Plants in dry climate have sunken stomata. Also, the number of stomata is reduced.

This is the correct answer. Nitrosomonas are nitrifying bacteria and their role is to change ammonia into nitrites. They conduct ammonification. Nitrobacter change nitrites into nitrates. They conduct nitrification. Pseudomonas are denitrifying bacteria and change nitrates into free nitrogen.

This is the correct option. Water is an abiotic component of ecosystem. 

Presence of vertebral column is not an aerial adaptation of a bird.

Ten percent law relates to the transfer of energy in successive trophic levels.

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

This is correct. Both these adaptations have been made by floating plants, such as water lily. Floating plants like water lily have poorly developed roots and root hair as water is not a problem to them. Floating plants have a thin and flexible stem so that they can sway and bend with the water movements and pressure.

The leguminous plants are important in agriculture because they help in nitrogen fixation of the plants.

The food chain in which microorganisms break down the energy-rich compounds synthesised by producers is a detritus food chain.

The pyramid of biomass is inverted in pond ecosystem.

The maximum amount of DDT accumulates in the body of birds feeding on fish as compared to other options due to their later sequential order in the food chain. It is an example of biological magnification.

Eutrophication is when the environment becomes enriched with nutrients. It causes algal blooms and reduced O₂ content in water bodies.

Yes, all are correctly matched. In addition to fur, polar bears have a thick layer of fat under the skin called blubber. This layer acts as an insulator and prevents the bear from extreme cold. Polar bears have wide paws with long curved nails called claws. These help them move on the snow. Wide paws work as a rudder while swimming. Because of the white fur, a polar bear can easily mix with its snowy background and can hide from its prey and predator.

Biogeochemical cycle can be broken down into 2 types of local cycles, such as phosphorus cycle, which involves elements with no mechanisms for long distance transfer, and global cycles, which invoke an interchange between the atmosphere and the ecosystem.

Proteins and nucleic acids have both oxygen and nitrogen.