Part 1: Preparation
Extinction, which is the permanent and complete loss of a species, is a natural process that has occurred at various rates throughout earth’s history. In fact, >99.9% of species that have existed on earth are now extinct and there have been at least five mass extinctions, where a large proportion of species and families (a broader, more inclusive taxonomic unit) have gone extinct in a geologically short period of time. The Cretaceous Extinction is the most familiar—it’s where the dinosaurs became extinct—but that wasn’t the largest of the mass extinctions; during The Great Dying, or Permian Extinction about 250 million years ago, at least 90% of all marine species were lost!
The background rate of extinction is estimated at about 1 species, per million that exist, per year (1 species/million/year). This is the rate of extinction, estimated from evidence like fossils, that we expect to occur naturally outside of the mass extinctions. But how does that compare to current rates of extinction?
To explore this question, begin by completing The Science Literacy: Working with Data activity on extinction on page 145 of your textbook in your notes. Be sure to review content and language concerning extinction, particularly that on p 138-141.
The sixth mass extinction is attributed to human impact. Go to the International Union for Conservation of Nature website (IUCN; http://www.iucnredlist.org).
Choose five species at random that are identified as vulnerable, endangered, or critically endangered. If you need help finding some species, use the search feature (https://www.iucnredlist.org/search) and filter the database by selecting “Redlist Category” and then checking the appropriate boxes (i.e., vulnerable, endangered, and critically endangered).
Read about each species you’ve selected, and, for each, identify their IUCN Redlist Status and describe the reasons for their endangerment.
Write a brief summary of your findings by:
Creating a list of all the threats you encountered for your five species, and categorize the threats as either human-caused or caused by natural events.
Describe the major threats to the species you’ve chosen—which threats do species have in common? Are the commonalities human-caused or natural?
Does human impact play a role in the endangerment (i.e., Redlist Status) of these species?