Co-ordinated Sciences Biology B1: Characteristics of Living Organisms

Cambridge IGCSE Co-ordinated Sciences 0654 Biology B1 defines seven characteristics used to recognise living organisms: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. The mark-bearing skill is precise application, especially when an unfamiliar organism does not display every characteristic visibly at the same moment.

B1.1 Movement

Movement is an action by an organism or part of an organism that causes a change of position or place. The definition includes whole-body movement, such as an animal walking, and movement of part of an organism, such as a shoot bending toward light, a flower opening or a human arm lifting.

Movement need not be fast. A time-lapse sequence can reveal a plant response that is too slow to notice directly. Do not make locomotion, movement from one place to another, the definition of all biological movement.

Respiration

Respiration is the chemical reactions in cells that break down nutrient molecules and release energy for metabolism. It occurs in living cells. Breathing and gas exchange help supply and remove gases, but they are not themselves the definition of respiration.

Energy released by respiration supports active transport, movement, synthesis of large molecules, cell division and temperature regulation. Avoid saying cells "produce energy"; respiration transfers energy from nutrient molecules into forms that cells can use.

Sensitivity

Sensitivity is the ability to detect and respond to changes in the internal or external environment. A change that is detected is a stimulus. The response may involve movement, secretion, altered growth or another physiological change.