When a stimulus is applied to a receptor in the skin, an action potential is propagated along a neuron to the brain, where another signal is sent back to the muscle for a response. Which of the following best describes what occurs when the action potential reaches a chemical synapse at the end of an axon?
(A) The action potential jumps from one axon to the next connecting axon.
(B) The action potential travels through the synapse to the next connecting dendrite.
(C) The action potential jumps the synapse to the next connecting dendrite.
(D) The action potential causes a release of neurotransmitters that travel across the synapse.
Ans: (D) The action potential causes a release of neurotransmitters that travel across the synapse.
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The phenomenon through which populations of organisms change over several generations is termed ______.
A. homeostasis B. growth and development C. reproduction D. biological evolution E. organization
Which of the following molecules is (are)
formed at the end of the electron transfer process?
a. ATP only b. NADPH only c. ATP and NADPH d. NADP+ e. ATP and NADP
This white blood cell degranulates in response
to injury or antigens and stays anchored in cells closely associated with neurons. This white blood is a(an)
a. mast cell. b. eosinophil. c. basophil. d. dendritic cell. e. neutrophil
Which piece of evidence BEST supports the "multiregional evolution" model of the evolution of modern humans?
A) Molecular clocks date the last common ancestor of modern humans to about 171,500 years ago. B) Present-day human populations from Africa have greater genetic diversity than non-African populations. C) African Homo ergaster/erectus appear almost simultaneously with Asian Homo erectus, 1.6 to 1.9 million years ago. D) Both Asian fossil Homo erectus and modern Asian human populations show a high frequency of shovel-shaped incisors. E) There is no solid evidence supporting the multiregional hypothesis.