Why might life be much older than LUCA?
What will be an ideal response?
ANS:
LUCA was the last ancestor to leave descendants (all of the present life on Earth) and thus may have been de-rived from former life-forms. LUCA represents a phylogenetic event horizon beyond which we cannot see.
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What led to the increase in oxygen levels in the atmosphere on primitive Earth?
a. the first photosynthetic reactions b. photosynthetic cells that used water and not H2S as a source of electrons c. the development of cellular respiration pathways in cells d. the use of glycolysis in cells e. photosynthetic pathways that stripped oxygen off of carbon dioxide and retained only the carbon in subsequent steps
Infection with the Ebola virus is characterized by:
A) a progressive onset of high fever. B) internal and external hemorrhage. C) the formation of cutaneous blisters. D) paralysis of the respiratory muscles.
The ultimate source of energy for most life on Earth is:
A) oxygen. B) the sun. C) the metabolic processes found in all living things. D) heat from the Earth.
Which is true regarding somites in an embryo?
A) Somites are found inside the notochord. B) Somites will become vertebrae. C) Somites will form the skull. D) Somites will form the lungs.