AP Biology: Homeostasis Practice Questions
Test yourself on AP Biology: Homeostasis with 12 original AP Exams practice questions. Pick an answer to see instant feedback and a full explanation.
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1. Which statement best describes homeostasis in a multicellular organism?
Explanation. Homeostasis maintains internal variables such as temperature, water balance, pH, and glucose within functional ranges. It does not remove all external variation, and many homeostatic responses require energy.
2. A mammal begins sweating when body temperature rises above a set point. Which feedback pattern does this example show?
Explanation. Negative feedback reduces deviation from a set point. Sweating promotes evaporative cooling, which counteracts the rise in body temperature.
3. Why is negative feedback common in homeostatic systems?
Explanation. Negative feedback detects a change and triggers responses that oppose that change. This helps keep internal conditions within ranges compatible with cellular processes.
4. Which example best illustrates positive feedback rather than negative feedback?
Explanation. Positive feedback amplifies an initial change. During labor, contractions stimulate oxytocin release, and oxytocin strengthens contractions until birth interrupts the cycle.
5. After a meal, blood glucose rises and pancreatic beta cells release insulin. What is insulin's homeostatic effect?
Explanation. Insulin helps lower elevated blood glucose by promoting glucose uptake and storage as glycogen in target tissues. This is part of a negative feedback loop.
6. A freshwater protist uses a contractile vacuole to expel excess water. Which homeostatic challenge is it addressing?
Explanation. Freshwater is often hypotonic relative to the cytoplasm, so water enters by osmosis. A contractile vacuole helps maintain water balance by collecting and expelling excess water.
7. Why can disrupting protein shape affect homeostasis?
Explanation. Proteins such as enzymes, receptors, channels, and pumps help regulate internal conditions. Temperature or pH changes that alter protein shape can disrupt those functions.
8. In thermoregulation, what role do receptors usually play?
Explanation. Receptors sense changes in a regulated variable. In thermoregulation, temperature-sensitive cells can detect deviations and help trigger responses through signaling pathways.
9. A plant closes stomata during a hot, dry afternoon. What is a likely tradeoff of this homeostatic response?
Explanation. Closing stomata conserves water by reducing transpiration. The tradeoff is that less carbon dioxide enters the leaf, which can limit photosynthesis.
10. Which statement connects cell membranes to homeostasis most accurately?
Explanation. Cell membranes are selectively permeable. Channels, carriers, pumps, and the lipid bilayer help regulate ion, water, nutrient, and waste movement, supporting internal balance.
11. When blood carbon dioxide rises, chemoreceptors contribute to changes in breathing rate. What is the main homeostatic purpose of this response?
Explanation. Carbon dioxide affects blood pH through carbonic acid chemistry. Adjusting breathing rate helps regulate carbon dioxide levels and supports pH homeostasis.
12. A student claims that homeostasis means internal conditions never change. Which correction is most accurate?
Explanation. Homeostatic variables fluctuate around set ranges. The key idea is regulation within tolerable limits through sensing, signaling, and response, not absolute unchanging constancy.
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FAQ
What homeostasis concepts are high yield for AP Biology?
Know negative feedback, positive feedback, set points, receptors, effectors, thermoregulation, osmoregulation, glucose regulation, pH balance, membrane transport, and plant water-balance tradeoffs.
How do I identify negative feedback in a question?
Look for a response that reverses or reduces the original change, such as sweating after overheating or insulin release after blood glucose rises.
Why do AP Biology questions often ask about homeostatic tradeoffs?
Organisms balance competing needs. For example, closing stomata saves water but limits carbon dioxide intake, and increased ventilation can support pH balance while using energy.