SI5- symbiosis

• symbiosis is a co-evolved, intimate relationship between members of two diffrent species.
• parasitism and mutualism are two types of symbiotic relationships.
• A parasite is an organism that lives on or in the body of another organism which is known as the host. Examples are tick, flea, tapeworm, fluke.
• in a parasitic relationship the parasite benefits in terms of an energy and/or nutrient gain, whereas the host is harmed by the loss of energy and /or nutrients.
• • protozoan/ mosquito and humans (malaria)
  • tapeworm and pig
• Due to their limited metabolism, the majority of parasites cannot survive out of contact with a host.
• transmission is the spread of a parasite to a host.
• Transmission can occur by direct contact, via resistant stages or via a vector
• Direct contact is when the parasite is passed directly from one host to another when the two organisms are in close physical contact
• Some parasites have resistant stages (cysts) which can survive out of the host in extreme environmental conditions for a period of time until a new host comes into contact with them
• A vector is an intermediate organism that transfers a parasite from one host to the next
• The organism on or in which the parasite reproduces sexually/ produces eggs is the host
• Some parasitic life cycles involve intermediate (secondary) hosts to allow them to complete their life cycles
• Mutualism is an interdependent relationship in which both partner species benefit
• examples of mutualistic relationships:

  • algae (shelter) and fungi (nutrients) in lichens
  • Egyptian plover (nutrients) and crocodile (hygiene)