Saturday, 14 January 2012

Endosymbiosis: Biology Research for the IB Classrom

In a recent article New Scientist magazine exposes a fascinating organism which is difficult to classify. What's more exciting to scientists is that it looks like a living example of endosymbiosis, the process which is thought to have created the mitohondrion and the chloroplast.
This species would be a novel example of evidence to support the endosymbiotic theory in Option D1.8 or an interesting example of endocytosis in Topic 2 Cells. High quality microscope images of these organisms, including TEM and SEM images can be found in the original research. These would be great new examples for calculating cell size or magnification using scales bars in Topic 2.1.
Like a chamaeleon, M.chamaeleon changes colour depending on the colour of the algae it has engulfed.
This single celled organism, called Mesodinium chamaeleon is a eukaryote, so it has a nucleus and mitochondria.
They engulf algae called cryptomonads and keep them alive inside food vacuole. The algae produce sugars by photosynthesis as they are gradually digested in the food vacuole. At times just a swolen chloroplast remains in the food vacuole.
Sometimes they engulf a red algae and other times a green algae, hense the name M. chamaeleon.
A cousin of this ciliate, M. rubrum, only engulfs red algae, forms a long lasting endosymbiotic relationship with the algae and is often found in the algal blooms that form red tides.

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