Marine biology involves the study of various plant and animal species that live in the ocean, sea, or any other water body, and how the interactions between the species and the environment affect them and their habitat. Since, most phyla and genera consist of different marine as well as terrestrial species, classification of the marine organisms is done based on environment, rather than taxonomy. This field of study is significant, as 71% of our planet's surface is covered with water. Also, this marine environment constitutes about 90% of the total habitable area on the planet. Due to this vast nature, 50-80% of all life-forms on this planet are marine organisms. It is essential to study this branch of science, since most of the planet is covered by oceans and other water bodies, therefore, the marine environment plays a major role in the overall health of our planet's environment/atmosphere. Also, study of marine organisms, would prove beneficial for research and development purposes, in order to develop pharmaceutical, biomedical, as well as alternate energy applications. Owing to latest technological advancements and increased understanding of the marine biome, marine biologists have managed to discover, identify, and classify quite a few species of organisms. However, despite these efforts, almost two-thirds of the total marine biodiversity still remains unknown. Therefore, modern-day marine biologists have taken up the task of mapping the marine species of animals and plants with the help of latest technologies. Some of the marine biologists, who have greatly contributed to this field are given below. Index Jakob Johan Adolf Appellöf was a Swedish marine zoologist. In 1877, Adolf Appellöf graduated from the famous University of Uppsala, earned his doctorate in zoology, and took up a temporary position as a lecturer in zoology at the same university. Later on, he took up a position of a conservator at the Museum of Bergen, Norway. With the help of a Bunsow, a sawmill magnate, Adolf Appellöf founded Klubban Biological Station of University of Uppsala. This institute specialized in the study of marine biology and was situated on the western coast of Sweden. He was the member of both the Royal Swedish Academy and the Royal Society of Sciences in Uppsala. His research on cephalopods (mollusks) was a significant contribution to the field of marine biology. He was a U.S. marine zoologist. Samuel Stillman Berry graduated from the University of Stanford (1909) and then pursued M.S. from Harvard. He specialized in the study of cephalopods and received his doctorate on the same subject from the Stanford in the year 1913. For the next five years he worked as a research assistant at the Scripps Institution for Biological Research, California. Later, he continued his research in malacology, as an independent researcher. The aspirants of marine biology currently use his research work as a basis and/or reference for their studies. He has written over 200 articles on malacology, and has discovered 401 mollusc taxa. His works provide insight into various features of chitons, cephalopods, and snails. He was a renowned German marine biologist. He graduated in zoology from the University of Leipzig. In 1892, he was appointed as a professor in the same university. Carl Chun initiated and headed the German deep-sea expedition on August 1, 1898. He, along with his team members, explored the seas around the continent of Antarctica, and also, the Bouvetøya and the Kerguelen islands. His research subjects were cephalopods and plankton. Carl Chun discovered, and also named, a species of squid, the Vampire Squid. He was a French researcher and ecologist who studied the lives of underwater animals and plants. He was basically a French naval officer, who was also a popular filmmaker, author and researcher. He is popularly known as Captain Cousteau or Jacques Cousteau. He, along with Emily Gagnan (French engineer), developed the first open-circuit scuba diving equipment known as "Aqua-Lung". He was a pioneer of marine conservation and a member of L'Academie francaise. Captain Cousteau founded the Underseas Research Group, at Toulon, and the French office of Underseas Research, at Marseille. He was also the director of the Oceanographic Museum of Monaco. He was a German marine biologist. He had mastered not only medicine but also zoology. He received his doctorate in 1865. In 1874, he founded "Stazione Zoologica" in Naples. He was the director of this organization until his death. A thesis which proposed the theory of the origin of vertebrates, known as Der Ursprung der Wirbelthiere und das Princip des Functionswechsels: Genealogische Skizzen, was submitted by him in 1875. She is an American oceanographer and a renowned marine biologist. Sylvia graduated from the University of Florida in 1955 and went on to achieve her master's degree from the same university. She received her doctorate from Duke University in 1966. She was a curator of phycology at the Academy of sciences, California, a research associate at University of Berkeley, Harvard University, and also a Radcliffe Institute scholar. In 1970, she headed the first women's team of aquanauts for a project known as the Tektite Project. She was the chief scientist for National Oceanic and Atmospheric Administration, US. Currently, she is a deep sea explorer-in-residence of National Geographic channel. Sylvia Earle has authored over 125 books on marine science including "Exploring the Deep Frontier", "The Atlas of the Ocean", and so on. He was a German marine scientist and an environmentalist, who was born in East Prussia. He completed his studies in Natural Sciences in Königsberg, and worked as a lecturer in the Zoological Institute of Munich. He carried out research and studies in limnology. Bruno studied the different fish types and their habitation. During his lifetime, he was the director of the Royal Bavarian Research Station for Fisheries. Hofer also served as the vice-president of the Bavarian Association of Fishermen, and as the editor of the magazine "Allgemeine Fischereizeitung". Hofer specialized in fish parasitology and pathology. He was an English marine biologist and a renowned zoologist. He was a qualified medical practitioner who was passionate about marine life and zoology. He worked as a research assistant and a librarian in the Zoological Department at the British Museum. During his tenure at the British Museum, he was in charge of the natural history department. William Leach researched widely on crustaceans and mollusks. Insects, birds, and mammals also comprised his field of study. "Zoological Miscellany", "Synopsis of Mollusca of Great Britain", and a systematic catalog of the "Specimens of the Indigenous Mammalia and Birds", that are preserved at the British Museum, are some of his popular works. He was a notable Russian anthropologist, ethnologist, and marine biologist, who graduated from St. Petersburg University. In Italy, he met Anton Dohrn, who instilled the idea of starting a research station. Maklai shifted his base from Russia to Australia. With the help of the Linnean Society, he founded a zoological center, known as the Marine Biological Station, in Watsons Bay, Sydney. This was the first marine biological research institute in Australia. He was a famous Scottish-Canadian oceanographer and marine biologist. He graduated from the University of Edinburgh. He is known as the "Father of Modern Oceanography". Murray coined the term oceanography. John Murray first brought to light the existence of the mid-Atlantic ridge and oceanic trenches. One of his major contributions to marine biology was the "Bathymetric" survey of 562 freshwater lochs of Scotland. During his lifetime, he wrote many articles and journals on oceanography. He is a noted German hydrobiologist. Rosenthal completed his education from Freie Universitat, Berlin. He later studied hydrobiology and fishery in Hamburg. Rosenthal presented a thesis on mass rearing of larval herring. He is acknowledged for his research in fish farming and ecology. Harald Rosenthal focused on aquaculture and ballast water. He is the founder and president of the World Sturgeon Conservation Society, and is also, an active member of the Royal Swedish Academy of Sciences. She was a renowned marine biologist who researched widely on Teredo, a genus of mollusks, that wreaks havoc on docks and boats. She graduated from Bridgewater State College, and went on to earn a doctorate from Harvard. Ruth has published over 200 scientific articles, and a book. Turner specialized in shipworm research. Ruth Turner was the first female marine biologist to make use of Alvin, a deep ocean research submarine. He was a Scottish marine biologist, who was the chief scientist on the Challenger Expedition. Charles Thompson specialized in the field of deep sea biological conditions. His interest in crinoids prompted him to persuade the Royal Navy to allow him the usage of HMS Lightning and HMS Porcupine, for deep sea dredging. Charles threw light on such facts as the existence of marine life (vertebrates and invertebrates) at 1200 m below the ocean surface. Another fact brought to light was the considerable variability of deep-sea temperature. The book, "The Depths of the Sea", was written by Charles Thompson. He was closely associated with John Murray, the oceanographer. He was a marine biologist, who was an expert on marine ecosystems and zooplankton. Alister Hardy was one of the chief scientists on the RRS Discovery, as part of the Discovery Investigations. He specialized in the study of marine mammals such as whales. He designed and built the "Continuous Plankton Recorder" (CPR), to collect plankton samples. His research of plankton is continued by an organization called the Sir Alister Hardy Foundation for Ocean Science (SAHFOS). HE is a marine biologist who specializes in neurophysiology of the marine life. He graduated from the University of California, Riverside, and pursued his doctorate at the University of California, Santa Cruz. Later, he went on to pursue his postdoctoral degree in neurophysiology from Centre National de la Recherche Scientifique, Marseilles, France and from the University of California, San Diego. Currently, Joseph Ayers is associated with Biomimetic, an underwater robot program. "Neurotechnology for Biomimetic Robots", "Biomechanisms of Swimming and Flying", "Dr. Ayers Cooks with Cognac", and "The C Around Nahant" are some of the research books authored by him. She is an Australian marine scientist, who is an expert in thew field of diatoms and their distributtion in the Southern ocean. She specialized in micropaleontology for her doctoral degree, at the Australian National University and the University of Bordeaux, France. She went on to pursue post-doctoral research on the dynamics of sea ice with regards to those of the Southern Ocean. Her research has provided valuable data and insight as to how sea ice helps drive the circulation of the ocean. Also, climatic and fishery models based on this data, can help determine the effect of sea ice on the fishery industry, marine food web, and the interaction and relationship between sea surface and terrestrial climate. She is currently engaged in studying the role of diatoms in the carbon transport cycle in the ocean (surface to ocean floor). She was an American marine biologist, conservationist, and environmentalist. She had a master's degree in zoology, and had studied the embryonic development of the pronephros in fish, for her masters dissertation. She was, initially, an aquatic biologist in the U.S. Bureau of Fisheries, but later went on to become a nature writer. She has written numerous books, advancing the cause of marine exploration and conservation. her published works have inspired many movements for environmental protection and conservation, and also led to the creation of the U.S. Environmental Protection Agency. Some of theses books include "The Edge of the Sea", "Under the Sea Wind", "Silent Spring", etc. She was posthumously awarded the Presidential Medal of Freedom by Jimmy Carter. He was an American oceanographer and marine biologist, who worked the famous ichthyologist Alexander Agassiz, after graduating from Harvard. he later worked at the Museum of Comparative Zoology in 1905 and joined Harvard's faculty in 1906. He helped found the Woods Hole Oceanographic Institution in 1930. During his lifetime, he published over a hundred research papers along with several scientific books. He was a world-renown expert on coelenterates and elasmobranchs. His research and publications, earned him the Daniel Giraud Elliot Medal from the National Academy of Sciences, in 1948. His book, "Fishes of the Gulf of Maine", is still used by students as an exhaustive reference. 26 species and 2 genera of organisms have been named after him, to honor his contributions to the field of marine biology. She was an American ichthyologist, famous for her research on poisonous fish and sharks. She is sometimes referred to as "The Shark Lady". She carried out her graduate studies regarding fish populations, at the Scripps Institute of Oceanography in La Jolla, at the American Museum of Natural History in New York, at the Marine Biological Laboratory in Woods Hole, Massachusetts, and at the Lerner Marine Laboratory in Bimini. Her research formed the subject of her first book, titled "Lady With a Spear". For her doctoral studies, she studied the reproduction of platys and swordtail fish. Later, she earned a Fullbright Scholarship, that allowed her to carry out ichthyological research at the Marine Biological Station in Hurghada, Egypt. She helped found the former Cape Haze Marine Laboratory, now known as the Mote Marine Laboratory in Sarasota, Florida. She was awarded the Medal of Excellence by the American Society of Oceanographers, in 1994. She has been honored by having several species of fish named after her. He is an oceanographer and marine biologist, well-known for his research on kelp forest ecology. His research focuses on gaining an understanding of the marine ecosystems.He is the only person to be awarded the George Mercer Award (1974) and the W.S. Cooper Award (2000) from the Ecological Society of America. he has also documented various environmental issues such as the detrimental effects on the environment of overfishing, the phenomenon of El Niño and its effect on coastal ecology, etc. He has published several articles in the premier scientific journal, "Science". His papers, are also, few of the most cited ecological references. He was an Austrian biologist and a pioneer in the field of diving and underwater filming. He is responsible for the redevelopment of the aqualung, to produce the rebreather, which allows recycling of the user's exhaled breath. He is also famed for his behavioral research of fish, which led to the proposal of his theory of energon. the theory/hypothesis claims that all biological life-forms on the planet possess behavior that have emerged from a common origin. During his lifetime he tried to fuse together the various concepts from the fields of behavioral science, marine biology, and management science. A few other famous marine biologists are Jean Bouillon, Malcolm Clarke, Ernst Haeckel, Gotthilf Hempel, Johan Hjort, Stephen Hillenburg, Martin Johnson, Otto Kinne, Nancy Knowlton, Syed Zahoor Qasim, Jack Rudloe, and Takasi Tokioka.