Browse exam-wise, subject-wise, and country-wise MCQs with explanations.
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Fish generally have single circulation: heart to gills to body and back to heart. The heart contains one atrium and one ventricle.
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Phagocytosis is the engulfment and digestion of particles or microbes by immune cells. It is an important nonspecific defense mechanism.
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Platelets help form clots by adhering at injury sites and triggering coagulation. This prevents excessive blood loss.
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Erythrocytes carry respiratory pigments such as hemoglobin for oxygen transport. A low count reduces oxygen delivery to tissues.
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Hemolymph is the circulating fluid of many invertebrates with open circulatory systems, especially arthropods. It may transport nutrients, wastes, hormones, and immune cells.
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Closed circulatory systems keep blood within vessels, allowing more controlled pressure and distribution. Annelids such as earthworms are classic examples.
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In open circulatory systems, hemolymph leaves vessels and bathes tissues in body cavities. Arthropods and many molluscs show this arrangement.
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Autocrine signaling occurs when a cell releases a messenger that binds receptors on the same cell. It is common in growth and immune regulation.
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Paracrine signals act locally on nearby cells, unlike classical endocrine hormones that travel through circulation to distant targets.
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Cells can reduce receptor number or signaling after prolonged stimulation. This decreases sensitivity and helps prevent overstimulation.
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Across invertebrates, chemical messengers coordinate development, reproduction, metabolism, and behavior, although glands and molecules differ among groups.
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Hormones such as glucocorticoids can alter immune responses. This shows endocrine regulation interacts with defense and homeostasis.
