Which of the following is a major cause of loss of biodiversity ?

Options

A. Habitat loss and fragmentation
B. Over-exploitation
C. Alien species invasion
D. Co-extinction

Answer

To determine the major cause of loss of biodiversity, we can analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Biodiversity Loss**: Biodiversity loss refers to the decline in the variety and variability of life forms on Earth. This can occur due to various factors, including habitat destruction, over-exploitation, and the introduction of non-native species.

2. **Evaluating Habitat Loss and Fragmentation**:
- Habitat loss occurs when natural environments are altered or destroyed, often due to human activities such as deforestation, urbanization, and agriculture.
- Fragmentation refers to the breaking up of habitats into smaller, isolated patches, which can hinder the movement of species and reduce genetic diversity.
- Both habitat loss and fragmentation significantly impact species survival, as they disrupt ecosystems and the relationships between species.

3. **Considering Over-Exploitation**:
- Over-exploitation involves the excessive hunting or harvesting of species, leading to population declines and potential extinction.
- While this is a serious issue, it is often a consequence of habitat loss, as species that are already struggling due to habitat destruction are more vulnerable to over-exploitation.

4. **Analyzing Alien Species Invasion**:
- The introduction of non-native species can lead to the extinction of indigenous species, as seen in the case of Neel Perch in Lake Victoria.
- Although this is a significant factor in biodiversity loss, it is often a secondary effect of habitat alteration, where new species are introduced into disrupted ecosystems.

5. **Co-extinction**:
- This occurs when the extinction of one species leads to the extinction of another species that is dependent on it.
- While co-extinction is a critical concept, it is often a result of the primary causes of biodiversity loss, such as habitat destruction.

6. **Conclusion**: After evaluating all the options, it is clear that **Habitat Loss and Fragmentation** is the major cause of biodiversity loss. It encompasses the most significant impacts on ecosystems and species survival.

### Final Answer:
The major cause of loss of biodiversity is **Habitat Loss and Fragmentation**.