Question

With the help of an example, explain how alien species invasion causes biodiversity loss.

Answer 1

Hint: Biodiversity is described as the combined diversity at all the levels of the biological organization right from macromolecules within the cells, genes, species, ecosystem, biomes. This biodiversity of a region is altered by the introduction of a new foreign organism into that region as it causes altered biotic interactions.

Complete answer:
Complete disappearance or extinction of a species results in complete loss of genetic information contained in it.
Causes of biodiversity losses, the world is facing accelerated rates of species extinction, largely due to human activities. The four major causes of biodiversity losses, called “The Evil Quartet”.
1.Habitat loss and fragmentation
2.Overexploitation
3.Alien species invasion
4.Co-extinction
Alien species invasion: New species entering a geographical region are called exotic or alien or non-native species. When alien species are introduced unintentionally or deliberately for whatever purpose, they may cause the disappearance of native or indigenous species through changed biotic interactions.
A few examples of exotic species are as follows:
-Nile Perch, is a large predator fish that was introduced into Lake Victoria of east Africa. It killed and eliminated ecologically unique assemblages of over 200 species of cichlid fish that were endemic to this freshwater aquatic system.
-Water Hyacinth (Eichhornia) was introduced by Europeans in India. It has clogged water bodies including wetlands at many places resulting in the death of several aquatic plants and animals.
-Carrot grass is a weed that came to India as a contaminant with imported wheat. It has occupied all open areas exterminating many herbs and shrubs.
-Lantana is a straggling shrub of tropical America that came to India accidentally. Today it has become a serious weed that has replaced many species in forests.

Note: Exotic species have the maximum harmful impact on the island ecosystem because of small size and a small number of species.
Some exotic species also use up more resources than other organisms and hence their introduction into another ecosystem can cause biodiversity loss in that ecosystem.
Therefore, Islands harbor much of the world’s threatened biodiversity.