That Rapid Growth in the Human Population Means That More Waste Is Produced
Students should learn:
- that rapid growth in the human population means that more waste is produced
- that humans reduce the amount of land available for other animals and plants by building, farming, quarrying and dumping waste.
- explain how human population growth has occurred
- explain why raw materials are rapidly being used up and more waste is being produced
- describe the effects of population growth on land and resources.
- analyse and interpret scientific data concerning human population growth and environmental issues.
Waste may pollute:
– water, with sewage, fertiliser or toxic chemicals
– air, with smoke and gases such as sulfur dioxide, which contributes to acid rain
– land, with toxic chemicals such as pesticides and herbicides, which may be washed from the land into waterways. [B3.4.1 b)]
Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste. [B3.4.1 c)] / Chapter map: How humans can affect the environment
Lesson structure / Support, Extend and Practical notes
Starters
How many people in the World? – Hold a brief competition to guess how many people are alive on Earth today. The students should write their estimates on cards and all stand up, holding up their estimates in front of them. Count alternately upwards and downwards towards the actual number, telling students to sit down as their answers are discounted. (5 minutes)
What sort of problems do we have if we go to pop festivals? – Show a picture of masses of people at a festival like Glastonbury. Show some figures to illustrate how the festival has grown over the years (you can search the internet) Ask: ‘What are the problems? How do we cope with the basic needs of living?’ Support students by prompting them to think of their basic requirements. Extend students by getting them to draw comparisons with refugee camps and also to consider long-term effects on the environment. Draw comparisons with the human population on the whole of the planet. (10 minutes)
Main
- Consider how many babies will be born during this lesson. The figure is about 240 babies per minute. The point can be very pertinently made by keeping a running total on a board at the front, with a student adding to the total every 5 minutes (about 1200 every 5 minutes).
- As an alternative, project an internet-based global human population tool such as Worldometer This can run throughout the lesson with notes of the numbers being taken every few minutes.
- Supply or project a partially-completed graph of population numbers, and ask students to suggest what will happen over the next few hundred years if population growth continues as it is today. It might be interesting to compare World population with projected numbers for the developed World, Europe or the UK.
- This topic lends itself well to research projects. The class could split up into small groups, each group taking one aspect and prepare a report for the rest of the class. The topics could include ‘pollution’, ‘use of resources’, ‘wildlife’, ‘quarrying’, ‘housing and roads’, ‘waste disposal’, etc.
- Each group would need to be given a brief for their research project and access to suitable resources. A library box on each topic would be helpful. Probably some homework time could be allocated to this for the research, and the reports given in class, together with worksheets, so that students could make notes on the topics that other students researched.
Spaceship Earth analogy – Project a spaceship picture and draw out the ‘Spaceship Earth analogy’ – we have broken into the store room, the life support system is failing and breeding is occurring quickly on finite resources. Ask the students to compose a radio message from the spaceship, asking for help or advice from anyone out there. Support students by getting them to fill in the blanks in a pre-prepared message. Extend students by asking them to be more specific about the type of help they think will be needed. (5 minutes)
Baby counter – Look at the count started at the beginning of the lesson. Create and show a PowerPoint presentation of real baby photographs very rapidly. If you give each one a name, then this emphasises what is really happening and that it will have an impact on them and their children in the future. If you have the resources, it could be good to vary the ethnic origin and names of the children in proportion to the increases in World population. Discuss what it is that balances this rapid increase in the population of the World. (10 minutes) / Support
Give students a picture of a very crowded room and ask them to imagine what could happen if all the people they knew come to live in their house. Ask: ‘What problems would there be?’ They could fill in a list or be shown pictures to act as visual prompts.
Extend
Ask students to analyse why people in the developing World have such large families. They could write an article suggesting how to get round this problem.
Course / Subject / Topic / Pages
Biology / Biology / B3 4.1 The effects of the population explosion / Pages 264-265
Learning objectives / Learning outcomes / Specification link-up / Kerboodle
Students should learn:
- that more waste is being produced which may pollute water with sewage, fertilisers or toxic chemicals
- that land can be polluted with toxic chemicals that can be washed into water.
- describe how pesticides and herbicides can pollute the land
- understand the need for the proper treatment of sewage
- describe what happens when water is polluted by fertilisers.
- assess the impact of land and water pollution on the environment.
– water, with sewage, fertiliser or toxic chemicals …
– land, with toxic chemicals such as pesticides and herbicides, which may be washed from the land into waterways. [B3.4.1 b)]
Controlled Assessment: B4.3 Collect primary and secondary data. [B4.3.2 a) b) c) e) f)]; B4.4 Select and process primary and secondary data. [B4.4.1 a) b)], [B4.4.2 a) b) c)]; B4.5 Analyse and interpret primary and secondary data. [B4.5.4 a) b) c)]
Lesson structure / Support, Extend and Practical notes
Starters
You don’t know what you’ve got ’til it’s gone – Play some suitable sections from the Joni Mitchell song ‘Big Yellow Taxi’. Give the students a copy of the lyrics. Ask them to comment on any sections that they identify with or which touch them in any way. The song was written in Hawaii in response to the parking lots, which blight the natural beauty of some areas. (5 minutes)
Word meanings. Show the students flashcards with the words ‘pesticide’, ‘herbicide’, ‘pollution’, ‘sewage’, ‘eutrophication’, ‘toxic’ and ‘fertilisers’ on. Ask for individual student responses to these words. Support students by giving them the more straightforward terms (pollution, sewage, pesticide). Extend students by giving them all the terms and getting them to think about definitions, especially of the more straightforward ones. (10 minutes)
Main
- Consider what happens to our waste. Build up a list of waste materials from households and sort out what is biodegradable, what is recyclable and what needs to be treated to avoid polluting the land. Draw out the need for proper treatment of sewage. Contrast what happened to human waste before sewage treatment was introduced and the link with the spread of infectious diseases. Show pictures of sewage treatment plants and draw up a flow chart to summarise what happens to sewage. If possible, and convenient, organise a trip to a sewage treatment plant. As an alternative, get students to find out what happens to the sewage in their area.
- Students could discuss the positive and negative aspects of farming and produce one poster depicting the benefits of farming and another to show farming as damaging to the environment. This could be done in groups, making use of ICT and the posters displayed for further class discussion.
- Provide an exposition or PowerPoint presentation on DDT – its successful use as an insecticide, worldwide use and subsequent ban, as it was discovered to accumulate in food chains and also in the fatty tissue of humans. The BBC website has a comprehensive article on DDT, why it was banned and its present uses.
- The effect of additional nitrates and phosphates on the growth of water plants, such as duckweed (Lemna sp.) or algae, can be demonstrated by setting up the following experiment using different concentrations of a commercial fertiliser (see ‘Demonstration support’).
- The data collected can be used to plot graphs showing the number of leaves produced at each concentration over time. Students can link this experiment to the effect of fertiliser run-off on the vegetation in streams and ponds. This experiment introduces many ‘How Science Works’ concepts.
Keywords matching activity – Using a digital utility such as Hot Potatoes ( create a set of keywords and a set of definitions. The students have to match these to each other. (5 minutes)
Every label tells a story – Show the students the labels from a number of herbicides and pesticides (label information is freely available from the internet. Get them to draw from the labels any information they see as relevant regarding the safety of use of these products. Support students by giving them simplified versions of the labels or asking them for very specific, easily located data. Extend students by setting them more difficult and demanding tasks related to the labels. (10 minutes) / Support
Give students the stages in the treatment of sewage which they have to put in order. If these are on slips of paper, the students can stick them into their notebooks.
Extend
Ask students to find out more about bioaccumulation and biomagnifications using the internet. They could produce a poster explaining the terms and giving more examples.
Demonstration support
The effect of additional nitrates and phosphates on the growth of water plants
Equipment and materials required
Small beakers; tap/pond water; Lemna plants; commercial fertiliser (Baby Bio).
Details
Fill five small beakers with water from the same source (tap water or pond water) and add different concentrations of the fertiliser to four of the beakers, leaving one untreated as the control. Refer to the manufacturer’s instructions to decide on the concentrations to use. Mark the beakers with the concentration used. Mix thoroughly and place ten duckweed plants in each beaker. Count and record the number of leaves on the plants in each beaker. Place all the beakers in the same conditions of light and temperature. Record the total numbers of leaves on the plants at weekly intervals. One set of beakers could be started about 3 weeks beforehand, so that some results are available in the lesson. Students could continue to monitor these, together with those set up during the lesson.
Safety: Care when handling the fertiliser.
Course / Subject / Topic / Pages
Biology / Biology / B3 4.2 Land and water pollution / Pages 266-267
Learning objectives / Learning outcomes / Specification link-up / Kerboodle
Students should learn:
- that air can be polluted with smoke and gases, such as sulfur dioxide, which contributes to acid rain
- that acid rain may damage trees
- that plants and animals cannot survive if the water in rivers and lakes becomes too acidic
- that tiny solid particles polluting the air can cause global dimming.
- describe how acid rain is formed
- describe some of the effects of acid rain on living organisms
- explain how air pollution can result in global dimming.
- analyse and interpret scientific data concerning the effects of acid rain.
– …air, with smoke and gases such as sulfur dioxide, which contributes to acid rain. [B3.4.1 b)]
Analyse and interpret scientific data concerning environmental issues. [B3.4]
Controlled Assessment: B4.1 Plan practical ways to develop and test their own scientific ideas. [B4.1.1 a) b)]; B4.3 Collect primary and secondary data. [B4.3.1 a)], [B4.3.2 a) to f)]; B4.4 Select and process primary and secondary data. [B4.4.1 a) b)], [B4.4.2 a) b) c)]
Lesson structure / Support, Extend and Practical notes
Starters
Demonstration of combustion and the production of acid gases – Wearing eye protection, set fire to a bunch of matches inside a gas jar using a fuse (Care!). Have some hydrogencarbonate indicator (or universal indicator) in the bottom of the jar. Shake the jar after the ignition and ask the students to observe the colour change. (5 minutes)
The acid test – If it is raining, send a student out to collect a sample of rainwater. If it is not raining, then use a sample collected earlier. Revise the pH scale and then test the rainwater with pH paper. They could also test tap water, some more acid things and some alkaline liquids so that the colour change is obvious. Support students by getting them to record the results of these tests as colours on a bar chart. Extend students by getting them to compare the pH of rainwater with that of local pond water. They could also explain why rainwater is likely to be acid. (10 minutes)
Main
- Consider the effect of acid rain on seedlings (see ‘Practical support’). This practical can either be set up as a class demonstration or the students could set up their own experiment, working in groups. The investigation introduces ‘How Science Works’ concepts: predictions can be made, observations recorded and conclusions drawn.
- An alternative to the experiment suggested above would be to investigate the effect of acid rain on the germination of cress seedlings (see ‘Practical support’). Make daily observations and count the number of seeds that germinate in each dish. Calculate the percentage germination and display the results graphically. Again, this exercise could be used to introduce ‘How Science Works’ concepts.
- Demonstrate the gases produced by fossil fuels by burning some coal or other sulfurous fuel (see ‘Practical support’).
- This demonstration can be linked to a survey of the fumes emitted by generating power using fossil fuels, the introduction of ‘cleaner’ petrol etc. Some research on the components of the waste gases would benefit any discussions on the links between burning fossil fuels and acid rain. Students could be provided with some facts and figures available from chemistry textbooks or the internet.
- The People’s Century series (from PBS) has some good material on acid rain, its sources and effects.
Acid lake effects – Acid rain causes the water in freshwater lakes to become acidic. Ask students to suggest what effects a change in pH might have on life in freshwater, to include the effects on insects, insect larvae, water plants an all stages of fish development. (5 minutes)
Air pollution – Search the web for images of ‘smog’ and show students the effects of air pollution. Read a description of what it was like to be in a ‘pea souper’. Ask students to write a time travelling ‘Thank you’ letter to the people responsible for the Clean Air Act, making our cities more pleasant places. Support students by giving them some phrases to incorporate into a letter. Extend students by encouraging them to include references to health, wildlife, buildings and the environment generally. (10 minutes) / Support
Ask students to imagine what it would be like if the clouds rained vinegar! Give them a picture of a giant vinegar pot shaking over the roofs of a town. Ask: ‘What would happen to the animals and plants? How could the rain be like vinegar?’ Show them the results of ‘Demonstration of combustion and the production of acid gases’ and compare with the colour change if vinegar is tested.
Extend
Get students to research sulfur in proteins and make a link with the amino acid cysteine, as a component of proteins in plants and animals. This in turn links with the sulfur released when fossil fuels are burned.
Practical support
Investigate the effect of acid rain on seedlings
Equipment and materials required
Three or four trays or pots of cress seedlings, 1 M HCl, 0. 1 M HCl and 0.5 M HCl. CLEAPSS Hazcard 47A Hydrochloric acid – corrosive.
Details
For each investigation, you will need three or four trays or pots of cress seedlings, all at the same stage of growth. One set should be sprayed with water, one with 0.1 M HCl and one with 0.5 M HCl. If desired, a fourth set could be sprayed with 1.0 M HCl. The pots should be kept in the same place and observed after a few days.