Were there any eukaryotic cells on Earth 1.5 billion years ago?
A) Yes, they first appear in the fossil record around 3.5 billion years ago.
B) Yes, they first appear in the fossil record around 2 billion years ago.
C) No, they do not appear in the fossil record until around 1 million years ago.
D) No, they do not appear in the fossil record until around 500 million years ago.
B
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Nucleic acids have primary, secondary, tertiary, and quaternary levels of organization.
Answer the following statement true (T) or false (F)
An incompletely dominant gene controls the color of
chickens so that BB produces black, Bb produces a slate-gray color called blue, and bb produces splashed white. A second gene controls comb shape, with the dominant gene R producing a rose comb and r producing a single comb. If a pure-breeding, black chicken with a rose comb is mated to a splashedwhite chicken with a single comb in the F2 generation, what fraction of the offspring will be blue with rose comb? a. 9/16 b. 3/8 c. 3/16 d. 1/8 e. 1/16
Although the placenta acts as a filter for many harmful substances, some are able to pass from mother
to embryo. They include a. alcohol. b. toxins in cigarette smoke. c. caffeine. d. drugs. e. all of these.
The structure in cnidarians with both digestive and circulation functions is the ________
Fill in the blank(s) with correct word