Answer:

It is not a secret that the ecological situation on our planet is rather complicated. Apart from the common worries about global warming, industrial pollution, and rain forests being cut down, there is also the huge problem of the extinction of species; and while humanity can, hopefully, somehow stop the processes it is directly causing, it is unclear whether this extinction can be prevented or at least slowed down.

Although the words “mass extinction” definitely sounds alarming, it is not something uncommon for our planet. At the moment, we are witnessing the sixth mass extinction of species. During the past 500 million years, there already were five mass extinctions (with the largest of them being the Permian-Triassic and the Cretaceous-Tertiary extinctions, 245 and 65 million years ago respectively), causing from 14% to 84% of the genera or families to completely disappear from the fossil record. During the first of them, the majority of the marine invertebrates, as well as a huge number of terrestrial plants and insects disappeared; the second one mostly affected the dinosaurs. Even in a relatively not-so-distant past, some animal species had gone extinct completely: about 11 thousand years ago, during the Pleistocene-Holocene period, about 100 terrestrial species died out, including mammoths, saber tooth tigers, rhinos, and some birds (NCBI).

Answer:

It is not a secret that the ecological situation on our planet is rather complicated. Apart from the common worries about global warming, industrial pollution, and rain forests being cut down, there is also the huge problem of the extinction of species; and while humanity can, hopefully, somehow stop the processes it is directly causing, it is unclear whether this extinction can be prevented or at least slowed down.

Although the words “mass extinction” definitely sounds alarming, it is not something uncommon for our planet. At the moment, we are witnessing the sixth mass extinction of species. During the past 500 million years, there already were five mass extinctions (with the largest of them being the Permian-Triassic and the Cretaceous-Tertiary extinctions, 245 and 65 million years ago respectively), causing from 14% to 84% of the genera or families to completely disappear from the fossil record. During the first of them, the majority of the marine invertebrates, as well as a huge number of terrestrial plants and insects disappeared; the second one mostly affected the dinosaurs. Even in a relatively not-so-distant past, some animal species had gone extinct completely: about 11 thousand years ago, during the Pleistocene-Holocene period, about 100 terrestrial species died out, including mammoths, saber tooth tigers, rhinos, and some birds (NCBI).

Moreover, there are two kinds of extinction: the one after which there is no “replacement” of an extinct species with a new, more adapted one—the “dead-end extinction” which is basically the end of a certain evolutionary lineage; and taxonomic extinction, which implies that during the evolutionary process, certain species had changed to such an extent that they should be considered a different species (NCBI).

Currently, there are 14,000 to 35,000 endangered species only in the United States; 16,928 species worldwide stand on the edge of dead-end human-caused extinction, and in order to save them, a significant amount of effort should be made. This is especially difficult considering the fact that every species’ extinction can lead to the disappearance of other species that are somehow bound to it: for example, if bees die out, many types of plants will not be able to reproduce, and will have either to adapt quickly,