Question

Summarize the major stages of chemical evolution.

Short answer

The process of chemical evolution has taken place in three stages, namely- inorganic stage, organic stage, biological stage.

Step-by-step solution

Step 1. Chemical evolution

This process describes the appearance of the first life forms on earth due to chemical changes. When the earth was formed, it was quite unstable as there were frequent volcanic eruptions earthquakes, which resulted in various combinations of molecules forming biomolecules.

Step 2. Stage first of chemical evolution- Inorganic stage

Scientists have considered that the atmosphere was made up of gases like hydrogen, ammonia, water vapors, and methane in an early stage. Oxygen was absent during this time, and there were intense ultraviolet radiations from the sun which finally resulted in the conversion of these substances into biomolecules such as amino acids. Gradually oxygen was formed, which resulted in ozone formation blocking UV radiations. The instability of the earth due to frequent volcanic eruptions has also contributed to the formation of these chemicals.

Step 3. The second stage of chemical evolution- Organic stage

In the second stage, the simple formed molecules combined to form larger biomolecules like proteins, fats, and carbohydrates. These biomolecules are aggregated to form Protobionts which have properties of living things.

Step 4. The third stage of chemical evolution –Biological stage

In this stage, the protobionts gained other features of living things, such as started reproducing and passing on the genetic information in the form of molecules. Various other phenomena like mutation, natural selection, etc., resulted in various changes in the genetic makeup of an organism due to which new life forms originated, which are the early Prokaryotes.