QCAA Biology Alternative Sequence Homeostasis

Negative feedback opposes the initial change in a variable. If the variable drops below the set point, the mechanism will increase it, so it does not always result in a decrease.

Negative feedback mechanisms are essential for survival and health; they protect the body by maintaining stable internal conditions rather than causing damage.

Homeostasis maintains a dynamic steady state, which often requires continuous energy expenditure to keep concentrations different between compartments, rather than a true chemical or physical equilibrium.

Nociceptors are sensory receptors that detect pain or tissue damage, not chemical changes in the blood.

Thermoreceptors are specialized to detect changes in temperature, not the concentration of gases in the blood.

Mechanoreceptors detect physical or mechanical changes such as pressure, stretch, or vibration, rather than chemical concentrations like blood oxygen levels.

The nervous system transmits signals via electrical impulses and neurotransmitters, rather than transporting hormones throughout the body.

The excretory system is responsible for removing waste products from the body, not for transporting signaling molecules like hormones.

While the endocrine system produces and secretes hormones, it does not have its own transport network and relies on the bloodstream for distribution.

Insulation, such as fur, feathers, or blubber, is considered a structural or anatomical adaptation rather than a physiological process.

Hibernation involves a deliberate drop in body temperature and metabolic rate to conserve energy, rather than actively maintaining normal body heat.

Kleptothermy is a behavioral adaptation where an animal shares or steals body heat from another organism, not a physiological process.

Increasing exoskeleton permeability would lead to greater water loss, which is counterproductive to maintaining water balance.

Uric acid is a nitrogenous waste product that is actively secreted and excreted to remove nitrogen from the body, not reabsorbed for osmoregulation.

Maintaining an internal environment isotonic to the external environment is the strategy of an osmoconformer, whereas osmoregulators actively maintain an internal osmolarity different from their surroundings.

Depolarization is initiated when a stimulus opens voltage-gated sodium channels, rather than closing them.

During depolarization, the membrane actually becomes highly permeable to sodium ions ($Na^+$), allowing them to cross the membrane.

If the threshold potential is not reached, the all-or-none principle dictates that an action potential and its subsequent depolarization phase will not occur.

While oxygen is released through stomata as a byproduct of photosynthesis, the specific term transpiration refers to the loss of water, not oxygen.

Plants absorb nitrogen from the soil through their roots in the form of nitrates or ammonium; they do not lose it as a gas through their stomata.

Carbon dioxide is primarily taken in through the stomata for photosynthesis. While it can be released during cellular respiration, this gas exchange is not called transpiration.