Hormones -- such as melatonin and cortisol; the former signals the body to go to bed, while the latter signals for the sleeping person to wake up -- are created by physiological changes.
Carbon dioxide is a colorless and non-flammable gas at normal temperature and pressure. Although much less abundant than nitrogen and oxygen in Earth's atmosphere, carbon dioxide is an important constituent of our planet's air. A molecule of carbon dioxide (CO2) is made up of one carbon atom and two oxygen atoms. Carbon dioxide is an acidic colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth's atmosphere as a trace gas.
Answer:
Why are cells small? because they can absorb nutrients much more efficiently. Because they are smaller they can efficiently absorb enough food. When a cell doubles in size the volume increases much more then the surface area, which is why large cells cannot receive enough food efficiently for their volume.
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The
two categories that are used to classify physical changes are Reversible and
Irreversible.
Reversible
means that the matter can convert to gas, liquid and solid and then convert
back to gas, liquid or solid. So it means it can convert back and forth.
<span>Irreversible
means that matter cannot be converted back as it is before.</span>
