The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
Answer:
moss hornworts seed plants
Explanation: there plants that could be in the water.
Answer:
Red blood.
Explanation:
Red blood is for oxygenated blood, while blue blood is for deoxygenated blood.
The blood in Isabelle's left ventricle would be red, in other words, oxygenated. The left ventricle has oxygenated blood because this blood was first in the right ventricle. Then, it went to the pulmonary arteries, which led the blood to the capillaries close to the alveoli in the lungs. In this area, the deoxygenated blood dropped the CO₂ and took O₂ becoming oxygenated blood. Now, this blood is color-coded red and will go to the pulmonary venules, then to the pulmonary vein, and from there, it will go to the left atrium. Lastly, it will go to the left ventricle to start the systemic circulation, which is the one that distributes the oxygenated blood in the body.
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