Proteins are made from that are joined by

Proteins are made from amino acids that are joined by peptide bonds. 
An amino acid is a simple organic compound and is constructed from a carboxylic acid and an amino. Amino acids are the building blocks of proteins. Proteins play a very important role in almost all of the biological processes in our body. 
A peptide bond is a chemical bond which is formed between two molecules. In an amino acid, the carboxylic acid of one molecule reacts with the amino group of another molecule. This process releases a water molecule. The two molecules are then "stuck together" due to the condensation reaction or the release of the water molecule. 

1.fossils 2.analogous organs 3.homologous organs