Earth Science

Life on Earth

Characteristics and Origins of Life

Study Tip
The central dogma of biology validates the importance of the Miller-Urey experiment: DNA transcribes into RNA, which translates into amino acids, which combine to form proteins,  the building blocks of life.

The Origin of Life

  • Characteristics of Life: to be considered alive a molecule must...
  • Be organic. The organic molecules needed are amino acids, the building blocks of life.
  • Have a metabolism
  • Be capable of replication
Study Tip
The central dogma of biology validates the importance of the Miller-Urey experiment: DNA transcribes into RNA, which translates into amino acids, which combine to form proteins,  the building blocks of life.
  • Learning about the origin of life: to look for information regarding the origin of life, scientists…
  • Perform experiments to recreate the environmental conditions found at that time
  • Study the living creatures that make their homes in the types of extreme environments that were typical in Earth’s early days
  • Seek traces of life left by ancient microorganisms, also called microbes, such as microscopic features or isotopic ratios indicative of life
Polypeptide chains
Amino acids form polypeptide chains

Amino Acids

  • Amino acids are the building blocks of life because they create proteins
  • Linked together by covalent bonds to form polymers called polypeptide chains
  • Proteins are the most abundant class of biological molecules
  • Miller-Urey Experiment
  • Might have also originated at hydrothermal vents or deep in the crust where Earth’s internal heat is the energy source
  • Placed hydrogen, methane, and ammonia in a flask of heated water that created water vapor, which was called primordial soup and simulated the Earth’s early atmosphere. Sparks simulated lightning, and the gases combined to form water-soluble organic compounds including amino acids
Miller-Urey experiment
Setup of the Miller-Urey experiment

Earth Science

  • Might have also originated at hydrothermal vents or deep in the crust where Earth’s internal heat is the energy source
  • Meteorites containing amino acids currently enter the Earth system and so meteorites could have delivered amino acids to the planet from elsewhere in the solar system
Concept Check
  • Why must something that is alive be capable of replication?
  • Why do scientists that are interested in the origin of life study extreme environments?
  • How do scientists learn about the origins of life?