Answer:
a) The population density of a fish in a lake can be measured by the number of fish caught per trap in the lake.
b) Total frogs present in the pond = 100 frogs Number of frog births per year = 20
The birth rate of the population= Number of frog births per year/ Total population of frogs \frac{20}{100}= 0\cdot 2 offsprings per year.
