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Patterns in Life: Diversity and Classification 247 Meet a Scientist Threads of Curiosity Birbal Sahni Why do classification systems keep changing? Does that was an eminent indicate how science works? Yes, science evolves and scientist who progresses as we learn new things. For example, Aristotle’s studied fossil system worked for his time, but with new tools (like plants. He microscopes) and technological advancements (like staining founded the Birbal Sahni techniques), scientists discovered microorganisms. These Institute of Palaeosciences discoveries helped us understand the natural world better. (BSIP) in Lucknow, which Accordingly, the biological classification changed. The continues his work on ancient biological classification (and science) thus, is an ongoing plants and past environments process of reasoning and change. even to this day. His studies helped link present-day plants with their ancestors and 12.9 Fossils as Evidence showed that life on the Earth has a long, connected history. When we talk of diversity changing over time, what His work continues to inspire evidence do we have? Fossils are preserved remains of young scientists to explore plants and animals found in layers of rocks, sand and how fossils reveal the story of mud. Generally, older layers contain simpler organisms, our planet. while newer layers show more complex forms. From giant dinosaurs to early humans and ancient plants, some important fossils have been discovered in India. Fossils act Pause and Ponder as natural records that help us understand how life has  7.  Does the term ‘biodiversity’ changed over millions of years. relate only to the variety of organisms, or does it 12.10 Biodiversity Under Threat encompass other elements? Each species, large or small, plays an important role in  8.  If you find a new organism nature. Plants produce food and oxygen, animals pollinate in a pond, what features will you observe to classify it and flowers and disperse seeds, and microorganisms recycle why? nutrients. Human activities, such as pollution, deforestation, the overuse of resources and climate change are reducing  9.  Why do genetic studies biodiversity. When one species disappears, others that provide deep information about living beings? depend on it may also decline in number and eventually 10. How can changes also, disappear. in climate affect the biodiversity? Threads of Curiosity When scientists discover a new organism, they compare it with thealreadyknownspecies.Sometimes,thespeciesnamereflects their place of discovery, or honours a scientist. The Purple Frog (Nasikabatrachus sahyadrensis) from Kerala has a species name after the Sahyadri Hills (Fig. 12.20). The Purple Frog lives underground for most of the year and comes out only during the monsoon to breed. It belongs to an ancient family of frogs as understood from fossils. Its discovery in 2003 helped scientists understand ancient amphibian groups Fig. 12.20: A purple frog resting on and highlighted the need for biodiversity conservation in the wet soil Western Ghats.