A penguin's feet are nearly as cold as ice, while the bird's core body temperature is much higher. Which of the following explains this observation?
A. countercurrent heat exchange between warm blood in arteries and cold blood in veins
B. countercurrent heat exchange between warm blood in veins and cold blood in arteries
C. blood supply to legs shut off by vasoconstriction
D. no muscles in the feet of penguins to generate heat
E. heat cannot diffuse from body core to feet because feet are too far away
A. countercurrent heat exchange between warm blood in arteries and cold blood in veins
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The work of Bartel's group on the ribozyme RNA replicase supports which conclusion?
A) An RNA world could produce molecules that could self-replicate. B) Natural selection requires human oversight. C) DNA must have come before RNA. D) Life cannot come from nonlife.
Epistasis and multiple alleles differ in that
A) epistasis is an interaction between two genes, and multiple alleles are variants of the same gene. B) epistasis affects males and multiple alleles occur in females. C) epistasis only occurs in genes that have multiple alleles. D) in epistasis one gene masks another, but one allele cannot mask the effect of another.
The liquid component of blood is referred to as
A. lymph. B. cytosol. C. interstitial fluid. D. plasma. E. intracellular fluid.
Which feature of cancer cells is targeted by most forms of chemotherapy?
A) anchorage independence B) cell division C) invasiveness of surrounding tissues D) metastasis