One critical requirement for life to arise on Earth was time for:a
the atmospheric temperature to increase sufficiently.
b. molecules to accumulate and react with one another.
c. the Earth's various climates to stabilize.
d. the salinity of the oceans to stabilize.
e. the ozone layer to form, so that the level of ultraviolet radiation was reduced.
B
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A human fetus that has the genotype XO will be designated female because:
A. female sex is determined by the presence of a gene on the X chromosome. B. female sex is determined by the absence of TDF, a protein produced by a gene on the fetus's Y chromosome. C. female sex is determined by only one X chromosome. D. female sex is determined by the presence of TDF, a protein produced by a gene on the fetus's X chromosome.
Heterospory refers to having ____
a. both male and female gametes b. two types of spores in two different types of sporangia c. both male and female parts on the same plant d. separate male and female plants e. both sporophyte and gametophyte generations
All EXCEPT which of the following are
disadvantages to sociality? a. predator avoidance b. cannibalism c. competition for food d. contagious diseases e. parasite infestation
Which of the following is a correct association?
A) kinase activity and the addition of a tyrosine B) phosphodiesterase activity and the removal of phosphate groups C) GTPase activity and hydrolysis of GTP to GDP D) adenylyl cyclase activity and the conversion of cAMP to AMP