Which statement is true about starfish, sand dollars, and sea urchins?
a. They are sessile.
b. They are radially symmetrical.
c. They have outer skeletons or shells made of chitin.
d. They belong to the arachnids.
e. They all have a distinct head, thorax, and abdomen.
Answer: b. They are radially symmetrical.
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Cell theory is one of the foundations of biology. What are the tenants of the cell theory? Check all that apply.
_____ All organisms are made up of more than one cell. _____ All cells have the ability to move. _____ Cells carry genetic material passed to daughter cells during cellular division. _____ Cells arise from other cells through the process of cell division. _____ Organisms are formed through spontaneous generation _____ All living organisms consist of cells
Biologists refer to the fit of an organism to its environment as _______.
a. selection b. adaptation c. resistance d. regulation
Regulation of transcription of bacterial genes takes place at which two levels?
What will be an ideal response?
Humans intrude into the nitrogen cycle by
A. disposing of human manure rather than allowing it to recycle. B. manufacturing nitrogen compounds to apply to agricultural fields. C. using antibiotics that destroy important bacteria in the nitrogen cycle. D. tying up nitrogen in human body mass because of overpopulation.