Organisms normally the least in number in a food chain are Orca whales. The killer whale, also referred to as the orca whale or orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. 

In a lake polluted with pesticides, water fowls will contain the maximum amount of pesticides. Waterfowl are members of the family Anatidae. They are strong swimmers with medium to large bodies. They have historically been an important food source, and continue to be hunted as game, or raised as poultry for meat and eggs. 

The timber wolves, rabbits and vegetation in a particular region of Assam together constitute part of a community. A community is all of the living organisms in a particular area at a particular time. A population is all of one species in one area at one time. A species is a group of organisms that look alike and can breed among themselves and a genus is a broader division of classification. 

None of these is a commonly used pesticide.

Ozone is not a major greenhouse gas.  Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe. However, the most widely accepted scientific assessments relating to climate change suggest that the radiative forcing of troposphere ozone is about 25% that of carbon dioxide.  

All the plants, animals and protists living in a forest make up a community. A community is all of the living or biotic things in one place at one time. A population is just one species in one area at one time. A phylum is a subdivision of a kingdom. 

Ducks and carnivorous fish in a certain pond are secondary consumers. Secondary Consumers are the organisms which depend on the primary consumers for food. Ducks and carnivorous fishes are considered as secondary consumers in a pond ecosystem because they consume zooplankton which is the primary consumer. 

Cassava is a plant product used to make biodegradable plastic. Tapioca is a starch extracted from cassava.  In India, the term tapioca is used to represent the root of the plant (cassava), rather than the starch. Tapioca root can also be used to manufacture biodegradable plastic bags. 

Rate of lung cancer is not affected due to depletion of the stratospheric ozone layer. UVB causes no melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to cataracts. It is always important to protect your skin and eyes from the sun. Ozone layer depletion increases the amount of UVB and the risk of health effects. 

Some ponds look green from a distance because of the excessive growth of algae. The excessive growth of algae being green in color gives a false impression that the pond is green from a distance. 

'A lot of carbon dioxide is used in the process of decomposition and its decreasing level kills aquatic organisms' is an incorrect statement. Phosphorus and nitrogen combined with carbon dioxide are the main supplies that can turn your pond from clean to green very quickly. All aquatic plants and algae make their own energy through photosynthesis which uses sunlight and carbon dioxide to create energy and oxygen as the byproducts. Carbon dioxide released in the process of photosynthesis is used in aerobic decomposition. 

The 1987 Montreal Protocol was signed to phase out the use of CFC's, found to be causing depletion of the ozone layer. The Montreal Protocol on Substances that Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion. 

A river said to be ‘dead’ when the river becomes highly polluted to sustain aquatic life. 

Leather belts are easily biodegradable. Leather product is naturally biodegradable and chemicals are added to prevent that. Leather products can last thousands of years and the toxic chemicals with which they are infused leach into the environment during that time. 

The function of a water treatment plant is that. It acts upon the harsh chemicals and toxic materials which are present in water and converts them into less toxic and easily decomposable materials. They pump in raw untreated water from a well, lake or river. Remove the odor and bad taste by aeration remove settable solids, disinfect the water, adjust the PH of the water, filter the water, then pump it out for your use.