Download 4. Human Impact on the Environment

Life On Earth
National 5 Biology
4.
Human Impact on the Environment
4.1
Increasing Food Production
4.1.1
Intensive Farming
4.1.2
Fertilisers
4.1.3
Pesticides
4.2
Habitat Destruction
4.3
Biological Control
4.4
Genetic Modification
Learning Intentions
By the end of this unit you should be able to:
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Explain the link between population size and food yield
Describe farming techniques that can increase food yield
Describe the importance of fertilisers
Explain how fertilisers can lead to a reduction in biodiversity
Identify examples of human activities that damage the environment
Explain the link between human activities and a decrease in biodiversity,
giving named examples
Explain the importance of indicator species
Discuss how genetic modification can lead to increases in crop yield
Introduction -The human population is growing at a faster rate than ever
before. This rapid and massive increase in population is called a population
explosion. Humans face many challenges in order to cope with such an increase in
population size. A larger number of humans will have serious implications for the
ecosystems in which we live.
Learning Activity 1 – Data Handling
Study the graph on the next page.
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1. Use the information in this graph to describe the change in the size of the
human population over the past 200 years.
2. Convert the information in the graph into a table.
3. In pairs or groups, discuss what causes an increase in the size of a
population.
4. In pairs or groups, discuss the challenges caused by increasing human
population.
You can find out the most up to date global population figures by following this link.
http://www.worldometers.info/world-population/
http://www.breathingearth.net/
Alternatively watch the flash video ‘How many people can live in Planet
Earth’.
You may wish to have a class discussion about what you can learn from these
websites.
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National 5 Biology
4.1 Increasing Food Production
4.1.1 Intensive Farming
The most obvious consequence of an increase in the size of any population is that
the increasing population needs increased food yield to maintain its size. For
humans, this means that one of the greatest challenges of the 21 st Century will be
to improve farming techniques so that enough food is produced to support the
expanding population. To achieve this, farming methods will have to become more
intensive.
Monoculture is an intensive farming technique of producing or growing a single crop
or plant species over a wide area and for a large number of consecutive years.
Battery Farming means confining animals to small spaces as they grow. This
reduces the amount of energy they lose from movement therefore more energy is
available for growth.
Intensive farming also makes use of pesticides to kill of any insects that eat the
crops and herbicides to kill of weeds or other unwanted plants that would compete
for nutrients.
Intensive farming often results in a large increase in the amount of food that is
produced which reduces the cost of producing the food making it cheaper for
consumers. However intensive farming techniques usually also result in a decrease
in biodiversity.
Learning Activity 2
1. Explain the need for intensive farming.
2. Describe what a monoculture is.
3. Link your learning – think back to biotic factors. What is the link between
herbicides and competition?
4.1.2 Fertilisers
The Nitrogen Cycle – Living things, as well as being partly made from
protein, need to be able to synthesise a wide variety of proteins in order to
survive. In your own body for instance, DNA contains the code needed to make
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National 5 Biology
the proteins that control what your cells do, e.g. enzymes that speed up chemical
reactions, hormones that send messages between different parts of the body and
antibodies that fight infections.
Nitrogen is an essential element for making protein. It is not possible to make
proteins with out it. Animals can obtain nitrogen from their diet, by eating plants
or other animals. Plants can obtain nitrogen from the soil. However, there is a
finite (limited) amount of nitrogen on Earth. Nitrogen needs to be constantly
recycled in a series of event called the Nitrogen Cycle.
Learning Activity 3
Read the questions below carefully. Think about what the answers might be.
1. What do plants and animals need nitrogen for?
2. How is nitrogen gas turned into nitrates?
3. How do animals get the nitrogen they need?
4. Name three ways nitrogen from living things can be returned to the soil.
5. What do detritivors and decomposers do?
6. What is the difference between nitrifying bacteria and denitrifying
bacteria?
You need watch the video link below and use it to help answer the questions.
Pay attention!
https://www.twigonglow.com/film/the-nitrogen-cycle-1224/
Ask your teacher to check your answers and make any corrections before
attempting the next task.
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National 5 Biology
Learning Activity 4
Collect an nitrogen cycle diagram. Use the answers to your questions to complete
it, then paste it into your jotter.
Algal Blooms
An algal bloom is a rapid increase or accumulation in
the population of algae (typically microscopic) in a
water system. Cyanobacteria blooms are often
called blue-green algae.
Algal blooms can be caused by fertilisers leaching
into rivers and lakes. The minerals in the fertilisers
encourage the algae to grow very quickly.
When the algae die the bacteria that decompose them undergo a massive
population explosion. As they respire they use up all of the oxygen in the water,
meaning that the animals living in the water die from lack of oxygen.
Learning Activity 5
1. What are algae?
2. How do fertilisers cause algal blooms?
3. Explain how algal blooms lead to a decrease in biodiversity.
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National 5 Biology
4.1.3 Pesticides
A pesticide is a substance used to kill any organism thought to be a pest. Common
pesticides include herbicides for destroying unwanted plants, insecticides for
killing insects, fungicides for controlling the gowth of mould and disinfectants for
preventing the spread of bacteria.
Pesticides are commonly used in intensive farming to protect food crops. A
disadvantage of this is that humans and other animals are exposed to pesticides
through the food chain. There are serious concerns about the effects that
pesticides can have on human health and biodiversity generally.
Learning Activity 6
1. Explain what a pesticide is and explain why humans would use them.
2. Use the information from thew passage to complete the table below:
Bioaccumulation
Because some pesticides are not biodegradable they can work their way up the
food chain. Organisms higher up the food chain
receive larger doses of the pesticides and this can
be harmful.
Learning Activity 7
1. Write a sentence to explain what
bioaccumulation means.
2. Why do animals at the top of the food chain
get the largest dose?
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National 5 Biology
A Short History of DDT
In the 1940’s, during the second world war, a
pestidice called DDT was used to control diseases like
malaria and typhus amongst soldiers and civilians.
After the war DDT was used extensively in
agriculture because it was effective at killing the
insects that damaged food crops. Unfortunately DDT
had some uninitended side effects. This included
poisoning of non-target populations and led to a
decline in the numbers of several species, such as the
Bald Eagle. Due to it’s overuse some mosquito
populations (which spread malaria) developed
resistance to the pesticide, making them much harder
to kill. There is also evidence that persticides like
DDT can be washed into rivers and lakes which can
affect the organisms living in the water. As a result
of these side effects, the use of DDT has been
banned worldwide since 2004.
Adverse Effects of Pesticides: Neonicotinoids and Honey Bees
Neonicotinoids are a type of insecticide that are highly effective against a wide
range on crop pests. They have become increasingly popular because they are
toxic to insects at very low doses, but are not toxic to mammals. The use of
neonicotineoids has however been widely linked to a decline in the number of
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honeybees. In 2013 noenicotinoid use was banned in Europe but not in the USA.
Honeybees are important pollinators and several species of plants rely on them in
order to reproduce. Several of our most important food crops are entirely or at
least partly dependent of honeybees for pollination. According to the Florida
department of agriculture the value of honey production during 2012 in Florida
alone was worth $23million.
Learning Activity 8 – Research
You can use this weblink
http://edis.ifas.ufl.edu/pi122 Use web link
above to do some research about pesticides and complete the answers to these
questions.
1. Describe how pesticides affect the honey bee population.
2. What effect would a reduction in honey bee population have on biodiversity?
3. What could the impact of this loss in biodiversity have on people?
Learning Activity 9 – Handling Data
Consider the information in the graphs below.
Think about how the imformation in each graph is related.
Graph 1 – Honey Bee population 1947-2014
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Graph 2 - Neonicotinoid Use in the UK
Graph 3 – Value of honey bee to UK Economy
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National 5 Biology
Life On Earth
National 5 Biology
1. Use graph one to describe the overall trend in honey bee population
between 1947 and 2014.
2. What improvements would you make to graph one to make it easier to
understand?
3. Explain what graph two shows.
4. Is it possible to prove that increased neonicotinoid use is responsible for
honey bee population decline using graphs one and two? Explain your
answer.
5. What information would you need to show that there is a direct link
between neonicotinoid use and honey bee population decline?
6. Use the information provided to describe the effects that a decline in the
number of honeybees could have on humans and on the environment.
Do some research to see what else you can find out about the effect of pesticides
on honeybees and the impact that this has on the environment and society. Try to
find at least two pieces of evidence: one piece of evidence linking neonicotinoids
to honey bee decline and one piece of evidence shows the importance of honey bees
to food production. Produce an information leaflet with your findings.
4.2 Habitat Destruction and the Effects on Biodiversity
Human activities such as agriculture, industry and construction have led to the clearing
of huge areas of natural habitat for farming, mineral extraction, timber and building.
This destruction of habitat has drastically reduced the biodiversity in such areas.
Deforestation has taken place in many parts of the world and continues to take place
today.
The tropical rainforest is one of the most diverse and complex ecosystems and is very
rich in its variety of species.
Large areas are being burned or bulldozed and these
forests are disappearing at an alarming rate.
At one time much of Britain was covered with
oak woodland and Scotland had the huge
Caledonian pine forest.
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Over the last few
Life On Earth
hundred
National 5 Biology
years
these
areas
have
been
steadily cleared. Today there is very little
of
these
natural
woodlands
left,
even
hedgerows are being removed to allow for
larger fields.
More recently, forests of coniferous trees such as spruce and pine have been planted to
produce timber for construction and paper. These new forests, however, have much less
biodiversity.
Desertification is the process by which fertile land becomes desert, typically as a result
of drought, deforestation or inappropriate agriculture eg overgrazing.
Pollution is another result of human activity.
Sulphur dioxide is a gas produced by
the combustion of fuels such as coal, oil
and
petrol.
This
causes
habitat
destruction by directly damaging many
plants.
It also dissolves in water to
produce an acid, so rain water is
contaminated.
This acid
rain
can
destroy ecosystems, including forests and lochs.
Untreated sewage provides food for bacteria which use up the oxygen dissolved in
water. Lack of oxygen reduces biodiversity in rivers by killing many animal species.
Deforestation and pollution have caused such great loss of habitats that there is now a
biodiversity crisis which concerns many world governments. This has led to increasing
international action to conserve and carefully utilise biodiversity.
Learning Activity 10
Complete your notes by answering these questions.
1. Name 2 main human activities which can cause habitat destruction.
2. Explain the effect of deforestation on habitat destruction, with reference to:
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an explanation of the term
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the 4 main reasons for carrying out this process
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the 3 types of woodland affected by this process
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the impact of the new forests being planted
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the effect on biodiversity.
Life On Earth
National 5 Biology
3. Explain the effect of sulphur dioxide on habitat destruction, with reference to:
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how this gas is produced
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the effect on plants
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the name of the substance formed when dissolved in water
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the effect of this substance on ecosystems
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the effect on biodiversity
4. Explain the effect of untreated sewage on habitat destruction, with reference to:
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the effect on the number of bacteria in the water
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the effect on the levels of dissolved oxygen
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the effect on biodiversity.
5. Explain what is meant by the term biodiversity crisis.
Indicator Species
Indicator species are species that give scientists information about the conditions
present in an ecosystem. For example, the presence or absence a particular
species may indicate an environmental condition such as
a disease outbreak, pollution, species competition or climate change. Indicator
species can be among the most sensitive species in a region, and sometimes act as
an early warning of environmental change to monitoring biologists.
Learning Activity 11
Insert and complete the Indicator Species in a Polluted River diagram from your pack
into your notes.
Insert and complete the Effect of Pollution diagram from your pack into your notes.
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National 5 Biology
4.3 Biological Control
Biological control is a method of controlling pest species that can be used as an
alternative to using pesticides. Often organisms that are predators of the pest
organism are released. These feed on the pest organism and reduce the number of
pests.
Learning Activity 12
Watch the following video to see two examples of crop protection using biological
control of pests:
http://www.youtube.com/watch?v=Hj3DwimxvvY
Read page 328-329 of National 5 biology text book and complete activity 3.5.14
on p340
4.4 Genetic Modification
Learning Activity 13
Read the following questions:
1.
2.
3.
What does genetic modification really mean?
What is a transgenic organism?
Give an example of a transgenic organism and explain how this organism
benefits humans.
Now watch the video clip below. You should be able to use the information in the
video clip to answer the questions above. You may have to watch the clip more than
once.
https://youtu.be/JMPE5wlB3Zk
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Learning Activity 14
The link below will give you information about why certain genetically modified
organisms are produced. Read the article carefully. You are looking for a reason
why genetically modified crops could have higher yields than other types of
crops. Once you find the reason, try to summarise it in one or two sentences.
http://www.who.int/foodsafety/areas_work/foodtechnology/faq-genetically-modified-food/en/
Learning Activity 15 - Bt Cotton Case Study
Collect the Bt Cotton Case Study information sheet. Read it carefully then
complete the activities below.
1. Bt cotton plants are described as ‘transgenic organisms’. Do you agree with
this description? Explain your answer.
2. In the passage, what is major cause of cotton crop loss?
3. In what way has Bt cotton been genetically engineered?
4. Explain why it was hoped that Bt cotton would increase yield and reduce the
need for insecticides at the same time.
5. Explain how use of Bt cotton might increase biodiversity.
6. Using the evidence from Graph 1 and Graph 3, describe the impact
introducing Bt cotton has had.
7. What evidence is there from Graph 2 to show that Bt cotton may be
responsible for increased insecticide resistance?
8. Table 1 shows the number of tonnes of insecticides used by cotton farmers.
Select the data for ‘sucking insects’, ‘bollworms’ and ‘total insecticides’ for
the years 2001, 2006 and 2011. Rearrange this data as a bar graph (round
the numbers to the nearest hundred or thousand).
9. Using the bar graph you created in Q8 complete the following questions:
a. Describe the effect Bt cotton had on the amount of insecticides used
between 2001-2006.
b. Describe the trend in the amount of insecticide used to overall between
2006 and 2011.
c. Compare the trend in the amount of insecticide used to kill bollworms and
to kill sucking insects between 2006 and 2011.
d. Like bollworms, sucking insects also feed on cotton plants and cause
reduction in crop yield. Why do you think cotton farmers have had to
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start increasing the amount of insecticide they use to kill sucking insects?
Use the data from table one to justify your answer.
10. Overall, do you think the use of Bt cotton is a good idea? Justify your
answer.
Self Evaluation - How well did I do?
How well can you describe the key words/phrases below? Take turns at explaining
what they mean to the person sitting next to you, and then let them explain them
to you.
fertiliser, pesticide, monoculture, insecticide, herbicide, fungicide, yield,
biodiversity, deforestation, pollution, indicator species, sulphur dioxide,
sewage, genetically modified, transgenic, mutation, adaptation, natural
selection, speciation
Use the success criteria sheet to reflect on and evaluate your learning from this
section.
Think carefully and answer the following questions:
1. What skills have you developed over the past few lessons? How do you know
and how could you prove it to someone?
2. What areas have you found difficult? What strategies are you going to use
to overcome these problems?
Discuss this with your teacher and set yourself a learning target – this is what you
will do to improve your knowledge and skills. Update Didbook with a comment about
what you have done well, what you want to improve at doing and how you will do
this.
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