The earliest stromatolites were probably formed by
A) anoxygenic phototrophs.
B) anoxygenic lithotrophs.
C) oxygenic phototrophs.
D) oxygenic lithotrophs.
Answer: A
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Consider the data in Fig. 46.8 illustrating the age structure of France and India. In many parts of the world, the average age of reproductive maturity is increasing as humans move from urban to rural environments
Suppose that the current average age of first reproduction is 15 years in India and 20 years in France. How would a 5-year increase in the average age of reproductive maturity in both countries be expected to affect the per capita birth rate, and would this effect be greater in France or in India? A. increase in per capita birth rate, greater effect in India B. increase in per capita birth rate, greater effect in France C. decrease in per capita birth rate, greater effect in India D. decrease in per capita birth rate, greater effect in France
Estradiol is a potent stimulator of vitellogenesis (yolk production) in egg-laying vertebrates. Increasing evidence suggests that many pollutants, for instance those derived from pulp mills, may mimic the actions of estradiol. If one were to place a sexually immature fish in water containing pulp mill effluents, what might you expect would occur?
A. The rate of vitellogenesis would decline. B. The rate of vitellogenesis would increase. C. The fish might reach sexual maturity sooner. D. The rate of vitellogenesis would decline and the fish might reach sexual maturity sooner. E. The rate of vitellogenesis would increase and the fish might reach sexual maturity sooner.
An immune response to a tissue graft will differ from an immune response to a bacterium because _____
A) MHC molecules of the donor may stimulate rejection of the graft tissue, but bacteria lack MHC molecules B) the tissue graft, unlike the bacterium, is isolated from the circulation and will not enter into an immune response C) a bacterium cannot escape the immune system by replicating inside normal body cells D) the graft will stimulate an autoimmune response in the recipient
The cardiac muscle is supplied with nutrients from the blood within the heart itself.
Answer the following statement true (T) or false (F)