The main regulator of the calcium level in the blood is
a. parathyroid hormone.
b. thyroid hormone.
c. thymosin.
d. growth hormone.
e. insulin.
A
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____________________ is an abnormal change in the shapes, sizes, and organization of cells in a tissue. Fill in the blank(s) with the appropriate word(s)
Over the past century, sagebrush has dramatically expanded its range over the Colorado plateau's grasslands. This development has been attributed to the overgrazing of the area's grasses by cattle and sheep. This example indicates that
A) sagebrush could not exist anywhere in the absence of cattle and sheep. B) grazing has no effect on the distribution of plants. C) the relationship between sagebrush and grasses is mutualistic. D) the range of sagebrush is normally limited by competition with grasses. E) sagebrush is the dominant competitor over grasses.
Plants in the desert-adapted families Cactacea (cactus) and Euphorbia (euphorbs) share many of the same physical characteristics, such as succulent stems that store water and CAM photosynthesis, but they do not share a recent common ancestor. This evidence suggests that these families are an example of
A. divergent evolution. B. convergent evolution. C. homologous structures. D. vestigial structures.
When creating a gene library, how is recombinant DNA introduced into bacterial cells?
A) viral vectors B) gel electrophoresis C) plasmids D) DNA polymerase E) restriction enzymes