Our Environment Test - 33

The preference of food habit depends on the available food, a single species may occupy more than one trophic level at the same time in the ecosystem. Birds are the primary consumers when they eat seeds on the other hand secondary consumers when they feed on worms and insects.

A)  Correct Option – C
B)  Explanation for correct option -

The two forms of oxygen found in the atmosphere are a diatomic molecular form that has a chemical formula as O22 or oxygen, the life-giving gas that we breathe in to survive. 
Another is a triatomic molecular form that has a chemical formula O33 called ozone gas, which protects us from harmful UV rays.

• A food chain is a linear path in which an organism gets food, it starts with plants and ends with animals. A network of many food chains is called a food web. 
• A food web consists of all the food chains in a single ecosystem. Each living thing in an ecosystem is part of multiple food chains. 
• Each food chain is one possible path that energy and nutrients may take as they move through the ecosystem. All of the interconnected and overlapping food chains in an ecosystem make up a food web.

• Predators are the animals that kill or hunt other animals for food and the animal which is killed is called prey. So, the lion is the predator that hunts for wild beasts for its food. 
• Secondary consumers are carnivores or omnivores that feed on primary consumers that are herbivores. Therefore, the lion is a secondary consumer. Wild beasts eat plants, therefore, the wild beast is the primary consumer.

Global warming is caused by increased concentration of greenhouse gases in the atmosphere. Increased organic matter in lakes causes eutrophication. Ozone depletion is mainly related to the use of CFC-based products. Acid rain is the result of increased sulphur and nitrogen oxide levels in the atmosphere. Increased use of pesticides causing the death of predators will cause accumulation of nonbiodegradable compounds like DDT in the food chain. Thus, the correct answer is option D.

• Biological magnification is the process of transfer of chemical toxins in increasing concentration when moving up the food chain e.g., DDT, mercury.
• Products like ozone, aldehydes, and peroxyacetyl nitrates (PAN) are called secondary pollutants. The mixture of these primary and secondary pollutants forms photochemical smog. 
• Sulfur dioxide ($$SO_2$$) and nitrogen oxides (NOx) are the principal pollutants, that cause acid precipitation. $$SO_2$$ and NOx emissions released to the air react with water vapour and other chemicals to form acids that fall back to Earth. 
• Carbon dioxide ($$CO_2$$) is the primary greenhouse gas emitted through human activities. Human activities are altering the carbon cycle, both by adding more $$CO_2$$ to the atmosphere and by influencing the ability of natural sinks, like forests, to remove $$CO_2$$ from the atmosphere.