One of the accepted scientific theories describing the origin of life on Earth is known as chemical evolution. According to this theory, which of the following events would need to occur first for life to evolve?
A. onset of photosynthesis
B. origin of genetic material
C. Synthesis of organic molecules
D. formation of the plasma membrane
The Correct Answer and Explanation is:
The correct answer is C. Synthesis of organic molecules.
Explanation:
The theory of chemical evolution proposes that life originated from simple chemical compounds in Earth’s primordial environment. Before the emergence of life, molecules essential for biological functions, such as amino acids, nucleotides, and lipids, needed to be synthesized from simpler molecules present in the early Earth’s atmosphere and oceans. This process is known as the synthesis of organic molecules.
These organic molecules would have been the building blocks for more complex structures, such as proteins and nucleic acids, which are critical components of living cells. The formation of these organic molecules, such as amino acids and simple sugars, is believed to have occurred through natural processes, including reactions driven by energy sources like lightning, UV radiation, and volcanic activity. Once these organic molecules were available, they could undergo further chemical reactions to form larger macromolecules, such as proteins and nucleic acids, which are essential for life.
Why “Synthesis of Organic Molecules” Comes First:
- Onset of Photosynthesis (A): Photosynthesis, which generates energy from sunlight, would require complex biochemical pathways like those in plants or certain bacteria. This process could not have occurred before the synthesis of basic organic molecules, as it relies on the existence of these molecules to create the energy necessary for life forms.
- Origin of Genetic Material (B): The origin of genetic material, such as RNA or DNA, is another critical step in the evolution of life. However, for genetic material to form, organic molecules like nucleotides must first be synthesized and assembled.
- Formation of the Plasma Membrane (D): The plasma membrane is essential for creating a boundary for life, maintaining internal conditions, and enabling the exchange of materials with the environment. However, the formation of a membrane-like structure would not be possible without the availability of organic molecules, including lipids, which are key components of membranes.
Therefore, the synthesis of organic molecules would be the first essential step in the chemical evolution of life, followed by the formation of more complex structures like genetic material, membranes, and eventually the onset of photosynthesis.