Biodiversity And Conservation

(a) The pie chart represents the global diversity of vertebrates. Based on the typical representation:
- A: Amphibians
- B: Reptiles
- C: Birds
- D: Mammals
- The largest section corresponds to Fishes, as they represent the most diverse group among vertebrates.
Redrawn Pie Chart: 


(b) Two examples of recently extinct animals: 1. Passenger Pigeon (Ectopistes migratorius): Went extinct in 1914 due to overhunting and habitat destruction. 2. Western Black Rhinoceros (Diceros bicornis longipes): Declared extinct in 2011 due to poaching.

Biologists explain the higher species richness in tropical regions through the following reasons:
- Stable Climate: Tropical regions have a stable climate over long periods, which supports the survival and evolution of diverse species.
- Higher Solar Energy: These regions receive abundant solar energy, increasing productivity and resource availability, which supports a higher number of species.
- Absence of Severe Climatic Changes: Unlike temperate regions, tropical areas experience minimal climatic disruptions, allowing uninterrupted species evolution.

- Biodiversity hotspots are regions with high species richness and a high degree of endemism, making (A) true.
- However, there are 36 biodiversity hotspots worldwide, not 22, making (R) false.

(A):
Step 1: For (i), tropics show the greatest species diversity because:
1. They have a stable climate with less seasonal variation, allowing uninterrupted evolutionary processes.
2. High solar energy and moisture contribute to high productivity, supporting a wide variety of species.
3. Tropical regions have existed for a longer period without glaciation, giving more time for species diversification.
Step 2: For (ii), the species-area relationship graph shows a rectangular hyperbola when plotted on a standard scale, and a straight line on a log scale. Alexander von Humboldt studied this relationship and observed that species richness increases with area but only up to a limit. His equation is , where is species richness, is area, is a constant, and ranges between 0.1 to 0.2 for small areas.
OR
(B):
Step 3: For (i), three major causes of biodiversity losses are:
1. Habitat loss and fragmentation: Deforestation and urbanization destroy habitats.
2. Over-exploitation: Excessive hunting, fishing, and harvesting reduce populations.
3. Introduction of alien species: Non-native species may outcompete or prey on native species, disrupting ecosystems.
Step 4: For (ii), ‘Ex situ’ conservation involves conserving biodiversity outside its natural habitat. Examples include:
1. Gene banks (e.g., seed banks)
2. Zoological parks and botanical gardens
These methods help preserve genetic material and endangered species.

1. RNA interference (RNAi) Technology:
   • In this method, specific genes responsible for nematode infestation are silenced.
   • The nematode Meloidogyne incognita affects tobacco plant roots.
   • To counter this, a DNA sequence producing both sense and antisense RNA strands for the nematode’s essential genes is introduced into the plant using Agrobacterium vectors.
   • These complementary RNA strands form double-stranded RNA (dsRNA) inside the host plant cells.
   • The dsRNA triggers the RNA interference (RNAi) mechanism, degrading the nematode’s specific mRNA.
   • As a result, the target gene is silenced, protecting tobacco plants from nematode attack.
2. Polymerase Chain Reaction (PCR) Process:
   • PCR is a technique to amplify a specific segment of DNA.
   • The process involves multiple cycles of:
     • Denaturation: Double-stranded DNA is heated to separate into single strands.
     • Annealing: Primers bind to the specific target sequences.
     • Extension: DNA polymerase extends primers to synthesize new DNA strands.
   • Each cycle doubles the DNA quantity.
   • Repeating this process for around 30 cycles results in over a billion copies of the desired DNA fragment.

(a) Restoration through Lantana removal:

• Removal of Lantana camara allowed native grasses and legumes to regenerate.
• These native plants are crucial for maintaining the herbivore population, which is the primary prey base for tigers.
• Increased herbivore availability in turn supports a stable and growing tiger population.
• It also helped in reducing human-wildlife conflict, as animals were no longer forced to migrate outside the reserve in search of food.

(b) Concerns due to Lantana camara invasion:

• Lantana camara is an invasive alien species that displaces native flora.
• It forms dense thickets, reducing biodiversity and food sources for herbivores.
• Its spread degrades the natural habitat, leading to ecosystem imbalance.
• The loss of native vegetation and prey drives tigers to venture into human settlements, increasing conflict and threat to their survival.