Can a species ectinct be replaced?

In a strict sense, once a species has become extinct, it cannot be replaced by the exact same species. However, there are a few ways in which a similar species can evolve to fill a similar niche in the ecosystem.

Convergent evolution occurs when two or more unrelated species evolve similar traits independently in response to similar environmental pressures. For example, the saber-toothed cat (Smilodon) and the Tasmanian tiger (Thylacinus cynocephalus) both evolved saber-like teeth for hunting prey. Although these two species are not closely related, they developed similar traits in order to survive in their respective environments.

Ecological replacement occurs when a new species evolves to fill the ecological niche of an extinct species. For example, after the extinction of the woolly mammoth, the American mastodon (Mammut americanum) evolved to fill the role of a large herbivore in North America. Although the mastodon was not as closely related to the mammoth as the saber-toothed cat was to the Tasmanian tiger, it was able to fill the mammoth's ecological niche and thrive in the same environment.

Reintroduction is the process of introducing a species back into its former range after it has become extinct in that area. For example, the California condor (Gymnogyps californianus) was once extinct in the wild, but it has been successfully reintroduced to several locations in California and Arizona. Reintroductions can help to restore the ecological balance of an ecosystem by bringing back a species that plays an important role in the food chain.

In some cases, a new species can evolve to fill the ecological niche of an extinct species so closely that it is difficult to tell the difference between the two. This is known as mimetic radiation, and it occurs when a new species evolves to mimic the appearance and behavior of an extinct species in order to avoid predators or compete for resources. For example, the African jacana (Actophilornis africanus) is a bird that evolved to mimic the appearance and behavior of the extinct Madagascan ibis (Lophotibis cristata). The jacana is able to survive in the same environment as the ibis because it is able to avoid the predators and competitors that would otherwise threaten its survival.

While a species that has become extinct cannot be replaced by the exact same species, it is possible for other species to evolve to fill a similar niche in the ecosystem. This can occur through convergent evolution, ecological replacement, reintroduction, or mimetic radiation.