During prenatal development, the ectoderm folds over to form the __________, or primitive spinal cord.

Correct Answer: B

Rationale: The correct answer is B. During prenatal development, the ectoderm folds over to form the neural tube, which eventually develops into the brain and spinal cord. The neural tube is the precursor to the central nervous system, including the primitive spinal cord. Choices A, C, and D are incorrect because the mesoderm does not form the neural tube, the endoderm is not involved in the formation of the central nervous system, and neuron tract is not the structure that forms the primitive spinal cord.

Correct Answer: A

Rationale: A rise in the baby's heart rate during pregnancy is usually followed within five seconds by a burst of motor activity. This indicates that the baby is responding to stimuli and is an important sign of healthy fetal development. A period of sleep, a rise in Liz's heart rate, or a drop in Liz's body temperature are not typically immediate responses to changes in the baby's heart rate. Sleep is less likely to be a direct response to changes in heart rate, Liz's heart rate is independent of the baby's heart rate changes, and a drop in Liz's body temperature is not a common immediate response to fetal heart rate changes.

Correct Answer: B

Rationale: The statement that the genetic makeup of the mother and the developing organism plays an important role in the harm done by teratogens is true. Genetic factors can influence susceptibility to teratogens, and the interaction between genetic and environmental factors plays a significant role in determining the impact on the developing fetus. This highlights the importance of considering both genetic and environmental influences when assessing risks to prenatal development. Choice A is incorrect as passive smoking can indeed be harmful to the developing fetus. Choice C is incorrect as the negative impact of teratogens is often not reversible. Choice D is incorrect as serious defects can occur throughout prenatal development, not just in the germinal period.

Correct Answer: D

Rationale: The difficulty in isolating the precise damage caused by illegal drugs during pregnancy is due to the fact that drug users often take several drugs, display other high-risk behaviors, and suffer from other stresses. This makes it challenging to identify the specific impact of each individual factor on prenatal development. Choices A, B, and C are incorrect because they do not address the complexity of the situation involving drug users during pregnancy. Most drug-using mothers refusing to participate in teratology research, the majority of babies not surviving, or drug-using mothers quitting during the first trimester do not directly explain the difficulty in isolating the precise damage caused by illegal drugs during pregnancy.

Correct Answer: A

Rationale: Terrance exhibits a combination of physical abnormalities like a thin upper lip, short eyelid openings, a small head, and a smooth philtrum, along with developmental delays and cognitive impairments. These characteristics are indicative of fetal alcohol syndrome (FAS), which is caused by maternal alcohol consumption during pregnancy. FAS is a severe condition resulting from prenatal alcohol exposure and is characterized by a range of physical, cognitive, and behavioral issues. Choice A, fetal alcohol syndrome, is the correct answer as it aligns with Terrance's symptoms and the effects of maternal alcohol consumption during pregnancy. Choices B, C, and D are incorrect because they do not encompass the full spectrum of symptoms and impairments presented by Terrance, which are specific to fetal alcohol syndrome.