There are several online resources and databases that provide access to a wide range of research papers for the Zoology optional subject. These resources are valuable for students preparing for the UPSC examination or conducting research in the field of zoology. Here are some recommended online platforms:

1. **EduRev**:
- EduRev offers a comprehensive collection of study materials, including research papers, for various subjects, including Zoology.
- It provides access to a wide range of research papers from reputed journals and scholarly sources.
- EduRev also allows users to upload and share their own research papers, fostering a community of knowledge sharing.

2. **National Digital Library of India (NDLI)**:
- NDLI is a government-funded online platform that provides access to a diverse range of educational resources, including research papers.
- It offers access to research papers from reputed Indian institutions and universities.
- NDLI allows users to search for research papers by subject, author, institution, and keywords, making it easier to find relevant materials.

3. **Directory of Open Access Journals (DOAJ)**:
- DOAJ is a comprehensive directory that indexes and provides open access to thousands of research papers from various disciplines, including zoology.
- It includes research papers from both established and emerging journals, ensuring a wide range of perspectives.
- DOAJ allows users to search for research papers using keywords, subject categories, and other filters.

4. **Google Scholar**:
- Google Scholar is a widely used search engine that indexes scholarly literature, including research papers in zoology.
- It provides access to research papers from various sources, including academic publishers, universities, and research institutions.
- Google Scholar's advanced search options allow users to filter results by publication, author, and year, making it easier to find relevant research papers.

By utilizing these online resources and databases, students and researchers can access a diverse range of research papers in the field of zoology. These platforms offer a convenient way to stay updated with the latest research, explore different perspectives, and enhance their understanding of the subject.