The thing that would mostly make the results of the experiment invalid would be the students themselves. No one is built the same, and the exact same food can have very different effects on different people.
A. Hormones act as signal molecules between all body systems
Peripheral Chemoreceptors (Carotid + Aortic Bodies) and Central Chemoreceptors in the Medulla Oblongata detect high Carbon Dioxide levels in the blood during exercise. The respiratory centre in the Medulla Oblongata + PONS stimulate the intercostal muscles and the diphragm to contract in order to increase the rate and depth of breathing as to decrease levels of Carbon dioxide in the blood.
The thyroid gland secretes thyroxine which speeds up metabolism (the rate at which cells use glucose)
Soaring is a science when birds remain airborne and moving without flapping their wings. They are maintaining thrust and gliding downward but staying aloft
<h3 /><h3>Further explanation</h3>
Soaring birds is where the birds can maintain flight without wing flapping, because they using rising air currents. Many gliding birds are able to lock their extended wings by means of a specialized tendon. Some land birds such as vultures and certain hawks, sustain flight for long periods without flapping their wings.
For example soaring California Condor spreads its primary feathers so that each acts as a small, high-aspect-ratio wing. This reduces turbulence at the wingtips and helping the condor to stay aloft circling slowly in thermals.
Vultures have a low aspect ratio (ratio of length to width of the wing) which generally produce a lot of drag. Vultures overcome the problem of by flying with their primary feathers extended, creating slots between them. Each primary serves as an individual high-aspect-ratio wing. This high-aspect-ratio reducing wingtip turbulence and lowering the stalling speed of the wings. This helps vultures to circle in thermals, maintaining thrust by gliding downward, but staying aloft by sinking at a rate slower than the hot air rising.
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<h3>Answer details</h3>
Grade: 9
Subject: biology
Chapter: animals
Keywords: birds
Probably B) strenuous exercise. If not B then it's probably A. I don't know for sure though
It was ancient fossils containing ----Ancient bacteria---