In the present paper the structures and dynamics of a food chain preypredator model are proposed and studied. The two stages and refuge in prey and two predators (top and mid) are considered. Different types of functional responses have been proposed. The conditions, which guarantee the existence of equilibrium points, have been investigated. Uniqueness and boundedness of the solution of the system are proven. The local and global dynamical behaviors are discussed and analyzed. Finally, numerical simulations are carried out not only to confirm the theoretical results obtained, but also to show the effects of the refuge and the variation of each parameter on our proposed system.
…………………………………………………………………………………………………….... Introduction:-The first pattern formation of predator-prey model was introduced in 1927 by the well-known Lotka[15] and Volterra[28] which starting from a simple and classical supposition, more complexity but factual predator-prey models have been constructed by mathematicians and ecologists. In 1992, Berryman [6] considered that the dynamic interaction between predators and preys has long taken and go on to be one of the most important and central subjects which play a great role in each of the mathematical ecology, natural, social, and technological sciences, especially in the research on biology and ecology [5,17,26,27].Many researchers working in these fields paying a great amount of attention to improve and generalize the pattern formation of prey-predator models to more involvement and realistic system, and merging this advantage into many applications that give the nature of existence and global asymptotic stability of predator-prey models a great interest.On the other hand, the dynamical behavior of prey-predator models has been investigated by a lot of articles and peppers which results a significant expansion in the structural of the prey -predator models to involve multispecies; different functional responses, several types of food chain, refuge, harvesting, stage-structure, several types of diseases…etc.Lately, Samantha[25] studied the existence and global asymptotic stability of a delay predator-prey model with disease in the prey, Paletal. [20][21][22][23][24]proposed prey-predator harvesting model under impreciseness by considering biological parameters as interval number, Naji and Mustafa [19] studied the dynamics of an eco-epidemiological model with nonlinear incidence rate. Majeed and Shawka studied prey-predator model involving SI and SIS infectious disease in prey population and the disease transmitted within the same species by contact and external