Which trophic level organisms do secondary carnivores use as food?

In a pond,we see plants which are free-floating; rooted-submerged; rooted-emergent; and rooted with floating leaves. Identify the type of plant for each of the following:

Plant Name	Type
$(1)$ Hydrilla	....................
$(2)$ Typha	....................
$(3)$ Nymphaea	....................
$(4)$ Lemna	....................
$(5)$ Vallisneria	....................

The relationship of eating and being eaten is called:

An ecosystem can be described as:

What regulates the rate of function of an ecosystem?

$A$ pond can be classified under which type of ecosystem?