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Chapter 9: Problem 10

Why are small populations more susceptible to extinction from demographic stochasticity than are larger populations?

Short Answer

Expert verified
Answer: Smaller populations are more susceptible to extinction due to demographic stochasticity because random fluctuations in their population size have a greater proportional impact than in larger populations, making them more vulnerable to significant declines. Additionally, smaller populations are more likely to experience reduced genetic diversity due to random genetic drift, which can compromise their ability to adapt to changing environmental conditions and further increase their risk of extinction. On the contrary, larger populations can better buffer against such random fluctuations and are less likely to go extinct due to demographic stochasticity.

Step by step solution

01

Understanding Demographic Stochasticity

Demographic stochasticity refers to the random fluctuations in population size due to birth and death rates as well as immigration and emigration. These fluctuations can cause a population to grow or shrink over time, and in some cases even lead to extinction. The effects of demographic stochasticity are more pronounced in smaller populations.
02

Effects of Demographic Stochasticity on Small Populations

In small populations, demographic stochasticity can have a significant impact because even a small change in the number of individuals can represent a large proportion of the entire population. For example, if a population of 10 individuals loses two members, it represents a 20% decline. These fluctuations can result in a higher likelihood of extinction. Furthermore, a small population is more likely to lose genetic diversity due to random genetic drift, which can reduce the population's ability to adapt to changing environmental conditions and increase the risk of extinction.
03

Effects of Demographic Stochasticity on Large Populations

In larger populations, demographic stochasticity is usually less pronounced because a small change in the number of individuals has a smaller proportional impact on the overall population size. For example, if a population of 1,000 individuals loses two members, it represents only a 0.2% decline. This means that larger populations are better able to buffer against random fluctuations in birth and death rates and are less likely to go extinct due to demographic stochasticity.
04

Conclusion

In summary, small populations are more susceptible to extinction from demographic stochasticity because random fluctuations in their population size have a greater proportional impact than in larger populations. Additionally, smaller populations are more likely to experience reduced genetic diversity due to random genetic drift, which can further increase their risk of extinction.

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Most popular questions from this chapter

What is a life table, and what information (data) is required to construct one?

Identify two factors that could possibly cause a population to decline to extinction. How might these factors be influenced by population size?

What is the difference between a discrete \((\Delta N / \Delta t)\) and continuous \((\mathrm{d} N / \mathrm{d} t)\) model of population growth? What is the difference between geometric and exponential growth?

To use a life table to project population growth, what assumption must be made regarding the age-specific rates of survival \(\left(s_{x}\right) ?\)

What environmental factors might result in random yearly variations in the rates of survival and birth within a population?
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