Download human-impact

Quick Question
1. What do humans require to live?.
Food, oxygen and water.
2. Give an estimate of the current world
population.
7,253,730,323 (in August 2014)
3. Can you think of any problems caused
by an increase in human population?
Increased demand for food, increased pollution ……
National 4 Biology
Key Area 2:
Impact of population growth and natural hazards
on biodiversity
National 5 Biology
Key Area 5:
Human impact on the environment
National
4&5
outcomes
By the end of the lesson
you will be able to …..
• Describe the effect of an increased
human population on the environment
• Describe what a pesticide is and why it
is used
• Define the term bioaccumulation
• Describe the effect bioaccumulation
has on the environment
Breaking news:
In October 2011 the world population has reached
7 billion...
A newly born baby girl named Danica Camacho, the
Philippines' symbolic seven billionth baby, as part of
the United Nations' seven billion global population
projection, lies on the chest of her mother Camille in
government's Fabella Maternity hospital in Manila on
Monday Oct. 31, 2011.
Can you think of any problems this might cause?
A happy occasion?
• The birth of the seven
billionth person on Earth
came with a warning from
the WHO:
“We should really focus on the
question of whether there will
be food, clean water, shelter,
education and a decent life for
every child," he said. "If the
answer is 'no,' it would be
better for people to look at
easing this population
explosion."
Human Impact on the
Environment
• Increasing human
population requires an
increased food yield.
• This is achieved by
• Intensive
agriculture
• Use of fertilisers
• Use of pesticides
Think, Pair, Share!
What are
pesticides?
Who uses
them?
Why are they
used?
Pesticides
• Pesticides are chemicals
used to kill organisms that
are in competition with or
eating crop plants.
• There are several types
of pesticides:
 Herbicides are used
to kill plants
 Insecticides are
used to kill insects
Pesticides
• Pesticides will
either:
– break down and
become harmless
over time
– or persist in the
environment (not
broken down).
Bioaccumulation
• It was discovered that pesticides, e.g. DDT, bioaccumulates
(builds up) in the bodies of organisms.
• It is passed from one organism to the next through the
food chain.
• As the chemical is passed on up the food chain it increases
in toxicity and can reach lethal levels.
• Every molecule of DDT sprayed in the 50’s is still in food
chains today!
Bioaccumulation
If they eat enough DDT,
birds lay eggs with very
thin shells that break
before they are ready to
hatch.
How might this effect the
sparrowhawk population,
and the other members of
the food chain?
Pesticide Problems:
Bioaccumulation
Bioaccumulation
SentenceisActivity!
the build up of
harmful
Use the
chemicals
cards toinmake
the bodies
up the of
definition organisms.
for bioaccumulation.
Pesticide Problems:
Bioaccumulation
bioaccumulate
Pesticides, e.g. DDT, _____________
bodies
(builds up) in the _________
of organisms.
It is passed from one organism to the next
through the _____
As the
food_______.
chain
chemical is passed on up the food chain it
toxicity and can reach
increases in _______
lethal levels.
_______
 food chain
 toxicity
 bioaccumulate
 Bodies
 lethal
Quick Question
1. What is bioaccumulation?
The build up of harmful chemicals in the bodies of organisms
2. Match the term with it’s description.
A. Intensive farming
1. Farming method that uses
chemicals and machinery to
maximise yield.
B. Fertiliser
2. A chemical used to kill
organisms competing with crops.
C. Pesticides
3. A chemical added to soil to
improve it’s nutrient content
National
5
outcomes
By the end of the lesson you
will be able to …..
• Describe the use of biological control
and GM crops as an alternative to
pesticides.
Pesticides & Fertilisers
• Pesticide and
fertiliser use have
positives and
negatives
• Pesticides –
bioaccumulation
• Fertilisers – algal
bloom
Biological Control
• An alternative to
pesticide use
• Biological control is the
control of a pest species
by the introduction of a
natural enemy or
predator.
• E.g. using ladybirds to
control greenfly
infestations.
Ladybirds will munch
50-60 greenfly a day!
GM crops
• Used as an
alternative to
pesticides
• Genetically modified
(GM) crops are
produced when a
useful gene from
another organism is
inserted into the cells
of a plant.
GM crops
enable more
food to be
produced.
reduce
reliance on
pesticides.
 unethical
 insects and
weeds can develop
a mutation against
the resistant
plant.
 can lead to
genetic pollution
Quick Question
1. Name an alternative to chemical fertilisers
Manure OR compost OR growing leguminous plants
2. What is biological control?
The use of a natural predator to control a pest species
3. Give an example of biological control
Ladybirds and greenfly
National
5
outcomes
By the end of the lesson you
will be able to …..
• Define the term “Indicator Species”
• Describe how indicator species can be
used to indicate pollution levels.
Which is cleaner?
• 30 seconds to decide… which do you
think is cleaner?
• How do you know?
Which would you rather drink?
• 30 seconds to decide… which do you
think is safer to drink?
• How could you know?
Where would you rather
breathe?
• 30 seconds to decide… where do you
think it is safer to breathe?
• How could you know?
Pollution
Would you expect the same organisms
to be present in both rivers?
• Biologists use the presence or absence of
certain species to assess how polluted an
ecosystem is – Indicator species
Indicator Species
• Indicator species are species that by
their presence or absence indicate
levels of pollution. E.g.
– freshwater invertebrates indicate water
pollution
– Lichen indicate air pollution