The study of life in the oceans - from microscopic plankton to the largest animals on earth, the blue whales. Like biology, marine biology has many, diverse fields of study contained within it including the study of the molecules within cells (molecular biology), the functions and adaptations of organisms (physiology), and populations of organisms and their interactions with each other and their environment (ecology). What unites these areas as marine biology is the saltwater environment, whether it be the coastal wetlands and estuaries, rocky shorelines and beaches, coral reefs and kelp forests, or the vast open-ocean habitat and abyssal sea. This biology draws on other sciences such as chemistry, physics, geology, and oceanography, and includes disciplines such as marine microbiology, phycology (the study of algae), marine toxicology, fisheries and aquaculture, deep-sea ecology, invertebrate zoology, ichthyology (the study of fish), marine mammalogy, and marine conservation biology.