Snakes are included under which category in a food chain?

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

What is the correct sequence in a hydrosere (hydrarch succession)?

The following diagram shows the phosphorus cycle. Identify the producers in it.

Read the given statements and determine how many of them are correct.
$(1)$ Secondary succession depends on the condition of the soil and the availability of water.
$(2)$ Air,water,and land are abiotic factors of an ecosystem.
$(3)$ The structure of an ecosystem includes the cycling of nutrients and the unidirectional flow of energy.
$(4)$ The primary source of energy in an ecosystem is the sun.

Give scientific reasons: Coral reefs are not found in the regions from West Bengal to Andhra Pradesh,but are found in Tamil Nadu and on the east coast of India.