TEAS 7 Science Practice Test

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: C

Rationale: The correct answer is C: skin. Skin is the primary physical barrier that the body uses to prevent infection. It acts as a protective barrier, preventing pathogens from entering the body. The outer layer of the skin, known as the epidermis, is made up of tightly packed cells that are difficult for pathogens to penetrate. Additionally, skin produces oils and sweat that contain antimicrobial properties, further protecting against infections. Explanation for why other choices are incorrect: A: Mucus membranes play a role in preventing infections in certain areas like the respiratory and digestive tracts, but they are not the primary physical barrier used by the body. B: Stomach acid is a chemical barrier rather than a physical barrier against infections. D: Urine helps to flush out pathogens from the urinary tract but is not the primary physical barrier used by the body.

Correct Answer: D

Rationale: The correct answer is D: Combustion reaction. In a combustion reaction, a compound reacts with oxygen gas to produce carbon dioxide and water. In this equation, 2C₆H₁₄ (hexane) reacts with 19O₂ to produce 12CO (carbon monoxide) and 14H₂O (water). This reaction is characteristic of combustion, where a fuel (hexane) reacts with oxygen to release energy in the form of heat and light. Summary: A: Substitution reaction involves replacing one element or group in a compound with another element or group. This is not demonstrated in the given equation. B: Acid-base reaction involves the transfer of protons between substances. There are no acids or bases involved in the given equation. C: Enzyme reaction involves the catalysis of a chemical reaction by an enzyme. Enzymes are not mentioned in the given equation.

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: A

Rationale: The correct answer is A: calcium. Bone is primarily composed of calcium phosphate, which provides strength and rigidity to the bone structure. Calcium is crucial for bone formation and mineralization. Magnesium and potassium are important for various bodily functions but are not the primary components of bone. Collagen is a protein that provides flexibility and support but is not an inorganic material found in bones.