The Precambrian supereon, in which life first appeared and diversified to multicellular eukaryotes, lasted approximately ___ of the geologic timescale.

A. 50%

B. 30%

C. 15%

D. 85%

E. None of the answer choices is correct.


D. 85%

Biology & Microbiology

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In humans and other mammals, dosage compensation is achieved by:

A. males transcribing double the normal amount of copies of X-chromosome genes. B. females decreasing transcription of both X chromosomes by ½. C. females eliminating one X chromosome in each cell. D. females inactivating the paternal X chromosome in each cell. E. females randomly inactivating one X chromosome in each cell.

Biology & Microbiology

Asexual reproduction can involve all of the following processes EXCEPT

a. fission. b. fertilization. c. fragmentation. d. budding. e. parthenogenesis.

Biology & Microbiology

The carbon dioxide needed for photosynthesis enters the plant through the:

a) roots. b) thylakoid. c) stroma. d) root hairs. e) stomata.

Biology & Microbiology

Which hormone affects the greatest variety of cell types?

A) parathyroid hormone B) melatonin C) growth hormone D) calcitonin

Biology & Microbiology