Understanding Biodiversity Statements

The question asks us to identify the correct statements about biodiversity from the given options. Let's analyze each statement carefully.

Statement A: Biodiversity and Ecosystem Stability

This statement claims that biodiversity can support ecosystem stability. Ecosystem stability refers to the ability of an ecosystem to resist disturbance and recover quickly from it. A more biodiverse ecosystem typically has a wider variety of species, each playing different roles. If one species is affected by a disturbance, other species might be able to take over its function, making the overall ecosystem more resilient. For example, in a diverse plant community, if one plant species is susceptible to a disease, others may be resistant, ensuring the ecosystem's productivity doesn't collapse entirely. Therefore, statement A is generally considered correct.

Statement B: Human Activities and Species Extinctions

This statement says that human activities have sharply increased species extinctions. Human activities such as habitat destruction, pollution, climate change, overexploitation, and introduction of invasive species are widely recognized as the primary drivers of the current high rate of species extinctions, often referred to as the 'sixth mass extinction'. Scientists estimate that current extinction rates are far higher than the natural background extinction rate. Thus, statement B is correct.

Statement C: Habitat Fragmentation and Biodiversity Impact

This statement suggests that habitat fragmentation has no adverse impact on biodiversity. Habitat fragmentation occurs when a large, continuous habitat is broken into smaller, isolated patches. This process can lead to several negative consequences for biodiversity, including:

• Reduced habitat area, which can support smaller populations.
• Increased isolation of populations, reducing gene flow and increasing the risk of inbreeding.
• Increased edge effects (changes in environmental conditions like light, temperature, and wind at the boundaries between habitats).
• Increased vulnerability to external disturbances and invasive species.

These factors collectively lead to a decline in biodiversity within the fragmented landscape. Therefore, statement C, claiming no adverse impact, is incorrect.

Statement D: Proportion of Invertebrates Among Known Species

This statement claims that about 70% of all known species are invertebrates. Invertebrates, which include insects, arachnids, molluscs, crustaceans, and many other groups, constitute the vast majority of described animal species. While exact percentages can vary slightly depending on new discoveries, scientific data consistently shows that insects alone account for more than half of all known species, and invertebrates in total make up approximately 70% (or even more, depending on estimates) of all known species on Earth. Thus, statement D is correct.

Conclusion

Based on our analysis:

• Statement A is correct.
• Statement B is correct.
• Statement C is incorrect.
• Statement D is correct.

We are looking for the option that includes the correct statements (A, B, and D). Let's look at the provided options:

Option 1: A, B and C only (Incorrect, C is false)

Option 2: A, B and D only (Correct, A, B, and D are true)

Option 3: B, C and D only (Incorrect, C is false)

Option 4: A, C and D only (Incorrect, C is false)

The correct answer is the one that includes statements A, B, and D.

Therefore, statements A, B, and D are correct.

Revision Table: Biodiversity Statements Analysis

Based on the analysis, the correct combination of statements is A, B, and D.

Additional Information: Threats to Biodiversity and Conservation

Biodiversity is crucial for ecological balance, providing essential ecosystem services like pollination, water purification, and climate regulation. However, it faces significant threats primarily due to human activities. Understanding these threats is key to effective biodiversity conservation efforts.

• Habitat Loss and Fragmentation: This is the leading cause of biodiversity loss. Clearing forests, wetlands, and grasslands for agriculture, urban development, and infrastructure directly destroys habitats and isolates remaining populations.
• Overexploitation: Excessive hunting, fishing, and harvesting of species can reduce their populations to unsustainable levels or lead to extinction.
• Pollution: Various forms of pollution, including chemical pollutants, plastic waste, and nutrient runoff, can harm organisms and degrade habitats.
• Climate Change: Shifting climate patterns force species to adapt, migrate, or face extinction. Changes in temperature, precipitation, and extreme weather events disrupt ecosystems.
• Invasive Species: Introduction of non-native species can outcompete native species, spread diseases, and alter ecosystem structure and function.

Conservation strategies involve protecting habitats (e.g., national parks, reserves), sustainable resource management, pollution control, climate change mitigation, and species-specific conservation programs.