4 Human influences on the environment Flashcards
What has happened to the numbers of humans since we first appeared on earth?
Our numbers have grown drastically.
Why have our numbers grown drastically?
Due to our intelligence.
What are we referring to when we say intelligence?
Unlike other species, we have not adapted to one specific environment, we have changed many environments to suit our needs.
What is the correlation between our numbers and technology?
As our numbers have grown, so has the sophistication of our technology.
What is an example of an increase in the sophistication of our technology?
Early humans made tools from materials readily to hand. Today’s technology involves much more complex processes.
What has happened as a result of this sophistication of our technology?
As a result, we produce ever-
increasing amounts of materials that pollute our air, soil and waterways.
What has changed in terms of how much humans influence their environment?
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.
What are examples of the increasing demands that we make on the environment?
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.
What is a modern farm?
It is a sort of managed ecosystem.
Why is it called a managed ecosystem?
Many of the interactions are
the same as in natural ecosystems.
What is an example of these interactions?
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
What is an image of a food web on a farm?
What must farmers get from their farms?
Profit.
How do farmers try to get as much profit as possible?
They try to control the environment in such a way as to maximise the yield from crop plants and livestock
What are factors that can be controlled by a farmer to maximise crop yields?
- Soil ions (nitrates).
- Soil structure.
- Soil pH.
- Carbon dioxide, light, and heat.
How are soil ions (nitrates) controlled?
Adding fertilisers to the soil or growing
in a hydroponic culture .
Why are soil ions (nitrates) controlled?
Extra mineral ions can be taken
up and used to make proteins and
other compounds for growth
How is soil structure controlled?
Ploughing fields to break up compacted
soil; adding manure to improve drainage and aeration of heavy, clay soils
Why is soil structure controlled?
good aeration and drainage allow
better uptake of mineral ions (by
active transport) and water.
How is soil pH controlled?
Adding lime (calcium salts) to acidic
soils; few soils are too alkaline to need
treatment.
Why is pH controlled?
Soil pH can affect crop growth as
an unsuitable pH reduces uptake of
mineral ions.
How are carbon dioxide, light, and heat controlled?
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.
Why are carbon dioxide, light, and heat controlled?
All may limit the rate of
photosynthesis and the production
of the organic substances needed
for growth.
What is an image which shows crops grown by hydroponics in a glasshouse?
What is an image which shows crops grown in large tunnels made of transparent polythene, called polytunnels?
Why are glasshouses/greenhouses and polytunnels used?
This is because they can provide very controlled conditions for plants to grow.
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.
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.
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.
What do nitrates in the soil do?
Nitrates from the soil supply nitrogen that is needed to make proteins in plants.
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).
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.
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.
How will the farmer replace the lost nitrogen?
A farmer usually adds some kind of fertiliser.
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.
What is an image that shows the nitrogen cycle on a farm?
What are the two main types of fertilisers?
- Inorganic.
- Organic.
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.
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.
What does adding farmyard manure to the soil do?
Adding farmyard manure returns some nitrogen to the soil.
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.
Therefore, what do farmers do to replace the lost nitrogen?
Most farmers apply inorganic fertilisers
to replace the nitrates and other mineral ions lost.
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.
What is another way to replace lost nitrates?
It is by growing a legume crop in a field one year in four.
Why do legumes help in replacing lost nitrates?
Legumes have nitrogen-fixing bacteria in nodules on their roots.
What do these bacteria do?
These bacteria convert nitrogen gas in the soil air to ammonium ions.
Where do these ammonium ions go?
Some of this is passed to the plants, which use it to make proteins.
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.
What is done with this ammonia?
This is then oxidised to nitrate by nitrifying bacteria and made available for next year’s crop.
What are pests?
Pests are organisms that reduce the yield of crop plants or stock animals.
What is the yield?
The ‘yield’ of a crop is the amount produced for sale.
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.
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.
How can pests be controlled?
- Using pesticides.
- Using biological control methods.
What are pesticides?
They are chemicals used to kill pests.
How are pesticides named?
They are named according to the type of organism they kill.
How are pesticides used?
A farmer uses pesticides to kill particular pests and improve the yield from the crops or livestock.
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.
How does a farmer know if he should use pesticides?
Whether or not a farmer uses pesticides is largely a decision based on
cost.
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.
What is one problem with using pesticides?
One problem with using pesticides is that a pest may develop resistance to the chemical.
How can pesticides develop a resistance to the chemical?
Through natural selection.
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.
What is another problem with pesticides concerning our environment?
Other problems are to do with the fact that pesticides can cause environmental damage.
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.
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.
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.
What is a diagram of the changes in the level of carbon dioxide in the atmosphere?
What is an image of season fluctuations in carbon dioxide levels?
What is a diagram of the ‘normal’ greenhouse effect?
What is a diagram which shows the formation of acid rain and its effects on living organisms?
What is an image that shows how lichens are sensitive to pollution levels?
What is a diagram that changes in oxygen levels and types of organism living downstream from a sewage
outlet into a river?
What is an image that shows these species?
What is a diagram of an algal bloom caused by fertiliser?
