Key themes of understanding Ethics, Integrity, and Aptitude for UPSC include the importance of ethical governance, the role of public servants in promoting integrity, and the need for a robust moral framework. Ethics involves recognizing and addressing dilemmas faced in administrative functions. Integrity signifies adherence to ethical principles while managing public resources. Candidates must also focus on aptitude in making sound decisions that benefit society. Familiarity with case studies and ethical scenarios helps candidates apply theoretical knowledge to practical situations, crucial for essay writing and interviews in the examination process.