Class 10 Our Environment Exemplar
Multiple Choice Questions:
Q-1: Which of the following is an artificial ecosystem?
(a) Pond (b) Crop field (c) Lake (d) Forest
Solution: (b)
Crop filed is an artificial ecosystem. It is an agricultural land created by man. Pond, lake and forests are natural ecosystem, as they are self-sustainable and do not need human interference for their maintenance.
Q-2: In a food chain, the third trophic level is always occupied by
(a) carnivores (b) herbivores (c) decomposers (d) producers
Solution: (a)
In a food chain, the third trophic level is always occupied by carnivores that feed on herbivores.
The various steps in a food chain at which the transfer of food (or energy) takes placed are called trophic levels.
Plants (producers or autotrophs) occupy the first trophic level, herbivores constitute the second trophic level, carnivores constitute the third trophic level and higher carnivores occupy the fourth trophic level.
Q-3: An ecosystem includes
(a) all living organisms
(b) non-living objects
(c) both living organisms and non-living objects
(d) sometimes living organisms and sometimes non-living objects
Solution: (c)
All the interacting organisms in an area together with the non-living constituent of the environment form an ecosystem.
Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall. Wind, soil and minerals.
Q-4: In the given food chains, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level
a) 5 kJ (b) 50 kJ (c) 500 kJ (d) 5000 kJ
Solution: (d)
According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level. In this food chain at the 4th trophic level, only 5 kJ energy is available to the snake. So, the energy available at the 4th producer level will be 500 kJ. It can be shown as
Q-5: Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as
(a) eutrophication (b) pollution
(c) bio-magnification (d) accumulation
Solution: (c)
Bio-magnification is the accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level. The maximum concentration of these chemicals are accumulated in human beings as they occupy top level in any food chain.
Eutrophication is the process by which a water body becomes enriched in dissolved nutrients that stimulate the growth of aquatic plant life usually resulting in depletion of dissolved oxygen.
Pollution is the introduction of contaminants into the natural environment that cause adverse change.
Q-6: Depletion of ozone is mainly due to
(a) chlorofluorocarbon compounds (b) carbon monoxide
(c) methane (d) pesticides
Solution: (a)
Depletion of ozone is mainly due to chlorofluorocarbons (CFCs). These are synthetic chemicals which are used as refrigerants and in the fire extinguishers.
Carbon monoxide leads to air pollution. It causes harm to humans by combining with haemoglobin, thus affecting carrying capacity of blood.
Methane is a greenhouse gas, released from power stations, chemical industries etc. Pesticides are not degradable, thus causes biological magnification.
Q-7: Organisms which synthesis carbohydrates fro inorganic compounds using radiant energy are called
(a) decomposers (b) producers
(c) herbivores (d) carnivores
Solution: (b)
Organisms which synthesis carbohydrates from inorganic compounds using radiant energy are called producers e.g., all green plants, blue-green algae.
Organisms which consume the food produced either directly from producers or indirectly by feeding on other consumers are the consumers. They can be classified as herbivores, carnivores and omnivores. Organisms which feed on dead plants and animals are called decomposers or saprophytes.
Q-8: In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of
(a) heat energy (b) light energy
(c) chemical energy (d) mechanical energy
Solution: (c)
The 10% of energy available for transfer from one trophic level to the next in an ecosystem is in the form of chemical energy.
The autotrophs (or producers) capture the energy present in sunlight and convert it into chemical energy. This energy is passed onto other trophic levels to support all the activities of the living world.
Q-9: Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the
(a) food web (b) ecological pyramid
(c) ecosystem (d) food chain
Solution: (a)
Organisms of a higher trophic level feeding on several types of organisms belonging to a lower trophic level constitute the food web.
A series of organisms through which food energy flows in an ecosystem is called food chain.
An ecosystem consists of all the living beings of an area non-living components of the their environment.
The graphic summary of the trophic structure and energy transfer in an ecosystem is called ecological pyramids.
Q-10: Flow of energy in an ecosystem is always
(a) unidirectional (b) bidirectional
(c) multidirectional (d) no specific direction
Solution: (a)
Flow of energy in an ecosystem is always unidirectional. This is because the energy that is captured by the autotrophs cannot revert back to the solar input and the energy which passes to herbivores cannot back to autotrophs.
The energy moves progressively through various trophic levels, so, it may not be available to previous level.
Q-11: Excessive exposure of humans to UV-rays results in
(i) damage to immune system (ii) damage to lungs
(iii) skin cancer (iv) peptic ulcers
(a) (i) and (ii) (b) (ii) and (iv) (c) (i) and (iii) (d) (iii) and (iv)
Solution: (c)
The UV-rays have extremely harmful effects on human beings, other animals as well as plants.
It can cause skin cancer, damage the eyes by causing cataract, also damage immune system by lowering the body’s resistance to diseases.
Q-12: 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
(a) (iii) (b) (iv) (c) (i) and (iii) (d) (ii) and (iv)
Solution: (d)
Substances that cannot be broken down by biological processes in nature are non-biodegradable e.g., polythene, detergent, PVC, plastic, Bakelite, DDT etc.
On the other hand, substances that are broken down by biological processes are said to be biodegradable e.g., wood, paper, leather, grass, animal bones etc.
Q-13: Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Defficient food supply
(c) Polluted air
(d) Water
Solution: (a)
Decrease in energy at higher trophic levels limits the number of trophic levels in a food chain. At each trophic level, a large portion of energy is utilized for the maintenance of organisms that occur at that trophic level.
So, organisms at higher level gets less and less energy at successive levels. The number of trophic levels are limited to 3-4 because after that, the energy available for the next level will be too small i.e., it will be insufficient to sustain life of the organisms.
Q-14: Which of the statement is incorrect?
(a) All green plants and blue-green algae are producers
(b) Green plants get their food from organic compounds
(c) Producers prepare their own food from inorganic compounds
(d) Plants convert solar energy into chemical energy
Solution: (b)
Green plants get their food form inorganic compounds using radiant energy of the sun in the presence of chlorophyll.
All green plants and blue-green algae are called producers as they can prepare food from inorganic substances by photosynthesis.
Producers capture the solar energy and convert it into chemical energy.
Q-15: Which group of organisms are not constituents of a food chain?
(i) Grass, lion, rabbit, wolf
(ii) Plankton, man, fish, grasshopper
(iii) Wolf, grass, snake, tiger
(iv) Frog, snake, eagle, grass, grasshopper
(a) (i) and (iii) (b) (iii) and (iv) (c) (ii) and (iii) (d) (i) and (iv)
Solution: (c)
The sequence of living organisms in a community in which one organism consumes another organism to transfer energy is called a food chain.
Food chain (ii) is an aquatic food chain in which grasshopper cannot take part. The correct sequence is
In food chain (iii) wolf, snake and tiger are carnivores, there is no herbivore to eat grass.
(i) is forest food chain
Similarly (iv), is also food chain in a grassland
Q-16: The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about
(a) 1% (b) 5% (c) 8% (d) 10%
Solution: (a)
The green plants capture about 1% of the energy of sunlight that falls on their leaves for the process of photosynthesis.
This energy is converted into chemical energy as food. At the subsequent level, 10% energy is available.
Q-17: In the given figure, the various trophic levels are shown in a pyramid. At which trophic level is maximum energy available?
There is progressive decline in the amount of energy available from producer to higher trophic levels, i.e.,
Solution: (c)
The maximum energy is available at T1 There is progressive decline in the amount of energy available from producer to higher trophic levels, i.e., T1>T2>T3>T4 (energy)
This is because at each trophic level a large portion of energy is utilized for maintenance of organisms at that trophic level and lost as heat.
Q-18: What will happen if deer is missing in the food chain given below?
(a) The population of tiger increases
(b) The population of grass decreases
(c) Tiger will start eating grass
(d) The population of tiger decreases and the population of grass increases
Solution: (d)
If dear is missing in the given food chain, there will not be sufficient food for the tigers. Some of the tigers will die because of starvation and hence, the population of tigers will decreases. Since grass is eaten by deers, the population of grass will also increase when deer is missing.
Q-19: The decomposers in an ecosystem
(a) Convert inorganic material to simpler forms
(b) Convert organic material to inorganic forms
(c) Convert inorganic materials into organic compounds
(d) do not breakdown organic compounds
Solution: (b)
The decomposers in an ecosystem covert organic material to inorganic forms, that go into the soil and are once again used up by the plants. Decomposers feed on dead remains and waste products or organisms.
Producers convert inorganic materials into organic compounds like sugar and starch using sunlight in presence of chlorophyll.
Q-20: If a grasshopper is eaten by a frog, then the energy transfer will be from
(a) producer to decomposer
(b) producer to primary consumer
(c) primary consumer to secondary consumer
(d) secondary consumer to primary consumer
Solution: (c)
In a food chain, if a grasshopper is eaten by a frog, then the energy transfer will be from primary consumer to secondary consumer.
Grasshopper feeds on producers i.e., the grass/plants. So, it occupies the level of primary consumer. Frogs, eating grasshopper thus becomes the secondary consumer.
Q-21: Disposable plastic plates should not be used because
(a) they are made of materials with light weight
(b) they are made of toxic materials
(c) they are made of biodegradable materials
(d) they are made of non-biodegradable materials
Solution: (D)
Disposable plastic plates should not be used because they are made of non-biodegradable materials like plastics etc. The non-biodegradable materials cannot be broken down into harmless substances in nature, so they are major pollutant of the environment.