An ecosystem must have a continuous external source of energy. This is the most appropriate option.

A producer in terms of biology refers to the first trophic level in a simple food chain. A food chain will not begin in the absence of producer.

The individuals of a species in a given locality constitute population.

All the living organisms on Earth constitute the biome.

Pedology is the study of soil.

Branch of botany dealing with distribution of plant on earth's surface is called phytogeography.

The stem of water plants usually has a well-developed arenchyma.

The study of interaction between living organisms and environment is called ecology.

Since all of the above mentioned are the examples of zooplankton, so this is the correct option.

Plants which are commonly found at the top of mountains are alphines.

Plants and animals living in a given area form a community.

Removal of the soil by the action of wind and water is known as erosion.

Study of plant environment is known as ecology.

Sunken stomata are present in xerophytes.

The least porous soil is clay soil.

Soil that is made of particles that have been carried by water and then deposited is called silt.

Industrial waste is the main factors of water pollution.

If all the plants of the world die, all the animal will also die due to shortage of oxygen.

The soil that cracks and shrinks most as it dries is clay soil.

The principle apparatus that works to analyse the soil is sieving.

Xerophytes are abundantly found in deserts.

Plants that are attached to stones and rocks are lithophytes.

Chalk is not a necessary compound of soil.

Free oxygen will not cause any atmospheric pollution.