Deck 10: An Introduction to Marine Ecology

Question 1

Two species of sea urchins live practically side-by-side in sandy bottoms. The two species appear to have the same diet: drift seaweeds and other bits of organic matter. They are able to live in the same environment without competing with each other. How might they be able to share their habitat and food resources?

Answer 1

The marine ecology is extremely complex with interwoven network of biotic and abiotic components. The area under marine ecology is extremely vivid and varies according to the depth of the water. The upper section holds the organisms capable of photosynthesis, while the lowest section holds the organisms capable of living in the dark.
The two species of sea urchins can avoid competition with each other by eating at different times of the day i.e. 1 species can eat in the morning and the other can eat at night. Varying the feeding levels in the sand is another important method of avoiding competition (top of the sand or bottom of the sand). Feeding at the different area on the beach is another simple method of avoiding competition. Changing the feeding habit is another method of sharing food, while one species can eat algae, the other can eat other type of organic matter.

Question 2

It is not always easy to categorize a particular case of symbiosis. Suppose a certain species of snail is always found living on a certain coral. No one has found evidence that the snail harms the coral, so the relationship is classified as an example of commensalism. How would you go about testing this hypothesis? What kinds of observations might lead to the conclusion that the snail is a parasite, or that it has a mutualistic relationship with the coral?

Answer 2

Symbiosis is the process of an interconnection between the two species. Both the species live in contact with each other and support the life of each other. There have been instances where an individual species is unable to survive in the absence of other species.
The relationship between snail and corals can be easily tested by removing the snail from the coral and putting it on another coral. Following this separation, the growth of both the type of corals can be compared with each other. This could help in testing whether the snail has actually helped the corals or not. In case some section of the coral goes missing after introducing snail, this could prove the parasitic nature of the snail. If changing the location of snails increased the mortality rate of the snails, this could prove that the snails were actually benefited by the presence of corals. The mutual benefit of corals and snails observed in the form of parallel growth could be an example of mutualistic relationship.