In 1959, Eugene Wigner presented a talk on The Unreasonable Effectiveness of Mathematics in the Natural Sciences. Many papers on the unreasonable effectiveness of mathematics in this field, that field, and some other field quickly followed suit. As an opposing point of view, the unreasonably effective (800+ papers, 30+ books) mathematician I.M.Gelfand noted that (emphasis mine)
Eugene Wigner wrote a famous essay on the unreasonable effectiveness of mathematics in natural sciences. He meant physics, of course. There is only one thing which is more unreasonable than the unreasonable effectiveness of mathematics in physics, and this is the unreasonable ineffectiveness of mathematics in biology.
I.M. Gelfand said this after developing an interest in biology due to the premature death of his son. He organized a weekly seminar that attracted the best minds in Russian biology and mathematics. Gelfand's interest in biology resulted in pioneering work in the field of biomathematics. Not only is mathematics applicable to some aspects of biology, biology has motivated many new developments in mathematics.
Just a few of the areas where biology has inspired new mathematics:
Mathematics inspired by population modeling
Modeling population dynamics has been a fruitful application of mathematics starting with Euler, who studied age distributions in stable populations (Euler 1760). What about unstable populations? One of the seminal papers (if not the seminal paper) in the development of chaos theory was written by Robert May in 1976. May was educated as a physicist (where mathematics is unreasonably effective), but then switched to biology (where mathematics is supposedly unreasonably ineffective). His paper on population dynamics (May 1976) discusses the logistic map, $x_{n+1} = \lambda x_n(1-x_n)$, which he used to model population dynamics. This paper marked the beginning of chaos theory.
Mathematical techniques inspired by evolution and animal behavior
The contributions of biology to optimization theory are immense. Evolution has motivated a number of techniques used in mathematics and artificial intelligence, including evolutionary programming (Fogel 1966), evolutionary strategy (Rechenberg 1973), genetic algorithms (Holland 1975).
Emulating animal behavior has provided a number of other optimization techniques. These include the critter of the month optimization techniques, starting with ant colony optimization (Dorigo 1996). Ant colony optimization has been used to attack a large number of problems from very diverse fields. Now there are bees algorithms, bacterial colony optimization algorithms, foraging algorithms, all based on the behaviors of simple creatures. I won't give references for all of these; there are now entire journals dedicated to this subject (e.g., the IEEE Transactions on Evolutionary Computation). Collectively, these fall into the category of swarm intelligence. One last technique that I will give a reference on is particle swarm optimization (Kennedy 1995, Eberhart 1996).
Mathematics inspired by DNA sequencing
The above areas are new areas of applied mathematics. The problem of how to sequence DNA produced not only new applied mathematics (e.g., the image below from Letunic 2007) but new theoretical mathematics as well.

All of these developments led Joel Cohen (Cohen 2004) to conjecture that mathematics is biology's next microscope, only better; biology is mathematics' next physics, only better.
References
Joel E. Cohen (2004), "Mathematics is biology's next microscope, only better; biology is mathematics' next physics, only better." PLoS Biology 2.12:e439.
Marco Dorigo, et al. (1996), "Ant system: optimization by a colony of cooperating agents," IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics 26.1:29-41.
Leonard Euler (1760), "Recherches générales sur la mortalité et la multiplication," Mémoires de l’Académie Royal des Sciences et Belles Lettres 16:144–164.
Russell Eberhart and James Kennedy, "A new optimizer using particle swarm theory," Proceedings of the Sixth International Symposium on Micro Machine and Human Science.
Lawrence J. Fogel, et al. (1966), "Artificial intelligence through simulated evolution," Wiley.
John H. Holland, (1975), "Adaptation in Natural and Artificial Systems," University of Michigan Press (second edition, MIT Press, 1992).
James Kennedy and Russel Eberhart (1995), "Particle swarm optimization," Proc. IEEE International Conf. on Neural Networks.
Ivica Letunic and Peer Bork (2007), "Interactive Tree Of Life (iTOL): an online tool for phylogenetic tree display and annotation," Bioinformatics 23.1:127-128.
Robert M. May (1976), "Simple mathematical models with very complicated dynamics," Nature 261.5560:459-467.
Ingo Rechenberg (1973), "Evolutionsstrategie Optimierung technischer Systeme nach Prinzipien der biologischen Evolution," (PhD thesis), Friedrich Frommann Verlag, Struttgart-Bad Cannstatt.
Eugene P. Wigner (1960), "The unreasonable effectiveness of mathematics in the natural sciences," Communications on Pure and Applied Mathematics 13.1:1-14.
Richard courant lecture in mathematical sciences delivered at New York University, May 11, 1959.