User:Sumner.44/sandbox

Topic: How does symbiosis help drive evolution?

Sources: Darwin's Blind Spot: Evolution beyond Natural Selection by Frank Ryan Symbiotic planet: a new look at evolution by Lynn Margulis Niche Differentiation in the Dynamics of Host-Symbiont Interactions: Symbiont Prevalence as a Coexistence Problem Insect symbiosis / edited by Kostas Bourtzis, Thomas A. Miller Symbiosis in cell evolution : microbial communities in the Archean and Proterozoic eons / Lynn Margulis

Suggestions “I think it should be noted somewhere that symbiosis is not altruistic. The organisms in symbiosis may benefit from each other but it is purely out of a need to survive and not from a desire to help the other. Cleaner fish consume parasites off of sharks but do not do this to benefit the shark but simply as a source of food. And likewise, a shark doesn't allow a cleaner fish to get close enough simply so the fish can have a meal. It allows the fish to do this so that the shark itself can be free of parasites. There are many other examples that can be given.Also, I think in the amensalism section of the article, it should be stated that there are two types of amensalism: competition and antibiosis. In competition, one organism excludes another from a resource. In antibiosis, one organism secretes a chemical killing the other while the one that secreted the chemical is unaffected.Lastly, the examples for commensalism could be better. For example, epiphytes growing on a woody plant. The epiphyte uses the woody plant as support and for access to sunlight. The woody plant is unaffected by this.”

Added sentences “There are two types of amensalism, competition and antibiosis. Competition is where a larger or stronger organisms deprives a smaller or weaker one from a resource. Antibiosis occurs when one organism is damaged or killed by another through a chemical secretion. An example of antibiosis is the black walnut, (Juglans Nigra), secreting juglone, a substance which destroys many herbaceous plants within its root zone. ”

CHANGED TOPIC TO BIOLUMINESCENCE

FINAL DRAFT HERE:

Bioluminescence is a phenomenon that has repeatedly arisen in many different genera. There are approximately 700 genera which contain bioluminescent species and of these, approximately 70% are marine (Widder). The majority of these species live in deep sea habitats where the light from the sun cannot penetrate. The question many scientists struggle with is how bioluminescence arose in these many species with no real correlation between each other. “Harvey (1952) listed the luminous genera in each major group of organisms, in the context of an overall systematic framework, noting that it was ‘as if a handful of damp sand has been cast over the names of various groups written on a blackboard, with luminous species appearing whenever a mass of sand struck (Herring)”. This phenomenon has seemingly evolved by chance across a random board of species. This is the mystery which scientists are trying to decipher; how the independent lineages of bioluminescent species evolved. Bioluminescence is the ecologically functional emission of light by living organisms. It is produced by the oxidation of a light-emitting molecule called luciferase or a photoprotein (a light protein) in combination of a catalyzing enzyme. Luciferase receives its name by being derived from “Lucifer”, the root of which means “light-bearer”. It is the generic term used to describe the class of oxidative enzymes used in bioluminescence. Species are luminous either through a relationship with bioluminescent bacteria, which is rare, or possess the gene for luciferase, if not always the light-emitting luciferase itself. Each luminous species may use a slightly varying method of creating light. Four luciferans are the primary source of light emission in marine life. Luciferans are conserved while luciferases and photoproteins are derived from many evolutionary lineages. All Cnidarians use coelenterazine as their luciferan while hydrozoans use phytoproteins. Defining the independent origins of luminous species is the most difficult problem. When speaking about bacterial symbionts, the trait only needs to evolve once while each host species needs to develop the appropriate light organs in order to maintain and cultivate the microbes. An example of this is varying species of bioluminescent molluscs having to independently evolve the trait at least 7 different ways (Haddock). One hypothesis for the evolution of luminescence in marine organisms, based on recent evidence, has suggested that it is the luciferans themselves that have formed the phenomena of bioluminescence and the central role of luciferases is not that of efficient oxygenases but “rather to optimize the environment for luciferin chemiluminescence and to reduce unproductive quenching of the excited state emitter by surrounding molecules” (Rees). Coelenterazine is a luciferin that is central to bioluminescence in marine life in general and displays the importance of luciferins in the evolutionary history of bioluminescence. Coelenterazine is a strong antioxidant and is found in at least nine different phyla. As organisms that depend on vision continued to venture deeper into the depths of the ocean to escape predators, “the reduced oxidative stress in deeper waters shifted the selection pressure from the antioxidative to the chemiluminescent properties of this molecule” (Widder). Natural selection favored the development of more highly sensitive eyes to be able to detect visual signals. Because of this, it is possible a mutation in an enzyme responsible for the breakdown of pigment molecules could have result in luminescence which immediately caused the emitter to experience selective pressures for the mutation (Widder). Mapping the evolutionary history of bioluminescence is difficult due to the fact that it has no solid path to trace. As stated before, the phylogenic occurrence of bioluminescence is ‘as if a handful of damp sand has been cast over the names of various groups written on a blackboard, with luminous species appearing whenever a mass of sand struck”. It has evolved approximately 40 different times, often between species of the same genera. One thing can be inferred from the evolution of bioluminescence of numerous independent phylogenies, it is a relatively easy system to create. Many species have evolved this trait using different or similar chemistries which only adds to the complication of mapping this trait. Convergent molecular evolution could have resulted in independent systems coding for a fit type of molecule for a bioluminescent reaction (Hastings). Furthermore, some species exhibit traits where only one sex is luminous and the other is not. Similarly, certain species carry the trait as an ephemeral characteristic in which it is restricted to either adults or juveniles. Further still, some species experience luminosity on a cyclic basis such as the seasons or time of day. Diet can also play an important role in the ability to be luminous where two populations of the same species have the capabilities to be luminous but only one displays the phenomenon because they have acquired the proper nutrients. Because of these differences, accurately identifying organisms which possess the luminous trait is vital. The taxonomic definition of a species is well noted but a genus is less so and because of this, the genera in different groups may vary greatly. This means a genera may be under continuous revision as new data is collected (Herring). It becomes increasingly difficult when live specimens are not easily obtained such those that live in the deep sea where many luminous species occur. The possible functions of bioluminescence are an area of which many studies have been conducted. Observing these functions in a natural state becomes increasingly difficult when most of the organisms exhibiting this trait exist in the deep sea where accessibility is limited or restricted. Reproducing such conditions in a laboratory may shed some light on the purpose of bioluminescence but results may not always reflect what truly happens in a natural habitat. Because of this, the functions that scientists have determined may not be completely accurate. With that stated, bioluminescence can be used defensively, offensively, or for communication within a species. Defensively, a quick flash of light can be used to startle an incoming predator enough to allow the prey to escape. Similarly, a luminous tag may be used as a diversion when it is detached much like a lizard detaching its own tail while it continues to twitch and the lizard escapes. Even further, the consumed luminous tag can continue to glow inside of the predator’s stomach. This presents an inherent risk in consuming the tag since most deep sea creatures are transparent. The light emitted from inside the predator can attract other, larger predators causing the luminous predator to become prey. Another form of defense is counter-illumination which is a form of camouflage. This entails matching the amount of light streaming in from the surface disrupting any shadow that would appear. Offensively, bioluminescence is mainly used as a lure to attract potential prey. An example of this is the anglerfish having a luminous barbell which dangles in front of its mouth. It can also be used to illuminate the predator’s surroundings and locate available prey. It is possible that Diaphus uses its “headlamps” in this manner. A quick flash of light can also be used to temporarily stun a prey item. This has been repeatedly demonstrated by squid who quickly flash their tentacle when taking bait from a fishing line. A combination of counter illuminating and prey attraction has been hypothesized for the cookie-cutter shark. This relatively small shark takes bites out of its faster moving prey. Scientists have been hypothesizing that this could occur because the shark possess a band below its mouth which confuses its prey into thinking the shark is one of their own prey luring them closer to the shark. The shark can then quickly take a bite out and then swim away from any harm. Lastly, bioluminescence can be used as a form of communication between members of the same species, mainly for mating displays. The best-studied species which participates in this is the Caribbean Ostracods. These organisms show species-specific signaling to attract the appropriate mate of the appropriate species (Haddock). These functions can be utilized in any combination of each other. The shallow flashlight fish, Photoblepharon, uses its sizable suborbital light organ for anything, from acquiring prey, communication, to defense from its predators. All of these functions are present because they have undergone selection in which these traits were advantageous for the organism. Bioluminescence has arisen in many different phyla and in varying methods even though the phylogenic pathways of its evolution are hazy. Scientists are suggesting many hypotheses as to how this phenomenon occurred. The varying chemical compositions of the reactions that different groups use can shed some light on how it evolved. The random occurrence of it within species or genera is the main problem scientists struggle with. More recent evidence has suggested that the shift of luciferans is the main driver behind the evolution of bioluminescence. Bioluminescence has many uses in marine creatures such as defense, attaining prey, and as a form of communication within species. Because there is not sufficient data to come to a concise conclusion, new evidence is continuously being added which in turn modifies past hypotheses. As scientists further research, the evolution of bioluminescence can further be evaluated between species and phyla.

300 words added to article; "..." is what I edited.

Bioluminescence in some animals is produced by symbiotic organisms "such as bacteria, though this is usually rare."

Under "Distribution" "Edmund Harvey, as U.S. zoologist and physiologist whose work in marine biology contributed to the early study of bioluminescence, listed the luminous genera in each major group of organisms, in the context of an overall systematic framework, noting that it was "as if a handful of damp sand has been cast over the names of various groups written on a blackboard, with luminous species appearing whenever a mass of sand struck"."......Some marine species exhibit traits where only one sex is luminous and the other is not. Similarly, certain marine species carry the trait as an ephemeral characteristic in which it is restricted to either adults or juveniles. Further still, some marine species experience luminosity on a cyclic basis such as the seasons or time of day. Diet can also play an important role in the ability to be luminous where two populations of the same species have the capabilities to be luminous but only one displays the phenomenon because they have acquired the proper nutrients.

Under "Distraction" "Also, a quick flash of light can be used to startle an incoming predator enough to allow the prey to escape. Some species use a luminous tag in a similar fashion to that of a lizard detatching it's own tail to escape predation. Even further, if the predator consumes the luminous tag, it itself is at risk of predation since most deep-sea animals are transparent. The luminous tag inside of the attacker's stomach can pose as a lure to larger predators."

"Squid have also been shown to quickly flash their tentacles when attacking prey in an attempt to stun the prey item."

"for species-specific signaling to attract an adequate mate of the appropriate species."

"Also, a quick flash of light can be used to startle an incoming predator enough to allow the prey to escape. Some species use a luminous tag in a similar fashion to that of a lizard detaching its own tail to escape predation. Even further, if the predator consumes the luminous tag, it itself is at risk of predation since most deep-sea animals are transparent. The luminous tag inside of the attacker's stomach can pose as a lure to larger predators."

"Bioluminescence has arisen in numerous independent lineages which leads to the inference that this system is relatively easy to create."