The first reefs on earth were built by:
A. bacteria.
B. calcified sponges.
C. proteinaceous sponges.
D. algae.
E. corals.
A
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A toxin that is secreted and acts upon a specific cellular target is called a(n)______
Fill in the blank(s) with the appropriate word(s).
Carbon-14 is useful in determining the age of a fossil up to about
A. 40,000 years ago. B. 10,000 years ago. C. 20,000 years ago. D. 50,000 years ago. E. 100,000 years ago.
The Vienna Convention for the Protection of the Ozone (1985) and the Montreal Protocol (1987) included agreements for the phasing out of:
A) nuclear weapons. B) synthetic pesticides. C) chlorofluorocarbons. D) emissions of carbon dioxide. E) smelting of heavy metals.
In his book The Origin of Species, Darwin argued that species living today descended from a succession of ancestral species. What mechanism did Darwin propose to explain how evolution occurs?
A. competition B. natural selection C. artificial selection D. overproduction