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Fittoniya [83]
3 years ago
6

Which fossils provide information as to the mode of formation of an oxygen-rich atmosphere by about 2 billion years ago?

Biology
1 answer:
Oksanka [162]3 years ago
7 0

Answer:

The fossils that provide information on the formation of an oxygen-rich atmosphere are the stromatilites from the Precambrian era. These are layered and columnar fossils consisting mainly of cyanobacteria which were the original life form back then. These bacteria took in carbon dioxide and produced oxygen by photosynthesis as early as 2.5 billion years ago (the earth is about 4.5 billion yrs old).

Explanation:

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Answer:

C. Molecules such as cyclins are in high concentration in the cytoplasm of a dividing cell and will signal the fused cells nucleus to undergo mitosis

Explanation:

Various stages of the cell cycle are under tight regulation. Specific proteins such as cyclins and cyclin-dependent protein kinases determine if the cell would progress from one stage of the cell cycle to the next. When a cell is in the metaphase, the cyclins specific for mitosis are present in a higher amount in the cell. These cyclins bind to the specific CDKs and activate them.

The activated CDKs then phosphorylate proteins that make the cell to move through various stages of mitosis. Therefore, fusing a G1 cell with a cell in metaphase of mitosis would trigger mitosis in the G1 cell due to the presence of mitosis specific cyclins in the second cell.

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3 years ago
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3 years ago
Certain types of ________ have a relationship with certain plants where they help convert nitrogen into a usable form.
Viefleur [7K]

Answer:

Answer is C. Bacteria

Certain types of bacteria have a relationship with certain plants where they help convert nitrogen into a usable form.

Explanation:

Nitrogen is abundant in the atmosphere, but plants cannot use it because of the absence of a necessary enzyme, nitrogenase, which converts nitrogen into a usable form.  So they form a symbiotic relationship (mutually-beneficial arrangement) with nitrogen fixing soil bacteria (rhizobia) which perform biological nitrogen fixation. Biological nitrogen fixation is a process in which the symbiotic nitrogen-fixing bacteria coverts atmospheric nitrogen into ammonia and organic derivatives that plants can use to synthesize proteins.  This bacteria form nodules on the roots of plants like legumes in which nitrogen fixation takes place.

Both plants and bacteria benefit from this symbiotic relationship, as the plant obtains ammonia to synthesize proteins from nitrogen in the atmosphere while bacteria obtain carbon compounds from the plant produced through photosynthesis and a secure environment to grow. As the plant roots leave behind some of the usable form of nitrogen in the soil, this process also increase soil fertility.

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Answer:

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Explanation:

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D. Nucleus

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