Where did the invertebrates come from: A brief overview

Where did it all begin?

          In the beginning all there was on earth were Prokaryotes, organisms that lack membrane enclosed organelles and a nucleus, and they don't have linear chromosomes. The Prokaryotes can be split into the two kingdoms Eubacteria, which include Cyanobacteria and Spirochetes, and the other Archaea (Archaebacteria). Everything else in the world now a days is classed under the Eukaryotes which is comprised of four kingdoms Fungi, Plantae, Protista and, Animalia. All of the invertebrates are part of the kingdom Animalia.

          The kingdom Animalia is defined as multicellular, ingestive, heterotrophic organisms, that is to say that the feed on other organisms and organic materials. All of the animal kingdom has a common ancestor that would have been a Prokaryote mean that you and I come from the same place as the invertebrates did.

           The earliest known record of life on Earth is somewhat of a debate. One record was found to be 3.8 billion years old however, they were trace records which could have also just been mineral deposits. The earliest known record that isn't contested is 2 billion years old but these also contain multicellular organisms which suggests that life must have evolved earlier than this date. Therefore at our current understanding the best estimates guess that life first appeared between 3.8 and 2.5 billion years ago.

           After life developed on the planet it began to evolve. At about 1.6 billion years ago plants and animals had their last common ancestor which means it took somewhere from 2.2 to 0.9 billion years for animals to first appear in the Earths oceans. Fossil records suggest that the earliest time for invertebrates to have existed was at least 600 million years ago (mya) with most extant species found today being found in the fossil record by 500 mya. It then took another 130 million years for any of the animal kingdom to walk on land and become a terrestrial species.

            So since the beginning it took the invertebrates 3.2 to 1.9 billion years to evolve from their prokaryote ancestors. Next time I'll start to go into more detail of where early life started and how the invertebrates came to rule the planet for a time.