List four causes of biodiversity loss.  

The loss of biodiversity is caused by:
1. Over population: It is the main cause of bio-diversity loss. Deforestation, over-utilization of natural resources, poaching, pollution, etc., are some of the direct results of increasing population leading to erosion or loss of biodiversity.
2. Introduction of exotic species: Species originating from a particular area when introduced into new natural environments, it can lead to imbalance in biodiversity
3. Pollution: Human activity influences the natural environment which produces negative effects that alter the flow of energy, the chemical and physical constitution of the environment etc.
4. Over-exploitation of resources: Overuse of resources connected with capturing and harvesting, the resources may become exhausted and it leads to loss of biodiversity.
5. Natural calamities such as floods, cyclones, landslides and avalanches, volcanism, etc., are also responsible for depletion of biological diversity.