The survivorship curves of the American robin, a type of migratory songbird, and the common green darner, a type of migratory dragonfly, are shown below. What statement is best supported by the survivorship curves? A. A very high proportion of common green darners reach adulthood and live to older ages. B. Younger American robins have higher death rates than older American robins, while younger and older common green darners have similar death rates. C. American robins have a high survival rate for most of their lifespan and then decline rapidly in old age. D. American robins have similar death rates throughout their lifespan, while the death rate of common green darners changes over their lifespan.

Neelaredoxin is a 15-kda protein that is a gene product common in anaerobic prokaryotes. it has superoxide-scavenging activity, and it is constitutively expressed. in addition, its expression is not further induced during its exposure to o2 or h2o2 (silva, g., et al. 2001. j. bacteriol. 183: 4413–4420). which of the following statements best describes neelaredoxin synthesis? a-neelaredoxin is produced at all times; levels are constant even when exposed to o2 or h2o2.b-neelaredoxin is produced at all times; exposure to o2 or h2o2 increases expression. c-neelaredoxin is produced at all times; exposure to o2 or h2o2 decreases or prevents expression. d-neelaredoxin is only produced when there is exposure to o2 or h2o2.

Give an example of a trait that is controlled by more than one gene.

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?