Chapter 25 — Chapter 25 — Ecology

Ecology is the study of relationships of organisms with other organisms and the environment. Levels: 1. Species — 'a group of organisms that share similar physical and genetic characteristics and, most importantly, can interbreed to produce fertile offspring' (Indus River Dolphin). 2. Population — individuals of the same species in the same area at the same time (Markhors of Chitral Gol National Park). 3. Community — all populations of different species living and interacting in an area (Karachi mangrove: trees, mudskippers, crabs, shorebirds). 4. Ecosystem — biotic community plus abiotic components (sunlight, soil, water, air); energy flows one way, nutrients cycle (Thar Desert). 5. Biome — large region defined by climate, soil, altitude and adapted organisms (coniferous forest of Murree and Swat; desert of Thal and Thar; freshwater Indus system). 6. Biosphere — global sum of all biomes, from Arabian Sea trenches to Himalayan peaks and kilometres into the atmosphere; the 'global ecosystem'.