CBSE Questions for Class 10 Biology Our Environment Quiz 9 - MCQExams.com

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.

• 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.

Solid waste that are generated must be segregated as dry waste and wet waste. This would help in better treatment and disposal of waste.

Secondary consumers are the organisms that feed on primary consumers. 

0. Producers  $$\rightarrow$$  1. Primary consumers $$\rightarrow$$ 2. Secondary consumers $$\rightarrow$$ 3. Tertiary consumers

A food chain can be described as a series of energy dilutors, the energy that fails to reach the next level being dissipated as heat or movement. Most of the energy contained in the food of animal consumers is used by them during the processes of food collection, digestion, and other essential metabolic activity.

• In a food chain, the carnivores eat up herbivores, or in other words, the secondary consumers consume the primary consumers. So, we can say that if the number of carnivores decreases, the number of herbivores like deer go on increasing as they will not get eaten up. So, the removal of most of the carnivores will result in an increased population of deer.
• Apart from this, we also know that as we move from one tropic level to another, the amount of energy goes on decreasing. This is according to the 10% law according to which, at each trophic level, 10% energy is lost. So, each food chain is only 3-4 tropic levels long due to these energy losses.
  

• DDT (Dichlorodiphenyltrichloroethane) is an organochlorinated compound that is stable in nature. The level of DDT increases as the food chain progresses.
• It means, the primary consumers will have more DDT concentration than the producers, the secondary consumers will have more than primary consumers and so on. 
• The highest concentrations will be seen in the top carnivore. As the consumers at each successive trophic level consume more food to fulfil their energy requirements. 
• Therefore, DDT accumulates in higher concentrations in successive trophic levels. This process is called biomagnification.

Hence, the correct answer is 'Increases'.

Biomagnification, also known as bioamplification or biological magnification, is the increasing concentration of a substance, such as a toxic chemical, in the tissues of tolerant organisms at successively higher levels in a food chain. Biomagnification process occurs when certain toxic chemicals and pollutants such as heavy metals, pesticides or polychlorinated biphenyls (PCBs) compounds go up the food chain by working their way through the environment and into the soil or the water systems after which they are eaten by aquatic animals or plants. Biomagnification occurs in the higher trophic levels of the food chain/web , where exposure to chemicals takes place mostly through food consumption rather than water uptake. Spraying a marsh to control mosquitoes will cause trace amounts of DDT to accumulate in the cells of microscopic aquatic organisms causing accumulation which cannot be metabolized.

Herbivores are called primary consumers, as they feed on autotrophs.

The ozone layer is the common term for the high concentration of ozone that is found in the stratosphere around 15–30 km above the Earth's surface. It covers the entire planet and protects life on earth by absorbing harmful ultraviolet-B (UV-B) radiation from the sun. 

Ozone layer depletion increases the amount of UV-B radiation that reaches the Earth's surface. This increases the temperature of the Earth's surface which results in the melting of polar ice caps and mountains snow caps. It also increases the chances of skin cancer, eye disorder like cataract, etc.