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.
Explanation:
The rate of photosynthesis increases withe increase in temperature. Photosynthesis like any other chemical reaction responds positively to an increase in temperature.
At high temperatures, enzymes that takes part in the photosynthesis can be destroyed. This is 20°C where enzymes are usually denatured.
- Photosynthesis is the process where green plants manufacture their food using inorganic substances from the environment.
- During photosynthesis, plants combines carbon dioxide with water and produces organic molecules and oxygen.
- Like any other chemical reaction, the reaction will proceed faster with an increase in temperature.
Hypothesis: If temperature is increased then the rate of evolution of oxygen gas increases because the rate of chemical reactions increases with increase in temperature.
Since oxygen is a by product of photosynthesis, we can quantify its rate of production as temperature increases.
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Answer:
Bones are organs composed of hard living tissue providing structural support to the body – it's scaffolding. It is a hard matrix of calcium salts deposited around protein fibers. Minerals make bone rigid and proteins (collagen) provide strength and elasticity. ... The outer layer of bone is called Cortical bone.
