Biological Classification — BIOLOGY STD 11 Science — Question

Some bacteria are autotrophs, i.e., they synthesise their own organic food or ATP from inorganic substances, they are of two types:

1. They may be photosynthetic autotrophs and use light energy to synthesise their food.
2. They may be chemosynthetic autotrophs, which oxidise some inorganic compounds and use the energy released for the synthesis of their food.

Many are heterotrophs, i.e. they do not synthesise their food, but depend on an external source; they are of two types:

1. Some are parasites and depend on living organisms for their food.
2. Some are saprotrophs and depend on dead and decaying organic matter for food.