• Question: How did animals first start. How were the first given birth to.

    Asked by 07heaneys to Alastair, Emma, Hywel, Keith, Vicki on 18 Jun 2010 in Categories: .
    • Photo: Keith Brain

      Keith Brain answered on 18 Jun 2010:

      Its likely that we life started off as self-copying molecular, probably of compounds that looked like DNA or RNA. Over a long time (very long time!) these molecules might have started to aggregate together, share raw material etc …

      One part of this story that is interesting is how self-replicating DNA/RNA molecules might have become organised into cells, which are covered a layer of fats. But fatty acids are rather simple molecules, made of carbon, hydrogen and oxygen (with a touch of phosphorus in the cells that around now). If such fats were around in the early earth, then the formation of balls of chemicals surround be a fatty layer is quite easy to achieve. If you take such fat, shake it about, then it spontaneously forms myceles or liposomes which can trap molecules inside. Lots of fancy skin creams contain liposomes – which are just balls of fat … shaken, not stirred 😉

    • Photo: Alastair Sloan

      Alastair Sloan answered on 18 Jun 2010:

      Animals first started when the Earth cooled and the basic chemicals formed some genetic material called RNA. We think that RNA is the first “life” as it can self replicate. Once that had formed then over millions of years it evolved into single cell life then multicellular organisms. Mutations and changes for these organisms to adapt to their surroundings meant that organisms and lifeforms evolved over millions of years to be the diverse animals of today.

      How were the first given birth to, well we are not really sure. The early major colonisers of Earth were the dinosaurs who laid eggs, only mammals give birth to live young. The early mammals were outnumbered by the dinosaurs so didnt really develop that much, but after the dinosaurs became extinct the mammals developed quickly. That’s important because the early mammals (similar to the modern day platypus) still laid eggs, but the early marsupials gave birth to live young. However, these were underdeveloped, so the larger marsupials kept them in a pouch until they developed fully (like a kangaroo today). As mammals evolved, they became far more efficient and the females developed placentas which meant that their young were born much more developed. This is a great example of evolution, because by being born developed actually makes them more resistant to predator attack

    • Photo: Vicki Stevenson

      Vicki Stevenson answered on 18 Jun 2010:

      Ok – I’m a bit shakey on this one as it’s not really my area.
      I think that initially they were simple cells floating around in the sea, then these developed into more complex cell based life, which gradually developed into the first animals – sponges seem to be the first animals and they seem to be able to propagate by fragments of them falling off and developing into new sponges. Things gradually got more complex from there until we reached animals that actually give birth

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