This substitution score matrix called is derived from protein families that are characterized by blocks of conserved amino acid sequences.

BLOSUM

Explanation:

A substitution matrix is a matrix used in bioinformatics (and also in computational biology) to determine/estimate the rate at which one character -which is specified by a nucleotide sequence in nucleic acid alignments or by one amino acid in protein alignments-, changed to another character during the course of the evolution. The BLOcks SUbstitution Matrix (popularly known as BLOSUM) is a substitution matrix used to score one amino acid for another in a protein alignment. The BLOSUM substitution matrix is particularly useful to compare evolutionarily conserved regions between protein sequences and thus score their alignments, where each entry is indicated by a similarity score between two amino acids.

the trilobite is used as an index fossil for various geologic time periods as specific types of the trilobites were present in different geological time periods. they are a group of marine arthropods belonging to the class of trilobita.

explanation: