Differentiate between Commensalism and Parasitism.

Commensalism:
Commensalism is a type of symbiotic relationship between two species in which one species benefits, and the other is neither significantly harmed nor helped. In this interaction, one organism, the commensal, derives some benefit, such as obtaining food or shelter, without causing any notable effect on the host organism. The relationship is asymmetrical, and the commensal gains advantages without adversely impacting the host. An example is the relationship between barnacles and whales, where barnacles attach to the whale's skin, obtaining a substrate for attachment and transportation, while the whale is not significantly affected.

Parasitism:
Parasitism is another form of symbiotic relationship, but in this case, one organism, the parasite, benefits at the expense of the host organism. The parasite derives nutrients or resources from the host, often causing harm or damage to the host in the process. Parasitism is a type of exploitative relationship where the parasite benefits, and the host is adversely affected. Examples include ticks feeding on the blood of mammals or intestinal parasites affecting the digestive system of their host organisms. The relationship is typically obligatory for the parasite's survival, as it depends on the host for sustenance.