  A deterministic model of an age-structured population with genetics analogous
to the discrete time Penna model of genetic evolution is constructed on the
basis of the Lotka-Volterra scheme. It is shown that if, as in the Penna model,
genetic information is represented by the fraction of defective genes in the
population, the population numbers for each specific individual's age are
represented by exactly the same functions of age in both models. This gives us
a new possibility to consider multi-species evolution without using detailed
microscopic Penna model.
  We discuss a particular case of the predator-prey system representing an
ecosystem consisting of a limited amount of energy resources consumed by the
age-structured species living in this ecosystem. Then, the increase in number
of the individuals in the population under consideration depends on the
available energy resources, the shape of the distribution function of defective
genes in the population and the fertility age. We show that these parameters
determine the trend toward equilibrium of the whole ecosystem.
