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Symbiosis 1 2 3 4 5 Symbiosis is a close ecological relationship between the individuals of two different species. These relationships can be cooperative, antagonistic, defensive, reciprocal, harmful, communal, opportunistic, beneficial, or neutral. Symbiosis encapsulates the relationships that different species of organisms have with each other: the good, the bad, and the ugly. These interactions typically fall into one of three categories: mutualism, parasitism, and commensalism. 6 7 8 9 10 11 12 13 14 15 Mutualism A mutualistic relationship is one in which both organisms benefit from interacting with each other. They cooperate with each other to achieve a desired outcome that will be beneficial to both of them. Take the wrasse in the video clip for example. Cleaner wrasses have a mutualistic relationship with the large fish they service. The fish at the cleaning station line up to get the parasites picked off them; they are cleaned and free from harmful, blood-sucking parasites and the cleaner wrasse gets a nice meal from the fish. There are certain species of ‘cleaner’ shrimp that also perform this function. Both get something useful out of the deal, so the relationship is mutually beneficial. Same thing is true for certain apes like baboons and chimps that comb each other’s fur for ticks and lice. One gets a meal, the other gets cleaned. 16 17 18 Mutualism occurs in the plant world as well, with pollination being the primary example of mutualistic plant-animal relationships. Some more mutualistic symbioses for you to explore: honey badgers and honeyguides, ants and butterfly caterpillars, zooxanthelles and coral. 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Parasitism Parasitism is a relationship in which one organism benefits and the other is harmed. Parasitic interactions consist of a parasite (the organism doing the harm) and a host (the organism being harmed). In most cases, the parasite is smaller than the host. Parasitism is especially prevalent in the micro-faunal world. There are thousands of species of ticks, mites, leeches, chiggers, worms, mosquitoes, viruses, and bacteria that literally feed off their hosts. In many cases, parasitoids are host-specific, and as a result have undergone amazing evolutionary changes to co-evolve with their hosts. Although parasitism involves the pilfering of resources from one organism to another, it is in the parasites best interest not to completely debilitate its host, otherwise it will deplete its source of nourishment. When it comes to parasites there are many different types of parasites, and many different ways that organisms weasel resources away from each other. Brood Parasites Take the brown-headed cowbird, a seemingly harmless creature common in woodlands and suburbs across America. This cunning little critter is a brood parasite. Female cowbirds lie in wait for unsuspecting female passerines (perching birds) to leave their nests and move in to lay an egg in her nest while she is gone. When the resident female returns, she doesn’t know what hit her and spends her time and energy brooding the intruding egg along with her own. Once the eggs hatch the mother cares for all the babies, even the uninvited orphan. Oftentimes the cowbird grows faster and stronger than the resident hatchlings and can out-compete them in the nest, but the mother bird is devout and cares for it nonetheless. By parasitizing the passerine’s nest, the female cowbird ensures that her offspring are cared for with minimal energy expenditure on her part. While she doesn’t take anything directly from the mother bird, she is indirectly parasitizing her energy and resources. Appendix 1f1 42 43 44 45 46 47 48 49 50 Food Parasites Parasites can parasitize an animal’s energy, directly by consuming their body fluids, and indirectly by placing an energetic burden on them. That’s pretty bold, but some animals take bold to an even greater level. There are some creatures in the animal kingdom that will literally take the food out of another’s mouth! The parasitic jaeger, a predatory seabird, makes a habit of stealing food. They soar around while terns and other seabirds are fishing and chase them in the air to try and steal their food. Sometimes they are successful in capturing the food right from their mouths, but in most cases they harass the hunters so much that they tire and drop the food and the jaeger scoops up a free meal. 51 52 53 54 55 56 57 58 59 60 61 62 Commensalism A commensalistic relationship is one in which one organism benefits and the other organism is unaffected, meaning it is neither harmed nor benefitted. The classic example of commensalism is that of sharks and remoras. Remoras are scavenging fish that cruise around with sharks. Sometimes they swim alongside sharks, and sometimes they hitch a ride, attaching themselves via a suction-cup like appendage on their dorsal (top side) surface. The remoras wait for the sharks to make a kill, and when they do, snap up bits and pieces of the bloody, shredded flesh as the shark tears into it. They don’t pose any threat to the sharks, and don’t take the food from them, merely eat the scraps. One could argue, however, that when the remoras attach themselves to the shark, they create drag, which makes the shark have to work harder and expend more energy to get around, thus the remora is indirectly parasitizing the shark. While the drag the remora creates might be miniscule, the reasoning behind the theory is valid. 63 64 65 66 67 68 Another example of a commensalistic relationship is between cattle and cattle egrets. Cattle egrets are frequently found in fields foraging alongside herds of cattle. While the cows munch away on grass, they stir up insects which the egrets snap up. This may be more reflective of a truly commensalistic relationship as the egrets pose no real impediment to the cattle (or perhaps the cows have to expend more energy to watch where they are going to avoid stepping on the egrets!). 69 70 71 72 73 The Big Picture Symbioses are a dynamic way in which organisms of different species interact with each other. These relationships can be positive or negative depending on their nature and the extent with which the organisms are involved with each other. Below is a simple table to visualize the types of interactions that symbiotic relationships between organisms embody. Organism 1 Mutualism Parasitism Commensalism + 0 or n* *n=neutral Santana, E. 2012. "Symbioses" (OnLine) UntamedScience. Accessed Jun 06, 2012 at http://www.untamedscience.com/biology/ecology/symbioses For video see http://www.youtube.com/watch?v=zSmL2F1t81Q Appendix 1f2 + + + Organism 2 “Symbiosis” Guided Highlighted Reading for Summary Directions: With a highlighter pen, follow the prompts of the teacher and highlight what the prompts instruct you to highlight. The teacher reads the following: In lines #1-5, find and highlight the definition of symbiosis. (“Symbiosis is a close ecological relationship between the individuals of two different species.”) In lines #1-5, find and highlight the words that describe symbiotic relationships. (“…cooperative, antagonistic, defensive, reciprocal, harmful, communal, opportunistic, beneficial, or neutral.”) In lines #1-5, find and highlight the three main types of symbiosis. (“…mutualism, parasitism, and commensalism.”) In lines #6-15, find and highlight the definition of mutualism. (“A mutualistic relationship is one in which both organisms benefit from interacting with each other.”) In lines #6-15, find and highlight the assistance cleaner wrasses and the large fish provide each other. (“…they are cleaned and free from harmful, blood-sucking parasites and the cleaner wrasse gets a nice meal from the fish.”) In lines #16-18, find and highlight three examples of mutualism from the plant world. (“…honey badgers and honeyguides, ants and butterfly caterpillars, zooxanthelles and coral.”) In lines #19-29, find and highlight the definition of parasitism. (“Parasitism is a relationship in which one organism benefits and the other is harmed.”) In lines #19-29, find and highlight examples of parasites. (“…ticks, mites, leeches, chiggers, worms, mosquitoes, viruses, and bacteria….”) In lines #19-29, find and highlight the reason that parasites don’t usually kill their hosts. (“…it is in the parasites’ best interest not to completely debilitate its host, otherwise it will deplete its source of nourishment.”) In lines #30-41, find and highlight the advantages that the female cowbird has in this relationship. (“…the female cowbird ensures that her offspring are cared for with minimal energy expenditure on her part.”) In lines #42-50, find and highlight how parasites feed on their host’s energy directly and indirectly. (“…directly by consuming their body fluids, and indirectly by placing an energetic burden on them.”) In lines #51-62, find and highlight the definition of commensalism. (“A commensalistic relationship is one in which one organism benefits and the other organism is unaffected, meaning it is neither harmed nor benefitted.”) In lines #51-62, find and highlight the classic example of commensalism. (…sharks and remoras.”) In lines #63-68, find and highlight another example of commensalism. (“…cattle and cattle egrets.”) In the chart, find and highlight the symbol used for a positive relationship. (+) In the chart, find and highlight the symbol used for a negative relationship. (-)