Men experience a gradual decline in testosterone levels, sometimes called which can cause changes in physical and psychological health

The right answer is andropause.

Andropause is a set of physiological and psychological symptoms that are due to the decline of testosterone in older men. It would usually occur starting at the age of 45.

These symptoms range from decreased sexual appetite to the onset of erectile problems to a feeling of being short of energy. Periods of excessive sweating, insomnia and weight gain may also add to the impact of declining sex hormone production.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."    

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