There's been a lot of bad news for polar bears recently. In 2007, for example, scientists reported that if global warming continues unabated, the population could drop two-thirds by 2050.
Histamines are chemicals released by the body as an allergic response.They help the body by reacting when their are "intruders" so when enters, histamine acts as a messenger and sends out a signal for the body to create a reaction helping to get rid of teh intruder through some type of reaction.
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.
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Answer:
Cardiovascular endurance is the ability to exercise without becoming overly tired because your heart, lungs and blood vessels are healthy. Exercise examples include walking, jogging, cycling, dancing, running and bike riding. Distance swimming is also a good cardiovascular endurance exercise.
