• Question: How did life appear on earth?

    Asked by edrienepadua to Christina, Colin, Jess, Samaneh, Steve on 14 Jun 2013.
    • Photo: Christina Pagel

      Christina Pagel answered on 14 Jun 2013:

      I’m not a biologist or a chemist (in fact I gave both up after GCSEs!), but I think that a few billion years ago, Earth was hot and wet – so there was plenty of energy (which helps things grow) and plenty of water (which seems to be great at helping things happen) and also lots of complex molecules – like protein type molecules in the sea, which aren’t life themselves but are much more complicated than just say a gas or a metal. Some of these molecules began to start being able to replicate themselves (I think these were RNA molecules, which are a bit like our DNA and we still have them in our bodies) and once things can start replicating, then evolution kicks in – ie the better you are at replicating, the more of you there are and anything that helps you even a little bit will make you grow more than your rivals. Then the cells became more and more complex until you have recognizable simple celled life about 3.5 billion years ago….

    • Photo: Jess Bean

      Jess Bean answered on 18 Jun 2013:

      I think Cristina’s got that pretty well explained! As a person who did chemistry and biology A Levels, and a chemistry degree that’s pretty much what scientist think happened. What I would say is going on from “cells becoming more and more complex”.

      Scientists now think that cells became complex (and so able to form complex life-forms like animals and plants) by almost eating each other. At the very beginning life was essentially what our idea of bacteria is – a ball of goop containing enzymes and other molecules. They couldn’t become anything better as that requires ALOT of energy.

      At some point a different ‘thing’ formed that was like a bacterium but could make a chemical called ATP. ATP is the bodies way of making energy and means it does not need to be taken from other places. This different ‘thing’ – a descendent of the mitochondria in the cells that make us – was then thought to have been ‘eaten’ in some way by the bacteria like organisms. This meant bacteria could then spend less of their time making energy and more time evolving!

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