Which of the following respiratory surfaces lack physical protection from the external environment?

a. internal gills
b. lungs
c. tracheal system tubes
d. external gills


Ans: d. external gills

Biology & Microbiology

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At rest, a nerve cell has a high concentration of ____ inside and a high concentration of ____ outside

a. acetylcholine; chlorine b. sodium; potassium c. potassium; sodium d. calcium; phosphorus e. phosphorus; calcium

Biology & Microbiology

Which structure is a rod of stiffened support

tissue? a. A b. B c. C d. A and B e. none of these

Biology & Microbiology

Each cell is able to maintain an internal state of chemical and physical stability. This is called

a. metabolism. b. homeostasis. c. physiology. d. adaptation. e. evolution.

Biology & Microbiology

Which molecule is believed to have preceded the other two during the evolution of life?

A. DNA B. RNA C. Proteins

Biology & Microbiology