BBC Bitesize - Higher Biology - Symbiosis - Revision 3
Mutualistic Relationships Between Algae and Fungi (Excluding Lichens) Both symbiotic partners form well-defined structural and functional units. . Freshwater algae, e.g. Dunaliella and the autotrophic protozoan Euglena can establish a. Symbiosis is any type of a close and long-term biological interaction between two different Endosymbiosis is any symbiotic relationship in which one symbiont lives within the tissues of the . Eukaryotes (plants, animals, fungi, and protists) developed by symbiogenesis from a symbiosis between bacteria and archaea. The tiny lichen is a critical part of the food chain, but how do algae and fungi work together to form these symbiotic organisms?.
An example of competition is a sapling growing under the shadow of a mature tree. The mature tree can rob the sapling of necessary sunlight and, if the mature tree is very large, it can take up rainwater and deplete soil nutrients.
MUTUALISMS BETWEEN FUNGI AND ALGAE
Throughout the process, the mature tree is unaffected by the sapling. Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling. An example of antagonism is Juglans nigra black walnutsecreting juglone, a substance which destroys many herbaceous plants within its root zone. Whilst the presence of the grass causes negligible detrimental effects to the animal's hoof, the grass suffers from being crushed.
Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it. Cleaning symbiosis Cleaning symbiosis is an association between individuals of two species, where one the cleaner removes and eats parasites and other materials from the surface of the other the client.
These bacteria not only provide nutrients but also create the toxins that poison fish that eat the tiny dinoflagellates. When they have a sudden upwelling of nutrients, their numbers surge to create dangerous "red tides. Anabena azollae, the cyanobacterium symbiont of the floating fern Azolla. It lives in spaces between the cells of Azolla, to the left The ciliate protozoan Ophryoscolex is one of the largest in a cow's rumen.Amazing Microscopic video! Paramecium Bursaria showing symbiosis with green algae.
There are millions of such protozoa in the rumen. Each of them contain millions of bacteria that digest cellulose, the cow's primary food. Image credit Sharon Franklin. USDA Cattle depend on bacteria inside protozoa inside their rumen stomachs to digest their food Sheep depend on bacteria inside protozoa inside their rumen stomachs to digest their food Deer, like all grazers, depend on bacteria inside protozoa inside their rumen stomach to digest their food.
Water Buffalo, like all grazers, depend on bacteria inside protozoa inside their rumen stomach to digest their food.
A few basidiomycetes are also capable of forming lichens. These are not generally considered to be highly-developed relationships yet there is no doubt they function as lichens. The first of the two photos above shows Multiclavula mucida. In this species the basidia and basidiospores line the surface of the upright "fingers" and under cool moist conditions release the spores to drift in the wind.
The photobiont, a green alga, forms a thick crust of the the substrate, in this case rotten wood. The algae are enclosed by the hyphae of the mycobiont. In the second picture the mycobiont is Lichenomphalia umbellifera, a mushroom. The photobiont and its relationship with the phytobiont are the same as in M.
Since these sexual structures reproduce only the fungus, the resulting spores must be fortunate enough to land on an appropriate alga, or perish. However, there is another way. If the lichen can disperse propagules containing both myco- and photobionts then it will be able to develop in any suitable habitat. However, this type of reproduction is strictly clonal and does not allow for the kind of genetic recombination that occurs during sexual reproduction.
Clonal reproduction of lichens can occur in several ways. The simplest of these is simply to separate a piece of the thallus containing both alga and fungus and send it off by wind or water to develop in a new place. This kind of reproduction is common among lichens and generally effective.
There are more highly developed forms of clonal reproduction, two of which are represented in the photographs above. In the first the lichen has produced soredia. Soredia are small bundles of algae held together by fungal hyphae. They are small enough to be carried by wind yet guarantee the presence of both partners. The illustration above left shows a young thallus of the foliose lichen Peltigera didactyla. In this species the upper surface becomes dotted with soralia, special structures for the production of soredia.
In the photograph, the soralia have released granular masses of soredia. The other photograph above is a highly magnified view of isidia, small coral-like branches containing both mutualists that can break off and drift to a new habitat.
Symbiosis - Wikipedia
The lichen in the picture is Xanthoparmelia conspersa, a common lichen on exposed rock in New Brunswick. Lichen habitats One of the fascinating aspects of lichen biology is the ability of these organisms to occupy habitats that would be totally in inhospitable to other organisms. Thus we can find them growing on the ground in deserts, on the sides of dry rock, hanging from the branches of trees and and even growing on the backs of turtles. They are nearly as easy to find and study in the middle of winter as during the warmer months.
The first of the three photographs above was taken in Saskatchewan, out in an open prairie. The rock in the forground is the highest point in the immediate area; animals sitting there get a panoramic view of the grassland and all that is taking place there.
It is a favourite place for birds, especially birds of prey waiting for a mouse or vole that might be moving through the grass. The orange lichen is a species of Xanthoria that thrives on nitrogen-rich bird droppings left on the rock.
Similar species of Xanthoria, as well as members of the related genus Caloplaca, can be found on our seacoast on rocks frequented by gulls and cormorants. The second of the two pictures above is of White Horse Island, a small island in the Bay of Fundy supporting large colonies of nesting birds. The white colour of the rock is due to a thick layer of bird droppings; the orange material is a species of Caloplaca. The gravestone at left marks the resting place of Roland ThaxterProfessor at Harvard University and brilliant mycologist, known in particular for his monumental studies on the Laboulbeniales.
How Does Life Work? Symbiosis Crossing the Kingdoms Algae & Protozoa
Beside Roland's grave is that of his brother Karl. Both gravestones have become colonized by lichens and are now difficult to read. Click on the photograph to get an enlarged version of Roland's gravestone Another interesting thing about our coastal lichens is that some of them are highly tolerant of salt, a substance that is toxic to most fungi, including lichenized ones.