Intruders are people or creatures that enter a place without permission. They can be unwanted guests in a home, like a burglar trying to steal valuables, or animals that wander into gardens and cause damage. Intruders can create fear and concern for safety, making it important to have security measures in place, such as locks and alarms. In nature, intruders can also refer to species that invade new environments, disrupting local ecosystems. For example, the zebra mussel is an intruder in many lakes, outcompeting native species for food and space. Understanding intruders helps us protect our homes and the environment.