An individual receives a flu vaccine and is well protected for the current flu season. The following flu season, the individual fails to get another flu vaccine and comes down with the flu
What is the most likely explanation for vaccine ineffectiveness in the subsequent flu season? A) Antibiotic-resistant bacteria were able to overcome the effects of the vaccine.
B) The immune system becomes weaker when continually exposed to the same virus contained in the vaccine.
C) The flu virus mutated, leading to a new strain of virus that could escape detection by the immune system.
D) Most vaccines have a limited lifetime and eventually break down and become ineffective.
C
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The three phylogenetic trees shown here all contain the same members and all have a common ancestor, but are divided up in three different ways. Which tree has members circled that are of more than one evolutionary line and does not include the most recent common ancestor of the included lineages? What type of group is this?
A. Tree 1; monophyletic.
B. Tree 2; polyphyletic.
C. Tree 2; paraphyletic.
D. Tree 3; monophyletic.
E. Tree 3; polyphyletic.
Primary growth occurs at ____ and secondary growth occurs at ____
a. apical tissue; lateral tissue b. apical meristems; lateral meristems c. primary meristems; secondary meristems d. vascular cambium; cork cambium e. lateral cambium; apical cambium
Explain the pressure flow theory. What will be an ideal response?
Poisonous or physiologically active chemicals found in various fungi include all of the following EXCEPT
A. digitoxin. B. psilocybin, a structural analog of LSD and mescaline. C. ergot alkaloids. D. muscarine and muscaridine.