- Calculate percentage declines: Lions \((-53\%)\), Cheetahs \((-70\%)\), and Zebras \((-40\%)\).
- Observe that the decline of the prey species (Zebras) occurs alongside the decline of the predator species (Lions and Cheetahs).
- Recognize that in ecological systems, a significant reduction in food source (prey) typically restricts the capacity of an environment to sustain predator populations.
- Conclude that the second option is the best supported explanation: \(\boxed{\text{The dwindling zebra population has led to the decline of the predator lion and cheetah populations.}}\)
Explanation
- Analyze population trends
First, we analyze the data provided in the table to determine the trend for each animal population between 1990 and 2000:
- Lion population: Decreased from \(100,000\) to \(47,000\). The percentage change is \(\frac{47,000 - 100,000}{100,000} \times 100\% = -53\%\).
- Cheetah population: Decreased from \(25,000\) to \(7,500\). The percentage change is \(\frac{7,500 - 25,000}{25,000} \times 100\% = -70\%\).
- Zebra population: Decreased from \(750,000\) to \(450,000\). The percentage change is \(\frac{450,000 - 750,000}{750,000} \times 100\% = -40\%\).
All three species experienced significant population declines over the decade.
- Evaluate the explanations
Now we evaluate the provided explanations:
- Option 1: "Lion and cheetah populations compete for the food source of zebras, and lions outcompete cheetahs." While lions and cheetahs are both predators, the data shows that both populations declined significantly. While it's true the cheetah population decreased more sharply than the lion population, the data itself does not provide evidence for the mechanism of competition.
- Option 2: "The dwindling zebra population has led to the decline of the predator lion and cheetah populations." In ecological terms, prey availability is a critical factor for predator survival. Since the zebra population (the food source) dropped by \(40\%\), it is highly logical and scientifically supported to infer that this decline contributed to the decrease in the predator populations (lions and cheetahs) that depend on them.
- Option 3: "Overhunting of lion and cheetah populations has led to a decline in the food source population." The chart provides only population totals and no information regarding hunting practices or cause-and-effect relationships for the zebra population decrease.
- Option 4: "Lion and cheetah populations compete for the food source of zebras, and cheetahs outcompete lions." Similar to Option 1, the data does not provide evidence for this specific competitive outcome.
Comparing these, the decline in the primary food source (prey) is the most direct ecological explanation for the simultaneous decline of predator populations.
- Conclusion
Based on the analysis, the most logical ecological conclusion supported by the simultaneous decline in both the food source and the predators is that the reduced availability of prey hindered the predator populations. Therefore, the second statement is the best explanation.
Examples
This type of analysis is common in wildlife biology and conservation studies, where researchers examine population data to infer links between species. For instance, if a study finds that a decline in prey species like rabbits correlates with a drop in predator numbers like foxes, conservationists can prioritize habitat restoration for the prey to support the entire ecosystem's recovery. Understanding these patterns is essential for maintaining biodiversity and balanced ecosystems.