MCQ (Solution) - Our Home: Earth, a Unique Life Sustaining Planet

Question 1:

Which combination best explains why Earth can sustain liquid water on its surface?
Option A: Far from the Sun, thin atmosphere, no magnetic field
Option B: Very large size, no atmosphere, strong solar wind
Option C: Very close to the Sun, thick clouds, no ozone layer
Option D: Right distance (habitable zone), suitable atmospheric greenhouse effect, nearly circular orbit

Question 2:

Why is Venus hotter than Mercury on average despite being farther from the Sun?
Option A: It receives more sunlight due to its rotation
Option B: Its thick CO₂ atmosphere causes an intense greenhouse effect
Option C: Mercury has no atmosphere to reflect sunlight
Option D: Venus has a stronger magnetic field trapping heat

Question 3:

If Earth were significantly smaller (same density), which outcome is most likely?
Option A: Weaker gravity, atmosphere escapes more readily
Option B: Stronger gravity, thicker atmosphere 
Option C: No change to atmospheric retention
Option D: Instant formation of oceans

Question 4:

Which protective role does Earth's magnetic field primarily play?
Option A: Keeps oceans from evaporating by cooling air
Option B: Blocks harmful UV radiation directly
Option C: Deflects charged particles from the Sun and space, helping protect the atmosphere
Option D: Traps oxygen near the surface

Question 5:

Which statement correctly distinguishes the atmospheric "greenhouse effect" from a plant greenhouse?
Option A: Both trap air with glass walls
Option B: Atmospheres absorb and re-emit infrared; greenhouses mainly limit air exchange and convection
Option C: Both reflect UV back to space
Option D: Neither warms surfaces

Question 6:

Which Earth system pairing is correctly matched to its main components?
Option A: Atmosphere - rocks and minerals
Option B: Biosphere - nitrogen and oxygen gases only 
Option C: Geosphere - plants, animals, microbes
Option D: Hydrosphere - liquid, solid, and vapor water reservoirs

Question 7:

Which factor makes Earth's orbit especially favorable for climate stability?
Option A: Highly elongated orbit causing strong seasonal extremes
Option B: Nearly circular orbit limiting insolation swings through a year
Option C: Retrograde orbit around the Sun
Option D: No axial tilt, so no seasons

Question 8:

Which best explains why the ozone layer is vital to surface life?
Option A: It absorbs harmful ultraviolet radiation
Option B: It deflects solar wind particles
Option C: It produces greenhouse gases
Option D: It generates Earth's magnetic field

Question 9:

Which statement about geodiversity is correct?
Option A: It refers to the variety of animal species
Option B: It is the diversity of climate types only
Option C: It includes the variety of landforms, rocks, soils, and geological processes
Option D: It is the number of lakes and rivers alone

Question 10:

Which pairing of reproduction type and description is correct?
Option A: Asexual - offspring are genetic mixes of two parents
Option B: Sexual - one parent produces identical copies
Option C: Asexual - one parent produces genetically identical offspring
Option D: Sexual - no gametes involved

Question 11:

Which sequence correctly describes sexual reproduction in flowering plants?
Option A: Germination → pollination → fertilisation → seed
Option B: Seed → fruit → fertilisation → pollination 
Option C: Fertilisation → pollination → fruit → seed
Option D: Pollination → fertilisation → seed formation → fruit development

Question 12:

Which is an example of vegetative (asexual) propagation?
Option A: Seed formation in mango
Option B: Potato sprouting from "eyes" forming new plants
Option C: Pollination by bees in mustard
Option D: Internal fertilisation in mammals

Question 13:

Which set correctly lists the "triple planetary crisis" discussed in the chapter?
Option A: Deforestation, overfishing, desertification
Option B: Climate change, biodiversity loss, pollution
Option C: Ozone formation, photosynthesis, respiration
Option D: Earthquakes, volcanoes, tsunamis

Question 14:

Which global treaty pairing is correctly matched with its primary goal?
Option A: Montreal Protocol - reduce ozone-depleting substances
Option B: Paris Agreement - remove all CO₂ from the air immediately
Option C: Kyoto Protocol - protect whale populations
Option D: Earth Summit - ban all fossil fuels instantly

Question 15:

Why do sexually reproducing offspring differ from their parents and siblings?
Option A: They receive identical gene copies as each parent
Option B: They receive a unique combination of genes via gametes from both parents
Option C: Environment rewrites their genetic instructions after birth
Option D: All siblings inherit the same gene mix each time