I need a complex question about endangered species

An endangered species is an animal or plant that's considered at risk of extinction. A species can be listed as endangered at the state, federal, and international level. On the federal level, the endangered species list is managed under the Endangered Species Act.

The Endangered Species Act (ESA) was enacted by Congress in 1973. Under the ESA, the federal government has the responsibility to protect endangered species (species that are likely to become extinct throughout all or a large portion of their range), threatened species (species that are likely to become endangered in the near future), and critical habitat (areas vital to the survival of endangered or threatened species).

Here are two:

Why do some species survive while others go extinct?

Does extension proceed toward increasing complexity?