Lakshya Education MCQs

Question: Which among the following pictures are biodegradable substances?

Options:
A.1
B.2
C.3
D.1 and 2
Answer: Option B
: B

Paper is biodegrdable and hence the bagsmade out of paper arealso biodegradable.Polyethene bags and waste parts of mobile phones or any other electronic devices (e-waste)are non-biodegradable.

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Question 1. Bacteria plays important role in an ecosystem because 
  1.    they act as producers.
  2.    they act as decomposers.
  3.    they act as consumers.
  4.    they act as parasites.
Answer: Option B
: B

Microorganisms likebacteria and fungi, actasdecomposers as they break downcomplex organic substances into simpler inorganic substances that go into the soil. These inorganic substances are thenrecycled by plants.
Decomposers are considered to be of great importance as in theirabsence, earth would be filled with dead bodies.
Question 2. Current concentration of CO2 in atmosphere is:
  1.    270 ppmv
  2.    350 ppmv
  3.    430 ppmv
  4.    500 ppmv
Answer: Option C
: C

430 ppmv is thecurrent concentration of CO2in atmosphere.The global concentration of carbon dioxide in the atmosphere – the primary driver of recent climate change – has reached over 400 parts per million (ppm) for the first timethis year.The safe level of carbon dioxide in the atmosphere is 350 parts per million.
Question 3. Which is the country having the largest number of hydroelectric dams? 
  1.    India
  2.    China
  3.    Netherlands
  4.    USA
Answer: Option B
: B

China is the country which has the largest number of hydroelectric dams. Hydropower doesn't pollute the air like power plants that burn fossil fuels, such as coal or natural gas. Hydropower is a domestic source of energy, produced in the United States. Hydropower relies on the water cycle, which is driven by the sun, thus it's a renewable power source.
Question 4. Mountains are part of the natural ecosystem.
  1.    True
  2.    False
  3.    Decreased release of CFCs
  4.    Increase in sulphur dioxide and carbon monoxide
Answer: Option A
: A

An ecosystem is a community of living organisms in conjunction with the non-living components of their environment (things like air, water and minerals, light etc), interacting as a system. So, mountains are also a part of the natural ecosystem.
Question 5. The major cause for depletion of ozone layer in stratosphere can be attributed to:
  1.    Increase in the level of greenhouse gases
  2.    Increased release of CFCs
  3.    Decreased release of CFCs
  4.    Increase in sulphur dioxide and carbon monoxide
Answer: Option B
: B

The ozone depletion process begins when CFCs and other ozone-depleting substances (ODS) are emitted into the atmosphere. CFCs are extremely stable, and they do not dissolve in rain. After a period of time, CFC molecules reach the stratosphere. Due to the action of UV rays,CFCs release chlorine atoms.These chlorine atoms react with ozone molecules and destroy the ozone layer.
It is estimated that one chlorine atom can destroy over 1,00,000 ozone molecules before it is removed from the stratosphere.
Question 6. Which of the following constitutes a food chain?
  1.    Grass, Wheat and Mango
  2.    Grass, Goat and Human
  3.    Goat, Cow and Elephant
  4.    Grass, Fish and Goat
Answer: Option B
: B

Food chain is a series of organisms feeding on one another. From the given options, 'grass, goat and human' forms a food chain. Here, grass prepares its food during photosynthesis and becomes food for a goat, which in turn becomes food for humans. This food chain starts with producers (i.e.,grass) and ends in tertiary consumer (i.e. human).

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