Alexander John Nicholson (25 March 1895 – 28 October 1969) was an

Irish Australian Irish Australians ( ga, Gael-Astrálaigh) are an ethnic group of Australians, Australian citizens of Irish descent, which include immigrants from and descendants whose ancestry originates from the Ireland, island of Ireland. Irish Australians ...

entomologist Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...

who specialized in insect

population dynamics Population dynamics is the type of mathematics used to model and study the size and age composition of populations as dynamical systems. History Population dynamics has traditionally been the dominant branch of mathematical biology, which has ...

. He was Chief of the CSIR /

CSIRO The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government The Australian Government, also known as the Commonwealth Government, is the national government of Australia, a federal parliamentar ...

Division of Economic Entomology for 24 years and is credited with initiating the professional era in Australian entomology.Mackerras, I.M. 1970
Alexander John Nicholson 1895-1969
. ''Records of the Australian Academy of Science'' 2:66 - 81 He was a Foundation

Fellow of the Australian Academy of Science The Fellowship of the Australian Academy of Science is made up of about 500 Australian scientists. Scientists judged by their peers to have made an exceptional contribution to knowledge in their field may be elected to Fellowship of the Academy. ...

.D. F. Waterhouse,
Nicholson, Alexander John (1895–1969)
, ''Australian Dictionary of Biography'', National Centre of Biography, Australian National University. First published in Australian Dictionary of Biography, Volume 15, (MUP), 2000. Nicholson was born in Ireland. He studied at the

University of Birmingham , mottoeng = Through efforts to heights , established = 1825 – Birmingham School of Medicine and Surgery1836 – Birmingham Royal School of Medicine and Surgery1843 – Queen's College1875 – Mason Science College1898 – Mason Univers ...

and served in the British military in World War I. He came to Australia in 1921. Experiments He performed his experiments of population dynamics on the Sheep blowfly. The interesting thing about sheep blowfly females is that they must receive a meal before laying eggs near the tail or by exposed wounds. Next, the maggots hatch from the eggs
feeding on flesh
of the sheep which makes them grow bigger. The sheep possibly die when the maggots penetrate the skin and feed on their internal organs. Due to the need of a meal for blowfly females to lay eggs, density dependence effects on their populations was studied by Nicholson. Findings and Conclusions In Nicholson's first experiment he gave an abundance of food to the adult blowflies so females could lay egg

therefore leading to a massive amount of eggs laid. Then he made sure maggots only had 50 grams of food per day. So after the eggs hatched almost all of the maggots died prior to adulthood. This led to a decline in adult populations and then the population reached such low numbers that the eggs actually produced had ample food to reach adulthood. Hence, the adult population rose again, creating a constant cycl

In the second experiment he limited the amount of food for both maggots and adults. This resulted in a population increase until it hit the carrying capacit

This experiment exhibited the effects of density dependence on population. He is notable for the

Nicholson–Bailey model The Nicholson–Bailey model was developed in the 1930s to describe the population dynamics of a coupled host-parasitoid system. It is named after Alexander John Nicholson and Victor Albert Bailey. Host-parasite and prey-predator systems can also ...

References

1895 births 1969 deaths British emigrants to Australia Australian entomologists Fellows of the Australian Academy of Science Commanders of the Order of the British Empire Australian people of Irish descent Fellows of the Royal Entomological Society 20th-century Australian zoologists {{entomologist-stub