Introduction of exotic species refers to the intentional or unintentional introduction of non-native species into an ecosystem. This can have various impacts on the native species and the overall ecosystem. The correct answer to this question is option 'C', which states that the introduction of exotic species has an adverse effect on native species adversely. Let's delve into the details of this answer:

1. Adverse competition:
- Exotic species often have a competitive advantage over native species because they are not limited by the natural predators, diseases, or environmental factors that regulate the population of native species.
- They can outcompete native species for resources such as food, water, and shelter, leading to a decline in the population of native species.

2. Predation and predation pressure:
- Exotic species can become predators of native species that have not evolved defense mechanisms against them.
- This can lead to a significant reduction in the population of native species or even their extinction in extreme cases.

3. Disease transmission:
- Exotic species can introduce new diseases to native species, which they may have no immunity against.
- These diseases can spread rapidly and cause a decline in the population of native species.

4. Habitat alteration:
- Exotic species may alter the habitat by changing the composition of the vegetation or modifying the physical structure of the environment.
- This can negatively impact native species that are adapted to specific habitat conditions and disrupt their natural ecological interactions.

5. Genetic contamination:
- Hybridization between exotic and native species can occur, leading to genetic contamination of the native species.
- This can result in the loss of genetic diversity and the adaptation potential of native species.

Overall, the introduction of exotic species can have detrimental effects on native species and disrupt the balance of ecosystems. It is essential to prevent or control the introduction of exotic species to conserve biodiversity and protect native species from these adverse impacts.