Photosynthesis occurs in the organelle called the chloroplast
The organelle where photosynthesis occurs
Just as were “invented,” somewhere between 1.6 bya and 600 mya a eukaryote ate a cyanobacterium and both survived, and that cyanobacterium became the ancestor of all chloroplasts, which is the photosynthetic organelle in all plants. As with similar previous events, it appears that it , and all plants are descended from that unique event. The invention of the chloroplast , which were the first plants. The first algae fossils are from about 1.2 bya. Most algae species are not called plants, as they are not descended from that instance when a eukaryote ate a cyanobacterium. The non-plant algae, such as , also have chloroplasts, from various “envelopment” events when algae chloroplasts were eaten and the grazers and chloroplasts survived. Below is the general outline of the tree of life today, in which bacteria and archaea combined to make eukaryotic cells, and in which the bacterium enveloped into a protist to make plants, and all complex life developed from protists. (Source: Wikimedia Commons)
The organelle in plants in which photosynthesis occurs is the
Let us see now how protists and other little animals of ponds react to alteration to theirenvironment.
1 - Some microscopic algae, like the euglena, search out light (phototaxis) and to do thisthey use an organelle sensible to the light, named stigma. With a dark paper, cover thebottom part of a test tube holding a culture of euglena. The part of the test tube exposedto light should become green, rich with algae. Make the same experiment with othermicroscopic algae and with protozoa.
2 - Add two or three drop of distilled water to a little water drop collected in a pondand watch what happens to the protists. Very probably you will see them inflate and thenexplode. This occurs because of the different saline concentration inside and outside theprotists and the osmotic pressure which is produced inside their cells.
3 - Protists are sensitive to most chemicals and generally they react by running away; insome cases instead they approach them (chemotaxis). Prepare some microscope slides withprotists and observe through the microscope their behavior when you add acidic substances(i.e.: vinegar), basic substances (i.e.: backing soda), glucose, salt, sparkling water(rich of CO2), broth, milk, tiny grain of cheese, dyes, etc. At thebeginning use very low amounts of these substances, then increase their concentration.
4 - From a pond or an aquarium, collect a hydra and place it on a microscope slide with apair of water drops. Observing this tiny polyp through the microscope, probably you willsee some sucker shaped microorganisms (trichodina) moving on its body. Watch what happensafter adding a little drop of vinegar to their water! Trichodina will escape from thehydra and probably die. Hydra itself will have launched many of its harmful paralyzingdarts.
5 - Submit protists to different stimulus such as light, temperature, electric field(about 5 V in DC). In this last case, some protists will gather on the cathode (thenegative - pole). Also amebas are inclined to move towards the cathode. Change thepolarity of the current and observe the behavior of the protists.
Internet Keyword: phototaxis chemotaxis protists.