What complex polysaccharide imparts flexibility to the unevenly thickened cell walls of collenchyma cells?
a. pectin
b. cellulose
c. lignin
d. starch
e. wax
ANSWER: a
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Female fireflies identify males by their flashing patterns, which are often so complicated that signals sent by one
species cannot be understood by another species. This reproductive isolating mechanism is called ____.v
a. ecological isolation b. gametic isolation c. temporal isolation d. behavioral isolation e. mechanical isolation
Which form of artificial asexual reproduction is used in many vineyards to produce disease-resistant grapevines?
a. layering b. cutting c. grafting d. budding
Flooding, landslides, soil nutrient loss, and global climate change all result from:
a. the introduction of exotic plants b. desertification c. deforestation d. ozone depletion e. biological magnification
Since 1980, the proportion of adults in the
United States who are obese has ___ and the proportion of children who are obese has ___.
a. decreased by half---doubled b. doubled---decreased by half c. doubled---tripled d. tripled---doubled e. stayed the same---doubled