1. Euglena Plant or animal ? (document prepared by S. Kaelin, S. Moretti & A. Pylypenko under the direction of N. Muller Mirza - original source of the case IDEAS-IoE) under the direction of N. Muller Mirza - original source of the case IDEAS-IoE) (Université de Neuchâtel)

2. The cell’s structure  The cell is the basic unit of the living. Any organism, from the simplest to the most sophisticated, consists of cells, sometimes only one, sometimes several, even several billions of different types, in a very coordinated unit.

3. The cells’ structure  The existence of a nucleus makes it possible to gather cells in a unit, the EUCARYOTES, by opposition with the PROCARYOTES which do not have a nucleus  How to differentiate animal from plant?

4. The animal cell  The animal cells (50 micrometers) have a nucleus (genetic information), mitochondries (energy production), an endoplasmic reticulum (fabrication of proteins), apparatuses of Golgi (transformation of proteins) and lysosomes (bag of enzymes). Contrary to the vegetable cells, they do not have chloroplasts, cellular wall or vacuole. The animal cells are surrounded only by one membrane, making it possible the cell to be flexible and to yield to a pressure exerted on it.

5. The animal cell

6. The vegetal cell  Like the animal cells, the vegetable cells (200 micrometers) have a nucleus (genetic information), mitochondries (energy production), an endoplasmic reticulum (fabrication of proteins), ribosomes (synthesis of proteins), apparatuses of Golgi (transformation of proteins) and lysosomes (bag of enzymes). However, a vegetable cell is surrounded by a cellular wall made of cellulose, which makes it more rigid.  Moreover, the vegetable cells contain vacuoles, which contain the vacuolar liquid, and the chloroplasts, which contain chlorophyl, a green pigment. It is inside the chloroplasts that the process of photosynthesis takes place by which the plant produces its own food.

7. The vegetal cell

8. Euglena  One can find euglena in the ponds rich in organic matter  They are unicellular, free organisms (swimming in water thanks to one whip)  The length of the cells varies from 20 to 300 µm; they are cylindrical, or oval  There are in general many chloroplasts of color green-clearly, although certain species are colourless  The border animal-plant is not as distinct as for more complex organisms

9. Euglena structure

10.  Protozoon whipped in fresh waters  It is composed of chlorophyl and a rudimentary eye  Tank: part of euglena being used to store  Nucleus: contains the genetic information of the cell  Contractile vacuole: cavity of euglena able to contract  Cellular membrane: membrane wrapping euglena  Chloroplast: organelle of euglena, sits of photosynthesis  Nucleole: has the shape of a sphere which is in the euglena’s nucleus  Stigma: part of euglena sensitive to the light  Whip: mobile filament and length being used for the locomotion of euglena

11. Euglena  Euglena can be nourished in two ways:  organic production of matter from CO2 by photosynthesis, thanks to their chloroplasts: AUTOTROPHISM (property of the photosynthetic plants);  absorption of dissolved organic matter in the water, which is digested: HETEROTROPHISM.

12. Euglena  The following experiment is carried out: euglenes are put in the darkness during several days; they are nourished thanks to the dissolved organic matter in water  What does it occur when one replaces them in the light? Some become again green and start again photosynthesis: their chloroplasts become again functional. In other cases, rarer, the euglenes lose their chloroplasts and remain heterotrophic, even in the darkness.  Did they become animals?

13. Euglena : darkness/light DarknessLight

14. Question of debate  Euglena: plant or animal?  Has euglena an animal or vegetal structure?  Does euglena behave like an animal or a plant?  What does reveal its mode of food?

15. Protests  To hold account of the difficulty for distinguishing animal-plant, one gathered the unicellular animals and the unicellular plants in a common unit: PROTESTS.

16. Protests  The protest term (from protos in Greek = first) indicates one of the kingdom of living gathering all the mobile and unicellular living beings.  Some of them, like the amoeba, resemble typical animal cells.  Others, like euglenes, borrow characteristics at the same time from animal and vegetable cells.