What are antigens, and how do lymphocytes “recognize” them?

What are antigens ? - Antigens is a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

How do lymphocyte "recognize" them ? - However, the T-cell receptor differs from the B-cell receptor in an important way: It does not recognize and bind antigen directly, but instead recognizes short peptide fragments of pathogen protein antigens, which are bound to MHC molecules on the surfaces of other cells.

An ecosystem is in a certain area and includes living and non living plus there is weather conditions and a biome is a large amount of area with similar climate.so ecosystem is based on weather and biome is based on the average climate