Why exotic species becomes invasive sometime and starts spreading fast because of

Options

A. natural predators
B. abundant natural competitor
C. invaded land does not have its natural predators
D. mutation in their genome

Answer

### Step-by-Step Solution:

1. **Understanding Exotic Species**: Exotic species are organisms that are introduced to a new geographical area where they do not naturally occur. This introduction can happen through various means, such as human activity, trade, or accidental transport.

2. **Invasiveness of Exotic Species**: When these exotic species are introduced, they can sometimes become invasive. An invasive species is one that spreads rapidly and causes harm to the environment, economy, or human health.

3. **Role of Natural Predators**: In their native habitats, species have natural predators that help keep their populations in check. These predators play a crucial role in controlling the population of the prey species.

4. **Lack of Natural Predators**: When an exotic species is introduced to a new area, it often lacks its natural predators. This absence allows the exotic species to flourish unchecked, leading to rapid population growth.

5. **Consequences of Rapid Spread**: Without natural predators to control their population, these exotic species can outcompete native species for resources such as food, space, and light, leading to ecological imbalances.

6. **Example of Invasive Species**: A classic example is the prickly pear cactus, which was introduced to Australia in the 1920s. Without its natural predators, it spread uncontrollably across millions of hectares of land.

7. **Control Measures**: The population of the prickly pear cactus was eventually controlled by introducing a natural predator (a cactus-feeding moth) from its native habitat, demonstrating the importance of natural predators in managing invasive species.

8. **Final Answer**: Therefore, the reason exotic species become invasive and spread rapidly is primarily due to the absence of their natural predators. Hence, the correct answer is option C: "they invade land and don't have their natural predators."