1.
In a food chain, the initial organism is usually:
Correct Answer
A. pHotosynthetic
Explanation
In a food chain, the initial organism is usually photosynthetic because photosynthetic organisms, such as plants and algae, are able to convert sunlight into energy through the process of photosynthesis. They are the primary producers in the food chain, meaning they produce their own food and provide energy for other organisms in the chain. Other organisms, such as herbivores, feed on these photosynthetic organisms, starting the transfer of energy through the food chain. Saprophytic organisms feed on dead organic matter, while parasitic organisms rely on other living organisms for their nutrition.
2.
In the following groups of materials, which group (s) contains only non-biodegradable items?
(i) Wood, paper, leather
(ii) Polythene, detergent, PVC
(iii) Plastic, detergent, grass
(iv) Plastic, Bakelite, DDT
Correct Answer
D. (ii) and (iv)
Explanation
Group (ii) contains only non-biodegradable items because polythene, detergent, and PVC are all synthetic materials that do not break down naturally. Group (iv) also contains only non-biodegradable items because plastic, Bakelite, and DDT are all synthetic materials that do not decompose easily in the environment.
3.
If a grasshopper is eaten by a frog, then the energy transfer will be from:
Correct Answer
C. Primary consumer to secondary consumer
Explanation
When a grasshopper is eaten by a frog, the energy transfer is from the primary consumer (frog) to the secondary consumer (predator of the frog). In this case, the frog is the primary consumer as it consumes the grasshopper, which is a producer. The energy flows from one trophic level to the next, with the primary consumer being at a higher trophic level than the grasshopper. Therefore, the correct answer is "Primary consumer to secondary consumer."
4.
In the figure given alongside, the various trophic levels are shown in the form of a pyramid. At what trophic level the maximum energy is available.
Correct Answer
C. T1
Explanation
The trophic level T1 represents the producers, such as plants, which convert sunlight into energy through photosynthesis. As the energy flows through the food chain, it decreases at each trophic level due to energy loss through respiration, heat, and waste. Therefore, the maximum energy is available at the first trophic level, T1.
5.
Sahara Desert was formed over a period of time due to one of the following uncontrolled activities of man:
Correct Answer
C. Excessive killing of large carnivores
Explanation
Excessive killing of large carnivores could have contributed to the formation of the Sahara Desert. Large carnivores play a crucial role in maintaining the balance of ecosystems by controlling the population of herbivores. When large carnivores are excessively killed, the herbivore population increases rapidly, leading to overgrazing of vegetation. This overgrazing can result in the depletion of plant life and the desertification of the area. Without the natural checks and balances provided by large carnivores, the ecosystem becomes imbalanced, ultimately leading to the formation of a desert.
6.
What percentage of sun’s energy falling on the leaves of green plants is utilized by the plants in the process of photosynthesis and stored as chemical energy of food?
Correct Answer
A. 1 percent
Explanation
Only 1 percent of the sun's energy falling on the leaves of green plants is utilized by the plants in the process of photosynthesis and stored as chemical energy of food. This means that the majority of the sun's energy is not converted into food by the plants and is instead lost as heat or reflected back into the environment.
7.
The flow of energy in an ecosystem is always:
Correct Answer
A. Unidirectional
Explanation
The flow of energy in an ecosystem is always unidirectional because energy enters the ecosystem through the producers (such as plants) that convert sunlight into chemical energy through photosynthesis. This energy then flows through the food chain as consumers (such as herbivores and carnivores) eat the producers or other consumers. However, energy cannot flow back to the producers, as they cannot consume other organisms. Therefore, the flow of energy in an ecosystem is always in one direction, from the producers to the consumers.
8.
The excessive exposure of humans to ultraviolet rays result in:
(i) Damage to immune system
(ii) Damage to lungs
(iii) Skin cancer
(iv) Peptic ulcers
Correct Answer
D. (i) and (iii)
Explanation
Excessive exposure to ultraviolet rays can lead to damage to the immune system and an increased risk of developing skin cancer. Ultraviolet rays can suppress the immune system, making individuals more susceptible to infections and diseases. Additionally, prolonged exposure to ultraviolet rays can cause DNA damage in the skin cells, leading to the development of skin cancer.
9.
Most of the water surface of a lake is covered with algae. This algae is a part of the food chain which also includes small fish, bird, larvae and big fish. Which of the following will obtain the maximum energy?
Correct Answer
C. Larvae
Explanation
Larvae will obtain the maximum energy because they are at a lower trophic level in the food chain. As energy moves up the food chain, there is a loss of energy at each level. The algae, being at the lowest trophic level, have the most energy available. The small fish, bird, and big fish will all receive less energy as they are higher up in the food chain and have to rely on consuming organisms below them. Therefore, the larvae, being closer to the energy source, will obtain the maximum energy.
10.
If the energy transferred to a tertiary consumer in a food chain is 10 J, how energy was available to the primary consumer?
Correct Answer
C. 1000 J
Explanation
The energy transferred to a tertiary consumer in a food chain is only a fraction of the energy available to the primary consumer. As energy flows through each level of the food chain, it is lost as heat and used for metabolic processes. Therefore, in order for 10 J of energy to be transferred to a tertiary consumer, a larger amount of energy, such as 1000 J, must have been available to the primary consumer.
11.
O2 is converted into O3 by the action of:
Correct Answer
B. Ultraviolet radiations
Explanation
Ultraviolet radiations are responsible for converting O2 into O3. When high-energy ultraviolet radiation from the sun interacts with oxygen molecules in the atmosphere, it breaks the O2 molecules apart. The resulting oxygen atoms then combine with other oxygen molecules to form ozone (O3). This process, known as photodissociation, occurs in the ozone layer of the Earth's atmosphere and plays a crucial role in protecting us from harmful ultraviolet radiation.
12.
The ten percent law is associated with:
Correct Answer
B. Transfer of chemical energy from one organism to another
Explanation
The ten percent law states that only about ten percent of the energy available at one trophic level is transferred to the next trophic level. This is because energy is lost as heat during metabolism and other biological processes. Therefore, the correct answer is "Transfer of chemical energy from one organism to another" as it accurately describes the concept of energy transfer between organisms in a food chain.
13.
What will happen if deer is missing in the food chain given below? Grass
Correct Answer
D. The population of tiger decreases and the population of grass increases
Explanation
If the deer is missing in the food chain, the population of tiger will decrease because deer is one of its main food sources. Without deer, the tiger will have less food available, leading to a decrease in its population. On the other hand, the population of grass will increase because there will be no deer to eat it. With the absence of deer, the grass will thrive and its population will grow.
14.
Name the process in which a harmful chemical enters the food chain and gets concentrated at each level in the food chain.
Correct Answer
B. Biomagnifications
Explanation
Biomagnification is the process in which a harmful chemical enters the food chain and becomes more concentrated as it moves up each level. This occurs because organisms at higher levels consume many organisms at lower levels, accumulating the chemical in their bodies. As a result, the concentration of the chemical increases at each trophic level, posing a greater risk to organisms higher up in the food chain.
15.
A natural phenomenon that becomes harmful due to pollution is?
Correct Answer
C. Greenhouse effect
Explanation
The greenhouse effect is a natural phenomenon that becomes harmful due to pollution. It occurs when certain gases in the Earth's atmosphere trap heat from the sun and prevent it from escaping back into space. This natural process is essential for sustaining life on Earth by keeping the planet warm enough to support living organisms. However, human activities, such as the burning of fossil fuels, have increased the concentration of greenhouse gases in the atmosphere, leading to an enhanced greenhouse effect and global warming. This pollution-induced greenhouse effect is causing significant environmental and climate changes, making it the correct answer.