| 1 | Bees (Apis spp.) | Pollination of crops and wild plants | Various (Some declining) | Global, incl. India | Pollinator collapse, Agri sustainability | 
| 2 | Phytoplankton | Base of marine food chains, O₂ production | - | Oceans | Ocean acidification, Climate Regulation | 
| 3 | Amazon Rainforest Trees | Carbon sink, ecosystem health | - | South America | Carbon sequestration | 
| 4 | Corals (GBR, etc.) | Biodiversity hotspots, reef building | Endangered | Indo-Pacific, GBR | Coral Bleaching, Biorock tech PYQs | 
| 5 | Mangroves (Rhizophora spp.) | Coastal protection, Blue carbon | Least Concern (some species VU) | India (Sundarbans), SE Asia | UPSC 2023: Blue Carbon ecosystems | 
| 6 | African Elephant | Seed dispersal, landscape engineer | Endangered | Africa | Flagship species | 
| 7 | Wolves (Gray) | Trophic regulation, ecosystem balance | Least Concern | North America, Eurasia | Rewilding concept | 
| 8 | Bats | Pollination, pest control | Various | India (Fruit bats, etc.) | Nipah Virus, Biodiversity regulation | 
| 9 | Anchovies, Sardines | Food chain base in marine ecosystems | - | Oceans | Marine trophic pyramid | 
| 10 | Mycorrhizal Fungi | Soil-plant nutrient exchange | - | Global | Sustainable agriculture | 
| 11 | Seagrasses (Posidonia) | Carbon sinks, prevent erosion | Varies | Coastal ecosystems | Blue Carbon, Dugong habitat | 
| 12 | Sphagnum Moss | Peatland formation, carbon storage | - | Boreal, temperate regions | COP discussions on peatlands | 
| 13 | Whales | Whale pump, ocean carbon sink | Endangered (Blue, etc.) | Oceans | Marine carbon cycle, Conservation | 
| 14 | Boreal Forest Trees | Carbon sequestration | - | Canada, Russia | Global carbon sink | 
| 15 | Kelp Forests | Marine biodiversity & carbon storage | - | Temperate coasts | Marine ecosystems | 
| 16 | Soil Microbes (Rhizobium) | Nitrogen fixation | - | Agricultural soils | PYQs on nitrogen-fixing species | 
| 17 | Oak Trees | Habitat support, carbon sink | - | N. Hemisphere | Reforestation | 
| 18 | Krill | Feed whales, penguins, base of food chain | Not Threatened | Antarctic oceans | Climate link, Ocean cycles | 
| 19 | Saiga Antelope | Steppe ecosystem balance | Critically Endangered | Central Asia | Poaching, Conservation status | 
| 20 | Lichens | Bioindicators of air pollution | - | Global | Ecological indicators | 
| 21 | Rice (Oryza sativa) | Staple food, water-intensive crop | Cultivated | India, Asia | Food security, Water-agri linkage | 
| 22 | Wheat | Food security crop | Cultivated | Global | MSP, Climate-resilient crops | 
| 23 | Maize | Food & biofuel crop | Cultivated | Americas, India | Bioenergy | 
| 24 | Soybean | Protein, oil, soil-fixing | Cultivated | Americas, Asia | Agri-economy | 
| 25 | Potato | Staple root crop | Cultivated | Andean origin, Global | Climate adaptation | 
| 26 | Cassava | Drought-resistant crop | Cultivated | Africa, Asia | Resilience in agriculture | 
| 27 | Chickens | Major poultry meat source | Domesticated | Global | Nutrition, economy | 
| 28 | Salmon | Nutrient transport, aquaculture | Vulnerable (Atlantic species) | N. Atlantic, Pacific | Fisheries management | 
| 29 | Cattle | Livestock economy | Domesticated | Global | Methane emissions, land use | 
| 30 | Bananas | Fruit crop, export economy | Cultivated | Tropical regions | Agri-diversity | 
| 31 | Snow Leopard | Apex predator, alpine indicator | Vulnerable | Himalayas | UPSC: Himalayan ecology | 
| 32 | Tigers | Flagship species, forest health | Endangered | India, SE Asia | NTCA, Project Tiger | 
| 33 | Polar Bears | Arctic species, climate indicator | Vulnerable | Arctic | Global Warming impact | 
| 34 | Pangolins | Insect control, heavily trafficked | Critically Endangered | Asia, Africa | Illegal wildlife trade | 
| 35 | Vultures (Gyps spp.) | Scavengers, prevent disease | Critically Endangered (India) | India, SA | Diclofenac ban, UPSC PYQ topic | 
| 36 | Orangutans | Seed dispersal, forest ecosystem | Critically Endangered | Borneo, Sumatra | Deforestation issues | 
| 37 | Gorillas | Forest ecosystem integrity | Endangered | Africa | Primatology, eco-balance | 
| 38 | Sea Turtles | Marine indicator species | Varies (e.g., Olive Ridley – VU) | Coasts, beaches | UPSC PYQ on mass nesting | 
| 39 | Rhinoceroses | Grazing balance, flagship species | Endangered (Black, Indian) | India, Africa | Kaziranga, Rhino poaching | 
| 40 | Monarch Butterfly | Pollinator, migration marvel | Endangered | Americas | Migration corridors | 
| 41 | Tardigrades | Survival in extreme conditions | Not Evaluated | Microscopic, global | Space biology, Research models | 
| 42 | Horseshoe Crabs | Biomedical applications (LAL test) | Vulnerable | US, Asia | COVID-19 vaccine, Biomedical use | 
| 43 | Venomous Snakes (Naja spp.) | Antivenom source | Varies | India | Snakebite mortality | 
| 44 | Ginkgo biloba | Living fossil, medicinal use | Endangered | China | Ethnobotany, Pharma | 
| 45 | Penicillium | Antibiotic revolution | - | Global | Penicillin discovery | 
| 46 | Cephalopods (Octopus, Squid) | Complex behavior, neurobiology research | Not Threatened | Marine | Neuroscience model | 
| 47 | Streptococcus pyogenes (CRISPR) | Gene editing tool discovery | - | Microbial labs | CRISPR technology | 
| 48 | Turmeric (Curcuma longa) | Medicinal properties, Ayurveda link | Cultivated | India | Bio-prospecting, AYUSH relevance | 
| 49 | Algae (Spirulina, Chlorella) | Future food, carbon absorber | - | Aquatic | Superfood, NASA research | 
| 50 | Tasmanian Devil | Facial tumor disease research | Endangered | Australia | Cancer research model |