If Earth were significantly smaller or larger, its habitability would be compromised due to changes in gravity, atmosphere, and geological processes. A smaller Earth, with weaker gravity, would struggle to retain a dense atmosphere, leading to insufficient pressure for liquid water and poor protection from solar radiation, much like Mars. It might also lack the mass to sustain plate tectonics, limiting nutrient cycling and climate regulation. Conversely, a larger Earth with stronger gravity could trap a thick, oppressive atmosphere, like Venus, potentially causing extreme temperatures and pressure that crush life. Increased geological activity might lead to excessive volcanism, disrupting stable climates. Both scenarios would likely prevent the delicate balance of conditions, liquid water, breathable air, and stable ecosystems required for life as we know it. NCERT Class 8 Science Chapter 13 Question Answer Our Home: Earth, A Unique Life Sustaining Planet (Exercise) Keep the Curiosity Alive (Pages 226-227)