A Level Biology Practice Exam

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What are ostia in the context of insect anatomy?

Muscles that assist in blood circulation
Pores that allow blood from the body to enter the heart
Neurons that signal heart contractions
Valves that regulate blood flow in the body

The correct answer is: Pores that allow blood from the body to enter the heart

Ostia are specialized pores in the context of insect anatomy that allow hemolymph, which is the fluid equivalent to blood in insects, to enter the heart. These openings function as one-way valves, facilitating the flow of hemolymph from the body cavity into the heart during the contraction of the heart muscle. When the heart relaxes, the ostia close to prevent the backflow of hemolymph, ensuring efficient circulation throughout the insect's body. This is crucial in maintaining proper circulation and nutrient distribution in an open circulatory system, typical of insects. Muscles that assist in blood circulation, signaling neurons for heart contractions, and valves that regulate blood flow are important concepts in biology, but they do not specifically represent the function of ostia within the circulatory system of insects.