Nektons are
Organisms that swim in water
Floating plants
Suspended lower plants
Animals associated with plants
Secondary productivity is rate of formation ofnew organic matter by
What is the ultimate source of energy for the ecosystems ?
Trees $\rightarrow$ Birds $\rightarrow$ Lice $\rightarrow$ Bacteria. Thus food chain is
The aquatic organism that can actively swim at will against the water current is
If the plant producer dies in the ecosystem, then the system is