All species on Earth today are descended from a cell that lived as early as:
a. 4 billion years ago.
b. 570 million years ago.
c. more than 5 billion years ago.
d. more than 10 billions years ago.
e. 1.4 billion years ago.
a
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Which statement is true?
a. Atmospheric nitrogen is abundant and easily fixed by plants and phytoplankton. b. Climate models used by scientists only incorporate human contributions to the atmosphere. c. Fossil fuels are regenerated too slowly to be considered a renewable resource. d. Carbon and other elements are permanently sequestered within sediment on the ocean floor.
Many cancers have a mutation that changes a valine to a glutamic acid in the RAF kinase protein which phosphorylates proteins that promote cell division. This mutant protein is a constitutively active kinase. What type of allele is this mutant allele?
A) hypomorphic allele B) hypermorphic allele C) null allele D) antimorphic allele
Suppose a cell lacks functional Shugoshin. What is the predicted effect on cohesin?
A) Cohesin will be cleaved prior to metaphase in mitosis. B) Cohesin will not be cleaved during mitosis or meiosis. C) Cohesin at the centromeres of sister chromatids will be cleaved during meiosis I. D) Cohesin on the arms of sister chromatids will be cleaved during meiosis II. E) Cohesin will be cleaved normally during mitosis and meiosis I.
In the summer of 2016, people sweltering in the midwestern United States didn't say, "It's not the heat, it's the humidity." Instead, they said "It's the cornsweat." Many blamed surrounding acres of cornfields for increasing the perceived temperature, already at record levels. Considering what you know about the water cycle, what information might address this idea?
A. Since most atmospheric water vapor over land comes from evaporation from lakes and rivers, corn has nothing to do with it. B. Since local temperatures are based on climate, and plants capture carbon dioxide, the fields of corn plants should actually decrease local temperatures. C. Most atmospheric water vapor in the Midwest has been blown there from water that evaporated from the ocean. Corn has nothing to do with it. D. Since 90% of the water in the atmosphere over land arrived there by evapotranspiration, it is reasonable to conclude that increased acreage of corn cultivation could increase local humidity.