![\sf{\qquad\qquad\huge\underline{{\sf Answer}}}](https://tex.z-dn.net/?f=%20%5Csf%7B%5Cqquad%5Cqquad%5Chuge%5Cunderline%7B%7B%5Csf%20Answer%7D%7D%7D%20)
The primary source of energy in a food chain is Sun, because producers are the ones that prepare food by themselves and that food is then passed on to higher levels in food chains. And as the producers make their from Sunlight, the primary source of energy in food chain is <u>Sunlight</u> .
Sunlight
Water(moisture)
Viable seed
Air
Answer:
Physical
Explanation:
The skin is a physical barrier.
Mechanical barriers are made by mucous membranes
Metabolic chemical reaction