4 Human influences on the environment Flashcards
1
Q
What has happened to the numbers of humans since we first appeared on earth?
A
Our numbers have grown drastically.
2
Q
Why have our numbers grown drastically?
A
Due to our intelligence.
3
Q
What are we referring to when we say intelligence?
A
Unlike other species, we have not adapted to one specific environment, we have changed many environments to suit our needs.
4
Q
What is the correlation between our numbers and technology?
A
As our numbers have grown, so has the sophistication of our technology.
5
Q
What is an example of an increase in the sophistication of our technology?
A
Early humans made tools from materials readily to hand. Today’s technology involves much more complex processes.
6
Q
What has happened as a result of this sophistication of our technology?
A
As a result, we produce ever-
increasing amounts of materials that pollute our air, soil and waterways.
7
Q
What has changed in terms of how much humans influence their environment?
A
Early humans influenced their environment, but the enormous size of the population today and the extent of our industries mean that we affect the
environment much more significantly.
8
Q
What are examples of the increasing demands that we make on the environment?
A
We make these demands for:
- Food to sustain an ever-increasing population.
- Materials to build homes, schools and industries.
- Fuel to heat homes and power vehicles.
- Space in which to build homes, schools and factories, as well as for leisure facilities.
- Space in which to dump our waste materials.
9
Q
What is a modern farm?
A
It is a sort of managed ecosystem.
10
Q
Why is it called a managed ecosystem?
A
Many of the interactions are
the same as in natural ecosystems.
11
Q
What is an example of these interactions?
A
Crop plants depend on light and mineral ions from the soil as well as other factors in the environment. Stock animals (sheep, cattle, etc.) depend on crop plants for food
12
Q
What is an image of a food web on a farm?
A
13
Q
What must farmers get from their farms?
A
Profit.
14
Q
How do farmers try to get as much profit as possible?
A
They try to control the environment in such a way as to maximise the yield from crop plants and livestock
15
Q
What are factors that can be controlled by a farmer to maximise crop yields?
A
- Soil ions (nitrates).
- Soil structure.
- Soil pH.
- Carbon dioxide, light, and heat.
16
Q
How are soil ions (nitrates) controlled?
A
Adding fertilisers to the soil or growing
in a hydroponic culture .
17
Q
Why are soil ions (nitrates) controlled?
A
Extra mineral ions can be taken
up and used to make proteins and
other compounds for growth
18
Q
How is soil structure controlled?
A
Ploughing fields to break up compacted
soil; adding manure to improve drainage and aeration of heavy, clay soils
19
Q
Why is soil structure controlled?
A
good aeration and drainage allow
better uptake of mineral ions (by
active transport) and water.
20
Q
How is soil pH controlled?
A
Adding lime (calcium salts) to acidic
soils; few soils are too alkaline to need
treatment.
21
Q
Why is pH controlled?
A
Soil pH can affect crop growth as
an unsuitable pH reduces uptake of
mineral ions.
22
Q
How are carbon dioxide, light, and heat controlled?
A
These cannot be controlled for field crops but in a glasshouse or polytunnel all can be altered to maximise yield of crops; burning fuels produces heat and carbon dioxide.
23
Q
Why are carbon dioxide, light, and heat controlled?
A
All may limit the rate of
photosynthesis and the production
of the organic substances needed
for growth.
24
Q
What is an image which shows crops grown by hydroponics in a glasshouse?
A
25
What is an image which shows crops grown in large tunnels made of transparent polythene, called polytunnels?
26
Why are glasshouses/greenhouses and polytunnels used?
This is because they can provide very controlled conditions for plants to grow.
27
What are the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses?
In glasshouses and polythene tunnels conditions can be controlled. This control means that all the limiting factors for plant growth can be set to the optimum conditions; this will result in more growth, so higher yield.
28
Why can these environments provide very controlled conditions for plants to grow?
- The transparent walls of the glasshouse allow enough natural light for photosynthesis during the summer months, while additional lighting gives a ‘longer day’ during the winter.
- The ‘greenhouse effect’ doesn’t just happen to the Earth, but also in
greenhouses! Short wavelength infrared radiation entering the glasshouse is absorbed and re-radiated as longer wavelength infrared radiation. This radiation cannot escape through the glass, so the glasshouse heats up. The glasshouse also reduces convection currents that would cause cooling.
- The glasshouse can be heated to raise the temperature if the outside
temperature is too low.
- If heaters use fossil fuels such as gas, this produces carbon dioxide and water
vapour. The carbon dioxide is a raw material of photosynthesis. The water
vapour maintains a moist atmosphere and reduces water loss by transpiration.
- If the plants are grown in a hydroponic culture this provides exactly the right
balance of mineral ions for the particular crop.
29
What is different about the cycling of nutrients of a farm, and naturally?
On a farm, the situation is quite different, particularly with regard to the
circulation of nitrogen.
30
What do nitrates in the soil do?
Nitrates from the soil supply nitrogen that is needed to make proteins in plants.
31
What kind of plants use these nitrates?
Some of these plants are crops that will be sold; others are used as food
for the stock animals (fodder).
32
What happens when these crops are sold?
When the crops are sold, the nitrogen in the proteins goes with them and is lost from the farm ecosystem.
33
What happens when the livestock is sold?
Similarly, when livestock is sold, the nitrogen in their proteins (gained from the fodder) goes with them and is lost from the farm ecosystem.
34
How will the farmer replace the lost nitrogen?
A farmer usually adds some kind of fertiliser.
35
What must the farmer do when he adds the fertiliser?
The amount of fertiliser added must
be carefully monitored to ensure the maximum growth and yield of the crop as using excess fertiliser wastes money.
36
What is an image that shows the nitrogen cycle on a farm?
37
What are the two main types of fertilisers?
- Inorganic.
- Organic.
38
What are many organic fertilisers made of?
Many organic fertilisers (such as farmyard manure) are made from the faeces of farm animals mixed with straw.
39
What are many inorganic fertilisers made of?
Inorganic fertilisers are simply inorganic compounds such
as potassium nitrate or ammonium nitrate, carefully formulated to provide
specific amount of nitrate (or some other ion) when applied according to the manufacturer’s instructions.
40
What does adding farmyard manure to the soil do?
Adding farmyard manure returns some nitrogen to the soil.
41
Why doesn't adding farmyard manure return all of the nitrogen to the soil?
But, as farmyard manure is made from livestock faeces and indigestible fodder, it can only replace a portion of the lost nitrogen.
42
Therefore, what do farmers do to replace the lost nitrogen?
Most farmers apply inorganic fertilisers
to replace the nitrates and other mineral ions lost.
43
What is a disadvantage of using inoranic fertilisers?
- Whilst this can replace all
the lost ions, it can also lead to pollution problems.
- Inorganic fertilisers do not improve soil structure in the way that organic
fertilisers can, because they do not contain any decaying matter that is an
essential part of the soil.
44
What is another way to replace lost nitrates?
It is by growing a legume crop in a field one year in four.
45
Why do legumes help in replacing lost nitrates?
Legumes have nitrogen-fixing bacteria in nodules on their roots.
46
What do these bacteria do?
These bacteria convert nitrogen gas in the soil air to ammonium ions.
47
Where do these ammonium ions go?
Some of this is passed to the plants, which use it to make proteins.
48
What happens at the end of the season?
At the end of the season, the crop is ploughed back into the soil, and decomposers convert the nitrogen in the proteins to ammonia.
49
What is done with this ammonia?
This is then oxidised to nitrate by nitrifying bacteria and made available for next year’s crop.
50
What are pests?
Pests are organisms that reduce the yield of crop plants or stock animals.
51
What is the yield?
The ‘yield’ of a crop is the amount produced for sale.
52
What are the two ways in which pests can harm yields?
- Lowering the amount by reducing growth, e.g. by damaging leaves and
reducing photosynthesis.
- Affecting the appearance or quality of a crop, making it unsuitable for sale.
53
What is an example of a pest?
Any type of organism – plants, animals, bacteria, fungi or protoctists, as well
as viruses – can be a pest.
54
How can pests be controlled?
- Using pesticides.
- Using biological control methods.
55
What are pesticides?
They are chemicals used to kill pests.
56
How are pesticides named?
They are named according to the type of organism they kill.
57
How are pesticides used?
A farmer uses pesticides to kill particular pests and improve the yield from the crops or livestock.
58
When do pests become problematic?
Pests are only a problem when they are present in big enough numbers to cause economic damage – a few whiteflies in a tomato crop are not a problem; the real damage arises when there are millions of them.
59
How does a farmer know if he should use pesticides?
Whether or not a farmer uses pesticides is largely a decision based on
cost.
60
What are the two factors that the farmer will have to put against one another?
The increase in income due to higher yields must be set against the cost
of the pesticides.
61
What is one problem with using pesticides?
One problem with using pesticides is that a pest may develop resistance to the chemical.
62
How can pesticides develop a resistance to the chemical?
Through natural selection.
63
What happens to the pesticides once the pest has built up a resistance to it?
It makes the existing pesticide useless, so that another must be found.
64
What is another problem with pesticides concerning our environment?
Other problems are to do with the fact that pesticides can cause environmental damage.
65
Why can pesticides cause environmental damage?
- They may be slow to decompose – they are persistent in the environment.
- They build up in the tissues of organisms – bioaccumulation.
- They build up and become more concentrated along food chains –
biomagnification.
- They kill other insects that are harmless, as well as helpful species, such as bees.
66
What should an ideal pesticide do?
- Control the pest effectively.
- Be biodegradable, so that no toxic products are left in the soil or on crops.
- Be specific, so that only the pest is killed.
- Not accumulate in organisms
- Be safe to transport, store and apply.
- Be easy to apply.
67
What is natural selection?
Process where certain individuals
in a population survive because they are better adapted to their environment. They are more likely to pass on their genes to their offspring. The mechanism of evolution.
68
What is bioaccumilation?
Build-up of pollutants such as
insecticides in the fatty tissues of an organism.
69
What is biomagnification?
Increase in concentration of
bioaccumulated substances along a food chain.
70
What is biological control?
The use of another organism to control
the numbers of a pest species.
71
What is the difference between pesticides and the use of biological control?
Instead of using a toxic chemical, biological control uses another organism to reduce the numbers of a pest.
72
What is an example of using a biological approach against whitefly tomato pests?
One way of controlling them in large glasshouses is to introduce a parasite that will kill the whiteflies. A tiny wasp called Encarsia parasitises and kills their larvae, reducing the numbers of adult whitefly.
73
What is a problem of the biological control?
A problem with biological control is that it never fully gets rid of a pest.
74
What would happen if the control organism killed all the pests?
If the control organism killed all the pests, then it too would die out, as it would have no food supply.
75
What is the aim of the biological control?
Biological control aims to reduce pest numbers to a level where they no longer cause significant economic damage.
76
What are the methods of biological control?
- Introducing a natural predator.
- Introducing a herbivore.
- Introducing a parasite.
- Introducing a pathogenic (disease-causing) microorganism.
- Introducing sterile males.
- Using pheromones.
77
Why does introducing a sterile male work?
These mate with the females but no offspring are produced from these matings, so numbers fall.
78
Why does using pheromones work?
These are natural chemicals produced by insects to attract a mate. They are used to attract pests (either males or females) to traps. The pests are then destroyed, reducing the reproductive potential of the population. Male-attracting pheromones are used to control aphids (greenfly) in plum crops.
79
What is one definition of pollution?
Contamination of the environment by harmful substances that are produced by the activities of humans.
80
What do human activities do?
They pollute the air with many gases.
81
What are the gases that contribute to pollution?
- Carbon dioxide.
- Methane.
- Carbon monoxide.
- Sulfur dioxide.
82
What have happened to the levels of carbon dioxide?
The levels of carbon dioxide have been rising for several hundred years.
83
What has happened to carbon dioxide over the past years?
Over the last 100 years alone, the level of carbon dioxide in the atmosphere
has increased by nearly 30%.
84
Why has carbon dioxide levels increased?
This rise is mainly due to the increased burning of fossil fuels, such as coal, oil and natural gas, as well as petrol and diesel in vehicle engines.
85
What has also really contributed to the rise of carbon dioxide along with these fuels?
The levels have increased as people have been cutting down large areas of tropical rainforest.
86
What are these forests called?
The lungs of the earth.
87
Why are they called the lungs of the earth?
Because they absorb such vast
quantities of carbon dioxide and produce equally large amounts of oxygen.
88
What does this extensive deforestation mean?
It means that less carbon dioxide is being absorbed.
89
What is a diagram of the changes in the level of carbon dioxide in the atmosphere?
90
What is an image of season fluctuations in carbon dioxide levels?
91
What is an explanation for the peaks and troughs that these levels of carbon dioxide experience?
In the autumn and winter, trees lose
their leaves. Without leaves they
cannot photosynthesise and so do
not absorb carbon dioxide. They
still respire, which produces carbon
dioxide, so in the winter months, they
give out carbon dioxide and the level in
the atmosphere rises. In the spring and
summer, with new leaves and brighter
sunlight, the trees photosynthesise
faster than they respire. As a result,
they absorb more carbon dioxide from
the atmosphere than they produce, so
the level decreases. However, because
there are fewer trees overall, it doesn’t
quite return to the low level of the
previous summer.
92
What has the increased levels of carbon dioxide and other gases do?
They contribute to global warming, or the enhanced greenhouse effect.
93
What is important to note about the greenhouse effect?
The ‘normal’ greenhouse effect occurs naturally.
94
Why does the greenhouse effect occur naturally?
Without it, more heat would be
lost into space and the surface temperature of the Earth would be about 30 °C lower than it is today, and life as we know it would be impossible.
95
What is the most commonly known greenhouse gas that is present in the Earth's atmosphere?
Carbon dioxide.
96
What are some of the other greenhouse gases?
Other greenhouse gases include water vapour (H2O), methane (CH4), nitrous oxide (N2 O) and chlorofluorocarbons (CFCs).
97
Are most greenhouse gases natural?
Most greenhouse gases occur naturally.
98
Which greenhouse gases don't occur naturally?
While some (like CFCs) are only produced by human activities.
99
What are CFC's?
Chlorofluorocarbons or CFCs
are complex organic molecules
containing carbon, chlorine and
fluorine.
100
What happened to CFC's?
They were once widely
used in fridges, spray cans
and as solvents, as well as in
making materials such as foam
packaging. Their use was banned
or phased out in many countries
in 1987, when they were found
to be damaging the ozone layer
in the upper atmosphere. (This
layer protects living organisms
by absorbing harmful ultraviolet
radiation from the Sun.
101
What is a diagram of the 'normal' greenhouse effect?
102
During the 'normal' greenhouse effect, what reaches the earth?
Short-wavelength infrared (IR) radiation from the Sun reaches the Earth.
103
What happens to this infrared radiation?
Some is absorbed by the Earth’s surface and emitted again as longer-wavelength IR radiation.
104
What do the greenhouse gases to this longer-wavelength IR radiation?
The greenhouse gases absorb and then re-emit some of this long- wavelength IR radiation, which would otherwise escape into space.
105
What does this whole process do?
This then heats up the surface of the earth.
106
What would a rise in the Earth's temperature by only a few degrees result in?
- Polar ice caps would melt and sea levels would rise.
- A change in the major ocean currents would result in warm water flowing
into previously cooler areas.
- A change in global rainfall patterns could result. With a rise in temperature,
there will be more evaporation from the surface of the sea, leading to more
water vapour in the atmosphere and more rainfall in some areas. Other
areas could experience a decrease in rainfall. Long-term climate change
could occur.
- It could change the nature of many ecosystems. If species could not migrate
quickly enough to a new, appropriate habitat, or adapt quickly enough to
the changed conditions in their original habitat, they could become extinct.
- Changes in farming practices would be necessary as some pests became
more abundant. Higher temperatures might allow some pests to complete
their life cycles more quickly
107
What is methane?
Methane is an organic gas.
108
When is methane produced?
It is produced when microorganisms ferment larger molecules to release energy.
109
What are the most significant sources of methane?
- Decomposition of waste buried in the ground (‘landfill sites’), by
microorganisms.
- Fermentation by microorganisms in the rumen (stomach) of cattle and other ruminants.
- Fermentation by bacteria in rice fields.
110
What kind of gas is methane?
It is a greenhouse gas, with effects similar to carbon dioxide.
111
What is so bad about methane?
Although there is less methane in the atmosphere than carbon dioxide, each molecule has a much bigger greenhouse effect.
112
What is carbon monoxide?
It is a toxic gas present in car exhaust
fumes and cigarette smoke.
113
How is carbon monoxide formed?
When substances containing carbon are burned in a limited supply of oxygen, carbon monoxide (CO) is formed.
114
What exactly are the substances that we are referring to?
This happens when petrol and diesel are burned in vehicle engines.
115
What kind of gases contain significant amounts of carbon monoxide?
Exhaust gases contain significant amounts of carbon monoxide.
116
Why is carbon monoxide dangerous?
It is a dangerous pollutant as it is colourless, odourless and tasteless and can be fatal.
117
Why can carbon monoxide be fatal?
Haemoglobin binds more strongly with carbon monoxide than with oxygen. If a person inhales carbon monoxide for a period of time, more and more haemoglobin becomes bound to carbon monoxide and so cannot bind with oxygen. The person may lose consciousness and eventually die, as a result of a lack of oxygen reaching the cells, so that organs such as the heart and brain stop working.
118
What is sulfur dioxide?
It is an important air pollutant.
119
When is sulfur dioxide formed?
It is formed when fossil fuels are burned, and combines with water droplets in the air.
120
What happens to sulfur dioxide?
It can be carried hundreds of miles in the atmosphere before falling as acid rain.
121
What is acid rain?
It is rain with a pH less than 5.5, caused by pollutant gases such as sulfur dioxide and nitrogen oxides
122
What is an explanation of how rain turns into acid rain?
Rain normally has a pH of about 5.5 – it is slightly acidic due to the carbon dioxide dissolved in it. Both sulfur dioxide and nitrogen oxides dissolve in rainwater to form a mixture of acids, including sulfuric acid and nitric acid. As a result, the rainwater is more acidic with a much lower pH than normal rain
123
What is a diagram which shows the formation of acid rain and its effects on living organisms?
124
What are lichens?
Small moss-like organisms.
125
What is a characteristic of lichens?
Some lichens are more tolerant of sulfur dioxide than others.
126
How can lichens be used?
In some countries, patterns of lichen growth can be used to monitor the level of pollution by sulfur dioxide.
127
What are the different lichens called?
The different lichens are called
indicator species as they ‘indicate’ different levels of sulfur dioxide pollution.
128
What is an image that shows how lichens are sensitive to pollution levels?
129
What would an increase in greenhouse gases cause?
An enhanced greenhouse effect and it may lead to global warming and its consequences.
130
What are the two major pollutants of freshwater?
- Sewage.
- Minerals from fertiliser.
131
What is sewage?
Sewage is wet waste from houses, factories, and farms.
132
What is done with different kinds of sewage?
In developed countries where large-scale sewage treatment takes place, industrial and agricultural sewage is usually dealt with separately from household sewage.
133
What does household sewage contain?
Household sewage consists of wastewater from kitchens and bathrooms and contains human urine and faeces, as well as dissolved organic and inorganic chemicals such as soaps and detergents.
134
How does sewage travel?
It is carried away in pipes called sewers, to be treated before it enters waterways such as rivers or the sea.
135
What happens if sewage is discharged untreated into waterways?
It produces two major problems.
136
What are these two major problems?
- Aerobic bacteria in the water polluted by the sewage use up the dissolved
oxygen in the water as they break down the organic materials. This reduction in the level of oxygen kills larger animals such as freshwater insects and fish.
- Untreated sewage contains pathogenic bacteria, which are a danger to human health.
137
What happens where untreated sewage enters a river?
The level of oxygen in the water
becomes very low as the aerobic bacteria and other microorganisms from the sewage decompose the organic matter.
138
What species can survive when untreated sewage enters a river?
Only species that are adapted to live in low-oxygen conditions, such as anaerobic bacteria, can survive
139
What happens as the water moves away from the outlet?
As the water moves away from the outlet, it becomes oxygenated again as it mixes with clean water and absorbs oxygen from the air.
140
What does this increase in oxygen levels mean in terms of species?
The increase in dissolved oxygen levels allows more clean-water species to survive.
141
What is a diagram that changes in oxygen levels and types of organism living downstream from a sewage
outlet into a river?
142
What is the aim of sewage treatment?
It is to remove solid and suspended organic matter and pathogenic microorganisms, so that cleaner waste can be discharged into waterways.
143
How can we monitor air pollution by sulfur dioxide?
As with air pollution by sulfur dioxide, the level of pollution by organic
material can be monitored by the presence or absence of indicator species.
144
What is an image that shows these species?
145
What is eutrophication?
It is the process where an aquatic habitat receives large amounts of minerals, either naturally or as a
result of pollution by sewage or fertilisers.
146
What enters the habitat through eutrophication?
The nutrients in question are inorganic mineral ions, usually nitrates or phosphates.
147
What can pollution of these minerals do?
Pollution by these minerals can have very harmful effects on an aquatic ecosystem.
148
What are the two main sources of excess minerals?
- From untreated or treated sewage.
- From artificial nitrate or phosphate fertilisers.
149
What is eutrophication usually caused by?
It is often caused by the use of artificial fertiliser.
150
How can we show that artificial fertilisers usually cause eutrophication?
Streams and rivers that run through agricultural land that have been treated with fertiliser can contain high concentrations of nitrate and phosphate.
151
Why do they contain high concentrations of nitrate and phosphate?
This is because nitrate is very soluble in water, and is easily washed out of the soil by rain.
152
What is this process known as?
Leaching.
153
What is leaching?
The process whereby mineral ions (such as nitrates) are washed out of the soil by rain.
154
What about with phosphate?
This is less of a problem with phosphate fertiliser, but phosphate is also washed into waterways by surface run-off of water.
155
What do these excess mineral ions do?
They stimulate the growth of all plants in the river or lake.
156
What is usually seen first from this stimulation of growth?
But this is usually seen first as a rapid growth of algae, called an algal bloom.
157
What is algal bloom?
It is a rapid increase in numbers of algal cells in an aquatic habitat. Often caused by eutrophication.
158
What can be observed during an algal bloom?
The algae can increase in numbers so rapidly that they form a thick scum on
the surface of the water.
159
What is a diagram of an algal bloom caused by fertiliser?
160
What happens following an algal bloom?
The algae soon start to die, and are decomposed by aerobic bacteria in the
water.
161
What happens because the bacteria respire aerobically?
They use up the oxygen in the
water.
162
What does the algae do in terms of other plants?
In addition, the algae block the light from reaching other rooted plants,
further decreasing the oxygen produced by photosynthesis.
163
What do these low levels of oxygen result in?
The low oxygen levels can result in fish and other aerobic animals dying.
164
What happens in severe cases due to these low levels of oxygen?
In severe cases, the water becomes anoxic (containing very little oxygen) and smelly from gases like hydrogen sulfide and methane from the bacteria.
165
What happens in terms of other microorganisms when the water becomes anoxic?
By this stage only
anaerobic bacteria can survive.
166
What is the sequence of events following eutrophication?
Increase in mineral ions
↓
Algal bloom
↓
Death of algae
↓
Decomposition by aerobic bacteria
↓
Bacteria use up oxygen
↓
Fish and other animals die
167
When is rapid eutrophication less likely?
Rapid eutrophication is less likely when farmers use organic fertiliser (manure)
168
Why is it less likely when farmers use organic fertilisers?
The organic nitrogen-containing compounds in manure are less soluble and so are leached less quickly from the soil.
