Succession proceeds from

What will happen to an ecosystem if:
$(a)$ All producers are removed;
$(b)$ All organisms of herbivore level are eliminated; and
$(c)$ All top carnivore population is removed?

Match the List-$I$ with List-$II$:

List-$I$	List-$II$
$a$. Carbon dissolved in oceans	$i$. $55$ billion tons
$b$. Annual fixation of carbon through photosynthesis	$ii$. $71 \%$
$c$. $PAR$ captured by plants	$iii$. $4 \times 10^{13} \ kg$
$d$. Productivity of oceans	$iv$. $2$ to $10 \%$

Choose the correct answer from the options given below:

Mr. $X$ is eating curd/yoghurt. For this food intake in a food chain,he should be considered as occupying:

Select the incorrect statement for the detritus food chain.

Match the following:

Trophic levels	Examples
$A$. First	$a$. Man
$B$. Second	$b$. Wolf
$C$. Third	$c$. Cow
$D$. Fourth	$d$. Phytoplankton