Flashcards in The Gift of Plants RR Deck (28):
The earth's first atmosphere was made up of...
The earth's second atmosphere was made up of...
nitrogen and carbon dioxide
What were the first chemicals in the earth's atmosphere?
hydrogen, oxygen, carbon, and nitrogen
What chemicals were first formed in the earth's atmsophere?
water, methane, and ammonia
What allowed early life to form?
ultraviolet light energizing small molecules that formed into larger molecules.
What was the problem with ultraviolet light?
It can also turn larger molecules back into smaller molecules, so early living things had to avoid it.
When might chlorophyll have been first formed?
likely very early on in the history of life on earth
What is the advantage of chlorophyll?
It allows the creation of food molecules directly from carbon dioxide and water using visible light, not ultraviolet.
What happened once chlorophyll emerged?
Ultraviolet-using organisms quickly died out.
How did early plants speed up the creation of the earth's second atmosphere?
As green plants multiplied, they produced oxygen at an ever increasing rate. The oxygen combined with the compounds of the first atmosphere to form the compounds of the second atmosphere.
About what time may plants have become the dominant life form on earth?
less than a billion years ago
What are the compounds of the earth's third atmosphere?
oxygen and nitrogen
How long did the third atmosphere last?
It is our atmosphere today.
Why did the third atmosphere emerge?
plants used up carbon dioxide and produced oxygen
Why could early life forms not engage in energetic activity?
There was not enough energy in their food.
What allowed animal cells to gain more energy from their food?
They could combine oxygen with food molecules as they were being broken down, which creates much more energy.
How much more energy does combining food molecules with oxygen produce?
about 20 times more
What did the early animals do with their extra energy?
develop tissues and organs that did not directly relate to eating
What was the main thing which early animals used their extra energy for?
developing hard, protective shells
When did the first fossils appear?
six hundred million years ago
What fraction of the history of life includes fossils?
When did life start to move to land?
400 million years ago
Why did life move onto land?
The ozone layer formed a protective barrier against ultraviolet light.
What is ozone?
Where is ozone found?
the upper atmosphere, about 15 miles above the surface
How is ozone formed?
energy from sunlight adds an extra oxygen to O2
What is a difference between land and sea life?
land life can develop complex appendages, while sea life must be streamlined because water is viscous