What is an example of an extrinsic control of cycles in population size?
a. the relationship between a species and its predators
b. hormonal changes
c. dispersal
d. population density
e. a single reproductive event
ANSWER: a
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The protrusible rasping organ in a mollusk's mouth that is used to scrape food from the substrate is
A. a veliger. B. a visceral mass. C. composed of nacre. D. a radula. E. an ammonite.
Answer the following statements true (T) or false (F)
1.Soil scientists use relative amounts of sand, silt, and clay to classify soils. 2.The B horizon soil consists of most of the humus found in soil. 3.The "wearing away" of soil by wind and water is called erosion. 4.Chemically, nutrients from inorganic fertilizers are not equivalent to nutrients from manure or compost. 5.A typical, mature tree consumes only about 5 gallons of water a day.
When constructing a genetic map of Zea mays, Creighton and McClintock used genetic markers as well as structural differences in the homologous copies of chromosome 9 that can be seen under the microscope
What are these structural differences called?
If a new anti-cancer drug is found effective in initial tests with mice, what do researchers conclude?
(a). If the drug was effective in a large number of mice, it will therefore be effective in humans. (b). If the drug was effective in a small proportion of mice, it will be effective in a small proportion of humans. (c). The mice have provided a positive control in this experiment that proves the drug is effective in humans. (d). The drug is effective in the mouse model; it must still be tested in humans. (e). The effect of the drug on mice has no bearing on the effect of the drug on humans.