TEAS 7 Science Practice Test

Correct Answer: D

Rationale: Natural selection is the correct answer. It is the mechanism where advantageous traits lead to better survival and reproduction, passing on those traits to offspring. This process drives evolution by selecting for traits beneficial for survival in a given environment. Gene flow involves the transfer of genes between populations, genetic drift is the random change in allele frequencies, and mutation introduces new genetic variations. These mechanisms do not specifically involve the differential survival and reproduction of organisms based on advantageous traits, making them incorrect choices for this question.

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.

Correct Answer: D

Rationale: The correct answer is D: neuromuscular junction. This is where nerve impulses travel to release neurotransmitters, such as acetylcholine, to stimulate muscle contraction. The sarcomere is the basic unit of muscle contraction, not the location of neurotransmitter release. Tendons connect muscles to bones and do not involve neurotransmitter release. The myelin sheath is a protective layer around nerves and is not directly involved in neurotransmitter release at the neuromuscular junction.

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.