74. A fast-twitch muscle fiber__?
(A) uses ATP quickly in short, fast contractions；
(B) has many capillaries；
(C) is rich in myoglobin；
(D) works aerobically.

70. The systems that coordinate communication are__? (A) skeletal and muscular；(B) circulatory and respiratory；(C) nervous and endocrine；(D) digestive and circulatory.

71. Which of the following best describes how a neuron fires? (A) Na+ ions cross the plasma membrane, initiating a wave that travels down the axon；(B) Vesicles carry neurotransmitters from the nucleus to the other end of the neuron；(C) Na+ ions enter one end of the neuron and diffuse to the other end, down the axon；(D) Neurotransmitters enter one end of the neuron and diffuse to the other end, down the axon.

72. If you had a friend who was unable to see color, you would expect that your friend's eyes had defective__? (A) cone cells；(B) rod cells；(C) cornea；(D) iris.

73. Observing a patient who has been given an experimental drug, you notice that it constricts blood vessels and slows digestion, making its effects similar to those of__? (A) calcitonin；(B) epinephrine；(C) insulin；(D) glucagon.

75. Systolic pressure reflects the__? (A) contraction of the atria；(B) relaxation of the atria；(C) contraction of the ventricles；(D) relaxation of the ventricles.

76. People are often noted to pick up and "adopt" a baby wild animal, which then leads to a set of dependent behaviors that the young animal learns very rapidly. The dependent behaviors will be retained through life, endangering the survivability of the animal around people or in the wild. This behavior is learned by__?(A) taxis；(B) imprinting；(C) habituation；(D) observation.

77. An ecosystem is defined as__? (A) all of the individuals of the same species living in an area； (B) the physical place and environmental surroundings in which individual organisms live；(C) the set of environmental resources that each organism requires for survival, growth, reproduction, etc；(D) the sum of living organisms and nonliving environmental components in an area.

78. Which of the following is not a type of symbiosis? (A) predation；(B) mutualism；(C) commensalism；(D) parasitism.

79. Why do populations that fragment in response to climate changes face a higher risk of extinction? (A) Population fragmentation leads to loss of genetic diversity；(B) Populations which have moved are subject to new predators；(C) Moving populations cannot breed as effectively；(D) The number of young decreases for several generations in new habitat.

80. How does damming or altering the path of a river destroy wetlands? (A) Fish can no longer migrate up and down the river；(B) Wetlands can no longer obtain nutrients from annual floods；(C) Wetlands can no longer obtain oxygen from the flowing water of the river；(D) Birds can no longer get to the wetlands.