Question

In textbook Chapter 18 section 18.3 you will find a description of “Trophic Cascades”.  Explain what this means.

      Describe how the concept of trophic cascade is related to the Keystone species concept in Chapter 17.

Answer 1

Trophic cascade: Trophic cascade is an important phenomenon to control the ecosystem by indirect interaction between the trophic levels of the food chain. Trophic cascade causes dramatic changes in structure,complexity and nutrient cycle of the ecosystem.

There are two types of trophic cascade: Top down trophic cascade and bottom up trophic cascade.

Top down trophic cascade is a trophic cascade where the abundance of top consumers or predators decreases the population of primary consumers. As a result the primary cosumers exploit and eventually primary producers will thrive.Thus the entire food web would be affected.

If the top consumer decreases in abundance then the primary consumer would thrive and it would cause the exploitation of primary producers.

In the bottom up cascade the abundance primary producer like plants, zooplanktons, phytoplanktons will control the population of primary and secondary consumers of higher trophic level in a food chain.

Keystone species is a species whose abundance effect largely on ecosystem. The ecosystem may experience dramatic changes if the keystone species are removed even if they are present in small number.

From the above it can easily be concluded that keystone species are those critical species which control the population of other species and causes the trophic cascade.