There are several case studies and examples that you can include in your answers for Paper II of the UPSC Zoology Optional Subject. These examples and case studies help to illustrate concepts and provide evidence for your arguments. Here are a few examples that you can consider:

1. Case Study: Peppered Moths
- The case of the peppered moths is a classic example of natural selection in action.
- Prior to the industrial revolution, peppered moths in England were predominantly light-colored, which helped them camouflage against light-colored trees.
- However, with the onset of pollution and industrialization, the lichen-covered trees became blackened, providing a better camouflage for dark-colored moths.
- As a result, the dark-colored moths had a higher survival rate due to their increased camouflage, leading to an increase in the population of dark-colored moths.
- This example highlights the role of natural selection in determining the frequency of different traits in a population.

2. Case Study: Finches of the Galapagos Islands
- The finches of the Galapagos Islands are another famous example of adaptive radiation.
- Charles Darwin observed that different species of finches on different islands had evolved different beak shapes and sizes, allowing them to exploit different food sources.
- This variation in beak morphology was driven by natural selection, as different beak shapes were better suited to different types of food.
- This case study provides evidence for the role of natural selection in driving speciation and the adaptive divergence of species.

3. Case Study: Cane Toads in Australia
- The introduction of cane toads to Australia is a notable example of an invasive species and its impact on native ecosystems.
- Cane toads were introduced in the 1930s to control pests in sugarcane fields, but they rapidly spread across the continent.
- Their toxic skin secretions make them poisonous to many native predators, leading to declines in native species populations.
- This case study highlights the ecological consequences of introducing non-native species and the importance of understanding the impacts of such introductions.

4. Case Study: Human Evolution
- The study of human evolution provides numerous case studies and examples of our evolutionary history.
- For instance, the fossil record reveals the transition from early hominids to modern humans, such as the Australopithecus afarensis ("Lucy") and Homo neanderthalensis.
- Genetic studies have also provided insights into human evolution, such as the discovery of interbreeding between early humans and Neanderthals.
- These case studies demonstrate the importance of studying our own evolutionary history to understand the processes that have shaped us as a species.

Including such case studies and examples in your answers will not only help illustrate your points effectively but also demonstrate your understanding of the subject matter. Remember to use these examples judiciously, focusing on their relevance to the specific question being asked.