Endemic species are species which are found isolated by geographical barriers.
Extinct species are species which are not found in areas where they may occur.
Rare species are species which are found rarely in the forests.
Normal species are found in forests easily.
Therefore, the correct answer is option 'C'.

Endemic species are species that are found in specific areas and are restricted to those areas due to geographical barriers. These barriers can include mountains, rivers, oceans, or any other physical feature that isolates a particular area from the surrounding regions. Endemic species have a limited distribution and are not found anywhere else in the world. These species have evolved in isolation and have adapted to the unique environmental conditions of their specific habitat.

Explanation:
Geographical barriers play a significant role in shaping the distribution of species. When a population of organisms becomes isolated from other populations of the same species, it can lead to the development of unique characteristics and adaptations over time. This process is known as speciation.

Endemic species are the result of speciation occurring in a specific isolated area. The geographical barriers prevent gene flow between the isolated population and other populations of the same species, leading to genetic divergence and the formation of distinct species. These species may have evolved unique traits and adaptations that allow them to survive and thrive in their specific habitat.

Examples:
There are numerous examples of endemic species around the world. One well-known example is the Galapagos Islands, which are home to a large number of endemic species. The Galapagos Islands are isolated in the Pacific Ocean, and the unique environmental conditions of each island have given rise to a variety of endemic species, including the famous Galapagos finches.

Another example is the lemurs of Madagascar. Madagascar is an island that has been separated from mainland Africa for millions of years, resulting in the evolution of a diverse array of endemic lemurs. These primates are found nowhere else in the world and have adapted to the specific habitats and food sources available on the island.

Importance:
Endemic species are of great importance for several reasons. Firstly, they contribute to the overall biodiversity of the planet. Each species plays a role in maintaining the ecological balance of its habitat, and the loss of an endemic species can have far-reaching impacts on the ecosystem.

Additionally, endemic species often have unique characteristics and adaptations that can be valuable for scientific research and understanding. Studying these species can provide insights into the processes of evolution and adaptation, as well as provide potential sources for new medicines and technologies.

Conservation:
Due to their limited distribution and vulnerability to environmental changes, endemic species are often at greater risk of extinction. Human activities such as habitat destruction, pollution, and climate change pose serious threats to these species. Therefore, it is crucial to prioritize their conservation and ensure the preservation of their unique habitats.

In conclusion, endemic species are those that are found in specific areas isolated by geographical barriers. They have evolved in isolation and have adapted to the unique environmental conditions of their habitat. These species play a crucial role in maintaining biodiversity and provide valuable insights into the processes of evolution. Protecting and conserving endemic species is essential to ensure the long-term survival of these unique and irreplaceable organisms.