More than amino acids linked together is considered a protein.

Over 50 amino acids in a chain are considered a protein.

More than 100 amino acids linked together is considered a protein.

Explanation:

The scientists categorize the links of amino acids based on the number of aminoacids:

Peptides: two to ten amino acids  

Polypeptides: 11 to 100 amino acids

Proteins are 100  and more of 100 amino acids.

A protein is a chain of amino acids linked by peptide bonds.  They are responsible of the biochemical reaction of cells.

spiders belong to a group of arachnids.

arachnids have the following traits :

they have two body parts.

they have eight legs unlike insects which have 6 legs.

they have no wings.

these traits distinguish them from insects.

the information that antonio is doubting us the statement that spiders differences are as a result of being first to evolve.

this is because the evolution of one species is independent of the other species.