Biology Exam #2 - Mutualistic Interactions

Coral Reefs Example

Coral Reefs - made of coral - coral pallops - bright colors, mountains, living portion of coral is all right on the surface, little pollops, bag like structures (polyp). when grows and dies, leaves behind calcium film, this rests on substrate it was growing on, and future polyp grows on top, and then film hardens in to calcite making structure. bulk of coral is just calcite formed from ancestors of coral reef, so every year, gets larger and larger. living portion is just individuals on surface of reef. coral reef tremendously diverse, greater amount productivity in ecosystem than any other on planet. b/c almost always warm water, shallow, and tremendously diverse = large productivity. large amount of biomass being accumulated in and around reef itself. health = greater range and brighter range of colors, the more you will attract other species. based on diversity and intensity of colors involved. coral polyp, is mostly clear, so in order for this to function in proper way need mutualistic relationship between polyp and algae zooxanthellae: photosynthetic, when zoo is near coral polyp, proper species with proper species, polyp incorporate and take in zoo, and sucks in particles, sticks into digestive bag, but does not digest, allows to assimilate inside cell membrane and exist inside cell wall. stays inside walls of coral polyp. photosynthetic, provides O2 and carbohydrate for polyp, polyp provide CO2 and protection from environment, so as result, have mutualistic relationship, very similar to lichens. color then that occurs in coral reef - result of different species of polyp interacting with different species of zoo. all of those colors occur bc different species of coral with different species of zoo in relationship with them. is this obligate? coral can survive on own without zoo, not very well, not indefinitely, but can survive, depending on species condition from 7 hours to several weeks. if zoo become too toxic, coral will expel from body, in idea that they will find new zoo and will be able to get something else less toxic. coral bleaching - injecting all their zoo. zoo can survive outside bc they are photosynthetic and plenty of CO2 so should be able to survive, but very subject to change in environment, which is why they benefit from protection from environment when live with coral polyp.

Frugivory (fruit-eating) example

Frugivory (fruit-eating) cedar wax wing - common fruit eater bird, 90% of diet is fruit. bears are another frugivore, along with chipmunks. good seed dispersal.

Honey Guide example of Facultative Mutualism

Honey guide - bird in Africa, greater honey guide. when greater honey guide approaches community or people outside of community if knows where honey bee hive is, it will fly toward people part of community (recognizes differences in communities between people in communities) bird flies up to people, provides call note completely different. this signals that the bird knows where the bee hive is. bird flies in the direction of the hive. length of time bird gone before it comes back is very accurate estimate of how far hive is, very accurate. bird knows that they are dealing with people, travel different speed than bird does. people follow bird. people can judge how high hive is based on how high bird perches. bird gets to hive, changes call note. makes different sound. hey, were here, within site of hive! bird can emphasize - knows when people are within site of hive, changes call note to say this. people finally find hive, use smoke to subdue bees, so can reach and take honeycomb and wax, and as leave as gesture of thanks to bird, leave some of honeycomb that has larvae inside, so bird can eat larvae and use honeycomb and wax to line nest. and then this happens all over again. insane relationship - bird and people talking to get mutual benefit. mutualism, facultative because bird can survive wihtout this, people can survive without honey, but this is facultativve relationship. some honey guides can evaluate if fire is good enough (sometimes) bc honey guides can die much easier from bee sting than humans can. apparently there are some instances where honey guide has a 3rd note call to say make fire smokier. ability of people to understand birds - leraning ability, vise versa, but something has to be innate. reall peculiar evolution happenign with these birdx. learn very easy to do this in life time - tremendous evolution effect. innate ability of birds to want to interact with people, realize importance of honey and larveae for themselves. learn by trial and error, that is why there is innate ability to do so. it is an adaptation of bird to interact iwth people.

Mycorrhizae example

Mycorrhizae example - most terrestrial plants have roots inside ground to gather water or nutrients from soil, i.e. potassium, magnesium, nitrites, etc. purpose of roots = pull stuff out of ground. good, but not good enough for plant to grow to ideal size. estimated that some between 85-95% plants have mutualistic relationship with fungi (mycorrhizae) - grows underground, grows with roots, helps roots gather nutrients and water, exists to make trees, grows, grasses, etc. grow the way they grow. our environment would look really different without it. Arbuscular - typical tropical plants and grasslands. what happens with this mycorrhizae is if you have plant root cells (think 3 square next to each other) and mycorrhizae will get between plant root cells, can penetrate cellulose layer that surrounds cell wall, really stiff membrane that surrounds plant cell and gets right up against cell membrane which is soft and pliable, make contact with cytoplasm wall of cell and be able to exchange stuff there. mycorrhizae will pick up nutrients and water of soil and roots will provide mycorrhizae with carbohydrates. compare to ectomycorrhizae - if you look at plant root cells again, this one forms sheet, and flood root hairs with water and nutrients. largely temperate (trees around here) all ahve ectomycorrhizae in roots. trees that don't have this sort of relationship will die if in nutrient poor soils without bacteria. root system of plant - mirror image of plant above ground. if you have tree growing, should take up that amount of space underground. mycorrhizae, depending on tree type, especially a type, will be in roots, and will extend out 15 to 20x amount of space of actual roots take up. also, have to imagine, where mycorrhizae are extending really far out, tend to involve not just single individual, but multiple individuals that are using the same fungus as neighboring tree. largest organisms ever - underground fungi that exist for miles and miles, going from plant to plant keep growing and growing and growing.

Ants on Acacia Trees Example

ants on acacia trees - live in savannas of Africa. being large plant and large tree, tend to be target for herbivores, especially large herbivores. acacia tree thorns can be really long and really sharp to keep herbivorse away, but doesn't work with small things like caterpillars, works for stuff like giraffes. on lots of acacia trees, there are ant colonies living nearby, they incorporate the tree itself into part of their territory, use tree for benefit for themselves, i.e. cut hole in hollow form and store stuff in it. use as storage facility for food, may even store eggs for developing larvae, tree is protective. when ants find themselves in tree that is under attack from large herbivore, ants go to tree's rescue. the ants crawl on branches being eaten and go onto face and into sinuses and everything of animal and start biting the herbivore, causing stinging and itching and burning. ants in africa can be quite nasty, resulting in softball size welts. crawl onto herbivore and attack, herbivore has counteradaptation to thorns by having really tough mouth parts, can grab branch leaves, thorns, and chew up no problem becaue skin is so tough. but sinus skin is really sensitive - ants start biting, giraffe will back away. if ant crawls on giraffe and giraffe moves away, ant wont be able to get back and will probably die. to consider single ant body an individual not really valid, but within hive or colony - genetically identical, as long as colony itself is surviving, individuals sacrifice slef bc doesnt make difference whether they are there or not as long as colony is there. if ants find acacia tree really young, ants protect tree, and cut down competition around acacia tree to reduce competition for it. anotherbenefit provided to tree as result of ants. so what cost do trees have to maintain this relatoniship, what is benefit of ants? ants use as storage, but bigger benefit - beltian bodies - little yellow things on end of leaflets of acacia tree leaves. beltian bodies loaded with protein, produced strictly for nts. acacia trees with ant colonies produce beltian bodies, acacian trees that do not have ants will not produce beltian bodies. beltian body is like a pyament to pay off ant mafia for protection. take beltain bodi back to colony and use as food source. that is big benefit ants get, and that is cost for acacia trees.

Commensalism

commensalism - a relationship where one individual benefits from the interaction and the other individual sees no benefit or cost (+/0). essentially, commensalism occur where one takes advantage of an existing behavior of another wihout affecting that individual. i.e Burdocks

Facultative mutualism

facultative mutualism - not required, can survive, can have offspring, even if this relationship does not exist. usually find this when have generalists - think pollinators, golden rod, queen anne's lace, clovers, several different species can pollinate golden rods, and bees can pollinate other flowers besides golden rod. if golden rod has mutualistic relationship with honey bees, golden rod could still survive bc there are other pollinators out there that can pollinate.

define mutualism

mutualism - a relationship where both individuals benefit from the interaction (+/+) although a mutualistic relationship is where both individuals benefitting, it would be unwise to think of this relationship as one that is willing of the species - do not think of the members involved as willingly generous individuals. each party has evolved to provide something to the other only b/c the resulting benefit to thesmelves is greater than the cost assoicated with the production of the benefit to the partner. as soon as the cost of producing the 'gift' to the partner, the individual should no longer partake in the relationship. consider description of mutualism as "reciprocal parasitism" on page 1069 of your textr. mutualism persists as long as both gain from relationship. mutualistic relationship - 2 parasitic events taking place at same time, I take stuff from you, I benefit, you take stuff from me, you benefit. as soon as costs sustain and become greater than what an individual is gaining from relationship, relationship will end. If costs sustaining are greater than the benefits, you should end the relationship. not going to get mutualistic relationship if one is having tremendous costs and little out of it, they are going to evolve to get out of this relationship. sometimes very difficult to measure relative value of benefit individual going to get. if individual has benefit that is very small and doesnt cost much for partner to give, but trremndously important to reproduce - benefit is QUITE LARGE. benefits and costs are relative in nature. one might seem small, but may be tremednously important and required so relationship continues . talk about mutualism as +/+, both parties get benefit, you must keep mind about costs. whats the costs/benefits, input/expenditure - to each inside relationship. keep ideas in mind. at same time, ask self what would have to happen in relatioship for it to fall apaart. easy answer is if costs are way greater than benefits, should get out. but for each individual example - need specifics to determine.

Nitrogen fixation bacteria

nitrogen fixation bacteria plants need nitrogen, nitrogen plentiful in atmosphere, N2 gas in atmosphere is most common gas in atmosphere. problem: plants can't use N2 gas in growing. nitrogen used by plant to build chloroplasts (which helps catch sunlight) made bc of nitrogen. b/c plants can't use gas nitrogen, it can be a huge limiting factor. this is why fertilizer has so much nitrogen. nitrates and nitrites - form that plants use, but these do not naturally occur. there is whole wide range of different organisms that can 'fix' nitration - take in atmospheric, and make different form - called nitrogen fixation. same as carbon fixation. take atmospheric and making into nitrate or nitrite. particular example is rhizobium bacteria, which live in soil and are able to fix nitrogen, convert atmospheric nitrogen into nitrate and nitrite. they do so whether plant is around or not. legumes, pod producing plants, live in symbiotic relationship with rhizobium bacteria in roots, and they are the ones fixing the nitrogen. allow plants to have useable form of nitrogen in body. little modules growing on roots of plants - inside host whole nitrogen fix rhizobium bacteria provide nitrates to plant, the more the plant can grow, the more carbs it will provide for bacteria. plant uses nitrates the bacteria is creating, the plant grows more, and produces more carbs for the bacteria. without these relationships we don't get plants growing the way they grow normally, if absent, don't grow as green or large as would with rhizobium bacteria.

Obligate Mutualism example

obligate mutualism - cellulose-digesting bacteria most organisms not solely herbivores, not going to be able to break through cellulose barrier and extract chemical energy out of plant cells. even herbivores don't have this ability unless have symbiotic bacteria living within thier gut. cellulose digesting bacteria break down cellulose, break down, break up and regular digestive processes of herbivore can extract carbs out of plants very nicely. obligate b/c bacteria can't survive outside of body, at most a couople hours before dying. herbivore can't survive wihout presence of cellulose digesting bacteria b/c wouldn't be able to get energy out of their food

Obligate relationship mutualism

obligate relationship mutualism - relationship / interaction itself is required for individuals to survive, what is survival again? yes, question of life or death, but frequently, survival is survival of reproduction and survivorship of genes. may be able to live bodily, but offspring might not live without relationship. mutualistic relationship where mutualism required for survival of at least genes ifn ot individual itself in order to survive generally speaking dont get obligate relationships where obligate for one and not the other - usually obligate for both or not for both.

Why is it easy to make incorrect assumptions about relationships between organisms?

scientists often make incorrect assumptions about the relationships between organisms because they don't know the full details of the relationship. sometimes truly mutualistic relationships are considered commensalistic because we do not know that the one member (who is not affected) is receiving some benefit. we also may assume that both members of a relationship are benefitting, even though one is not receiving a benefit or a cost (commensalism). this latter seems intentional by both parties, and is complex enough that there must be benefits that we are not able to detect. i.e. clownfish, brown-headed cowbird.

more on symbiosis - clownfish and anenome example

symbiosis - living almost in contact all the time, constant contact in order to maintain relationsihp. not all mutualistic relationships are symbiotic. symbiosis represents specific kind of mutualism. clownfish and anenome live in almost constant contact - clownfish does leave occassionally, but for most part, always stay near by anenome and maintain same anenome, constantly defneding agianst parasites, pathogens, predators, and keep algae from growing near it. at night, clownfish almost always inside ring of anenome. this one particular fish will stay with the same anenome as long as it is there. there are clownfish without and there are anenomes without this relationship, it is not required for either species to survive, but both species do better when they have this relationship taking place. the clownfish anenome relationship is more symbiotic than not.

What is the difference between mutualism and symbiotic relationships? Can a symbiotic relationship be mutualistic? Are mutualistic relationships always symbiotic?

the word symbiosis is often used to describe (and is often considered the same as) mutualism. this is NOT THE CASE, they are NOT necessarily the same. a symbiotic relationship may also be one of mutualism, the main difference is that in symbiotism the two individuals are in almost constant contact. i.e. lichens are a symbiotic relationship between algae and fungi - that is, they live together to form a single organism. look like coral above the water. pale gray stuff. lichen organism itself is so much like organism that for longest time though single organism. but actually a mutualistic symbiotic relationship between fungi and algae. constantly work with each other - fungus provide protection from environment, algae prevent fungi from dying out. fungi provides algae (algae photosynthetic, require CO2) fungi goes through process of respiration, which creates CO2 for algae. output of fungi is input for algae. sunlight able to penetrate through, and algae bodies can photosynthesize from CO2 and sunlight. creates carbohydrate, food source for fungus. oxygen used by fungus as well. each other's waste products become input requirements for other organism, and they can do quite well together. lichen is mutualistic (+/+) and symbiotic because always living together. this is different from say, a plant and a pollinator, who may form a mutualistic relationship around the pollinator event. BUT, the two do not live together, therefore , they are not symbionts (bees or polinators go back to their hive, do not live in plants).

Mutualism - can partners in a mutualistic relationship survive without it? define facultativ and obligative mutualism

yes and no. facultative mutualism - where individuals in the mutualistic relationship can exist without their mutualistic partner. obligative mutualism - where individuals in the mutualistic relationship are so dependent on the relationship that they cannot survive without it. what does the word 'survive' actually refer to? it could literally mean to live, or it may refer to the ability to pass genes onto the next generation (i.e. reproduce). usually it is either obligative or facultative - NOT a mix.