Question

Are all protists photosynthetic?

Answer 1

Protista is the unicellular eukaryotes found mainly in water. It resembles plants, fungi and animals in character. Most parasites are photosynthetic which are found in freshwater and oceans known as phytoplankton. The mode of nutrition depends upon their habitat.

Complete answer:
The Protista is a unicellular, eukaryotic organism phylogenetically it shows a relation with eukaryotes. The mode of nutrition of protists depends upon their nature and habitat. The Protista which bears chlorophyll are photosynthetic mainly found in freshwater and oceans and they are called phytoplankton like dinoflagellates, chrysophytes and euglena. Some protists are saprophytic which dwells on dead and decaying organic matter like slime mould whereas some protists are parasitic and protozoans like sporozoans, sarcodines, flagellates and ciliates.

Additional information:
Photosynthetic protists are autotrophic as they make their food like that of plants. It consists of several divisions and it mainly includes algae which are a unicellular small structure to giant seaweed size. Algae in photosynthetic protists are polyphyletic or paraphyletic. Some protists have uncommon ancestors which come under the polyphyletic group whereas paraphyletic show common ancestors. Algae are considered under monophyletic also but in general, they do not come under monophyletic because they do not have recent common ancestors like birds and reptiles.

Note:
Photosynthetic protists fix $80\%$ of carbon dioxide as it consists of chloroplast which perform photosynthesis similar to plants. Oxygenic photosynthesis is performed by plants, algae and cyanobacteria, where photosynthesis gets performed by Calvin cycle for fixation of carbon and carbon dioxide step by step, which consume ATP and NADPH.