Hey,
Freshwater is defined as having a low salt concentration — usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean). There are different types of freshwater regions:
Ponds and lakes
Streams and rivers
Wetlands
Symbiosis is close and often long-term interactions between different biological species. So basically it is "the living together of unlike organisms." The symbiotic relationship may be categorized as
mutualistic,
commensal, or
parasitic in nature. Some symbiotic relationships are obligate, meaning that both symbionts entirely depend on each other for survival. For example, many lichens consist of fungal and photosyntheitc symbionts that cannot live on their own. Others are facultative, meaning that they can but do not have to live with the other organism.
Symbiotic relationships include those associations in which one organism lives on another (ectosymbiosis, such as mistletoe), or where one partner lives inside the other (endosymbiosis, such as lactobacilli and other bacteria in humans). Symbiotic relationships may be either obligate, for instance, necessary for the survival of at least one of the organisms involved, or facultative, where the relationship is beneficial but not essential for survival of the organisms.
Know I will demonstrate symbiosis:
Bacteria that may exist in the pond metabolize organic matter (dead leaves, dead animals) releasing nutrients like
nitrogen,
phosphorous and
carbon dioxide. Algae use these compounds along with energy from sunlight for synthesis of food releasing
oxygen in wastewater. Oxygen-loving bacteria take up the oxygen released by algae, thus closing the cycle. This type of relationship between bacteria and algae is called
symbiosis. This is common among organisms living in small ponds and streams, where two or more species live together for mutual growth and development. Besides these, other microorganisms in wastewater stabilization ponds like protozoa, rotifers etc., also live in these waters and feed on algae and bacteria. So, next time you see some pond slime or green jelly balls in the water, think about the mosaic ecosystem they represent. These symbiotic relationships between the different forms of life in the gel masses could possibly explain the cosmic processes that started life on Earth, how it has changed since, and what it might be like millions of years in the future!
An example of competition can be as follows (Remember: competition means that both the interacting species do not benefit with this kind of symbiotic relationship.) Swallows (birds) and swifts (bird) feeding on the same pond.
Now you think of animals inside this pond and try to think of ways how they can/do benefit one another.
Hippos constantly have birds pecking on their backs. The birds benefit because they eat the little insects on the hippo, while at the same time hippos benefit because they become flee-less.