an animal or plant that attaches itself to another or plant and feeds on it
http://www.merriam-webster.com/dictionary/parasite
The term you are looking for is a "parasite." Parasites are organisms that live on or in other organisms, known as hosts, and derive nourishment from them. They can be classified as either external parasites, which attach themselves to the surface of the host, or internal parasites, which live inside the host's body.
To find an example of a parasite, you can use various methods:
1. Research: Utilize online resources, encyclopedias, or biology textbooks to search for common examples of parasites. Look specifically for those that attach themselves to other animals or plants.
2. Observation: Observe your surroundings, such as your garden or natural environments. Look for parasitic plants, like mistletoe, which attach themselves to the branches of trees and rely on their hosts for water and nutrients. Additionally, some insects, like ticks or fleas, are known parasites that feed on the blood of animals.
3. Seek expert advice: Consult a biologist, ecologist, or botanist who specializes in parasites. They can provide you with detailed information and examples specific to your geographic location or area of interest.
Remember, while researching examples of parasites, make sure to verify the information from multiple reliable sources to ensure accuracy.