Practice Pakistan questions with answers and explanations.
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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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Fever is a systemic innate response that can slow pathogen growth and enhance immune activity. It is not antigen-specific.
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Target tissues respond only when they have the appropriate receptor and signaling machinery. Circulation alone does not guarantee a response.
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Hormone action depends partly on how long the hormone remains active in circulation. Rapid degradation shortens the response.
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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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Inflammation increases local blood flow and vascular permeability, bringing immune cells and defensive proteins to injury or infection sites.
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Many invertebrates use neurosecretory cells, blending nervous and endocrine functions. These cells release chemicals that regulate growth, reproduction, and behavior.
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Sponges do not possess true organs or endocrine glands, but cells can communicate chemically to coordinate basic activities.
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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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Macrophages are phagocytes of innate immunity, but antigen presentation can help activate adaptive immune responses such as T cells.
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Excess hormone can overstimulate target tissues and disturb homeostasis. The exact effect depends on the hormone, receptor distribution, and feedback control.
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Cnidarians have simple nervous systems and chemical communication. They lack vertebrate endocrine glands but still coordinate feeding, movement, and reproduction.
