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:
An acid is a substance or compound that releases hydrogen ions (H+) when in solution. In a strong acid, such as hydrochloric acid (HCl), all hydrogen ions (H+), and chloride ions (Cl-) dissociate (separate) when placed in water and these ions are no longer held together by ionic bonding.
Answer:
The dependent variable would be B, whether or not the men develop baldness.
Answer:
°The process of photosynthesis is a physical change
Answer
The three metabolic pathways that make up aerobic respiration are really all parts of one larger pathway because the products of early pathways (like NADH) become <u>utilize</u> in the last one.
Explanation
Aerobic respiration is that type of respiration in which glucose molecule is broken down into CO2 and H2O in the presence of oxygen and 36 or 38 ATP molecules are produced.
Aerobic respiration complete in four main steps:
1. Glycolysis
In this step glucose is broken down into 2 molecules of pyruvate acid along with the production of 2 ATP molecules and 2NADH.
2. Oxidation of pyruvate
In this step pyruvate are oxidized in the presence of co-enzyme A to become Acetyl Co-enzyme A. Again 2NADH are formed in this step.
3. Kreb Cycle
It occus in mitochondria. Here acetyle coenzyme A enter Carbon fixation, reduction and regeneration phase. In this cycle 6 NADH, 2FADH2 and 2ATP are formed.
4. Electron transport chain
All NADH that are produced in above steps get oxidize and help in the production of ATP along with the release of electron and proton that help in the formation of water.
