A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.
-steroid
-nucleic acid
-ion
-carbohydrate
-protein
steroid
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Deduce why viruses are excluded from the ribosomal RNA-based tree of life
A) Some viruses contain multiple strands of RNA. B) Their genetic elements cannot be sequenced. C) They can infect other organisms, which complicates the genetic comparisons. D) They lack ribosomal RNA.
Cactus spines are modified leaves adapted for dry climates, while the leaves of the Venus fly trap plant are adapted to
capture insects. These structures are therefore ____.
a. analogous b. homologous c. recessive d. homozygous e. morphogenic
The plasma proteins in humans _____
A) maintain the blood's osmotic pressure B) transport water-soluble lipids C) carry out gas exchange D) undergo aerobic metabolism E) transport oxygen
At low population density, __________ is favored, quickly producing as many offspring as possible. Fill in the blank(s) with the appropriate word(s)