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The Evolution of Eggs. Pt. 1

When the first amphibians appeared, the land that they were emerging onto was only inhabited by invertebrates.  This unexplored territory would make a safe haven for their young. Particularly, when compared to the trials of an aquatic habitat.

However, for early amphibians to deposit eggs out of the water, evolution had many hurdles to surpass.

Nature seemed to be stuck in this evolutionary predicament for millions of years. Amphibious species spent their lives on land, away from the majority of the world’s predators. However they still needed  to return to the water to reproduce. This process continued ,until finally, a group of tetrapod’s evolved a unique adaptation, finally allowing them to breed on the land.

This signaled a major step towards life as we know it.

The creatures that made this gigantic evolutionary leap ,were most likely, small lizard-like descendants of ancient amphibians which had developed an amniotic egg.

These eggs differed from the usual designs that existed at the time. Previously they had all been near identical to the fish or amphibians eggs of today. Instead these amniotic eggs possessed a shell. This new design prevented the eggs from drying out. While possessing a membrane which supported tissue growth and dealt with the process of  gas exchange.

This meant that these newly evolved creatures could begin to colonise the land. Tapping into an unknown range of resources with almost zero competition.  This led to huge levels of diversification, allowing evolution to create distinctly different populations all which began to specialise around their ecology. Eventually becoming distinct groups, unrecognizable from each other.  These early colonisers are the ancestors of most modern-day land animals.

 

Fascinated by eggs designs ? Keep reading Wildlife One for the evolution of eggs part-two. Coming next month… 

Alexander S. Howson

Alexander S. Howson is a naturalist and nature writer.

Along with a heavy interest in Aquatics, birds and ecology. Alexander now directs a large deal of energy attempting to re-educate the public about aquatics and promoting the conservation of a range of wildlife species.

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