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: C

Rationale: The correct answer is C because isotopes are atoms of the same element that have different numbers of neutrons. Neutrons are the subatomic particles that do not have a charge and are found in the nucleus of an atom. Different isotopes of an element have the same number of protons (which determines the element's identity) but vary in the number of neutrons, leading to differences in atomic mass. This distinction in neutron number is the defining characteristic of isotopes. Choices A, B, and D are incorrect: A: Isotopes do not have different ionic charges as they have the same number of protons and electrons, maintaining overall charge neutrality. B: Isotopes can be found across different groups on the periodic table, not restricted to the same group. D: Isotopes can have the same electron configurations since electrons are primarily determined by the number of protons in the nucleus, which remains constant for isotopes of the same element.

Correct Answer: D

Rationale: Peristalsis is the correct term as it refers to the rhythmic muscle contractions that propel food through the digestive tract. First, the circular muscles contract behind the food bolus, pushing it forward. Then, the longitudinal muscles contract, shortening the tract and pushing the food further. This process continues in a wave-like fashion, aiding in digestion. A: Digestion refers to the breakdown of food into smaller molecules. B: Deglutition is the process of swallowing food. C: Defecation is the elimination of waste from the body. Therefore, peristalsis is the correct term as it specifically describes the muscle contractions that move food through the digestive system.

Correct Answer: C

Rationale: The correct answer is C, the law of independent assortment. This law states that alleles for different traits segregate independently of each other during gamete formation. This is due to the random alignment of homologous chromosomes during meiosis. The law of segregation (A) describes how alleles of a gene separate during gamete formation. The law of dominance (B) explains that one allele can mask the expression of another in heterozygous individuals. The law of predictive traits (D) is not a recognized Mendelian law and is therefore incorrect. In summary, the law of independent assortment best describes how alleles from different genes segregate independently during gamete formation.