Chapter 28, Problem 4A

Summary Introduction

To determine:

The steps that probably occurred first in the chemical and biological evolution of life.

Introduction:

Evolution is the process of change in all the forms of life among generations. The origin of cells is considered to be the first stage of life on Earth. The cell is the basic structural and functional unit of any living organism. It is the smallest unit of life which consists of cytoplasm enclosed within a membrane. This cytoplasm contains many biomolecules like proteins and nucleic acids. The cells are assumed to evolve in four phases:

Step 1. Organic Monomers: Monomers arise from the reaction in atmosphere.

Step 2. Organic Polymers: In this stage, the organic molecules are self-assembled to form a larger aggregate which is named Polymers.

Step 3. Protocells: A protocell has a lipid protein membrane which carries on energy metabolism. The molecules are packaged into protocells, which are like droplets enclosed with membrane that separate these polymers from the surroundings.

Step 4. Living cells: Protocell’s self-replication paid the way for inheritance possible by the process of passing on the genetic information. The first true cell was considered to contain RNA genes, which supports replication due to the presence of proteins.