Organisms and Populations – Complete NCERT Notes (Class 12)
Introduction Ecology is the study of interactions between organisms and their environment. This chapter focuses on two levels: Organism level → How individuals respond to environment Population level → How groups of organisms behave and grow 🌱 1. Organism and Its Environment Every organism interacts with two types of environment: 🔹 (A) Abiotic Factors Temperature Water Light Soil 🔹 (B) Biotic Factors Other organisms (predators, competitors, parasites, etc.) 🌡️ Temperature Effects Most organisms tolerate a specific temperature range. Stenothermal → Narrow range (e.g., coral reefs) Eurythermal → Wide range (e.g., humans) 👉 Temperature affects: Enzyme activity Metabolism Distribution of species 💧 Water Importance Life originated in water. Organisms are adapted to: Aquatic habitats Terrestrial habitats 👉 Example: Fish → gills Plants in desert → thick cuticle, reduced leaves ☀️ Light Essential for photosynthesis Affects: Flowering (photoperiodism) Animal behavior 👉 Examp...