B18 biology and ecosystems Flashcards
Why is a population growth much better than other animals?
better health care so people are living longer
new medicines are being developed so people don’t die of previously fatal diseases
farmers are able to produce more food using new breeds and equipment
we have no predators
we can clear waste
What is a negative effect associated with population growth?
As the human
population
increases, the volume of waste and
pollution
that is produced also increases. Polluting an
ecosystem
harms or kills the organisms that live within it.
Modern society is more consumable, which means humans manufacture more products and replace them more often. This consumption is not
sustainable
. Many natural materials, including fossil fuels, will soon run out and scientists argue that there is already too much waste.
Explain the three main types of pollution?
Water pollution
In some parts of the world, open sewers can lead into water courses, such as streams and rivers, which can cause serious illness in humans that may drink the contaminated water.
Some farmers use too many fertilisers, which can run off fields during heavy rain. This can pollute nearby streams and rivers leading to eutrophication. Some water pollution even comes from toxic chemicals released illegally by factories.
Air pollution
Combustion of fossil fuels and other fuels releases carbon dioxide. This contributes to the
greenhouse effect and leads to global warming. It also releases sulfur dioxide and nitrogen oxides which can cause acid rain. Air pollution can also be caused by tiny particulates from smoke which can cause smog. Some of the world’s major cities like Delhi in India and Karachi in Pakistan have dangerously high levels of air pollution.
Land pollution
The rubbish we throw out that is not
recycled goes into a land fill. These are huge holes in the ground into which our rubbish is dumped. Some things like batteries cannot be put into
landfill sites because of the toxic chemicals they contain. They must be recycled. Other land pollution comes when some people dump rubbish in public or other private places, often to avoid paying for it to be disposed of. This is called fly tipping and is illegal.
How does Land use affect the environment?
The larger the human population gets, the more land we require. More houses must be built, more resources found, more food must be grown and more waste is produced. This often means less space and fewer resources for other animals and plants.
Often biodiversity is significantly reduced when land is cleared for human uses, such as building, quarrying, farming and waste disposal. Think about the reduction in biodiversity, which occurs when an area of rainforest is cut down to grow crops.
How is consumerism not sustainable?
Modern society is more consumable, which means humans manufacture more products and replace them more often. This consumption is not
sustainable. Many natural materials, including fossil fuels, will soon run out and scientists argue that there is already too much waste.
What is deforestation and its effect?
For thousands of years humans have been deforesting small areas of woodland to build their own houses or grow crops to feed their families. However, in recent years the increase in the human population and development of industrial machinery has meant that much larger areas have been cleared. This is often by large companies who deforest to provide land for cattle, rice fields and growing crops for
biofuels.
Deforestation destroys the
habitats of the organisms that live there and through this kills individuals of many species. Scientists estimate that several hundred species of plant, animal and insect are lost each day partly as a result of deforestation. This means that deforestation is causing extinctions and dramatically reducing biodiversity.
What are bogs and how significant is their destruction
Bogs
are very wet areas of land without trees in which many types of moss grow. They are acidic and often have very low levels of nutrients. Here
decomposition
is very slow and peat is formed from partially decayed plants.
For many years peat was removed from bogs for gardeners to add to their soil or to burn as fuel. This dramatically reduced
biodiversity. Because peat takes such a long time to form, it is a
non-renewable
energy resource like fossil fuels.
Peat bogs are a very important store of carbon. We call them
carbon sinks. If all the peat was removed and burned this would quickly release a huge volume of carbon dioxide into the atmosphere and contribute to the
greenhouse effect
.
What is the greenhouse effect?
Without the
greenhouse effect
the
mean
temperature on Earth would be -18°C and there would be very little or no life. So the greenhouse effect itself is a good thing. The greenhouse effect traps some of the energy from the Sun, which keeps our planet at a suitable temperature for life.
The problem is that our increased release of
greenhouse gases
is causing an increase in the greenhouse effect called the enhanced greenhouse effect. This is leading to global warming.
Carbon dioxide, water vapour and methane are amongst the most common greenhouse gases. Since the start of the Industrial Revolution
in about 1750 the levels of carbon dioxide have increased by 40%.
What is global warming and its impacts?
Global warming is the increase in the mean temperature of the Earth. The ten hottest years since records began have been in the last 30 years. The mean increase in the last 100 years has been less than 1°C. This might seem small, but is enough to have devastating consequences on many
species in different parts of the world.
As the percentage of carbon dioxide in our atmosphere has increased so has the Earth’s mean temperature. Note that the shape of the first graph showing the amount of carbon dioxide in the atmosphere is ‘exponential’ and is a similar shape to graphs showing human population change over the same time period. When comparing graphs such as changes to carbon dioxide levels and temperature against time, note that the axes are drawn to different scales, and do not start at ‘0’.
The consequences of global warming are:
melting of the polar ice caps
the rise in sea level may one day threaten many cities such as London, New York and Amsterdam
weather patterns will change with more unusual weather
animals will migrate towards the poles to find habitats with suitable temperatures
tropical diseases may become more common in other regions, such as the Europe
many species will become
extinct
What is conservation?
Keeping the environment healthy and productive by careful use of its resources.
How to maintain biodiversity?
Scientists and concerned members of the public help maintain biodiversity by:
breeding programs to help preserve
endangered species
, like the panda
protection and development of new endangered
habitats, often by making National Parks
replanting hedgerows because there is higher biodiversity in them than the fields they surround
reducing deforestation and the release of
greenhouse gases
recycling
rather than dumping waste in landfill sites
What factors affect food security?
Food security is a measure of the availability of food required to support people of a household, region, country or any specified area. It is a measure of how much food there is, if it is of suitable quality and whether people can access it.
Having fully stocked supermarket shelves is something that perhaps some of us might take for granted. However, this high level of food security is not experienced by all people. In some parts of the world there is a shortage of food, which can result in starvation and death. The United Nations estimate that around nine million people die of hunger each year.
Food security is reduced by:
the increase in human
population
, as birth rates are increasing and many people have better access to medical care
changing diets mean scarce food resources are transported to be sold to other areas from areas which need them
new pests and
pathogens
that attack crops and farm animals
The effects of climate change are making farming more difficult in many areas
increased costs of farming
armed conflicts
Finding
sustainable
ways to feed people is an important problem for scientists.
What are the two types of farming?
Intensive farming
Intensive farming
uses machines, natural and artificial fertilisers, and
high-yield
crops to maximise the amount of food produced. Most of the meat, fruit and vegetables, dairy products and eggs found in our supermarkets come from intensive farming so it is important for our food security. Farmers growing
arable
crops can specialise in growing only one crop to maximise the food they produce. This is called
monoculture
. This can reduce key nutrients in the soil and can lower
biodiversity
.
Hedgerows have been removed from many fields to make them bigger and easier to farm. This allows farmers to make more food. Often, more animals and plants live in hedgerows than fields and so their removal can also reduce biodiversity.
Some intensive farming can also mean keeping livestock in smaller pens with regulated temperatures. This reduces the energy they need for movement and temperature regulation and so maximises their size and yield. Some animals are fed high protein foods to increase their growth. They can also be fed antibiotics in their food to prevent diseases. Many scientists think this is a contributing factor to antibiotic resistance in bacteria.
Advantages and disadvantages of intensive farming practices: Advantages: higher yields, more efficient use of land
Disadvantages; antibiotic resistance and ethical objections.
Some people object to some modern intensive farming methods. Some farms have become
organic to address this. Organic farmers do not use machines to the same extent as intensive farming. They do not apply artificial pesticides to their crops and use natural fertilisers such as
compost and manure. They rotate their crops to avoid monoculture.
What are sustainable fisheries?
Sustainable
fisheries do not reduce the overall number of fish, because the number of fish that are caught and killed does not ever exceed the birth of new fish.
At one point we thought that we could remove as many fish as we wanted from the oceans without any consequence. During this period, we drastically
overfished
some of our oceans and seas and reduced some
populations
to critically low numbers.
Some scientists think that as much as 85% of the world’s fish populations have been overfished. Common examples are cod in the North Sea and sole in the Irish Sea and English Channel. Overfishing can cause a critical point in populations that means certain
species cannot ever recover and will become
extinct.
To address overfishing many countries are adopting a more sustainable strategy for fishing. These include Iceland and New Zealand. Many countries have introduced fishing quotas which limit the amount of fish that can be caught and killed from specific species. The size of the gaps in fishing nets has also been increased to ensure that juvenile fish can reach reproductive maturity and have offspring before being killed.
What are the three environmental changes
Seasonal Geographical and As a result of human action
