Question

What information on the evolutionary history of animals has been obtained from fossils and from genotypes of modern species? List 2 or 3 major events in this history

Answer 1

Some of the information on the evolutionary history of animals that has been obtained from fossils and from genotypes of modern species are:

1. Eukaryotic animals have developed from prokayotes between 2500 and 1000 million years ago. This is evident from the fact that, mitochondria found in the cell of Eukaryotes have their own genetic material. It has been hypothesized that they have developed by a process known as endosymbiosis, where one cell is ingested by another and then not digested.

2. One of the major events in the geological timescale is the "CAMBRIAN EXPLOSION", where in the mere duration of 30 million years modern organisms like sponges, jellyfish and corals, flatworms, molluscs, annelids, insects, echinoderms etc developed. This is a period of great importance because it suggests that during this period our atmosphere must have started being rich in oxygen content which supported the growth of such diverse organisms. Research also suggests that the period before Cambrian explosion there was the evolution of the HOMEOBOX gene which is important for many developmental processes.

3. Archeopteryx from fossil records shows the divergence of two different groups of animals from a single one. Its characters was found to be a mixture of birds and reptiles and it said to be the transitional stage between birds and reptiles.

4.  DNA evidence also suggests that the great apes evolved during the Oligocene while  Hominids appear in the fossil record in the Pliocene.

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