The kerbs cycle is considered a cycle because

The Krebs cycle is considered a cycle because the final product is oxaloactic acid (more on that below)  is the molecule needed to accept an acetyl-CoA (also more on that below) molecule to start another turn of the cycle,

Explanation:

Oxaloactic acid: A crystalline organic compound. In the form of its conjugate based, is a metabolic intermediate in many process that occur in animals. It takes part in the urea cycle, gluconeogenesis, fatty acid synthesis, glyoxylate, citric acid cycle and amino acid synthesis.

chemical formula: HO2CC(O)CH2CO2H (Thanks google lol)

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acetyl-CoA: A molecule that participates in a lot of biochemical reactions in carbohydrate, lipid, and protein metabolism. Its main function is to deliver acetyl group to the citric acid cycle so that it can be oxidized for energy production

Hope this helps

Have a nice day((:

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

sorry, but you do not have posted the diagram.