Which of the following questions might scientists ask to most reliably determine if there has ever been life on Mars?
(A) How far from Earth was Mars 3.5 billion years ago?
(B) Is there scientific proof that Earth ever hadan oxygen-free atmosphere?
(C) Did Mars have the elements present in its atmosphere to support life?
(D) Was there oxygen gas on Mars 3.5 billion years ago?
Answer: (C) Did Mars have the elements present in its atmosphere to support life?
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Darwin's ideas on evolution were advanced for his time. His approach to science and natural selection were supported by what main tenet?
A. Species were unchangeable over the course of time. B. Operation of natural laws produces constant change and improvement. C. Various organisms and their structures resulted from a spontaneous action. D. The world is fixed and constant.
Compare the activation and functions of T and B cells. What will be an ideal response?
Which of the following is the correct sequence of these events in the origin of life?
I. formation of protobionts II. synthesis of organic monomers III. synthesis of organic polymers IV. formation of DNA-based genetic systems a) III, II, I, IV b) I, II, III, IV c) I, III, II, IV d) IV, III, I, II e) II, III, I, IV
A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example of
A) a cline. B) a bottleneck. C) relative fitness. D) genetic drift. E) geographic variation.