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Mutualism is the way two organisms of different species biologically interact in a relationship in which each individual derives a fitness benefit. (Wikipedia)


Example of mutualism ,Hummingbird and flower .

The hummingbird take aliment and nutrients of the flower and the flower assure its reproduction.(Pollen travel to another flower by the hummingbird)

There are three different types of mutualism:

Resource-Resource relationship

Example:A plant and a fungi

The plant gives carbohydrates to the fungi. This one gives to the plant phosphate and nitrogenous compounds.


Service-Resource relationship:

Example: A flower and a bee.

The flower gives food to he bee and the bee helps in the reproduction of the flower. ( The same function as the hummingbird)


Service-service relationhip:

Example: sea anemones and clownfish

The sea anemone protect clownfish from the predators ( The anemone has poison tentacles) and the clownfish protect anemones from fishes that eat anemones.



(Information from wikipedia)

In ecology, commensalism is a class of relationship between two organisms where one organism benefits but the other is neutral (there is no harm or benefit). There are two other types of association: mutualism (where both organisms benefit) and parasitism (one organism benefits and the other one is harmed).



Barnacles are highly sedentary crustaceans that must attach themselves permanently to a hard substrate, such as rocks, shells, whales or anything else on which they can gain a foothold. When they attach to the shell of a scallop, for instance, barnacles benefit by having a place to stay, leaving the scallop presumably unaffected.

The Nitrogen Cycle is the circulation of nitrogen in nature, consisting of a cycle of chemical reactions in which atmospheric nitrogen is compounded, dissolved in rain, and deposited in the soil, where it is assimilated and metabolized by bacteria and plants, eventually returning to the atmosphere by bacterial decomposition of organic matter.



Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonium (NH4+). Atmospheric nitrogen or elemental nitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. Fixation processes free up the nitrogen atoms from their diatomic form (N2) to be used in other ways. Nitrogen fixation occurs naturally in the air by means of lightning.


Type of fixation N2 fixed (1012 g per year, or 106 metric tons per year)
Industrial about 50
Combustion about 20
Lightning about 10
Total about 80
Agricultural land about 90
Forest and non-agricultural land about 50
Sea about 35
Total about 175
Data from various sources, compiled by DF Bezdicek & AC Kennedy, in Microorganisms in Action (eds. JM Lynch & JE Hobbie). Blackwell Scientific Publications 1998.

Depending on the type of microorganism, the reduced ferredoxin which supplies electrons for this process is generated by photosynthesis, respiration or fermentation.


Symbiosis- Andrea Jimeno

Symbiosis is the process by which an organism may coevolve to interact closely with another organism.



Some symbiotic relationships are obligate, meaning that both symbionts entirely depend on each other     for survival. For example, many lichens consist of fungal and photosynthetic symbionts that cannot live on their own. That is called mutualism because both of the organisms benefits each other.


Another type of symbiosis is commensalism.


The relationship between hermit crab and sea-anemone is an excellent example of Commensalism.

Hermit crab lives inside empty shell of mollusc. The sea anemone inhabits the outer surface of being unaffected in a relationship.Commensalism resutls in one organism benefiting and one being unaffected in a relationship.

Paristism is a relationship in which one organism benefits and the other one is harmed.

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out to both biological and non-biological processes.

Nitrogen compounds can be lost from soil as nitrates in water. Organic N is broken down to ammonia this is converted to nitrate  by the action of a  bacteria. Ammonia is oxidized to nitrite and then to nitrate . Many groups of “denitrifying bacteria” in soil reduce nitrate to oxides of nitrogen and N2 gas which can result in significant gaseous losses. Denitrifying bacteria use nitrate as a terminal electron acceptor in place of oxygen in anaerobic conditions, for example where soil is waterlogged, warm and contains plenty of organic matter.


Searching on Internet I found two good videos that explain the Nitrogen Cycle:

SOURCES: Images:

Text: Wikipedia, My head



Predation is the interaction between species in which one of them uses another species as food. Predation is a process of major importance in influencing the distribution, abundance and diversity of species in ecological communities.

The predator is the organism that eats another organism. The prey is the organism which the predator eats.

Some examples of predator and prey:

Lion and zebra

Bear and fish

Fox and rabbit

The words “predator” and “prey” are almost always used to mean only animals

that eat animals, but the same concept also applies to plants:

Bear and berry

Rabbit and lettuce

Grasshopper and leaf.









predation is a mechanism of population control. Thus, when the number of predators is low the number of prays should rise. When this happens the predators would be able to reproduce more and possibly change their hunting habits. When the number of predators rises, the number of prays decline. This results in food scarcity for predators that can eventually lead to the death of many of them.



Respiration is the process in which carbohydrates are converted to water and carbon dioxide, so that carbon is released again into the air. So, during this process, both animals and plants retur the carbon dioxide they had previously inhaled back to the atmosphere so that the carbon cycle can continue.


Water Cycle

The water cycle, describes the continuous movement of water on, above and below the surface of the Earth.

Water Cycle

Water Cycle II

Water Cycle III

The water cycle consists of four phases:

  • Evaporation/Transpiration.
  • Condensation.
  • Precipitation.
  • Collection.