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.