Biodiversity And Conservation

Step 1: Human Activities.
Human activities are the primary cause of biodiversity loss. These include:
1. Deforestation: Cutting down forests destroys habitats for many species, leading to a loss of biodiversity.
2. Pollution: Pollution from industrial, agricultural, and urban sources harms ecosystems and can lead to species extinction.
3. Overexploitation: Overhunting, overfishing, and excessive harvesting of natural resources deplete species populations.
4. Climate Change: Human-induced climate change alters habitats, affecting species' ability to survive.
5. Habitat Destruction: Urbanization and agricultural expansion destroy ecosystems that are crucial for biodiversity.
Step 2: Natural Factors.
In addition to human activities, natural factors such as invasive species, diseases, and natural disasters also contribute to biodiversity loss. Invasive species can outcompete native species, leading to their decline.
Step 3: Conclusion.
Biodiversity loss is mainly caused by human activities like deforestation, pollution, overexploitation, and climate change, though natural factors can also play a role.

Step 1: Understanding global diversity estimates.
Robert May, an ecologist, estimated that the global species diversity on Earth is around 7 million species. This includes both known and unknown species.
Step 2: Analyzing options.
(A) 7 million: Correct — Matches Robert May’s estimate.
(B) 1–5 million: Incorrect — This is lower than the actual estimate.
(C) 20–25 million: Incorrect — This is a higher estimate not supported by Robert May.
(D) 2 million: Incorrect — Much lower than accepted diversity estimates.
Step 3: Conclusion.
Therefore, according to Robert May, global species diversity is approximately 7 million.

Step 1: Understanding biodiversity distribution.
India is one of the 17 megadiverse countries in the world. Although it occupies only 2.4% of the world’s land area, it harbors a rich biodiversity.
Step 2: Percentage contribution.
India contributes about 2–4% of the world’s total species diversity. This highlights India’s ecological richness.
Step 3: Conclusion.
Therefore, the biodiversity of India is approximately 2–4% of global diversity.

Step 1: Background.
Lake Victoria, one of the largest lakes in Africa, was once home to hundreds of endemic Cichlid fish species.
Step 2: Cause of extinction.
The introduction of the alien species Nile Perch in Lake Victoria led to the extinction of more than 200 species of Cichlids. The Nile Perch acted as a predator and outcompeted the native fish.
Step 3: Analyzing options.
(A) Co-extinction: Incorrect — No evidence of linked species extinction here.
(B) Alien species invasion: Correct — Nile Perch invasion was the main cause.
(C) Overexploitation: Incorrect — Though fishing occurs, it wasn’t the major cause.
(D) Habitat loss: Incorrect — The environment remained largely intact.
Step 4: Conclusion.
Hence, the extinction of Cichlid fishes was due to alien species invasion.