The process of breathing, or ventilation , brings air to, and removes air from the exchange surface – the alveoli. The moving blood and ventilated surfaces mean that a steep concentration gradient can be maintained. This increases effective exchange.
Leslie argues that an organism called a Euglena is a plant because it is eukaryotic, has a nucleus, makes its own food, and is unicellular. Where is Leslie's error? Plants do not make their own food..
A spring is a natural discharge point of subterranean water at the surface of the ground or directly into the bed of a stream, lake, or sea. Water that emerges at the surface without a perceptible current is called a seep. Wells are holes excavated to bring water and other underground fluids to the surface.
Astronomers are able to detect the dimmer star because its gravity causes the bright star to . Astronomers can also spot the dimmer star by observing a phenomenon called a(n) binary.
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