Chose the correct statement(s)(a) A very thin envelope of gases that surrounded the earth at the time of its formation.(b) About 600 billion years ago plants and animals were formed on the Earth.(c) The two probable sources of oxygen in the atmosphere are photodissociation of watermolecule and evapotranspiration.(d) The evidence of oxygen in the ocean is noted between 2.5 and 3.0 billion years ago.(a) and (b)(b) and (c)(c) and (d)(a) and (d)

How did Earth's atmosphere become oxygen-rich?A.Biological activityB.Volcanic outgassingC.Ozone depletionD.Tectonic movementSUBMITarrow_backPREVIOUS

The Atmospheric Oxygen at 1.9 billion years ago, was percent that of the modern level. A- 10% B- 15% C- 70% D- 50%

Evaluate which of the following statements about the great oxygenation event are true. Cyanobacteria in the oceans produced a large amount of oxygen as the product of a chemical reactionThe proportion of carbon dioxide in the atmosphere increasedCyanobacteria in the oceans used up most of the oxygen in the atmosphere for photosynthesisBefore the event, no organisms were capable of photosynthesisTotal available marks: 5

(Q008) The great oxygenation event, which added abundant oxygen to the atmosphere beginning about 2.4 Ga, was due to theGroup of answer choicesappearance of Ediacaran fauna.evolution of photosynthetic organisms in oceans.emergence of multicellular organisms.appearance of photosynthetic plants on land.

Which gas formed a major part of the early atmosphere?Carbon dioxideNitrogenMethaneAmmonia2The early atmosphere contained a large amount of water vapour. What happened to this?It condensed to form the oceansIt evaporated into spaceIt was used by plants for photosynthesisIt was used by animals for respiration3Which process has reduced the levels of carbon dioxide in the atmosphere to the low levels we have today?Formation of sedimentary rocksAll of theseFormation of fossil fuelsPhotosynthesis4The levels of methane and ammonia in the early atmosphere decreased over time, while the level of nitrogen increased. What is the best explanation for this?Human activities such as burning of fossil fuels and farmingMethane and ammonia are unreactive, while nitrogen reacts with oxygenMethane and ammonia react with oxygen, while nitrogen is unreactivePlants absorb methane and ammonia, and they produce nitrogen5Which two gases together form approximately 99% of the modern atmosphere?Nitrogen and oxygenNitrogen and hydrogenOxygen and hydrogenOxygen and carbon dioxide6Approximately what percentage of carbon dioxide is found in the modern atmosphere?0.9%0.004%1%0.04%