Aspecies that is no longer in existence would best be characterized as which of the following?
threatened
endangered
extinct
dinosaurs

Extinct.

Explanation:

The IUCN red list classifies the organism as endangered , extinct, threatened and vulnerable organism. The organism are classified on the basis of their number and presence on the particular area.

Extinct species is the species that are no longer present on the earth. The extinct species has been eliminated due to the unfavorable environmental condition and due to human activities. No single organism is present of the extinct species.

Thus, the correct answer is option (3).

explanation:

the sequence of amino acids in a protein determines its function. the dna sequence of a gene determines the amino acid sequence of the resulting protein. thus, any changes in dna sequence can result in changes in protein function. this is called a mutation.