The dynamic aspect of an ecosystem is:

Identify the likely organisms $(1), (2), (3)$ and $(4)$ in the food web shown below.

The world's most problematic aquatic weed is

Biological equilibrium is an equilibrium among the

How many statements are correct?
$(a)$ Some animals like cockroaches,crows,etc.,are omnivores.
$(b)$ Detritus food chain $(DFC)$ begins with dead organic matter.
$(c)$ Each trophic level has a certain mass of living material at a particular time called as standing crop.
$(d)$ Species composition and stratification are two main structural features of an ecosystem.

Match the following columns.

Column-$I$	Column-$II$
$(a)$ Phytoplankton,grass	$(p)$ First trophic level
$(b)$ Man,Lion	$(q)$ Herbivore
$(c)$ Zooplankton,Cow,Grasshopper	$(r)$ Third trophic level
$(d)$ Birds,Wolf	$(s)$ Top carnivore