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The earth is about 4.5 billion years old, but life did not exist on this planet until about 3.6 billion years ago, when certain kinds of bacteria and algae began to appear.
The earliest evidence for life on Earth comes from fossilized mats of cyanobacteria called stromatolites in Australia that are about 3.4 billion years old. Ancient as their origins are,
these bacteria (which are still around today) are already biologically complex—they have cell walls protecting their protein-producing DNA, so scientists think life must have begun much earlier, perhaps as early as 3.6 billion years ago.
Land plants did not appear until about 450 million years ago; reptiles, 300 million years ago; and modern mammals, 75 million years ago. The first Primates appeared about 60 million years ago, and the first apelike men, about 10 million years ago. Man, himself, has been on earth for only about 200,000 years.
If the 4.5 billion year history of the earth were to be measured in proportion to one year, man would not appear until Dec. 31, at 10:30 in the evening!
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What percentage of the Earth's atmosphere is composed of oxygen?
About 21% of the Earth's atmosphere is composed of oxygen.
What percent of oxygen on the earth?
Oxygen makes up approximately 21% of the Earth's atmosphere.
What percentage of oxygen is present in the Earth's atmosphere?
About 21 of the Earth's atmosphere is made up of oxygen.
What is percentage of oxygen in earth planet?
The Earth's atmosphere is composed of about 21% oxygen. This oxygen is crucial for supporting life on Earth through processes like respiration and photosynthesis.
Is Earth running out of oxygen?
No, Earth is not running out of oxygen. The Earth's atmosphere is made up of about 21 oxygen, which is constantly being replenished through processes like photosynthesis by plants and algae.
Was oxygen on Earth before or after life on Earth?
Elemental oxygen did not appear on Earth until some time after life did. In fact, the oxygen was produced by life carrying out photosynthesis. The first organisms on Earth were anaerobic, meaning their life processes did not involve oxygen. To most organisms like this, oxygen was highly toxic.
Effects of no oxygen on earth?
Oxygen is main gas of earth. If there is no oxygen in the earth all the life in the earth should die.
When did oxygen start to appear in the atmosphere?
Oxygen began to accumulate in Earth's atmosphere approximately 2.4 billion years ago during the Great Oxidation Event, brought about by the emergence of photosynthetic organisms that produced oxygen as a byproduct of photosynthesis.
Where do you get your oxygen on earth?
we get oxygen from the trees
The constellations you see from earth appear to change as the?
Earth revolves around the sun. That is why the constellations we see from Earth appear to change.
Why can't earth's oxygen travel through space?
Earth's atmosphere, including the oxygen, is bound to Earth by gravity.
What is the diffenerce of earth and space?
There is oxygen and gravitational force on earth but there is no oxygen and gravitational force
What percentage of the Earth's atmosphere is composed of oxygen?
About 21% of the Earth's atmosphere is composed of oxygen.
How does oxygen make life sutable on earth?
Oxygen makes it human capable of breathing in earth that's why when there is oxygen, there is life.
Why do scientists think the first living cells to appear on earth were probably anaerobic heterotraphs?
Scientists believe that the first living cells on Earth were likely anaerobic heterotrophs because early Earth lacked oxygen, and these organisms do not require oxygen for their metabolism. Anaerobic heterotrophs can obtain the carbon compounds they need for energy from organic molecules in their environment, making them well-suited for the conditions of early Earth.
Did the primitive Earth have oxygen?
No. Oxygen is not believed to have been present in the early years of Earth's history.
What percent of oxygen on the earth?
Oxygen makes up approximately 21% of the Earth's atmosphere.
