External respiration is the exchange of respiratory gases between the organism and it takes place via a membrane with thin internal respiration is the exchange of gases between and the

External respiration is the exchange of respiratory gases between the organism and the outer environment. 

It takes place via a respiratory membrane with thin moist epithelial cells.

Internal respiration is the exchange of gases between blood and the cells.

The process of diffusion of gases (oxygen and carbon dioxide) in and out of the blood is respiration, internal and external respiration are the types of respiration.

option a and d is the correct answer

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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.