CBSE Class 12 Biology – Organisms and Populations

Chapter Overview

This chapter introduces the concepts of organisms and populations in ecology. It covers how organisms adapt to abiotic and biotic environmental factors, and how populations of a species behave in terms of size, growth, structure, and interactions with other populations.:contentReference[oaicite:0]{index=0}

Important Keywords

• Habitat: The physical environment where an organism lives.
• Niche: Role of an organism in its ecosystem.
• Eurythermal/Stenothermal: Tolerance to wide/narrow temperature ranges.:contentReference[oaicite:1]{index=1}
• Euryhaline/Stenohaline: Tolerance to broad/narrow salinity ranges.:contentReference[oaicite:2]{index=2}
• Population Density: Number of individuals per unit area.
• Birth/Natality & Death/Mortality Rate: Rates of births and deaths in a population.
• Sex Ratio & Age Pyramid: Female per 1000 males; graphical age structure.
• Intrinsic Rate (r): Rate of natural increase in populations.
• Carrying Capacity (K): Maximum population an environment can sustain.
• Ecological Interactions: Predation, competition, parasitism, mutualism, commensalism, amensalism.:contentReference[oaicite:3]{index=3}