In this paper, we modify the general-purpose heuristic method called extremal optimization. We compare our results with the results of Boettcher and Percus . Then, some multiobjective optimization problems are solved by using methods motivated by the immune system.
 M. R. Chen and Y. Z. Lu, “A Novel Elitist Multiobjective Optimization Algorithm: Multiobjective Extremal Optimization,” European Journal of Operational Research, Vol. 188, No. 3, 2008, pp. 637-651. http://dx.doi.org/10.1016/j.ejor.2007.05.008
 N. F. Britton, “Essential Mathematical Biology,” Springer, New York, 2003.
 R. Blanquero, E. Carrizosa and E. Conde, “Inferring Efficient Weights from Pairwise Comparison Matrices,” Mathematical Methods of Operations Research, Vol. 64, No. 2, 2006, pp. 271-284. http://dx.doi.org/10.1007/s00186-006-0077-1
 I. Das, “Applicability of Existing Continuous Methods in Determining Pareto Set for a Nonlinear Mixed Integer Multicriteria Optimization Problem,” 8th AIAA Symposium on Multidiscipline, Analysis and Optimization, Longbeach CA, 2000.
 J. R. Rao and P. Y. Papalambros, “A Non-Linear Programming Continuation Strategy for One Parameter Design Optimization Problems,” In: B. Ravani, Ed., Advances in Design Automation Montreal, Vol. 19, No. 2, Que, Canada, 17-21 September 1989, ASME, New York, pp. 77-89.
 J. Rakowska, R. T. Haftka and L. T. Watson, “Tracing the Efficient Curve for Multi-Objective Control-Structure Optimization,” Computing Systems in Engineering, Vol. 2, No. 6, 1991, pp. 461-471. http://dx.doi.org/10.1016/0956-0521(91)90049-B
 I. Das and J. E. Dennis, “Normal-Boundary Intersection: A New Method for Generating the Pareto Surface in Nonlinear Multicriteria Optimization Problems,” SIAM Journal on Optimization, Vol. 8, No. 3, 1998, pp. 631-657.
 E. Ahmed and M. El-Alem, “Immune Motivated Optimization,” International Journal of Theoretical Physics, Vol. 41, No. 5, 2002, pp. 985-990. http://dx.doi.org/10.1023/A:1015705512186
 P. Bak and K. Sneppen, “Punctuated Equilibrium and Criticality in a Simple Model of Evolution,” Physical Review Letters, Vol. 71, No. 24, 1993, pp. 40834086.
 D. Head, “Extremal Driving as a Mechanism for Generating Long-Term Memory,” Journal of Physics A: Mathematical and General, Vol. 33, No. 42, 2000, p. L387.
 E. Ahmed and M. F. Elettreby, “On Combinatorial Optimization Motivated by Biology,” Applied Mathematics and Computation, Vol. 172, No. 1, 2006, p. 4048.