1. Increased demand for food, increased pollution ……
Quick Question
What do humans require to live?.
Give an estimate of the current world population.
Can you think of any problems caused by an increase in human population?
Food, oxygen and water.
7,253,730,323 (in August 2014)
Increased demand for food, increased pollution ……

2. National 5 Biology Key Area 5: Human impact on the environment
Impact of population growth and natural hazards on biodiversity
National 5 Biology
Key Area 5:
Human impact on the environment

3. By the end of the lesson you will be able to …..
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

4. Breaking news:
In October 2011 the world population has reached 7 billion...
Can you think of any problems this might cause?
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.

5. 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."

6. 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
Remind them that they already covered intensive agriculture (with biodiversity) and fertilisers (with the nitrogen cycle)

7. Think, Pair, Share! What are pesticides? Who uses them?
Why are they used?

8. 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

9. Pesticides Pesticides will either:
break down and become harmless over time
or persist in the environment (not broken down).

10. 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!

11. 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?
Rapid decline in bird of prey and other bird species lead to a ban in many countries.
Birds – brown pelican and then a peregrine falcon (both decimated and pushed to the brink of extinction because of DDT use)

12. Pesticide Problems: Bioaccumulation
Sentence Activity!
Use the cards to make up the definition for bioaccumulation.
Bioaccumulation is the build up of harmful chemicals in the bodies of organisms.
Sentence available in B204

13. Pesticide Problems: Bioaccumulation
bioaccumulate
Pesticides, e.g. DDT, _____________ (builds up) in the _________ of organisms. It is passed from one organism to the next through the _____ _______. As the chemical is passed on up the food chain it increases in _______ and can reach _______ levels.
bodies
food chain
toxicity
lethal
food chain
toxicity
bioaccumulate
Bodies
lethal

14. Quick Question What is bioaccumulation?
The build up of harmful chemicals in the bodies of organisms
2. Match the term with it’s description.
1. Farming method that uses chemicals and machinery to maximise yield.
A. Intensive farming
B. Fertiliser
2. A chemical used to kill organisms competing with crops.
3. A chemical added to soil to improve it’s nutrient content
C. Pesticides

15. By the end of the lesson you will be able to …..
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.
Not a full lesson!

16. Pesticides & Fertilisers
Pesticide and fertiliser use have positives and negatives
Pesticides – bioaccumulation
Fertilisers – algal bloom

17. Ladybirds will munch 50-60 greenfly a day!
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 greenfly a day!

18. 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.

19. 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

20. Quick Question 2. What is biological control?
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

21. By the end of the lesson you will be able to …..
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.
Not a full lesson!

22. Which is cleaner? 30 seconds to decide… which do you think is cleaner?
How do you know?

23. Which would you rather drink?
30 seconds to decide… which do you think is safer to drink?
How could you know?

24. Where would you rather breathe?
30 seconds to decide… where do you think it is safer to breathe?
How could you know?

25. Pollution
Would you expect the same organisms to be present in both rivers?
Try and tease it out of them
Why would you not expect them to be the same?
What will there be more of in the ‘clean’ water? Link back to algal blooms.
Biologists use the presence or absence of certain species to assess how polluted an ecosystem is – Indicator species

26. 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