In an aquatic ecosystem, the aquatic plants are eaten by small invertebrates that in turn are eaten by crayfish, the crayfish are eaten by fish, and the fish are eaten by ducks. in terms of energy transfer, the organism feeding at the most efficient level is the small invertebrates crayfish fish ducks

Small invertebrates

Explanation:

Existing photosynthetic organisms (such as aquatic plants) capture about 2% of all solar energy that reaches the planet. They use this energy to produce organic substances through the photosynthesis process, and the energy is stored as chemical potential energy.

When a primary consumer (which in the case of the above question is the Small Invertebrates) feeds on photosynthesizing beings, the potential chemical energy stored in the organic compounds is transferred to him. These consumers then use the organic matter ingested for energy production, which in turn is used to perform some important processes for their survival. By serving as food to another organism (crayfish, in this case), primary consumers transfer this energy to this secondary consumer, but in a smaller and less efficient way.

For this reason, we can say that in the food chain shown in the above question, the organism that feeds at the most efficient level of energy transfer is the small invertebrates.

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.