खाद्य श्रृंखला में तीसरा पोषण स्तर (trophic level) हमेशा किसके द्वारा ग्रहण किया जाता है?

What primary ecological role do humans play in a food chain?

Which microscopic, single-celled photosynthetic organisms are known as the primary producers of the ocean, forming the base of marine food chains?

According to Lindeman's 10% law of energy transfer, which organism in the following food chain receives the least amount of energy? Grass → Grasshopper → Frog → Snake