How do insects overcome the inefficiency of their hemolymph flow in taking oxygen to their tissues?
A. Their bodies are tubular, thus increasing the body surface area where gaseous exchange takes place.
B. Insects have highly vascularized extensions of their body walls, called parapodia.
C. Their respiratory system consists of tracheae, which are tiny air tubes that take oxygen directly to the cells.
D. A countercurrent mechanism ensures that the maximum amount of oxygen is absorbed from the environment.
Answer: C
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Biologists are not yet able to apply the phylogenetic species concept to all forms of life because ____
a. individuals within populations exhibit genotypic and phenotypic variation b. detailed evolutionary histories have been described for relatively few groups of organisms c. many forms of life reproduce asexually d. evolutionary history cannot be determined for extinct species e. it does not distinguish closely related species that are nearly identical in appearance
In the modification of eukaryotic mRNA, ________ cap and ________ tail are usually added to the transcript.
A) an acetylated-guanine; a poly-cytosine B) a poly-guanine; a methyl group C) a poly-thymine; an acetyl group D) a methylated-guanine; a poly-adenine E) a methylated-adenine; a poly-guanine
What does DNA ligase do?
a. breaks the hydrogen bonds between base pairs b. seals gaps between assembled nucleotides c. provides energy for nucleotide assembly d. acts as an initiator to start the replication process e. seals the ends of the replicated DNA molecule
What kind of fruit is formed from fused ovaries of several individually pollinated flowers?
a. aggregate b. simple c. multiple d. accessory e. berries