Which organisms perform photosynthesis to prepare food for themselves and other organisms?

Pesticides like $DDT$ which are sprayed to kill pests on crops are found to be present in the soil,groundwater,water bodies etc. Explain how do they reach these places.

Which of the following is an example of biodegradable waste?

Write the appropriate names of the trophic levels $Z$ and $X$ in the figure given below.

Name two gases which are considered to be better than $CFCs$ and cause less damage to the ozone layer.

In the given food chain,suppose the amount of energy at the fourth trophic level is $5 \, kJ$,what will be the energy available at the producer level (in $, kJ$)?
Grass $\to$ Grasshopper $\to$ Frog $\to$ Snake $\to$ Hawk