Final answer:
Population growth would be slower in a hypothetical study starting with 4 females and 21 males due to the lower number of breeding females, option a. As females are responsible for bearing offspring, their smaller number limits population growth more significantly than the number of males.
Step-by-step explanation:
If a population study began with 4 females and 21 males, population growth would likely be slower due to a smaller initial female population, which would result in a lower birth rate. In biology, including population dynamics, it is often the number of breeding females that limits population growth because they are the ones that give birth to the next generation.
The imbalance with a larger number of males does not proportionally increase the population's growth rate as males can't bear offspring. The birth rate significantly affects the population size; if the birth rate is smaller than the death rate, the population decreases. Conversely, if the birth rate exceeds the death rate, the population increases. Other factors such as life expectancy, immigration, and emigration also influence population size but typically to a lesser extent than birth and death rates.
Demography analyzes trends like birth rates, death rates, and life expectancies to assess population growth or decline. A female-biased sex ratio can increase birth rates because it means more females are available to reproduce. However, with a smaller number of females, such as in the hypothetical scenario of 4 females, the potential for growth is limited regardless of the number of males present. Furthermore, a large disparity in the sex ratio can lead to unstable population dynamics, reflecting the importance of a balanced ratio for sustained population growth.
Therefore, the correct answer to how the population growth would vary if the study began with 4 females and 21 males is option (a): The population growth would have been slower due to a smaller initial female population, resulting in a lower birth rate.