The first cells evolved approximately ________ years ago
a. 2.7 billion
b. 2.2 billion
c. 5 billion
d. 3.8 billion
e. 3.2 billion
d
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How does sugar move through a plant?
1.Guard cells build up pressure, allowing dissolved sugars to enter the stomata. 2.Phloem in a sink region has lower pressure than in a source, so sugars flow out at the sink as water diffuses. 3.When the concentration of solute in the sieve tubes gets too low, osmosis allows water to flow in. 4.The pressure gradient allows dissolved sugars to reach high levels in the xylem, pushing them to a sink where they are released.
Fossils from which would be the oldest from
the Grand Canyon? a. hermit shale. b. redwall limestone. c. temple butte formation. d. bright angel shale. e. vishnu basement rocks
Which of the following groups is crucial to the structure and function of the sex hormones estrogen and testosterone?
A) Nucleic acids B) Lipids C) Carbohydrates D) Proteins
What are the three main components of modern cell theory?
What will be an ideal response?