The exchange of substances between the blood vessels and the surrounding tissues can only happen in the .

The exchange of substances between the blood vessels and the surrounding tissues can only happen in the capillaries.

Explanation:

Capillaries are the exchange vessels of our body. They form a network-like structure, called the capillary area. When blood, from the larger arterioles, spreads through the many capillaries in the capillary area, the blood pressure drops and the blood flows only at a slow speed. Through the thin, semi-permeable walls of the capillaries, the exchange of gas and substances between the blood and the surrounding tissue then takes place. Subsequently, blood continues to flow through the postcapillary venules, to which the capillary area has been reconnected. Blood pressure and blood flow increase and blood eventually reaches the heart through enlarged veins.

it will increase due to the time span

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.