The graphs shown represent the relationship between population size ($N$) and population growth rate ($\frac{dN}{dt}$). Which one of the following growth curves represents a density-dependent population that experiences a strong Allee effect?
The question requires identifying the graph that represents a density-dependent population experiencing a strong Allee effect. Let's break down the concepts:
- Density-Dependent Population: This refers to populations where the growth rate changes with population size, often slowing down as resources become limited.
- Allee Effect: The Allee effect describes a situation where the population growth rate is lower at small population sizes. The "strong" Allee effect means there's a critical population size below which the population growth rate becomes negative, leading to a decline if not corrected.
Now, let's analyze the graphs:
- Graph P: Initially, the growth rate is negative at small population sizes, indicating a decline, which is characteristic of the strong Allee effect. As the population increases beyond a critical size, the growth rate becomes positive, allowing population growth.
- Graph Q: The growth rate is always positive but decreases as population size increases, showing density dependence, but it doesn't indicate an Allee effect.
- Graph R: Displays density dependence, showing an increase and then a decrease in growth rate with population size, but no negative growth rate at small population sizes.
- Graph S: A linear increase suggests density-independent growth, which does not illustrate the Allee effect.
Based on this analysis, Graph P correctly represents a density-dependent population with a strong Allee effect.
Conclusion: The correct answer is Option P.
Important Questions from Population growth curves
The population of whirligig beetles in a lake grows or declines exponentially i.e.
$N(t) = N(0)e^{rt}$
where $N(t)$ is the population size at time $t$, $N(0)$ is the initial population size and $r$ is the per capita rate of population change, occurring only due to birth and death.
A researcher tracks population sizes for a year and finds the following:Time interval Number of beetles at start Number of beetles at end January - March 1000 150 April – June 150 3013 July – September 3013 100 October - December 100 2009 Assuming that the individual birth rates remain constant throughout the year and only death rates are affected, which one or more of the following statements is/are true?
(In your calculations, round off the birth and date rates to two decimal places)- The population size at which net recruitment is the highest is also when the greatest amount can be harvested, while ensuring the long-term survival of the population. The amount harvested at this population size is known as
Overfishing reduced food availability for sea lions in California, causing a decline in their population size. In 1972, under the US Endangered Species Act, fishing was banned from sea lion foraging areas. Subsequently, the population of sea lions increased in a logistic form as shown in the figure.
The per capita growth rate is highest in the interval __________ and the population growth rate is highest in the interval __________
Consider the logistic population growth model, given by $$ \frac{dn}{dt} = rn \left(1 - \frac{n}{k}\right) $$ where $r$ is the intrinsic growth rate, $n$ is the population size and $k$ is the carrying capacity. Which one or more of the following is/are assumption(s) of the model?
A population of unicorns is growing over time, but its rate of growth is declining. Which of the following graphs best represents this pattern of growth?
