Answer: (1) photosynthesis occurred
Explanation: The photosynthesis process in cianobacteria changed the composition of earth's atmosphera, rising oxygen levels. This could be possible since photosynthesis used energy from the sun to produce energetic intermediaries to synthesize sugars, and as byproduct due to water photolisis, is oxygen.
Answer:
Deuterium, (D, or 2H), also called heavy hydrogen, isotope of hydrogen with a nucleus consisting of one proton and one neutron, which is double the mass of the nucleus of ordinary hydrogen (one proton). Deuterium has an atomic weight of 2.014
Explanation:
<span>Sterilization of animals reduces the level of circulating reproductive hormones leading to increased longevity, typically due to reduce cancer mortality. The primary aim of animal sterilization is avoiding overpopulation, but this increased longevity could be an added benefit for an individual animal.</span>
I think the correct answer from the choices listed above is option B. Keratin is the protein in mammals which shows only a primary and secondary structure. Keratin is a fibrous protein forming the structural constituent of hair, feathers, hoofs, claws and many others.
