Energy in an ecosystem flows directly from
a. producers to tertiary consumers
b. producers to secondary consumers
c. tertiary consumers to secondary consumers
d. secondary consumers totertiary consumers

Explanation : The energy flow through the ecosystem flows from the producers, then to primary consumers, to secondary consumers, to tertiary consumers and so forth. The amount of energy that flows from one level to another is only 10%, the rest energy (90%) is lost in form of heat through various processes.

Therefore,Energy in an ecosystem flows directly from producers to secondary consumers.

The correct answers is option D, secondary consumers to tertiary consumers

Explanation:

In a food pyramid, the hierarchical placement of organisms  is as given below

a)Producer

b)Primary consumer

c)Secondary consumer

d)Tertiary consumer

Thus, from the above hierarchical order it is clear that producers cannot transfer energy directly to either the tertiary consumer or secondary consumer. Also a tertiary consumers cannot transfer energy to secondary consumers. Thus option D is only correct.