Biodiversity loss is accelerating globally, and NEET consistently tests whether you can distinguish the causes, quantify the relationship between habitat area and species richness, and match conservation strategies to their correct categories.
The species-area relationship (Alexander von Humboldt's observation, formalized by Arrhenius) states: log S = log C + Z log A. The slope Z ranges 0.1–0.2 for small regions within a continent, but steepens to 0.6–1.2 when the analysis spans entire continents. NEET questions frequently test whether you remember which Z-range applies where — confusing the two is a high-frequency error.
Causes of biodiversity loss — the "Evil Quartet" (Edward Wilson): habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions. Habitat loss is the most potent driver. The Amazon rainforest ("lungs of the planet") is being cut for soybean cultivation and cattle ranching. When a habitat is reduced to a fraction, the species-area curve predicts how many species will be lost.
Conservation strategies split into two categories:
A common NEET distractor places sacred groves under ex-situ or confuses biodiversity hotspots with biosphere reserves. Hotspots are biogeographic zones identified by high endemism and high threat (Norman Myers); biosphere reserves are administratively designated protected areas.
Biodiversity hotspots require two criteria: ≥1500 endemic vascular plant species AND ≥70% habitat loss. India has 4 hotspots: Western Ghats & Sri Lanka, Indo-Burma, Himalaya, and Sundaland (partially). NCERT Class 12 Biology Chapter 15, page 300, documents these as core evaluable facts.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which of the following is NOT one of Edward Wilson's "Evil Quartet" causes of biodiversity loss?
How many biodiversity hotspots are currently recognized in India?
Which of the following is an example of ex-situ conservation?
In the species-area relationship log S = log C + Z log A, a researcher studying bird species on small islands within a continent finds Z = 0.75. What can be inferred?
A biodiversity hotspot must satisfy two criteria for designation. Which combination is correct?
If a tropical forest of area A is reduced to 10% of its original area, and the species-area slope Z = 0.2, approximately what percentage of species would be predicted to survive?
Sacred groves are considered effective biodiversity conservation sites because they:
An island originally has 500 species and an area of 10,000 km². After deforestation, 90% of the area is lost. Using the species-area relationship with Z = 0.2, how many species are estimated to be lost?
Pattern: Species-area relationship application (from P.BIO.U10.UNIT_BUNDLE — recall + direct_application)
Given
- Original area: A₁ = 50,000 km² - Reduced area: A₂ = 5,000 km² (90% habitat loss) - Original species count: S₁ = 2,000 - Z = 0.2 (intra-continental region) - C is constant for both calculations
Required
Number of species predicted to survive after habitat loss, and the number lost.
Concept
The Arrhenius species-area relationship: log S = log C + Z log A. When comparing two areas in the same region, C cancels out, giving S₂/S₁ = (A₂/A₁)^Z.
Formula
S₂/S₁ = (A₂/A₁)^Z
Substitution
S₂/2000 = (5000/50000)^0.2 = (0.1)^0.2
Calculation
(0.1)^0.2 = 10^(−0.2) = antilog(−0.2) ≈ 0.631 S₂ = 2000 × 0.631 = 1262 species survive Species lost = 2000 − 1262 = 738 Note: 2000 (original species count) and 0.2 (given Z value) are problem-defined exact values and do not introduce rounding uncertainty into significant figures.
Final answer
Approximately 1,262 species survive; approximately 738 species are predicted to be lost.
Common trap
Students often assume that 90% area loss means 90% species loss (i.e., 1,800 lost). The power-law relationship with Z = 0.2 buffers the loss — actual predicted loss is ~37%, not 90%. Another trap: confusing "species remaining" with "species lost" (315 vs 185 in the MCQ above).
Similar NEET-style question
"A tropical region has 1,500 plant species in an area of 20,000 km². If the area is reduced to 2,000 km², estimate the number of plant species likely to survive (Z = 0.2)." [Answer: 1500 × (0.1)^0.2 ≈ 1500 × 0.631 ≈ 947 species] ---
In situ: national parks, biosphere reserves (e.g. Nilgiri, Sundarbans), sacred groves. Ex situ: zoos, botanical gardens, gene banks, cryopreservation. IUCN Red List: extinct, EW, CR, EN, VU, NT, LC, DD, NE.
-- NCERT Class 12 Biology, Ch. 13, p. 300Approximately 10% of energy at one trophic level is transferred to the next; rest dissipated as heat.
| Symbol | Quantity | SI Unit |
|---|---|---|
| E_n | energy at level n | kcal/m² |
Population grows exponentially at small N; growth slows as N approaches K (carrying capacity); equilibrium at N = K.
| Symbol | Quantity | SI Unit |
|---|---|---|
| N | population size | - |
| r | intrinsic rate of increase | /time |
| K | carrying capacity | - |
Number of species S in area A increases as a power law. Z (slope) = 0.1-0.2 for small areas, 0.6-1.2 for continents.
| Symbol | Quantity | SI Unit |
|---|---|---|
| S | species number | - |
| A | area | - |
| Z | slope | - |
| C | intercept | - |
These are the exact patterns that cause wrong answers in NEET. Each trap includes when it triggers and how to avoid it.
Category: Similar Terms
Mutualism benefits BOTH; commensalism benefits one, neutral for the other; parasitism +,−; predation +,−.
Question presents organism-pair interaction and asks for type.
Tabulate effects on each partner: (+,+), (+,0), (+,−), (−,−), (0,−), (0,0).
Root cause: term confusion
K-selected: large body, few offspring with high parental investment, long-lived (whales, humans, elephants). r-selected: small body, many offspring, low investment, short-lived (insects, weeds).
Root cause: concept gap
Pyramid of ENERGY is ALWAYS upright (10% law guarantees decreasing energy at higher trophic levels). Pyramid of NUMBER and BIOMASS can be inverted (e.g. ocean: small algae < large zooplankton at one moment).
44 questions from NEET 2020, 2021, 2022, 2023, 2024, 2025. Answers verified against NTA official keys.
Which of the following is the unit of productivity of an Ecosystem?
Which one of the following equations represents the Verhulst-Pearl Logistic Growth of population?
Who is known as the father of Ecology in India?
Epiphytes that are growing on a mango branch is an example of which of the following?
List of endangered species was released by-
Which of the following statements is incorrect?
The thickness of ozone in a column of air in the atmosphere is measured in terms of :
Which one of the following statements cannot be connected to Predation?
The gaseous plant growth regulator is used in plants to :
Which one of the following will accelerate phosphorus cycle?
Which one of the following statements is correct?
Which of the following statements is not true?
Which of the following is a correct statement?
Amensalism can be represented as: Select the correct answer from the options given
Select the correct pair. 141. Which of the following statements is incorrect?
In the exponential growth equation N = N ert, e t o
• ≈UÊ∑¸˜§Á≈U∑§ ˇÊ òÊ ◊ Á„◊-• œÃÊ Á∑§‚ ∑§Ê⁄UáÊ „Ê ÃË „Ò? temperature
Recurring question shapes from past papers. Each pattern shows why wrong options look tempting.
population interaction type confusion
Six interaction types form a 2x2 effect matrix (+,+), (+,-), (+,0), (-,-), (-,0), (0,0). Students who have memorised the symbols cannot always assign real organism pairs correctly: barnacles on a whale body = commensalism (+,0) not mutualism (+,+); mycorrhizal fungi on plant roots = mutualism not parasitism. The most common error is selecting mutualism for commensalism examples because both organisms are 'associated'.
ecological pyramid inversion error
Students learn that 'ecological pyramids can be inverted' from the examples of the number pyramid (tree-insects-birds) and the ocean biomass pyramid. They over-apply this to energy pyramids. The 10% law guarantees that energy ALWAYS decreases at each trophic level -- no realistic scenario inverts the energy pyramid. Questions ask which pyramid type 'can be inverted'; students select energy because they generalise the inversion rule.
k r selection confusion
K-selected species (large body, few offspring, high parental investment, long-lived: whales, humans, elephants) are confused with r-selected (small body, many offspring, no parental care: insects, frogs, bacteria). Students who associate 'reproducing as humans do = normal' call humans r-selected, or who associate 'complex animal = cared-for offspring' call oysters K-selected.
speciation type confusion
Sympatric speciation occurs in the same geographic area without physical isolation (e.g., polyploidy); allopatric speciation requires a geographic barrier. Students who cannot recall the Greek roots (sym = same, allo = different) confuse the two when a question describes a real-world scenario and asks which speciation type it illustrates.
Test yourself on this topic with real past-paper questions:
Practice this topic →Get a structured 30-day study plan and a complete formula booklet — delivered to your inbox instantly.