Part 2 – Patterns of Biodiversity (25 MCQs)

Q1. Which of the following correctly describes the latitudinal gradient of biodiversity?

a) Biodiversity increases towards poles
b) Biodiversity is highest in deserts
c) Biodiversity decreases from equator to poles
d) Biodiversity is uniform across the globe

Answer: c) Biodiversity decreases from equator to poles

Explanation:

(a) Incorrect → The opposite is true.
(b) Incorrect → Deserts are species-poor.
(c) Correct → Maximum in tropics, decreases towards poles.
(d) Incorrect → Not uniform.

Q2. The Amazon rainforest is called the “lungs of the planet” because:

a) It contains large numbers of animals
b) It contributes 20% of Earth’s oxygen
c) It has high CO₂ concentration
d) It is the coldest region

Answer: b) It contributes 20% of Earth’s oxygen

Explanation:

(a) Incorrect → Animals don’t make it lungs.
(b) Correct → Amazon = largest producer of O₂.
(c) Incorrect → It absorbs CO₂, not accumulates.
(d) Incorrect → Not a cold region.

Q3. Which biome shows maximum biodiversity?

a) Tropical rainforest
b) Temperate forest
c) Desert
d) Tundra

Answer: a) Tropical rainforest

Explanation:

(a) Correct → Highest species richness.
(b) Incorrect → Lower than tropics.
(c) Incorrect → Deserts = species-poor.
(d) Incorrect → Tundra = lowest.

Q4. The major cause of high tropical biodiversity is:

a) Low solar radiation
b) Constant environmental conditions
c) Frequent glaciations
d) Short evolutionary time

Answer: b) Constant environmental conditions

Explanation:

(a) Incorrect → Tropics get high solar radiation.
(b) Correct → Stability and productivity → high speciation.
(c) Incorrect → Glaciations occur in poles, not tropics.
(d) Incorrect → Tropics have long evolutionary time.

Q5. Species–area relationship was studied by:

a) E.O. Wilson
b) Robert May
c) Alexander von Humboldt
d) Charles Darwin

Answer: c) Alexander von Humboldt

Explanation:

(a) Incorrect → E.O. Wilson worked on conservation.
(b) Incorrect → Robert May estimated species number.
(c) Correct → Humboldt studied species–area curves.
(d) Incorrect → Darwin worked on natural selection.

Q6. According to species–area relationship, species richness increases with:

a) Increase in altitude
b) Increase in area
c) Decrease in area
d) Decrease in temperature

Answer: b) Increase in area

Explanation:

(a) Incorrect → Altitude increase = fewer species.
(b) Correct → Larger area = more species.
(c) Incorrect → Decrease in area reduces species.
(d) Incorrect → Lower temperature = fewer species.

Q7. The mathematical expression of species–area relationship is:

a) S = A + C
b) S = C + A^z
c) S = C A^z
d) S = zC^A

Answer: c) S = C A^z

Explanation:

(a) Incorrect → Not correct formula.
(b) Incorrect → Wrong placement of exponents.
(c) Correct → Humboldt’s equation.
(d) Incorrect → Not a standard form.

Q8. In the equation S = C A^z, what does “z” represent?

a) Number of species
b) Constant of proportionality
c) Slope of the line (species–area curve)
d) Area of region

Answer: c) Slope of the line (species–area curve)

Explanation:

(a) Incorrect → S = species, not z.
(b) Incorrect → C is the constant.
(c) Correct → z = slope.
(d) Incorrect → A = area, not z.

Q9. The value of “z” in species–area relationship for most regions is:

a) 0.1–0.2
b) 0.6–1.2
c) 2–3
d) 5–6

Answer: a) 0.1–0.2

Explanation:

(a) Correct → Normal habitats show z = 0.1–0.2.
(b) Incorrect → Applies to larger areas like continents (0.6–1.2).
(c) Incorrect → Too high.
(d) Incorrect → Not related.

Q10. Which type of curve does species–area relationship generally follow (on log scale)?

a) Straight line
b) Hyperbolic curve
c) Sigmoid curve
d) Inverted U-shaped

Answer: a) Straight line

Explanation:

(a) Correct → Log S vs log A = straight line.
(b) Incorrect → Hyperbolic not observed here.
(c) Incorrect → Sigmoid relates to logistic growth.
(d) Incorrect → Not an inverted U.

Q11. For very large areas such as continents, the value of “z” is:

a) 0.1–0.2
b) 0.2–0.4
c) 0.6–1.2
d) >2

Answer: c) 0.6–1.2

Explanation:

(a) Incorrect → For small regions.
(b) Incorrect → Not standard range.
(c) Correct → Continental scale has higher slope.
(d) Incorrect → Not as high as 2.

Q12. The reason why larger areas have more species is because:

a) More climatic variations
b) Higher chances of extinction
c) More habitats and niches available
d) Low productivity

Answer: c) More habitats and niches available

Explanation:

(a) Incorrect → Variation is not the main reason.
(b) Incorrect → Extinction probability increases in smaller areas.
(c) Correct → More niches = more species.
(d) Incorrect → Productivity is not low.

Q13. Who first proposed the species–area relationship?

a) Humboldt
b) Mayr
c) Wallace
d) Wilson

Answer: a) Humboldt

Explanation:

(a) Correct → Alexander von Humboldt.
(b) Incorrect → Mayr worked on species concept.
(c) Incorrect → Wallace on biogeography.
(d) Incorrect → Wilson on biodiversity conservation.

Q14. Which of the following ecosystems has the highest species–area curve slope (z value)?

a) Tropical forests
b) Grasslands
c) Continental areas
d) Deserts

Answer: c) Continental areas

Explanation:

(a) Incorrect → High but not maximum.
(b) Incorrect → Lower slope.
(c) Correct → Continents have z = 0.6–1.2.
(d) Incorrect → Deserts have low diversity.

Q15. Which is the main reason for high biodiversity in the tropics compared to temperate regions?

a) High seasonal variations
b) Long evolutionary time without glaciations
c) Low primary productivity
d) Less stable environment

Answer: b) Long evolutionary time without glaciations

Explanation:

(a) Incorrect → Tropics have low seasonal variation.
(b) Correct → Stability for millions of years favored speciation.
(c) Incorrect → Productivity is high, not low.
(d) Incorrect → Tropics are more stable.

Q16. The “species–area relationship” graph on normal scale is:

a) Sigmoid curve
b) Rectangular hyperbola
c) Parabolic
d) Inverted U-shaped

Answer: b) Rectangular hyperbola

Explanation:

(a) Incorrect → Sigmoid applies to logistic growth.
(b) Correct → On arithmetic scale, species–area curve = rectangular hyperbola.
(c) Incorrect → Not parabolic.
(d) Incorrect → Not U-shaped.

Q17. Which of the following is NOT a reason for higher tropical biodiversity?

a) Stable environment
b) High productivity
c) High seasonal variations
d) Longer evolutionary time

Answer: c) High seasonal variations

Explanation:

(a) Correct → Stability supports diversity.
(b) Correct → Productivity supports diversity.
(c) Correct answer → Seasonal variation reduces diversity.
(d) Correct → More evolutionary time supports speciation.

Q18. The species–area relationship was studied in which type of organisms by Humboldt?

a) Plants
b) Birds
c) Mammals
d) Reptiles

Answer: a) Plants

Explanation:

(a) Correct → Humboldt studied plants in different areas.
(b) Incorrect → Not birds.
(c) Incorrect → Not mammals.
(d) Incorrect → Not reptiles.

Q19. Which law is explained by species–area relationship?

a) Law of dominance
b) Law of limiting factors
c) Law of biodiversity increase with area
d) Law of segregation

Answer: c) Law of biodiversity increase with area

Explanation:

(a) Incorrect → Genetics.
(b) Incorrect → Ecology principle, not this.
(c) Correct → More area = more species.
(d) Incorrect → Genetics.

Q20. On a logarithmic scale, species–area relationship becomes:

a) Rectangular hyperbola
b) Straight line
c) Sigmoid curve
d) Inverted parabola

Answer: b) Straight line

Explanation:

(a) Incorrect → Normal scale curve.
(b) Correct → Logarithmic plot is straight line.
(c) Incorrect → Not sigmoid.
(d) Incorrect → Not parabola.

Q21. Which region has the highest number of species on Earth?

a) Temperate forests
b) Tropical rainforests
c) Deserts
d) Tundra

Answer: b) Tropical rainforests

Explanation:

(a) Incorrect → Lower richness.
(b) Correct → Maximum species.
(c) Incorrect → Lowest.
(d) Incorrect → Lowest.

Q22. According to the latitudinal gradient, which of the following is TRUE?

a) Biodiversity decreases from poles to equator
b) Biodiversity increases from poles to equator
c) Biodiversity is uniform in both poles and equator
d) Biodiversity is maximum in deserts

Answer: b) Biodiversity increases from poles to equator

Explanation:

(a) Incorrect → Opposite.
(b) Correct → Tropics > poles.
(c) Incorrect → Not uniform.
(d) Incorrect → Deserts are poor.

Q23. Which of the following is a reason for fewer species in temperate regions?

a) High evolutionary time
b) Frequent glaciations
c) Stable climate
d) High productivity

Answer: b) Frequent glaciations

Explanation:

(a) Incorrect → Time is less, not more.
(b) Correct → Glaciations reduced diversity.
(c) Incorrect → Temperate climate is less stable than tropics.
(d) Incorrect → Productivity is lower.

Q24. Which of the following is NOT related to species–area relationship?

a) Larger area → more species
b) S = C A^z
c) Straight line on log scale
d) Law of dominance

Answer: d) Law of dominance

Explanation:

(a) Correct → True.
(b) Correct → Equation.
(c) Correct → Logarithmic scale.
(d) Correct answer → Mendelian law, not related.

Q25. Which of the following best explains why tropics are biodiversity-rich?

a) Seasonal climate, low productivity
b) Long evolutionary time, high productivity
c) Frequent glaciations, low stability
d) Harsh environment, less competition

Answer: b) Long evolutionary time, high productivity

Explanation:

(a) Incorrect → Climate is not seasonal, productivity is high.
(b) Correct → Both stability and productivity favor diversity.
(c) Incorrect → Glaciations reduce biodiversity.
(d) Incorrect → Harsh environment decreases species.

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Part 2 – Patterns of Biodiversity (25 MCQs)