< b="" />Sequence of Substances During the Origin of Life on Earth< />

The origin of life on Earth is still a topic of scientific investigation and debate. However, several theories propose a sequence of substances that appeared during this process. The correct answer to the given question is option 'D', which includes the sequence of substances as ammonia, amino acids, proteins, and nucleic acids. Let's explore this answer in detail:

< b="" />1. Ammonia< />
Ammonia (NH3) is a compound that consists of one nitrogen atom bonded with three hydrogen atoms. It is believed to have been present on early Earth due to volcanic activity and the presence of nitrogen gas in the atmosphere. Ammonia could have played a role in the formation of organic molecules necessary for life.

< b="" />2. Amino Acids< />
Amino acids are the building blocks of proteins. They contain both an amino group (-NH2) and a carboxyl group (-COOH) attached to a central carbon atom. Amino acids can spontaneously form under certain conditions, such as the presence of energy sources like lightning or UV radiation, and the availability of organic compounds. These organic compounds could have been synthesized from the primordial soup of ammonia, water, and other simple molecules.

< b="" />3. Proteins< />
Proteins are complex macromolecules composed of chains of amino acids. They play crucial roles in various cellular functions and are essential for life as we know it. The formation of proteins requires the linking of amino acids through peptide bonds, which can be facilitated by the presence of certain catalysts like clay minerals or iron-sulfur clusters. These catalysts could have assisted in the assembly of amino acids into proteins.

< b="" />4. Nucleic Acids< />
Nucleic acids, such as DNA and RNA, store and transmit genetic information. They are composed of nucleotide units, which consist of a sugar molecule (ribose or deoxyribose), a phosphate group, and a nitrogenous base. It is believed that nucleotides could have formed from simple organic molecules present on early Earth, such as sugars, phosphates, and nitrogenous bases. The assembly of nucleotides into nucleic acids could have occurred through various chemical reactions.

< b="" />Conclusion< />
In summary, the correct sequence of substances that appeared during the origin of life on Earth is ammonia, amino acids, proteins, and nucleic acids. While this sequence is the most widely accepted, it is important to note that the exact processes and conditions leading to the origin of life are still under investigation and subject to ongoing research and debate.

See the situation on earth were anaerobic and there was rarely free oxygen avaible so oxidation was not general. so during evolution nitrogen should be evolved first then ammonia then etc as the sequence of polymerization can only happen if the forming atoms can exists in a unit