1.2 Systems

IB Knowledge Statements

1.2.1 Systems are sets of interacting or interdependent components

1.2.2 A systems approach is a holistic way of visualizing a complex set of interactions, and it can be applied to ecological or societal situations

1.2.3 In system diagrams, storages are usually represented as rectangular boxes and flows as arrows, with the direction of each arrow indicating the direction of each flow.

1.2.4 Flows are processes that may be either transfers or transformations.

1.2.5 Systems can be open or closed.

1.2.6 The Earth is a single integrated system

1.2.7 The concept of a system can be applied at a range of scales

1.2.8 Negative feedback loops = output of a process inhibits or reverse the operation of the same process. They are stabilising as they counteract

1.2.9 As an open system, an ecosystem will normally exist in a stable equilibrium (either steady state or one developing over time) – will be maintained by stabilising negative feedback loops

1.2.10 Positive feedback = disturbance leads to an amplification of that disturbance, destabilising the system and driving it away from its equilibrium

1.2.11 Positive feedback loops tend to drive a system towards a tipping point

1.2.12 A tipping point can exist within a system where a small alteration in one component can produce large overall changes, resulting in a shift equilibrium

1.2.13 A model is a simplified representation of reality; it can be used understand how a system works and to predict how it will respond to change.

1.2.14 Simplification of a model involves approximation and, therefore, loss of accuracy.

1.2.15 Interactions between components in systems can generate emergent properties.

1.2.16 The resilience of a system, ecological or social, refers to its tendency to avoid tipping points and maintain stability.

1.2.17 Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).

1.2.18 Humans can affect the resilience of systems through reducing these storages and diversity.

This section focuses on:

Defining systems and how to represent systems such as an ecosystem
Describing feedback loops in the biosphere (namely involving global warming, prey-predator relationship and canopy gap)
Describing the responses towards a change in the ecosystem

Part 1: Defining Systems

A system is a set of interrelated parts and the connection between them that unites them to form a complex whole and produces emergent properties.

Key ideas

Two systems connected. In reality, many systems are connected in a complex way.

Identify the flows in the system shown

For example, in a lake water system:

•Runoff from mountain, rivers flowing into lake = input

•Evaporation = output

•Detritus entering lake = transfer

•Decomposition of detritus = transformation

Three categories of systems are...

Open

System

Matters and energy are exchanged to the surrounding

Closed

System

No exchange of matter but energy can be gained or lost

Isolated

System

Matters and energy are not exchanged to the surrounding

Activity 1: Illustrate a simple system diagram in woodland or a mixed farming land

Activity 2

The picture on the right shows a coconut plantation site.

State the type of system? Explain your answer
Outline the inputs, outputs, transfers and transformations

1.2.1 Systems PYTRClass.pptx

Notes with Practice

1.2.1 Systems PYTRClass Answer.pptx

Notes with Answers

Part 2: Feedback Loops

Use the slider

An output of a system may be fed directly to the same system
In most cases, the output causes a change in the surrounding systems. The secondary output may result in amplifying or reducing the first system
If the system is amplified (hance more product is formed), it is known as positive feedback loop.
If the system is reduced (hence less product is formed), it is known as negative feedback loop.
Here, you can see two contrasting loops' examples involving plant growth. You may try it first before sliding to the next picture

Activity 1 Stimulator

Activity 1 Task

1.2.2 Systems PYTRClass.pptx

Part 3: Response to Change

In Part 3, we will talk about..

Defining emergent properties, steady-state equilibrium, stability of ecosystems and emergent properties
Understand the meaning of tipping points and resillience
Outline responses of systems towards external changes

Emergent Properties

•Interactions between components of a system can generate emergent properties.

•An emergent property is a property that a system has but which the individual components do not have.

Example: Predator-prey oscillations and trophic cascades are explained below

•Patterns of change occur that would not occur in isolated components

Predator-Prey

Oscillation

often controlled by negative feedback mechanisms that control population densities.
In the relative absence of the predatory, the population of prey begins to increase in size.
As the availability of prey increases, there is an increase in predator numbers, after a time lag. As the number of predators increases, the population size of the prey begins to decrease, again after a time-lag.
With fewer prey, the number of predators decreases again

Trophic

Cascade

impact that a top consumer has on the trophic level beneath it (i.e. its prey) and in turn the knock-on effect this has on lower trophic levels in the food chain.
Trophic cascades occur when predators limit the population size of their prey, which in turn enhances the chance of survival of the individuals in the next lower trophic level in the food chain.
Complex interactions between different trophic levels create emergent properties of the overall system.
Adding or removing top predators, either deliberately or indirectly through human activities, can lead to associated changes in the relative populations of predator and prey through a food chain.
This can result in dramatic changes in ecosystem structure and nutrient cycling.

Steady-state Equilibrium

the common property of most open systems in nature
- although constantly fed with inputs and outputs of energy and matter
- the overall stability remains steady i.e no net change over the longer term

there may be oscillations or fluctuations in the very short term.
- These fluctuations occur around a fixed level
- Eventually, deviations result in a return towards the average state i.e equilibrium

Stable system

This system can return to its original equalibrium after a disturbance

Unstable system

This system will form a new equalibium after a disturbance

Stability of a system is determined by its resilience which is the tendency to avoid tipping points.

Resilience

- Defines the stability of a system.
- High resillience = can return to the original equilibrium
- Depends on the abundance (diversity and size of storage) in biodiversity
- A more complex ecosystem (high value of Simpson’s index) has high ressillience
- Human activities often reduces resillience
- Models are used to predict tipping points and such models have strengths and limitations.
- The delays involved in feedback loops make it difficult to predict tipping points and add to the difficulty of modelling systems.
- Accurate predictions are critical as the costs of tipping points, both from environmental and economic perspectives, could be severe.
- Models that predict tipping points are, therefore, essential and have alerted scientists to the potential of large events.
- Continued monitoring, research and modelling is required to improve predictions.

Tipping points

Positive feedback loops often drive a system to its tipping point.
Tipping point = critical threshold where even a small change can have dramatic effects and cause a disproportionately large response in the overall system
Most projected tipping points are linked to climate change and represent points beyond which irreversible change or damage occurs.
Increases in atmospheric CO2 levels above a certain value (450 ppm) would lead to an increase in global mean temperature, causing melting of the ice sheets and permafrost.
Reaching such a tipping point would, for example, cause the melting of Himalayan mountain glaciers, a lack of freshwater and long-term damage to many Asian societies

Tipping point is reached

A small change causes the system to reach a new equilibrium

No tipping point

Gradual change allows the system to make

adjustments

Further Perspective

1.2.3 Systems PYTRClass.pptx

Notes

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