Hii...so the answer is
The four layers are the external oblique, internal oblique, transverse abdominals.
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Biotic factors include plants, animals, microbes, etc. The important abiotic factors include the amount of sunlight in the ecosystem, the amount of oxygen and nutrients that is dissolved in the water, temperature, etc. Sunlight is one of the most important abiotic factors for marine ecosystems.
A simple example is the connection between the circulatory and respiratory systems. As blood circulates through your body, it eventually needs fresh oxygen (O2) from the air. When the blood reaches the lungs, part of the respiratory system, the blood is re-oxygenated.
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