Morley Allan Jull was born in Burford, Ontario, Canada, on August 26, 1885, to John Henry and Ann Jane (Winskel) Morley. He married Marion Louise Monkley on July 5, 1930, and they had one son, Morley Allan. Jull attended the University of Toronto where he received his Bachelor of Science degree in 1908. He received a Master's of Science from McGill University in 1914 and a Ph.D. from the University of Wisconsin in 1921.
Prior to becoming a naturalized citizen of the United States in 1935, Jull worked at the West Virginia Experiment Station in Morgantown as a poultry assistant from 1908 until 1909. After that, he became the Poultry Commissioner in the British Columbia Department of Agriculture in Victoria, a position he held from 1909 until 1911, when he accepted a position as Head of the Poultry Department in the McGill University MacDonald College in Montreal, Canada. During the same period he also taught poultry courses at the University of Vermont and did poultry extension work in the state during two summers. He remained at McGill University from 1912 until 1923, when he moved to the United States to become the Senior Poultry Husbandman of Production Research for the United States Department of Agriculture. During his time as senior husbandman, he led work on quality improvement of poultry, egg, and meat production and assisted in the breeding of the world famous Beltsville White turkey, a smaller, "family-size" turkey. He left that position in 1936 to head the Department of Poultry Science at the University of Maryland, where he remained until retirement in 1956. In his position at Maryland, he led efforts to expand the departmental facilities, served as chairman of the University of Maryland Poultry Committee from 1936 until 1956, and conducted research on raising a fast-feathering bird, which would be easier to fatten and therefore less costly. In 1952, he won the National Poultry Science Teacher Award from the Poultry Science Association. In honor of Jull, the University of Maryland renamed the Poultry Building Jull Hall in 1954.
During retirement, he participated in the U. S. Overseas Mission as a Poultry Specialist and Consultant with the U.S. State Department's International Cooperation Administration in Egypt, Italy, Greece, and Lebanon. Prior to his work with the State Department, he participated in other international events. He represented the U. S. government at the Fourth World's Poultry Congress in Ottawa, Canada, in 1927 and the Fifth Congress in London, England, in 1930, and served on councils for the Ninth Congress in Paris, France, in 1951, and the Eighth Congress in Copenhagen, Denmark, in 1948. Domestically, he was the president of the Poultry Science Association, served on the advanced committee of the American Genetic Association, and was a member of both the Washington Academy of Science and the American Poultry and Hatchery Federation. He was an American Association for the Advancement of Science Fellow and a member of three honorary and fraternal societies: Phi Kappa Phi, Kappa Phi, and Sigma Xi. In addition to writing numerous articles, he authored four books: Poultry Breeding, Poultry Husbandry, Successful Poultry Management, and Raising Turkeys, Ducks, Geese, and Game Birds.
Morley Jull died on October 25, 1959, at Prince George's General Hospital and is buried in Fort Lincoln Cemetery, Bladensburg, Maryland.