Origin & Evolution of Life: January 2019

There are two dominant and contrasting classes of origin of life scenarios: those predicting that life emerged in submarine hydrothermal systems, where chemical disequilibrium can provide an energy source for nascent life; and those predicting that life emerged within subaerial environments, where UV catalysis of reactions may occur to form the building blocks of life.

Around 4 billion years ago there lived a microbe called LUCA: the Last Universal Common Ancestor. There is evidence that it could have lived a somewhat 'alien' lifestyle, hidden away deep underground in iron-sulfur rich hydrothermal vents.

Chaetognaths, or arrow worms, have a distinct jaw structure composed of dense protein matrix and a fibrous substance called chitin. These organisms display an ambiguous set of developmental and morphological features, making them difficult to categorize on the Tree of Life.