What does 'per capita births and deaths' mean? My book says, > If in a pond there are 20 lotus plants last year and through reproduction 8 new plants are added, taking the current population to 28, we calculate the birth rate as 8/20 = 0.4 offspring **per lotus per year**. .. > If 4 individuals in a laboratory population of 40 fruitflies died during a specified time interval, say a week, the death rate in the population during that period is 4/40 = 0.1 individuals **per fruitfly per week**. What does per lotus per year, and, per fruitfly per week imply?

_I will use an ever so slightly more specific scenario than what your book offers._

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At the beginning of 2017, there were **twenty** lotus plants in a pond. By the first day of 2018, **eight** of those twenty lotus plants reproduced. Using this information, we now want to describe the _birth rate_ of lotus plant population.

To do this, we need the number of plants that produced offspring, and, the population size at the beginning of 2017.

$$\frac{no. \ of \ parent \ lotus \ plants}{initial \ population \ size} = \frac{8}{20} = .4$$

This means that, when considering the twenty lotus plants that first existed at the beginning of 2017, each of those twenty plants contributed an _average_ of 4/10s of a lotus plant offspring for that year.

To generalize this, we say, "a birth rate of .4 offspring per lotus plant per year."

The same method and persective can also be applied to the fruitflies, however, they're considering _death rate_.