Organisms first became able to live on the land after the development of the ozone layer, because it protected them from the harmful effects of sunlight.
a. true
b. false
Ans: a. true
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When a species produces gametes of different sizes (select all correct choices):
A. the smaller are designated as male and are called sperm, or spermatozoa. B. the larger are designated as female and are called eggs, or ova. C. the smaller are designated as female and are called eggs, or ova. D. the larger are designated as male and are called sperm, or spermatozoa. E. None of these choices are correct.
What type of thinking is required?
What will be an ideal response?
Which statement does not apply to haptens?
A) Haptens are also known as incomplete antigens. B) Haptens are generally too small to be immunogenic on their own. C) Haptens must bind to a more complex molecule to stimulate an immune response. D) Antibiotics such as penicillin are often haptens. E) Haptens are any nonpathogenic substance, rather than a microorganism, which can stimulate an immune response.
Unlike an anion, a cation has a(n) _____.
A) negative charge B) positive charge C) neutral charge D) electric charge