Free oxygen formed on earth after
(1) photosynthesis occurred
(2) much of the iron in the oceans had oxidized
(3) two phase changes of water
(4) surface temperatures vaporized all the water

(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.

red color of the tomato due to the lycopene pigment in chromoplast, and the sunflower plastid is chromoplast

the right answer is a. skin cells forming from sunlight.

the liver is an organ endowed with a fantastic ability to regenerate

. thus, if a hepatectomy (ablation) of 70% of the hepatic mass is performed in the rat, there is complete recovery in 7 to 10 days.

prokaryotes are beings that have existed since the existence of life on earth, and do not come from another realm.

ribosomes are organelles that exist naturally in eukaryotes, either in free form or attached to the endoplasmic reticulum.

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