Symbiosis: the intimate and prolonged association between two or more organisms of different species. -Parasitism (+, -) -Mutualism (+, +) -Commensalism (+, o) hackberry nipple gall
Essentially any life form on Earth is a habitat. Human beings, sitting in SC-217 for Ecology lecture are, themselves habitat for an amazing array of organisms! A human being is a symbiosis. Up to 1000 species of microbe live in the human gut, and nearly as many on the human skin. Fungal and Bacterial. Gut flora has about 100x as many genes as in the human genome! Good evidence that this is not merely a commensal relationship…in fact, humans cannot survive without these microbes. Too much “sterilization” would kill you! Symbiosis
Parasites Parasites can have hugely varied life forms. Microscopic: viruses, bacteria, fungal. Associated with “disease” Bird flu virus
Parasites Parasites can have hugely varied life forms. Macroscopic: flatworms, roundworms, lice, ticks, smuts and “plants.” Mistletoe: a parasite on trees in N. American and Europe. Can induce kissing for those standing under during the Yuletide.
Parasites Parasites can be ecotoparasites or endoparasite. They can have intermediate hosts which may not have any negative consequences. They often move around using “vectors.” Relationships can be quite complex. Lyme disease is a bacterial parasite that is transmitted through tick bites. In general, the ticks are moved around by mammals_ especially white-tailed deer. The ecology of white-tailed deer, then is directly related to human health because of disease transmission. Ticks carry Lyme disease. Deer carry ticks
Parasites Many parasites/diseases of humans (and other animals) have very complex ecological relationships. Example: Malaria is a disease caused by a parasitic protozoan. The protozoan is transferred effectively by mosquitoes. (particularly Anopheles). Malaria infection kills ~ 1 million people/year.
Meningeal worm infection. Snails carry the larvae. Deer accidentally eat the snails when grazing. Larva escape the snails, move into the blood stream, infect tissues surrounding the brain, eventually move into the lungs. Parasites
Hosts evolve defenses, parasites evolve new mechanisms. Long-term interplay of selection between hosts and parasites..
Parasitism can, and often does, interact with other aspects of an organism’s ecology. In this case, the fish is infected with a parasite, its behavior changes, and then more of those individuals are eaten by birds.
Mutualism Mutualisms are extremely varied, influencing virtually every living organism (and, thus) ecosystem on Earth. As mentioned before, humans are a mutualistic assemblage. Some organisms are very clearly mutualists. Lichens are a fascinating example
Mutualism The mutualism is so tight for lichens that they are sometimes called “composite organisms!” They consist of an intimate mingling of fungus and algae. Fungal piece is the “mycobiont” and provides nutrients. An algea- generally green algae is the “photobiont” and provides energy through photosynthesis. If you think about it, that is a wicked combination! Lichens are extremely hardy organisms_ able to survive in very extreme conditions. (Example- on the shingles of your roof!). If you grow the fungus and algae separate from one another, they take on a very different form from the symbiosis.
Mutualism Corals are another interesting mutualism. In this case an animal (the coral “polyp”) is associated with an algae. The algae provides energy via photosynthesis. The coral provides protection and substrate to the algae.
Mutualism Rhizobium is a genus of bacteria that forms a mutualistic relationship with plants in the family Fabaceae (Legumes…think “peas”). When the bacteria are free in the soil, they act like bacteria. When they encounter root hairs of a legume plant they form a mutualism in which “nodules” are formed. Within these nodules, the bacteria can “fix” gaseous nitrogen to ammonia. This can have huge impacts on soil nitrogen availability.
Mycorrhizae is the name for a mutualism that occurs between plants and fungi. The fungi attach to root hairs of plants and can vastly increase the extent of the roots and increase the plants capacity for “foraging” for nutrient and water. The fungi, in turn, receives access to the produces of photosynthesis (energy!). There is a cost to forming the relationship for the plant (giving up energy) and these relationships are often associated with poor growing environments. Practically all plants do this!