What all living organisms have in common
All living organisms share certain characteristics. They are made of cells, need food for energy, and respire to release that energy; even plants respire day and night, and fish take in oxygen dissolved in water through gills. Living things grow, increasing in size and changing as they develop, and they reproduce to make more of their own kind, some through eggs, some by giving birth and plants through seeds or other parts.
Living organisms respond to stimuli, which are changes in their surroundings. You blink when dust enters your eye, cockroaches run when a light is switched on, and sunflowers turn towards the Sun. They excrete wastes produced inside their bodies. Living things also have a life span and eventually die. Over long periods, organisms develop adaptations that suit their habitats, such as thick fur in yaks of cold mountains, long roots in desert plants and streamlined bodies in fish. Scientists use these shared and differing features to classify organisms.
Why it matters
Understanding the features of life helps us decide whether something like a seed or a virus is living, and how organisms survive in extreme habitats. Knowing that living things respond and adapt explains why crops are suited to particular regions and why animals migrate. This topic leads into cells, classification and life processes.
Key terms
- Stimulus
- A change in the surroundings that causes a living thing to respond.
- Respiration
- The process by which living things release energy from food.
- Reproduction
- The process by which living things produce young ones of their own kind.
- Life span
- The period of time for which an organism usually lives.