unit 6

Question 1

what is the atmosphere composed of

Answer 1

of nitrogen (about 78%) and oxygen (about 21%)
These two gases make up the majority of the atmosphere and play vital roles in supporting life on Earth

Question 2

smaller amounts of gases contained in the atmosphere

Answer 2

Carbon dioxide, although present in relatively low concentrations (around 0.04%), is essential for maintaining the greenhouse effect, which helps regulate the Earth’s temperature, and is essential for photosynthesis
Argon is an inert gas that does not participate in chemical reactions but contributes to the overall composition of the atmosphere
Water vapour is a variable component that plays a crucial role in the Earth’s weather patterns, the formation of clouds and precipitation, and photosynthesis
Trace gases, such as methane, ozone, and nitrous oxide, are present in even smaller quantities but can have significant impacts on climate and atmospheric chemistry

Question 3

atmospheric layers

Answer 3

The atmosphere is stratified into different layers based on temperature changes
The inner layers of the atmosphere, where most interactions related to living systems occur, are the troposphere and the stratosphere

Question 4

troposphere

Answer 4

the lowest layer of the atmosphere, extending from the Earth’s surface up to about 10 kilometres
It is where weather phenomena, such as cloud formation, precipitation, and the mixing of gases, primarily occur
The troposphere contains the highest concentration of water vapour, carbon dioxide, and other trace gases that are important for the functioning of living systems and the regulation of climate

Question 5

stratosphere

Answer 5

Above the troposphere is the stratosphere, which extends from approximately 10 kilometres to 50 kilometres above the Earth’s surface
The stratosphere contains the ozone layer, a region with a higher concentration of ozone molecules that absorb and block most of the Sun’s harmful ultraviolet (UV) radiation
This layer is crucial for protecting life on Earth from excessive UV radiation and has important implications for the health of ecosystems

Question 6

The reactions occurring in the inner layers of the atmosphere, particularly the troposphere and the stratosphere, are crucial for maintaining the balance of gases, regulating climate patterns, and supporting life

Answer 6

Within the troposphere, chemical reactions involving pollutants, greenhouse gases, and atmospheric particles can impact air quality and climate
In the stratosphere, chemical reactions involving ozone play a vital role in maintaining the ozone layer and protecting the Earth from harmful UV radiation

Question 7

atmospheric systems

Answer 7

The atmosphere is a dynamic system that plays a crucial role in the Earth’s climate and weather patterns
As with other systems, the atmospheric system is made up of storages, flows, inputs and outputs

Question 8

storages within the atmosphere

Answer 8

The atmosphere acts as a storage for gases, including greenhouse gases like carbon dioxide and methane, which contribute to the greenhouse effect and influence the Earth’s temperature
These gases are present in different concentrations and can vary over time due to natural and human activities

Question 9

flows within the atmosphere

Answer 9

Within the atmosphere, there are constant flows of gases and particles, driven by processes such as air currents, weather patterns, and atmospheric circulation
These flows contribute to the movement and redistribution of gases and other substances within the atmosphere

Question 10

inputs within the atmosphere

Answer 10

The atmosphere receives inputs from various sources
Natural inputs include gases emitted from volcanic eruptions, gaseous emissions from plants and other living organisms, and dust particles from desert regions
Anthropogenic inputs, resulting from human activities, include the release of greenhouse gases, air pollutants from industrial processes, and aerosols from combustion and other human-made sources

Question 11

outputs within the atmosphere

Answer 11

The atmosphere also has outputs through different processes
It releases gases through natural processes like respiration and photosynthesis
Additionally, pollutants and aerosols can be removed from the atmosphere through precipitation, dry deposition, and chemical reactions

Question 12

exchanges and interactions with other earth systems

Answer 12

The atmosphere interacts with other components of the Earth system, including the biosphere (plants, animals, and microorganisms), hydrosphere (oceans, lakes, and rivers), and lithosphere (landmasses and rocks)
It exchanges gases and particles with these systems through various mechanisms - for example, the exchange of carbon dioxide occurs through photosynthesis by plants and respiration by organisms
These interactions involve the exchange of gases, energy, and particles, shaping climate patterns, weather events, and overall Earth system dynamics

Question 13

the composition of the atmosphere has changed significantly over geological time

Answer 13

For example, during the early stages of Earth’s history, the atmosphere had high levels of carbon dioxide and lacked oxygen
Over millions of years, photosynthetic organisms evolved and began to release oxygen as a byproduct, leading to the oxygenation of the atmosphere
Additionally, geological processes such as volcanic activity and meteorite impacts have influenced the atmospheric composition throughout Earth’s history

Question 14

clouds

Answer 14

The majority of clouds form in the troposphere
This layer is characterised by decreasing temperature with increasing altitude, creating conditions favourable for the cooling and condensation of water vapour

Question 15

clouds play a crucial role in the plants albedo affect

Answer 15

Albedo refers to the reflectivity of a surface, indicating how much solar radiation is reflected back into space
Clouds have a high albedo, reflecting a significant portion of incoming sunlight back into space
This reflection of solar radiation helps cool the Earth’s surface and lower the amount of energy absorbed by the planet, offsetting some of the warming effects caused by the greenhouse gases
In this way, the albedo effect from clouds contributes to the regulation of global average temperature

Question 16

clouds also act as a feedback mechanism in the climate system

Answer 16

In addition, low clouds have a net cooling effect by reflecting more sunlight, while high clouds can have a net warming effect by trapping more outgoing infrared radiation
The balance between different cloud types and their altitude can influence the overall albedo effect and temperature regulation

Question 17

Human activities impact the atmospheric composition through

Answer 17

altering inputs and outputs of the system
Changes in the concentrations of atmospheric gases such as ozone, carbon dioxide and water vapour have significant effects on ecosystems

Question 18

Atmospheric component affected by human activity: ozone

Answer 18

Release of ozone-depleting substances (e.g. CFCs used in aerosols, gas-blown plastics, pesticides, flame retardants and refrigerants) reduces the amount of atmospheric ozone Increases UV radiation reaching the Earth’s surface, harming organisms, including phytoplankton, plants, and humans

Question 19

Atmospheric component affected by human activity: carbon dioxide

Answer 19

Burning fossil fuels, deforestation and industrial processes all increase atmospheric carbon dioxide Enhances the greenhouse effect, leading to global warming and climate change, affecting ecosystems and biodiversity

Question 20

Atmospheric component affected by human activity: water vapour

Answer 20

Land use changes, agriculture and industrial processes can disturb atmospheric water vapour concentrations Alters precipitation patterns, contributing to droughts or excessive rainfall in certain regions, impacting ecosystems, agriculture, and water availability

Question 21

Atmospheric component affected by human activity: methane

Answer 21

Agriculture (livestock and rice production), fossil fuel extraction and use, and waste management (landfill sites) can increase atmospheric methane Enhances the greenhouse effect, leading to global warming and climate change, affecting ecosystems, melting permafrost (resulting in positive feedback) and ice caps, and contributing to sea-level rise

Question 22

Atmospheric component affected by human activity: nitrous oxide

Answer 22

Agriculture (fertiliser use, animal waste), combustion processes (e.g. in vehicle engines) and industrial activities all increase atmospheric nitrous oxide Contributes to global warming and climate change, and affects air quality

Question 23

Atmospheric component affected by human activity: aerosols

Answer 23

Aerosols (e.g. fine particles, such as soot and dust, as well as gases like sulfur dioxide and nitrogen oxides) are produced by industrial processes, biomass burning and vehicle emissions Alters radiative properties of atmosphere, affects air quality, and can influence cloud formation and precipitation patterns, impacting ecosystems and human health (fine particulate matter can be inhaled by humans and animals, leading to respiratory problems and other health issues) - atmospheric sulfur dioxide and nitrogen oxides lead to acid rain formation

Question 24

the sun emits energy in the form of solar radiation

Answer 24

solar radiation (including visible light and ultraviolet rays) that enters the Earth’s atmosphere
Some thermal energy is reflected from the Earth’s surface
Most thermal energy is absorbed and re-emitted back from the Earth’s surface
This energy passes through the atmosphere where some thermal energy passes straight through and is emitted into space

Question 25

greenhouse effect

Answer 25

when The greenhouse effect is a naturally occurring phenomenon
The greenhouse effect is important to ensure that Earth is warm enough for life
If it were not for the insulating effect of greenhouse gases, Earth would see similar dramatic temperature fluctuations to its neighbouring planets
Without the greenhouse effect, the average temperature would be much colder, making the planet uninhabitablesome thermal energy is absorbed by greenhouse gases such as carbon dioxide, methane and water vapour, and is re-emitted in all directions
These gases act like a blanket, allowing sunlight to pass through but preventing a significant amount of the infrared radiation from escaping back into space
This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm

Question 26

uv radiation

Answer 26

is a form of electromagnetic radiation emitted by the Sun
It is invisible to the human eye and is characterised by having shorter wavelengths than visible light

Question 27

ozone

Answer 27

is a form of electromagnetic radiation emitted by the Sun
It is invisible to the human eye and is characterised by having shorter wavelengths than visible light

Question 28

what happens when uv radiation from the sun interacts with ozone molecules

Answer 28

some of the ozone absorbs the energy and breaks apart, resulting in the formation of an oxygen molecule (O2) and a free oxygen atom (O)
This process of ozone destruction occurs naturally in the stratosphere due to the presence of UV radiation
However, under normal conditions, the free oxygen atom (O) can combine with another oxygen molecule (O2) to form ozone (O3) again

Question 29

what does ozone destruction and reformation create

Answer 29

a dynamic equilibrium in the stratosphere, where there is a continuous cycle of ozone molecules being broken apart and reformed
This dynamic equilibrium ensures that the concentration of ozone in the stratosphere remains relatively stable over time, as the rate of the forward reaction equals the rate of the backward reaction in the system, so the concentrations of the reactants and products remain relatively constant

Question 30

ozone depleting substances (ODSs)

Answer 30

Ozone-depleting substances (ODSs) are chemicals that cause stratospheric ozone depletion by breaking down ozone molecules
ODSs, including halogenated organic gases like chlorofluorocarbons (CFCs), are commonly used in various human activities and products:

Question 31

aerosols as an ODS

Answer 31

ODSs such as CFCs were previously used as propellants in aerosol products like sprays, foams, and deodorants
When released into the atmosphere during spraying, these substances can eventually reach the stratosphere and contribute to ozone depletion

Question 32

gas-blown plastics as an ODS

Answer 32

ODSs were also used as blowing agents in the production of foamed plastics
These agents help create air pockets within the plastic material, making it lightweight
However, during the manufacturing process or disposal of these products, ODSs can be released into the atmosphere

Question 33

pesticides as an ODS

Answer 33

Some pesticides, particularly those containing methyl bromide, a halogenated compound, have been used in agricultural practices for soil fumigation
When applied, these substances can volatilise and enter the atmosphere, where they can contribute to ozone depletion

Question 34

flame retardants as an ODS

Answer 34

Some pesticides, particularly those containing methyl bromide, a halogenated compound, have been used in agricultural practices for soil fumigation
When applied, these substances can volatilise and enter the atmosphere, where they can contribute to ozone depletion

Question 35

refrigerants as an ODS

Answer 35

ODSs were widely used as refrigerants in cooling systems, such as air conditioners and refrigerators
The most well-known examples are the chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs)
When these refrigerants leak or are improperly disposed of, they can reach the stratosphere and contribute to ozone depletion

Question 36

halogen atoms in the stratosphere

Answer 36

Halogen atoms (e.g. chlorine and bromine) from ODSs enter the stratosphere through these various human activities
Once in the stratosphere, these atoms can undergo a repetitive cycle of ozone destruction
The released halogen atoms react with ozone molecules, breaking them apart and reducing the concentration of ozone in the stratosphere
After the ozone molecules are destroyed, the halogen atoms can be regenerated and participate in further ozone-depleting reactions, perpetuating the cycle
This repetitive cycle of ozone destruction by halogen atoms increases the overall depletion of ozone in the stratosphere, resulting in an increasingly thinner ozone layer
With a thinner ozone layer, more ultraviolet radiation from the Sun can penetrate the Earth’s atmosphere, reaching the surface and potentially causing harmful effects on living organisms

Question 37

uv radiation effect on humans

Answer 37

Ultraviolet radiation from the Sun can have damaging effects on human living tissues
When excessive UV radiation reaches the surface of the Earth, it can lead to various health issues by damaging cells and tissues

Question 38

cataracts

Answer 38

Prolonged exposure to UV radiation can contribute to the development of cataracts
Cataracts cause clouding of the lens in the eye, leading to blurry vision and eventual vision loss if left untreated

Question 39

uv radiation effect on cells

Answer 39

UV radiation has the potential to induce mutations in DNA during cell division
When skin cells are exposed to UV radiation, it can lead to genetic alterations and mutations, which can disrupt normal cell growth and increase the risk of developing cancer

Question 40

skin cancer

Answer 40

UV radiation is a major risk factor for the development of skin cancer
UV rays can damage the DNA in skin cells, leading to uncontrolled cell growth and the formation of cancerous tumours
Prolonged or intense exposure to UV radiation, especially without proper protection, increases the risk of developing skin cancer

Question 41

sunburn

Answer 41

When the skin is exposed to excessive UV rays, it triggers an inflammatory response as a defence mechanism
Sunburned skin becomes red, painful, and may blister, indicating damage to the skin cells

Question 42

premature skin ageing

Answer 42

Chronic exposure to UV radiation accelerates the ageing process of the skin
It can cause the breakdown of collagen and elastin fibres, leading to wrinkles, sagging skin, and the development of age spots
Protecting the skin and eyes from excessive UV radiation is crucial to minimise the harmful effects
Measures such as wearing sunscreen with a high sun protection factor (SPF), using sunglasses that block certain UV rays, seeking shade during peak sun hours, and wearing protective clothing can help reduce the risk of UV-related health issues
Regular skin examinations and eye check-ups can help detect any potential UV-related damage or abnormalities early on, allowing for timely intervention and treatment

Question 43

uv radiation effects on biological productivity

Answer 43

Exposure to increased ultraviolet radiation can have significant effects on biological productivity, particularly on photosynthetic organisms such as phytoplankton, which play a crucial role in aquatic food webs
Phytoplankton convert sunlight, carbon dioxide, and nutrients into organic matter through photosynthesis

Question 44

how does uv radiation damage photosynthetic organisms

Answer 44

ncreased UV radiation damages photosynthetic organisms, such as phytoplankton, by causing DNA damage and inhibiting photosynthesis
When exposed to increased UV radiation, phytoplankton may experience reduced photosynthetic activity and growth, leading to a decrease in primary productivity in aquatic ecosystems

Question 45

what do phytoplankton play a vital role in

Answer 45

Phytoplankton play a vital role in nutrient cycling
They absorb nutrients from the water, convert them into biomass, and serve as a food source for other organisms
Reduced phytoplankton populations due to UV radiation damage can disrupt nutrient cycling processes, leading to imbalances and nutrient deficiencies in the ecosystem

Question 46

what is the effect of reduced phytoplankton

Answer 46

educed phytoplankton productivity can have cascading effects on higher trophic levels in aquatic ecosystems
Zooplankton, which feed on phytoplankton, may experience decreased food availability, affecting their growth and reproduction
This, in turn, can impact higher-level consumers, such as fish and marine mammals, which rely on phytoplankton and zooplankton as a food source
Changes in phytoplankton productivity disrupts overall ecosystem dynamics and stability

Question 47

what does the depletion of the ozone layer increase

Answer 47

The depletion of the ozone layer, which filters harmful UV radiation, increases the impact of UV radiation on aquatic ecosystems
Mitigating human activities that contribute to ozone depletion is therefore crucial for preserving the health and productivity of photosynthetic organisms and maintaining balanced aquatic ecosystems