THe bacteria that lives in the nodules of legumes are the only ones able to fix nitrogen gas into ammonia, which is later fixed by other bacteria in the soil to nitrites and nitrates that the plants can use.
some bacteria also performs denitrification, which converts ammonia back to nitrogen gas, allowing the cycle to continue
The lipid that acts as a chemical messenger. A hormone is a chemical messenger<span>. The hormone is a testosterone.</span>
With reference to the transition from HIV to AIDS, modern research indicates that without treatment, it takes approximately 10 years from first infection of the HIV virus to full-blown AIDS, with major opportunistic diseases then occurring in this period as the individuals will have severely weakened immune systems making them more easily susceptible to major opportunistic diseases like pneumonia, tuberculosis and Salmonella infections.
The answer is D.
Both mechanical and chemical digestion of food begin in the mouth.
Mechanical digestion involves physically breaking down food into smaller pieces. This happens in the mouth as the food is chewed. Adult humans have 32 specialized teeth which can tear, grind and chew different kinds of food.
Chemical digestion also begins in the mouth. It involves breaking down food into simpler nutrients that can be used by the cells. In the mouth, food is mixed with saliva. Saliva contains an enzyme called salivary amylase that begins the breakdown of carbohydrates. Salivary glands beneath and in back of the tongue secrete the saliva.