In hydrarch succession,the reed swamp stage is preceded by

As insecticides reach at higher trophic level in food chain,their concentration:

Which of the following statements regarding food chains are considered correct?
$(1)$ Removal of $80\%$ of tigers from an area results in greatly increased growth of vegetation.
$(2)$ Removal of most carnivores results in an increased population of deer.
$(3)$ The length of food chains is generally limited to $3-4$ trophic levels due to energy loss.
$(4)$ The length of food chains can vary from $2$ to $8$ trophic levels.

Broad-leaved forests of oak are found in

Identify the mismatched pair.

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