Menciona tres especies con reproducción sexual externa

Coral have a symbiotic relationship with what in order to eat?

You are given an electron micrograph of a bacterial cell. in the micrograph you can clearly see three thin layers of different densities surrounding the cell. based on the micrograph, you can infer that this cell is and would appear after application of the gram stain procedure. gram-negative / pink gram-positive / purple gram-positive / pink gram-negative / purple

How does this procedure serve as a method of birth control?