Not all sperm produced by the testes are functional. A sperm with a defective acrosome would
A) not be able to swim.
B) produce multiple flagella.
C) not survive the acid pH of a vagina.
D) not be able to penetrate a egg.
E) be able to swim, but would travel in circles, unable to navigate a female reproductive tract.
D
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When a cell secretes a growth factor that binds to receptors on its own membrane preventing it from proliferating, this is an example of ____.
A. direct intercellular signaling B. endocrine signaling C. contact-dependent signaling D. paracrine signaling E. autocrine signaling
Microbes that are found in hot springs or other extreme environments are most specifically likely to be
a. Gram-negative. b. Gram-positive. c. archaeans. d. cyanobacteria. e. proteobacteria.
Why aren't antibiotics used against the common cold?
A) Cold viruses have already evolved resistance to antibiotics. B) Colds are caused by viruses and have never been affected by antibiotics. C) Antibiotics are only active against infection in the blood but not the respiratory tract. D) They're only effective if you take them within the first few hours of the infection.
Which of the following is TRUE when describing Hebbian modification?
a. Hebb synapses are rearranged and will be clustered together and will be activated together. b. There is no correlation between synaptic connection and synaptic activity c. Synapses are never rearranged. d. a and b e. a and c