Some of the important change in trends by UPSC in CS (prelims) 2021 : 1. Science and Technology - Almost all questions on basic physics, chemistry and biology (more virus bacteria type questions) (with special emphasis on biotechnology). No questions from other technology areas 2. International Current Affairs - (The examiner has utilised syllabus term "Current events of national and international importance", so expect more questions on sports, awards, events etc.) - First time since the pattern is introduced in 2011, Sports related questions asked (International level) - No questions on routine government or institutions related questions 3. Geography - Two river based questions, One lake based, Typical forest vegetation, soil type based questions 4. Environment - Typical Plant Species related questions with use, Biodiversity questions have more linked to Ecology (primary producers, detrivores, symbiotic relationship etc.), Also more questions from Ecology part, UN Enviro...