Life on Earth - Biology

8.4 Life on Earth

  1. Analysis of the oldest sedimentary rocks provides evidence for the origin of life

▪ Identify the relationship between the conditions on early Earth and the origin of organic molecules

  Early earth contained no ozone layer so large amounts of UV radiation reached the earth, the reason for the absence of no ozone layer was their was little free oxygen. The volcanic emissions filled the atmosphere with methane, ammonia, hydrogen, carbon dioxide, carbon monoxide and small amounts of water vapour. The violent electrical storms and acidic rain formed the present warm and mineral - rich oceans.
  There are only two possible ways organic molecules could have formed either
  - formed on earth from simpler molecules
  - arrived from the cosmos

▪ Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth

  Meteorites and comets have been studied and have identified 74 amino acids. Certain types of meteorites such as the "carbonaceous chondrites" contain carbon - rich compounds and that life may have occurred from meteorites arriving to primitive earth, thus the theory of Panspermia.

▪ Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of life

  Theory 1 - Organic molecules arrived from the cosmos
  Certain types of meteorites such as the "carbonaceous chondrites" contain carbon - rich compounds. Theory says that these meteorites, the compounds in them, may have formed to simple organisms. Yet however the presence of these compounds are not sufficient enough to create life or form organic molecules

  Theory 2 - Chemicals for life formed on Earth
  Haldane and Oparin suggested that Earth had all the necessary basic chemical components for life on Earth. They hypothesised that the complex organic molecules could have been created from UV radiation, electrical discharges, and...