1.1.1 Water and carbon cycles as natural systems

Question 1

What are the five parts of a system?

Answer 1

Inputs, outputs, stores, flows, boundaries

Question 2

What are inputs?

Answer 2

Matter or energy that are added to the system

Question 3

What are outputs?

Answer 3

Matter or energy that leaves the system

Question 4

What are stores?

Answer 4

Where matter or energy builds up

Question 5

What are flows?

Answer 5

When matter or energy moves from one store to another

Question 6

What are boundaries?

Answer 6

The limits of the system

Question 7

How is a systems approach applicable to a drainage basin system?

Answer 7

In a drainage basin system, water enters as rain (input). The system’s watershed is the boundary. Some water is stored in the soil and in vegetation. Water travels from the drainage basin to the river and then down the river (flows). It leaves the system where the river meets the sea (output).

Question 8

Systems can be ………… or ………… .

Answer 8

open, closed

Question 9

What are features of open systems?

Answer 9

• Both energy and matter can enter and leave an open system - there are inputs and outputs of both.
• Example: drainage basins are open systems - energy from the Sun enters and leaves the system. Water is input as precipitation, and output as river discharge into the sea.

Question 10

What are the features of a closed system?

Answer 10

• Matter cannot enter or leave a closed system - it can only cycle between stores
• Energy can enter and leave a closed system - it can be input or output
• Example: the carbon cycle is a closed system - energy is input (e.g. from the sun by photosynthesis) and output (e.g. by respiration), but the amount of carbon on Earth stays the same because there are no inputs or outputs of matter

Question 11

If the inputs and outputs of a system are balanced, the system is in ………… .

Answer 11

equilibrium

Question 12

What is meant by dynamic equilibrium?

Answer 12

There are lots of small variations in the inputs and outputs of a system (e.g. the amount of precipitation entering a drainage basin varies). These variations are usually small, so the inputs and outputs remain balanced on average.

Question 13

What can be caused by large, long-term changes to the balance of inputs and outputs?

Answer 13

A new dynamic equilibrium

Question 14

Changes can trigger ………… or ………… feedback.

Answer 14

positive, negative

Question 15

What are positive feedback mechanisms?

Answer 15

• Positive feedback mechanisms amplify the change in the inputs or outputs
• This means the system responds by increasing the effects of the change, moving teh system even further from its previous state

Question 16

Give an example of a positive feedback loop.

Answer 16

temperatures rise -> ice covering cold parts of Earth melts due to higher temperatures -> less ice cover means less of the Sun’s energy is reflected -> less of Sun’s energy being reflected means more is absorbed by the Earth -> temperatures rise (again) etc.

Question 17

What are negative feedback mechanisms?

Answer 17

• Negative feedback mechanisms counteract the change in the inputs of outputs.
• This means that the system responds by decreasing the effects of teh change, keeping the system closer to its previous state.

Question 18

Give an example of a negative feedback loop.

Answer 18

large amounts of carbon dioxide emitted -> carbon dioxide in atmosphere increases -> extra carbon dioxide causes plants to increase growth -> plants remove and store more carbon dioxide from the atmosphere -> amount of carbon dioxide in the atmosphere reduces

Question 19

Why can the Earth be seen as a closed system?

Answer 19

Energy is input from the Sun and output to space, but matter is not input or output to space (except for the occasional space probe).

Question 20

The whole Earth system can be broken down into smaller parts called ……….. .

Answer 20

subsystems

Question 21

What are the Earth’s five subsystems?

Answer 21

cryosphere, lithosphere, biosphere, hydrosphere, atmosphere

Question 22

What is the cryosphere?

Answer 22

The cryosphere includes all the parts of the Earth system where it’s cold enough for water to freeze, e.g. glacial landscapes.

Question 23

What is the lithosphere?

Answer 23

The lithosphere is the outermost part of the Earth. It includes the crust and the upper parts of the mantle.

Question 24

What is the biosphere?

Answer 24

The biosphere is the part of the Earth’s systems where living things are found. It includes all the living parts of the Earth - plants, animals, birds, fungi, insects, bacteria, etc.

Question 25

What is the hydrosphere?

Answer 25

The hydrosphere includes all of the water on Earth. It may be in liquid form (e.g. in lakes and rivers), solid form (ice stored in the cryosphere) or gas form (e.g. water vapour stored in the atmosphere). It can also be saline (salty) or fresh.

Question 26

What is the atmosphere?

Answer 26

The atmosphere is the layer of gas between the Earth’s surface and space, held in place by gravity.

Question 27

The Earth’s subsystems are all ………… .

Answer 27

interlinked

Question 28

How are the Earth’s subsystems interlinked?

Answer 28

By the cycles and processes that keep the Earth system as a whole running as normal (e.g. the water cycle and carbon cycle).

Question 29

Why can the Earth system be considered a cascading system?

Answer 29

Matter and energy move between the subsystems - the output of one cycle is the input of the next.

Question 30

Changes that occur in one subsystem can affect what happens in ………… .

Answer 30

others