TEAS 7 Science Practice Test

Correct Answer: B

Rationale: The correct answer is B: sinoatrial node. The sinoatrial node is a cluster of specialized cells in the right atrium responsible for initiating the electrical impulses that regulate the heartbeat. It acts as the heart's natural pacemaker by setting the pace for the heart's contractions. The other choices are incorrect because: A: Sinus venosus is an embryonic structure in the heart, not the natural pacemaker. C: Atrioventricular node is responsible for conducting the electrical signal from the atria to the ventricles, not for generating the initial signal. D: Tricuspid valve is a heart valve that prevents backflow of blood from the right ventricle to the right atrium, not involved in generating electrical signals.

Correct Answer: A

Rationale: The correct answer is A because it accurately describes the path through which air moves during inhalation. Air enters through the mouth/nose, passes through the pharynx, then the larynx, trachea, bronchi, bronchioles, and finally reaches the alveoli in the lungs where gas exchange occurs. Choice B is incorrect because it reverses the order of the bronchi and bronchioles, and places the larynx and pharynx after the lungs, which is inaccurate. Choice C is incorrect as it skips the pharynx and larynx, and incorrectly places the lungs before the alveoli in the sequence. Choice D is incorrect as it reverses the order of the alveoli and bronchioles, and places the trachea, larynx, and pharynx after the lungs, which is not accurate in the flow of air during inhalation.

Correct Answer: D

Rationale: The correct answer is D: high polarity. Water molecules are polar, with a slightly positive end (hydrogen) and a slightly negative end (oxygen). This polarity allows water to form hydrogen bonds with other polar molecules, like ionic salt compounds, facilitating their dissolution. Adhesion (A) is the ability of water to stick to other substances, cohesion (B) is the ability of water molecules to stick to each other, and high specific heat (C) is the ability of water to resist temperature changes. These properties are not directly related to water's ability to dissolve ionic salt compounds.

Correct Answer: B

Rationale: The correct answer is B: semilunar valves. Semilunar valves are located at the exits of the heart's major blood vessels (pulmonary artery and aorta) and prevent blood from flowing back into the heart after it has been pumped out. Atrioventricular valves (choice A) prevent backflow between the atria and ventricles, tricuspid valves (choice C) and bicuspid valves (choice D) are specific types of atrioventricular valves. Therefore, choices A, C, and D do not primarily prevent blood flow from major blood vessels to the heart, making them incorrect.

Correct Answer: B

Rationale: In anaphase of mitosis, chromatids separate and move to opposite poles of the cell, ensuring each daughter cell receives a complete set of chromosomes. This ensures genetic stability and accurate distribution of genetic material. In metaphase, chromosomes align at the cell's equator but do not separate. Prophase is the initial stage of mitosis where chromosomes condense but do not divide, and telophase is the final stage where chromosomes decondense and nuclear envelopes reform. Therefore, anaphase is the correct phase where chromatids divide into chromosomes and migrate to opposite ends of the cell.