The Characteristics of Life

Living things aren't just "alive" - they possess specific characteristics that define life itself. All organisms must have organised cells, need food, require excretion, respond to their environment, and reproduce. Missing even one of these means it's not truly alive.

Metabolism is absolutely essential - it's the sum of all chemical reactions happening inside an organism. This includes anabolic reactions (building up, like photosynthesis) and catabolic reactions (breaking down, like respiration). Think of it as your body's constant chemical factory.

Two key processes drive all life: metabolism and continuity. Metabolism keeps you functioning day-to-day, whilst continuity ensures your species survives through reproduction. These work together - you can't have one without the other.

Key Point: One characteristic alone isn't enough to qualify as life - it's the interaction of all processes that creates living organisms.

Nutrition varies between organisms. Autotrophic organisms (like plants) make their own food, whilst heterotrophic organisms (like humans) must obtain food from other sources. The sun provides the basic energy for virtually all nutrition on Earth.

Excretion removes metabolic waste through organs like lungs, kidneys, skin, and stomata in plants. Response helps organisms react to environmental changes - animals respond rapidly, whilst plants respond much slower. Reproduction ensures species survival through sexual (two parents, variation) or asexual (one parent, identical offspring) methods.