Types of Systems (HL IB ESS OLD COURSE - IGNORE)

Open & Closed Systems

• 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)

• 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, spaceships or satellites), these are considered negligible

• Global geochemical cycles are approximated to closed systems due to the continuous recycling and redistribution of elements and compounds within the Earth's various natural "reservoirs", such as the atmosphere, hydrosphere, lithosphere, and biosphere

  • The overall quantities of elements remain relatively constant over geological timescales

  • For example, carbon moves between the atmosphere, oceans and terrestrial ecosystems through processes like photosynthesis, respiration and oceanic absorption, maintaining a dynamic equilibrium

  • The Earth's geochemical cycles operate on vast scales and with long-term stability, resembling closed systems on a global scale

• 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 are allowed to be exchanged across the glass boundary

• Biosphere 2 was an attempt to create a larger-scale artificially closed system

  • It was a self-contained experimental research facility designed to simulate Earth's ecosystems in a closed environment

  • Constructed in the late 1980s, it consisted of several interconnected ecosystems, including a rainforest, ocean, desert, savannah and agricultural area, along with living quarters for human inhabitants

  • The goal was to study the interactions between different ecosystems and humans in a controlled environment

  • To create a closed system, Biosphere 2 was sealed off from the outside world, with limited inputs of matter (energy could enter the system in the form of sunlight and heat)

  • Air and water were recycled, and food was grown within the facility to sustain the inhabitants

Isolated systems

• Neither energy nor matter are 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!)

Environmental Systems

Systems at different scales

• Systems are structures made up of interconnected parts that work together towards a common goal or function

  • In a similar way, environmental systems are interconnected networks of components and processes within the environment, found at various scales from single organisms to huge ecosystems

  • These environmental systems include interactions between living organisms, their habitats and physical elements like water, air and soil, shaping Earth's environment and influencing its dynamics and functions

• Environmental systems can be observed and analysed at a range of different scales

  • For example, a bromeliad (a type of plant commonly found in tropical rainforests) could represent a small-scale local ecological system

    • Within the leaves of the bromeliad, various organisms interact, forming a microcosm of life

  • The entire rainforest itself represents a large-scale ecosystem, where countless species interact within a complex web of relationships

    • Within the rainforest, there are predator-prey relationships, symbiotic relationships, species competing for resources and nutrient cycles all occurring within the system

  • It could also be argued that the entire planet can be considered to be one giant, self-contained system

    • The Earth's atmosphere, oceans and land are highly interconnected and regulate environmental conditions to maintain conditions suitable for life

Earth as a single integrated system

• Instead of just a collection of independent parts, Earth can be seen as a complex, integrated system comprised of many interconnected components, including:

  • Biosphere: includes all living organisms on Earth and their interactions with the environment

  • Hydrosphere: includes all water bodies on Earth, including oceans, rivers, lakes and groundwater

  • Cryosphere: includes all forms of frozen water on Earth's surface, such as glaciers, ice caps and permafrost

  • Geosphere: refers to the solid Earth, including rocks, minerals and landforms such as mountains and valleys

  • Atmosphere: includes the layer of gases surrounding the Earth, including the troposphere, stratosphere, mesosphere, thermosphere and exosphere

  • Anthroposphere: represents the sphere of human influence on the environment, including human activities, infrastructure and urbanisation

Gaia hypothesis

• The Gaia hypothesis (also known as the Gaia theory), initially proposed by James Lovelock in the 1970s, presents a holistic view of the Earth as a single, self-regulating system

  • Lovelock proposed that Earth's biota (living organisms) and their environment are closely linked and act together as an integrated system

  • His theory suggests that feedback mechanisms within Earth's systems help maintain stability and balance on a global scale, a bit like homeostasis in living organisms

• Variations and developments:

  • Initially, the Gaia hypothesis was introduced to explain how the composition of the Earth's atmosphere affects global temperatures and how these two factors are connected or "controlled" via complex feedback methods

    • For example, the presence of greenhouse gases, such as carbon dioxide and methane, in the Earth's atmosphere can increase global temperatures

    • In response to these rising temperatures, feedback mechanisms, such as increased evaporation leading to more cloud cover or enhanced plant growth absorbing more carbon dioxide, may act to mitigate temperature increases

  • Over time, the Gaia hypothesis has undergone various interpretations and refinements, with contributions from scientists such as Lynn Margulis

  • Some scientists have criticised the Gaia hypothesis for its anthropomorphism, comparing the Earth to a living organism, and lack of testability, while others consider it a useful theory for understanding Earth's interconnected systems