A skeletal muscle is a composition of several components bundled one into the other. At which structural level in the muscle does contraction
occur to bring about contraction in the whole muscle?
OA myofibril
B. muscle fiber
OC. myoneural junction
D. tendon
E. fascicle

Which of the following is not a symptom of desertification? a) decrease in salt content of the soil b) lowering of the water table c) reduced surface water d) increased soil erosion e) loss of native vegetation

Nucleic acid certain protein cell membranes certain carbohydrates

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.