3.5 - Symbiosis Flashcards
Symbiosis
Coevolved intimate relationships between members of two different species.
Parasitism
One organism benefits and the other is harmed.
Parasites benefit through gaining energy or nutrients.
Hosts are harmed through loss of resources.
Transmission of Parasites
Direct Contact
Parasite is passed from host to host directly e.g head lice
Transmission of Parasites
Resistant Stages
Stages in the parasite’s lifecycle where they can survive away from a host.
e.g some larvae can exist without a host for a long period of time
Transmission of Parasites
Use of Vectors
Parasite is carried to new hosts by another organism that isn’t a host itself.
Lifecyle of Parasite
Parasites often have limited metabolism so can’t survive when out of contact with their host.
A new primary host is reached through either: consuming the secondary host or the invasion of the parasite into the new host.
Direct Transmission
One host species
Parasite travels from host to host of the same species
E.g. head lice
Indirect Transmission
Requires a secondary host to complete their lifecycle.
Primary host acts as site of sexual reproduction whilst secondary hosts allow parasite to reach adulthood.
E.g. schistosoma
Mutualism
An interrelationship between two species that benefits both organisms.
Examples of Mutualism
Cellulose Digestion
Many herbivorous mammals lack the genes needed to produce enzymes that break down cellulose so have cellulose-digesting bacteria in their stomachs.
Herbivorous mammals benefit as they can digest cellulose and use the sugars as an energy source.
The bacteria benefit by receiving protection, warmth, and a constant supply of food.
Examples of Mutualism
Coral Polyps
Coral polyps contain photosynthetic algae in or near their cells.
Coral polyps benefit through gaining carbohydrates from photosynthesis to use as an energy source.
Photosynthetic algae benefit through receiving a safe habitat and a supply of nitrogen convert into proteins.
