The fossils of more than 250,000 species have been discovered, suggesting that ________
a. very few fossil species remain to be discovered
b. about half of all the organisms that lived on Earth have been described
c. the range of biodiversity was quite small during past epochs
d. many remain undiscovered and that the fossil record will never be complete
d
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The development of the reproductive tract and gametogenesis are primarily regulated by _____
A) gonadal steroids B) pheromones C) environmental factors D) diet
In the presence of water, nonpolar associations form between molecules or regions of molecules that are ____
a. partially charged b. hydrophobic and hydrophilic c. hydrophobic
d. fully charged e. hydrophilic
Measurements of bill length in a population of seed-eating birds reveals two distinct groups: small-billed individuals feeding on soft-shelled seeds and large-billed individuals feeding on hard-shelled seeds
This bimodal distribution most likely resulted from A) stabilizing selection. B) natural selection. C) directional selection. D) disruptive selection.
Pulmonary surfactant does all of the following except:a
reducing the cohesive forces of water molecules. b. reducing the surface tension of water. c. moving water across respiratory surfaces. d. preventing the alveoli from collapsing. e. reducing the energy required to stretch the lungs.