Andrew Roger, a molecular biologist at Dalhousie University in Canada, who was not involved in the study, also said these organisms evolved in a very different environment from today’s. Roger said that the Earth’s atmosphere did not contain significant levels of oxygen until 2.4 billion years ago and did not reach the present oxygen levels until 650 million years ago.
“Atmospheric oxygen levels probably played an important role in the evolutionary timing of eukaryotes, since most eukaryotes use oxygen for their metabolism,” he said . There is even the possibility that newly developed steroids have allowed the original eukaryotes to move into new oxygen-rich environments.”
It was a breakthrough step from a single-celled organism to a multi-celled organism, to an animal and then to us humans. Remember, it took just over 3 million years to evolve from apes to humans, but to evolve from single-celled organisms to multi-celled organisms took us billions of years.
Steroids are a class of organic compounds containing a characteristic arrangement of four cycloalkane rings joined together. Examples of steroids include the cholesterol-eating fats, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone. The core of the steroid consists of 20 carbon atoms bonded together taking the form of four fused rings: three cyclohexane rings (referred to as A, B, and C rings in the right figure) and one cyclopentane ring (D ring). . The steroids differ for each functional group attached to the four-ring core and the oxidation of the rings.
Steroids are fat-soluble organic compounds of natural or synthetic origin that are composed of 17 carbon atoms arranged in four rings and include sterols and bile acids, adrenal, and hormones. sex. Some steroids are of natural origin, such as digitalis compounds, and precursors of certain vitamins.