Birth and Death Rates in Populations — NEET Biology
✅ Asked in NEET 2023A population has certain attributes whereas, an individual organism does not. An individual may have births and deaths, but a population has birth rates and death rates. In a population these rates refer to per capita births and deaths. The rates, hence, expressed are change in numbers (increase or decrease) with respect to members of the population. Here is an example. If in a pond there were 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.
NTA tests whether you understand that birth and death rates are per capita measurements, not absolute numbers. The key concept: rates = new organisms/total population (or deaths/total population) over a specific time period. Students commonly mistake birth rate for total offspring or confuse it with population size. Remember: a population attribute always involves a ratio per individual. When you see a NEET question with population numbers and births/deaths, immediately set up the fraction: (births or deaths) ÷ (population size) = rate per individual per time unit. This distinction between population attributes and individual attributes is fundamental to population ecology and appears frequently in NEET.
This paragraph was tested 3 times in NEET.
There are 250 snails in a pond, and within a year their number increases to 2500 by reproduction. What should be their birth rate (in per snail per year)? (NEET 2023)
If 8 Drosophila in a population of 80 die in a week, the death rate is ____ individuals per Drosophila per week. (NEET 2022)
Which of the following is not an attribute of a population? (NEET 2020)
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