How does comparative data on genes of extant species help us to make estimates of what happened before the phylogenetic event horizon?
a. Common genes must have existed for a long time.
b. If the first life-forms consisted of RNA, then current RNA-coding genes must be the ancestral genes.
c. Common functional genes imply the minimal characteristics of early cells.
d. Because so many small genome bacteria are endosymbionts, the earliest cells must have been endosymbionts.
C
You might also like to view...
Endosymbiosis of cyanobacteria is widely accepted as an explanation for the development of chloroplasts. The presence of endosymbiotic cyanobacteria provided a cell with the advantage of ________.
A. a membrane-bound nucleus B. tolerance to oxygen C. an electron transport chain D. simple, rapid gene transfer E. photosynthesis
New cases of tuberculosis are frequently the result of reactivation of old dormant infections.
Answer the following statement true (T) or false (F)
Overproduction of the mineralocoticoid ______ causes excessive water retention
a. cortisol b. aldosterone c. epinephrine d. catecholamine e. ADH
Which of the following statements about the indirect value of trees is not true?
A. They provide shade and reduce the need for fans and air conditioning. B. In forests, they exert a natural "sponge effect" for the provision of freshwater. C. They break down dead organic matter and other types of wastes. D. Globally, they stabilize the climate because they take up carbon dioxide. E. They retain soil and prevent soil erosion.