TEAS Test 7 science quizlet

Correct Answer: B

Rationale: Antigenic variation is a strategy used by some viruses to evade the host's immune response. By constantly changing their surface antigens, viruses can avoid recognition and destruction by the immune system. This allows the virus to persist in the host and continue replicating, leading to prolonged infection and potential transmission to other hosts. Antigenic variation does not directly involve the production of toxins, survival outside a host, or rapid replication, making options A, C, and D incorrect in this context.

Correct Answer: C

Rationale: The correct answer is C, Cardiac muscle. Cardiac muscle fits the description provided in the question as it exhibits involuntary contractions, striations, and is predominantly located in the heart. Skeletal muscle, while also striated, is voluntary and not involuntary like cardiac muscle. Smooth muscle lacks striations and is typically found in the walls of internal organs. Elastic muscle is not a recognized type of muscle tissue in human anatomy, making it an incorrect choice.

Correct Answer: A

Rationale: Isotopes are variants of a single element that have the same number of protons, the defining characteristic of an element. They differ in the number of neutrons they possess, leading to isotopes having different atomic masses while retaining the same chemical properties. Choice B is incorrect because isotopes have the same number of neutrons and differ in the number of protons. Choice C is incorrect because isotopes have different masses due to varying numbers of neutrons, not different atomic numbers. Choice D is incorrect as isotopes do differ in the number of neutrons they possess.

Correct Answer: B

Rationale: Carbon is the correct answer as it is a critical element in DNA and RNA, forming the backbone of these molecules. Its ability to form diverse bonds allows for efficient storage and transmission of genetic information. Oxygen, nitrogen, and hydrogen are also present in DNA and RNA but do not serve as the primary backbone element for these molecules. Oxygen is involved in the structure but not as the backbone element. Nitrogen is present in the bases of nucleotides, and hydrogen bonds help stabilize the structure.

Correct Answer: D

Rationale: Calcitonin is a hormone produced by the thyroid gland that primarily functions to lower blood calcium levels. It achieves this by inhibiting bone breakdown and promoting calcium excretion by the kidneys. Therefore, the correct answer is D as it reflects the main role of calcitonin in calcium homeostasis. Choices A, B, and C are incorrect as they do not align with the primary function of calcitonin. Calcitonin does not stimulate metabolism and heat production (Choice A), increase calcium absorption from the intestines (Choice B), or enhance bone growth and development (Choice C).