The three basic variables that make up the life history of an organism area. life expectancy, birth rate, and death rate.b. number of reproductive females in the population, age structure of the population, and life expectancyc. age when reproduction begins, how often reproduction occurs, and how many offspring are produced per reproductive episoded. how often reproduction occurs, life expectancy of females in the population, and number of offspring per reproductive episodee. the number of reproductive females in the population, how often reproduction occurs, and death rate