Types of System (SL IB Environmental Systems & Societies (ESS))

• There are three main types of systems. These are:
  • Open systems
  • Closed systems
  • Isolated systems

• The category that a system falls into depends on how energy and matter flow between the system and the surrounding environment

Open Systems

• Both energy and matter are exchanged between the system and its surroundings
• Open systems are usually organic (living) systems that interact with their surroundings (the environment) by taking in energy and new matter (often in the form of biomass), and by also expelling energy and matter (e.g. through waste products or by organisms leaving a system)
• An example of an open system would be a particular ecosystem or habitat
• Your body is also an example of an open system - energy and matter are exchanged between you and your environment in the form of food, water, movement and waste

Closed Systems

• Energy, but not matter, is exchanged between the system and its surroundings
• Closed systems are usually inorganic (non-living), although this is not always the case
  • The International Space Station (ISS) could perhaps be seen as a closed system
  • It is a self-contained environment that must maintain a balance of resources, including air, water, and food, as well as waste management, energy production, and temperature control
  • The ISS cannot exchange matter with its surroundings

• The Earth (and the atmosphere surrounding it) could be viewed as a closed system
  • The main input of energy occurs via solar radiation
  • The main output of energy occurs via heat (re-radiation of infrared waves from the Earth’s surface)
  • Matter is recycled completely within the system
  • Although, technically, very small amounts of matter enter and leave the system (in the form of meteorites or spaceships and satellites), these are considered negligible
  • Artificial and experimental ecological closed systems can also exist - for example, sealed terrariums, containing just the right balance of water and living organisms (such as mosses, ferns, bacteria, fungi or invertebrates) can sometimes survive for many years as totally closed systems, if light and heat energy is allowed to be exchanged across the glass boundary

Isolated Systems

• Neither energy nor matter is exchanged between the system and its surroundings
• Isolated systems do not exist naturally - they are more of a theoretical concept (although the entire Universe could be considered to be an isolated system)

A system can be categorised based on how energy and matter flow between the system and its surrounding environment