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A SPONGE-LIKE SINGLE-CELL ANCESTOR

Focus: GS-III Science and Technology

Introduction

  • The Smithsonian Institution points out that an environment devoid of oxygen, and high in methane, was not fit for animal life, though it could ‘host’ microorganisms which could cope with the incoming sunlight and use it to generate energy for living.
  • This was around 3.4 billion years (Byr)ago, about 1 Byr after the Earth itself was born. In the process, these microorganisms generated the gaseous waste product called oxygen.
  • About 2 Byr later, thanks to this ‘great oxidation event’, the amount of oxygen on Earth became an important component of the Earths’ surface, and amenable for animal life.

Mistranslation of DNA

  • Choanoflagellates are the closest living relatives of animals that appeared nearly a billion years ago.
  • Thanks to recent genome sequencing efforts, they have been shown to possess some key processes, such as cell signalling, cell–cell adhesion, that were thought to be present only in multicellular animals.
  • Over time, animal cells also evolved to produce increased amounts of molecules called reactive oxygen species (ROS), which are involved in many essential cell activities but toxic at high levels.
  • In addition, more complexity necessitates a substantial increase in the genome size of the animal with concomitant increase in all transactions in the cell: DNA, the genetic material in the cells of the various organs, their transcription of the information to messenger RNA (mRNAs), then translation of these into the amino acid sequences that make individual proteins in the cells through what are called tRNAs — at least one per amino acid.
  • If a wrong interpretation of the genetic code at the protein level occurs, it will lead to functional disorders and even diseases.

Great Oxidation Event

  • Great Oxidation Event refers to a series of chemical changes that geologists and geochemists have observed in rocks that are between 2.5 and 2.3 billion years old.
  • These changes were the result of oxygen given off by ancient cyanobacteria (blue-green algae). Communities of this bacteria lived in shallow seawater and were preserved in rocks as structures called stromatolites.
  • Stromatolite means ‘layered rock’. It is a rocky structure created by the activity of colonies of single-celled bacteria, mostly cyanobacteria.
  • Oxygen first accumulated in Earth’s atmosphere at this time and has been present ever since.

-Source: The Hindu

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October 2022
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