Question

Differentiate between Photoautotrophs and Chemoautotrophs.

Answer 1

Hint: The prefix “photo” refers to light and “chemo” refers to chemical reactions. The major difference between photoautotrophs and chemoautotrophs is their source of energy.

Complete answer:
 Differences between these two groups based on their energy source, habitat and other features are given below

Photoautotrophs	Chemoautotrophs
These are the organisms that synthesize their food by utilizing energy from sun light by the process of photosynthesis.	These organisms derive energy from chemical reactions to synthesize their own food by the process of chemosynthesis.
They use sunlight as an energy source.	They use inorganic energy sources such as hydrogen sulfide, ammonia, ferrous iron, elemental sulfur, molecular hydrogen etc.
They grow on land or in water wherever they can get sunlight.	They live near deep sea hydrothermal vents and active volcanoes on the ocean floor where light cannot reach.
They cannot tolerate extreme temperatures. For photosynthesis the optimum temperature range is 35 – 40°C.	They flourish at temperatures that are high enough to kill other organisms. It is a unique characteristic of chemoautotrophs.
Photoautotrophs are the producers and they form the base of the energy pyramids.	The chemoautotrophs grow in extremely hostile environments and are the primary producers of such ecosystems because the photoautotrophs cannot survive in these extreme conditions.
Photoautotrophs include green plants and all photosynthesizing algae.	Chemoautotrophs include methanogenic bacteria, sulfur oxidizing bacteria, sulfur reducing bacteria, nitrifiers, anammox etc

Note:A good example of chemoautotrophic organism is Nitrosomonas which is a gram-negative bacterium. It oxidizes ammonia into nitrite, which is a basic step of nitrification. They play an important role in the nitrogen cycle. They enhance the bioavailability of nitrogen to plants. They are useful in waste water treatment i.e., the process of bioremediation.