These are the smallest functional units of matter that form all chemical substances and that cannot be further broken down by ordinary chemical or physical means.
A. protons
B. neutrons
C. electrons
D. atoms
E. molecules
D. atoms
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In a salt-wedge estuary the relationship between salinity and depth is that salinity:
a. is even from top to bottom. b. increases with depth. c. changes abruptly with depth. d. varies horizontally. e. decreases with depth.
What is a seed?
A. a mature pollen B. a diploid embryo C. a mature sporophyte D. a diploid spore E. a haploid gametophyte
Peptidoglycan is cross-linked between what constituents in gram-negative bacteria?
a. N-acetylglucosamine residues b. N-acetylmuramic acid residues c. phosphate groups d. DAP and D-alanine amino acids
The evolution of bilateral symmetry was a necessary precursor for the evolution of _______.
a. tissues b. segmentation c. a body cavity d. cephalization