All blood cells and platelets originate from stem cells
a. true
b. false
Ans: a. true
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Which of the following play a central role in animal camouflage?
a. pattern and simple colour b. pattern and behaviour c. simple colour and behaviour d. simple colour, pattern, and behaviour
Bacteria isolated from a hot tub at 39 °C are probably which of the following?
A. thermophiles B. psychrotrophs C. mesophiles D. hyperthermophiles
Which of the following statements is false?
A. The rapid depolarization phase of the action potential in pacemaker cells results from the influx of sodium through voltagegated sodium channels. B. The repolarization of the pacemaker cells following an action potential allows for the heart to relax between contractions. C. The resting membrane potential of cardiac pacemaker cells gradually becomes less negative on its own. D. Pacemaker cells repolarize by opening voltage-gated potassium channels. E. None of the answer options is false.
Which of the letters in the above figure represents
the anther where pollen is produced? a. A b. B c. C d. D e. none of these