Question

How many organisms in the list given below are autotrophs?
Lactobacillus, Nostoc, Chara, Nitrosomonas, Nitrobacter, Streptomyces, Saccharomyces, Trypanosoma, Porphyra, Wolfia
A. Six
B. Three
C. Four
D. Five

Answer 1

Hint: Autotrophs are those organisms which are capable of synthesizing their own food. In other words autotrophs can directly generate energy in the form of ATP by directly fixing carbon from the environment without depending on others. Autotrophs can use either light energy for this purpose in photosynthesis or by deriving energy from inorganic carbon sources in chemosynthesis.

Complete solution:
Now, if we see the whole list we find that Nostoc, Chara, Nitrosomonas, Nitrobacter, Porphyra, Wolfia are autotrophic organisms.
Option (1) is the correct answer as we find that there are six organisms which are autotrophic.
Nostoc, Chara, Wolfia and Porphyra are photoautotrophs as they use light energy to perform photosynthesis and fix carbon dioxide.
Similarly, Nitrosomonas and Nitrobacter are chemoautotrophs.
Option (2), (3) and (4) are incorrect answers.

Hence, Option (A) Six is the correct answer.

Additional information:
Both photosynthesis and chemosynthesis are processes by which organisms make food; photosynthesis is fueled by sunlight, whereas chemosynthesis is fueled by chemical energy.
Ecosystems rely on the capacity of certain species to transform inorganic substances into food that can be exploited (or eaten) by other creatures.
Photosynthesis, which is fueled by sunshine, is used to produce primary food in the majority of situations. Primary production occurs in a few situations using a chemical energy-based process known as chemosynthesis. All life on Earth is powered by photosynthesis and chemosynthesis working together.

Note:
Microorganisms are one of the most diverse organisms in terms of their methods of deriving nutrition. They may be photoautotrophic, chemoautotrophic, heterotrophic (parasitic, saprophytic, chemotrophic etc.), the nutritional sources including the energy, electron and carbon sources of the microorganisms are highly diverse from organic to inorganic substances.