1a. Water and carbon support life on Earth and move between the land, oceans and atmosphere

Question 1

What is the importance of water in supporting life on the planet?

Answer 1

• provides a medium that allows organic molecules to mix and form more complex structures
• oceans (occupy 71% of earth’s surface) moderate temperatures by absorbing heat, storing it and releasing it slowly
• clouds (made up of tiny water droplets and ice crystals) reflect around 1/5 of solar radiation and lower surface temperatures
• water vapour, a potent greenhouse gas, helps to maintain average global temperatures by absorbing long-wave radiation from earth (average global temp 15 degrees celsius higher than they would be otherwise

Question 2

What are the uses of water for humans?

Answer 2

• water makes up 65-95% of all living organisms and is crucial to their growth, reproduction and other metabolic functions
• water is the medium used for all chemical reactions in the body, including circulation of oxygen and nutrients
• sweating is a cooling process using evaporation
• water also an essential resource for economic activity - used tp generate electricity, irrigate crops, provide recreational facilities and satisfy public demand (drinking water, sewage disposal), as well as being important in industries such as food manufacturing and steel making

Question 3

What are the uses of water for flora?

Answer 3

• water makes up 65-95% of all living organisms and is crucial to their growth, reproduction and other metabolic functions
• plants require water for photosynthesis, respiration and transpiration
• photosynthesis takes place in leaves of plants, combining CO2, sunlight and water to create glucose and oxygen
• respiration in plants and animals converts glucose and oxygen to energy and releases CO2 and water
• plants also require water to maintain its rigidity and to transport mineral nutrients from the soil
• transpiration of water from leaf surfaces cools plants by evaporation

Question 4

What are the uses of water for fauna?

Answer 4

• water makes up 65-95% of all living organisms and is crucial to their growth, reproduction and other metabolic functions
• respiration in plants and animals converts glucose and oxygen to energy and releases CO2 and water
• in fur-covered mammals, reptiles and birds, evaporative cooling is achieved through panting
• in humans and animals, water is the medium used for all chemical reactions in the body, including circulation of oxygen and nutrients

Question 5

What is carbon?

Answer 5

• building block of life on earth, life as a whole is carbon based - built on large molecules of carbon atoms such as proteins, carbohydrates and nucleic acids
• common chemical element
  stored in carbonate rocks, such as limestone, sea floor sediments, ocean water (as dissolved CO2), the atmosphere (as CO2 gas) and in the biosphere (in agricultural crops and forest trees)

Question 6

What are the uses of carbon?

Answer 6

• available for human use as food, timber and paper
• carbon also used as an economic resource, fossil fuels such as coal, oil and natural gas power the global economy
• oil also used as a raw material in the manufacture of products ranging from plastics to paint and synthetic fabrics

Question 7

How does water cycle between the land, oceans and atmosphere?

Answer 7

water moves between the stores through precipitation, evapotranspiration, run-off and groundwater flow

Question 8

How does carbon cycle between the land, oceans and atmosphere?

Answer 8

main pathways between stores followed by carbon include photosynthesis, respiration, oxidation (decomposition, combustion) and weathering

Question 9

Key features of drainage basin system and global water cycle

Answer 9

drainage basin system
- open system (inputs and outputs of both energy and matter)
- consists of three main stores: atmosphere, oceans and land - ocean largest store, atmosphere smallest

global water cycle
- closed system (inputs and outputs of only energy)
- consists of three main stores: atmosphere, oceans and land - ocean largest store, atmosphere smallest

Question 10

Difference between the global and smaller cycle carbon cycles

Answer 10

global scale - closed system
smaller scale (eg. rainforest) - open system

Question 11

Explain the slow carbon cycle

Answer 11

• atmospheric CO2 absorbed by oceans, dissolved CO2, oxygen and calcium used by marine organisms to create calcium carbonate to form shells and skeletons
• when these organisms die they sink to the sea floor
• over millions of years, heat and pressure change shells into carbon rich sedimentary rock (eg. limestone), carbon is stored in these rocks for about 150 million years
• eventually tectonic processes subduct the limestone into the mantle, then eventually released into the atmosphere as CO2 from active volcanoes
• CO2 can also be released from rocks as a result of chemical weathering, weak acid rain dissolves carbonate chemicals, releasing CO2 into the atmosphere, rivers and oceans
  long term storage in sedimentary rocks holds 99.9% of all carbon on earth

Question 12

Explain the fast carbon cycle

Answer 12

• amount of carbon moved is small, but represents most of the carbon in circulation
• plants and microscopic-based phytoplankton both capture sun’s energy to photosynthesise
• photosynthesis absorbs CO2 from the atmosphere, producing carbohydrates which feed other aquatic life in the food chain
• respiration from plants and animals + decomposition when they die, then returns the CO2 back to the atmosphere