Question

Student to attempt either option-(A) or (B): (A)

• [(i)] How does alien species invasion cause a decline in biodiversity? Explain.
  How have the following contributed to biodiversity loss?
  • I. Nile Perch
  • II. Lantana and Eichhornia
  • III. Clarias gariepinus
• [(ii)] Why have certain regions been declared as biodiversity hotspots by environmentalists of the world? Name any two such regions in India.

OR
(B)

• [(i)] Write an equation for Verhulst-Pearl Logistic Growth Curve where:
  N = Population density at time ‘t’
  r = Intrinsic rate of natural increase
• [(ii)] Draw a graph for a population whose population density has reached carrying capacity.
• [(iii)] Draw a growth curve where resources are non-limiting to growth of population.
• [(iv)] Which growth curve is considered more realistic and why? Explain.

Hint:

Invasive species disrupt native ecosystems. Logistic growth models real-world population trends, considering environmental limits.

Answer 1

(A)

1. [(i)] Alien species invasion causes biodiversity loss by outcompeting native species for resources, altering habitats, or introducing new diseases.
   • Nile Perch: Introduced in Lake Victoria, it caused the extinction of over 200 native cichlid fish species.
   • Lantana and Eichhornia: These invasive plants choke native vegetation and water bodies, respectively, altering ecosystem structure.
   • Clarias gariepinus: An exotic African catfish introduced in Indian waters that threatens indigenous fish diversity by predation and competition.
2. [(ii)] Regions rich in endemic species and facing severe threats are declared as biodiversity hotspots. These areas are prioritized for conservation.
   Two biodiversity hotspots in India:
   • Western Ghats
   • Indo-Burma region

OR (B)

1. [(i)] The equation for Verhulst-Pearl Logistic Growth is:
   \[ \frac{dN}{dt} = rN\left(\frac{K - N}{K}\right) \] Where:
   • \( N \) = Population density at time \( t \)
   • \( r \) = Intrinsic rate of natural increase
   • \( K \) = Carrying capacity
2. [(ii)] % Logistic Growth Curve Graph
   (Draw an S-shaped sigmoid curve showing slow start, exponential growth, and leveling off at K)
   
3. [(iii)] % Exponential Growth Curve Graph
   (Draw a J-shaped curve showing continuous rise in population size)
   
4. [(iv)] The logistic growth curve is considered more realistic because:
   • It takes into account limited resources and environmental resistance.
   • It reflects the natural population growth trend where growth slows as resources become scarce and population approaches carrying capacity.