IB Environmental Systems & Societies SL

HAEF Psychico College

Topic 1 : Systems & Models

• What is a system?

an assemblage of parts and their relationship forming a functioning unit.

What are the components of a system?

• The Earth’s systems comprise interactions between the living ( Biotic ) and non-living ( Abiotic ) constituent parts. As in any system these interactions involve INPUTS, PROCESSING of the inputs to create OUPUTS.

• Lets look at the example of photosynthesis:So Photosynthesis comprises inputs, a process and outputs

Farm

A lake ecosystem

The Savvanah

Gaia

Types of System

• Systems are classified into 3 main types:

• OPEN• CLOSED• ISOLATED

OPEN SYSTEMS

• Open Systems: exchange matter and energy with their surroundings.

OPEN SYSTEMS

• Most systems are open, including ecosystems.• In forest ecosystems plants fix energy from

light entering the system during photosynthesis.

• Nitrogen is fixed by soil bacteria. • Herbivores that live within the forest canopy

may graze in adjacent ecosystems such as a grassland, but when they return they enrich the soil with faeces.

CLOSED SYSTEMS

• Closed Systems: exchange energy but not matter.• Closed systems are extremely rare in nature. No

natural closed systems exist on Earth but the planet itself can be thought of as an “almost” closed system.Light energy in large amounts enters the Earth’s system and some is eventually returned to space as long wave radiation (heat).

Biosphere 2

• Biosphere 2 was a human attempt to create a habitable Closed system on Earth. build in Arizona at the end of the 1980’s Biosphere 2 was intended to explore the use of closed biospheres in space colonization. Two major “missions” were conducted but both run into problems. The Biosphere never managed to produce enough food to adequately sustain the participants and at times oxygen levels became dangerously low

ISOLATED SYSTEMS

• Isolated Systems: An isolated system exchanges neither matter nor energy.

• These do not exist naturally. Though it is possible to think of the entire Universe as an isolated system.