The organism of a species that helps define an entire ecosystem is called:

The correct answer is Keystone species.

Key Points

• A keystone species is an organism that plays a critical role in maintaining the structure and functionality of an ecosystem.
• Removal of a keystone species can lead to significant changes in the ecosystem, often resulting in imbalance or collapse.
• Examples of keystone species include predators like wolves, herbivores like elephants, and even some plants like mangroves that stabilize coastal ecosystems.
• Keystone species influence the abundance and diversity of other species in their ecosystem, creating a ripple effect across trophic levels.
• The concept was first introduced by Robert Paine in 1969 after his study of intertidal zones and the impact of starfish on mussel populations.

Additional Information

• Typological Species:
  • Refers to the classification of species based on morphological similarities.
  • It is a concept used historically in taxonomy but does not account for genetic or ecological differences.
• Microspecies:
  • A term used for small, closely related populations or species that have very limited genetic variation.
  • Often found in plants where reproduction occurs through apomixis or self-pollination.
• Keystone Species Examples:
  • Sea otters: Control sea urchin populations, preventing overgrazing of kelp forests.
  • Beavers: Modify ecosystems by building dams, creating wetlands that support diverse species.
  • Pollinators: Such as bees are critical for plant reproduction and ecosystem stability.
• Trophic Cascade:
  • An ecological phenomenon triggered by the addition or removal of a keystone species.
  • It affects multiple levels of the food chain and can alter ecosystem dynamics.