Removal of a species leads to significant changes that spread throughout the food web. This species can be called as a:

Correct option is D

Introduction:

• A keystone species is one whose presence and role within an ecosystem has a disproportionate effect on other organisms within the system.
• If a keystone species is removed, it causes a dramatic shift in the food web and ecosystem structure.
  

Information Booster:

• A keystone species is an organism that helps hold the system together; without its presence, the ecosystem would be dramatically different or cease to exist altogether.
• These species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.
• Their removal often triggers a "trophic cascade" where the effects of their absence ripple through the entire food web, leading to significant changes in community composition and even physical habitat.
  
• Keystone species often maintain the structure and integrity of the community.
• They may be top predators, mutualists, or ecosystem engineers.
• Their removal can cause a trophic cascade and lead to ecosystem collapse or major alteration.

Additional Information: 

• Climax Species: These are species that make up a climax community, which is the relatively stable end product of ecological succession.

• Invasive Species: These are non-native organisms that, when introduced to a new area, cause environmental or economic harm.

• Flagship Species: These are "charismatic" species chosen to represent an environmental cause or a specific habitat.