Human impact and conservation

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Lektionsnotizen

Big idea: relationships between people and ecosystems

Big idea (key concept): Relationships. People are part of ecosystems. We depend on them for food, water and air, and our choices change them.
Related concept: Consequences. Every human activity has consequences for other living things, and some of these come back to affect people.
Global context: Globalization and sustainability. Problems such as climate change and overfishing cross borders. Solving them needs countries to cooperate and to use resources in ways that can last.
Biodiversity is the variety of living things in a habitat, an ecosystem or on the whole Earth. It is often measured as the number of different species.
Biodiverse ecosystems give us ecosystem services: pollination of crops, clean water, fertile soil made by decomposers, food, medicines from plants, and flood control. They also tend to be more stable, because if one species declines others can fill its role.
The human population grew from about 1 billion in 1800 to more than 8 billion today. More people need more land, food and energy, and produce more waste.
A species is extinct when no individuals are left alive. The main human causes of species loss are habitat loss, pollution, climate change, overexploitation and invasive species.

What a biodiverse landscape gives us

Habitat loss and land use

Habitat loss is the biggest threat to wildlife. Land is cleared for farming, housing, roads, mining and timber. Even when some habitat is left, it may be cut into small, separated pieces, which are too small for some species to survive.
Deforestation is the clearing of large areas of forest. Without trees, habitats are lost, roots no longer hold the soil so rain causes erosion, less rainwater is absorbed so flooding increases, and less carbon dioxide is removed by photosynthesis.
Burning or rotting felled trees releases the carbon they stored as carbon dioxide, which adds to climate change.
A monoculture is a single crop grown over a large area. It provides few habitats and food sources, so fewer species live there, and pests and diseases can spread quickly between identical plants.
Palm oil is grown in a monoculture in tropical countries, and much of it has replaced rainforest. It gives more oil per hectare than most other oil crops, so replacing it with another crop could need even more land.
Peat bogs are waterlogged ground that store a huge amount of carbon and support specialist species. Draining them for farming or fuel exposes the peat to air, so it decomposes and releases carbon dioxide.

Consequences of deforestation

Pollution: eutrophication and bioaccumulation

Eutrophication is what happens when too many nutrients enter water. Fertiliser or sewage run-off adds nitrates and phosphates, which make algae grow rapidly into an algal bloom on the surface.
The bloom blocks light, so plants below cannot photosynthesise and die. Decomposers such as bacteria multiply as they break down the dead material, and their aerobic respiration uses up the dissolved oxygen. Fish and other animals then die from lack of oxygen.
Eutrophication can be reduced by using less fertiliser, applying it at the right time, leaving strips of plants between fields and rivers, and treating sewage.
Plastic waste breaks down very slowly into tiny pieces. Animals swallow it or get tangled in it, and it is found in oceans all over the world.
Some poisons, such as the pesticide DDT and the metal mercury, are persistent: they are not broken down and not removed from the body. They are stored in the tissues of the organism.
Bioaccumulation is the build-up of a persistent poison in an organism. Because a predator eats many contaminated prey, the poison becomes more concentrated at each step of a food chain, so top predators are most at risk.
DDT thinned the eggshells of some birds of prey, such as peregrine falcons, and their numbers fell. It was banned in many countries from the 1970s, and several populations then recovered.

How eutrophication happens

Climate change

The natural greenhouse effect keeps the Earth warm enough for life. Short-wave radiation from the Sun passes through the atmosphere, the Earth gives out long-wave heat radiation, and greenhouse gases absorb some of it and warm the air. Without it the average temperature would be about −18 °C instead of about 15 °C.
Human activity has strengthened the effect. Burning fossil fuels and clearing forests release carbon dioxide. Cattle, rice paddies and landfill release methane.
Carbon dioxide in the air has risen from about 280 parts per million before the Industrial Revolution to more than 400 today, and the average global temperature has risen by about 1.1 °C. This is the enhanced greenhouse effect, or climate change.
Climate change harms biodiversity. Habitats shift towards the poles and uphill, so species that cannot move or adapt decline. Mountain species can run out of higher ground. Warmer seas bleach corals, and sea ice melts.
Climate change can also upset timing. If insects emerge earlier in a warmer spring but birds hatch at the old time, chicks may miss their food.
The ozone layer is a different problem. The hole in it is not the cause of global warming.

The greenhouse effect and the enhanced greenhouse effect

Overexploitation, conservation and sustainability

Overexploitation means using a resource faster than it can be replaced. Overfishing is catching fish faster than the population can reproduce, so the stock falls.
Sustainable fishing uses quotas (a limit on the catch), a minimum mesh size so young fish escape, protected breeding areas, banning damaging nets such as gillnets, and inspections of catches.
Sustainable forestry cuts only old trees, plants new ones to replace them, protects young trees, and monitors the forest.
Conservation is protecting and managing species and habitats. Strategies include national parks and reserves, laws and agreements that control trade in endangered species, captive breeding and reintroduction, seed banks and gene banks, wildlife corridors and green bridges, and education.
Sustainability means meeting the needs of people today without harming the ability of future generations to meet theirs.
Most decisions involve trade-offs. A reserve may protect a species but limit farmland, and a quota may protect a fish stock but reduce fishers' income for a while. To evaluate a trade-off, ask who benefits, who pays, what the evidence says, and what happens in the short term and the long term.

Nets and quotas protect fish stocks

Think like a scientist: how does fertiliser affect algae?

Question: how does the amount of fertiliser in pond water affect the growth of algae? A teacher sets up four identical clear bottles, each with 200 mL of the same pond water. The bottles receive 0, 1, 2 and 4 mL of a fertiliser solution. They are sealed, placed side by side on a bright windowsill and left for 10 days.
Variables: the independent variable is the volume of fertiliser solution. The dependent variable is the number of algal cells in a 1 mL sample, counted under a microscope. Control variables include the volume and source of pond water, the bottle type, light and temperature, and the time.
Control: the bottle with 0 mL of fertiliser is the control. It shows how much the algae grow in pond water alone.
Results (one experiment, mean of three repeats, thousand cells per mL): 0 mL gave 2, 1 mL gave 5, 2 mL gave 11, 4 mL gave 20.
Pattern: more fertiliser led to more algae in these bottles. The bottles are small and sealed, so the experiment does not show what would happen in a real lake with a stream, fish and changing weather.
Safety: keep the bottles sealed, never drink the water, and wash hands after handling pond water.
Inquiry task: write a conclusion using the data. Then evaluate the method: name one source of error, suggest one improvement, and explain how a farmer might use your results when deciding how much fertiliser to use, weighing crop yield against the risk to water.

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1.What does biodiversity mean?
Easy
- AThe total number of individual animals in a habitat today
- BThe amount of energy flowing through a food chain overall
- CThe variety of different species in a habitat or ecosystem
- DThe number of different habitats found within one country
2.Which of these are benefits that a biodiverse ecosystem can provide? (select all that apply)
Easy
- APollination of food crops
- BFaster soil erosion
- CPlants that give new medicines
- DClean water from healthy wetlands
- ELess carbon stored in the soil
3.A habitat with more species has higher biodiversity than a similar habitat with fewer species.
Easy
True or false?
4.
Two woodland plots each contain 100 sampled trees.
Woodland Number of tree species
A 3
B 7
Which statement is correct?
Easy
- AWoodland B has the higher biodiversity because it has more species
- BWoodland A has the higher biodiversity because it has fewer species
- CBoth woodlands have the same biodiversity because both have 100 trees
- DBiodiversity cannot be compared by counting the number of species
5.Match each cause of species loss to an example.
Medium
- Habitat loss
- Overhunting
- Invasive species
- Climate change
- Animals are killed faster than they can breed
- Warming melts the sea ice that polar bears hunt from
- A forest is cleared to make farmland
- A non-native rat eats the eggs of ground-nesting birds
6.Sea otters eat sea urchins, and sea urchins graze on kelp. If otters are hunted until almost none remain on a coast, what is the most likely effect on the kelp forest?
Hard
- AKelp grows faster because there are fewer predators in the area
- BNothing changes because otters do not eat kelp directly
- CUrchin numbers fall because they lose their main food supply
- DUrchin numbers rise and they overgraze the kelp, so the forest shrinks
7.Explain why humans should care about the loss of biodiversity.
Medium
8.What happens to soil on a steep slope when the trees are cut down?
Easy
- AIt becomes richer because more sunlight reaches the ground
- BRain washes it away because fewer roots hold it in place
- CIt is protected because the stumps trap all of the water
- DNothing changes because soil is held by rock rather than roots

Mehr Fragen

9.Which are consequences of large-scale deforestation? (select all that apply)
Medium
- ALoss of habitat for forest animals
- BMore carbon dioxide in the atmosphere
- CMore water held in the soil
- DIncreased soil erosion
- EA greater variety of species in the area
10.A forest covered 800 hectares. After 10 years of clearing it covers 600 hectares. What percentage of the forest was lost?
Medium
11.Why does a large monoculture usually support less wildlife than mixed farmland?
Easy
- ACrops of one kind always release poisons that kill the other plants nearby
- BIt offers few habitats and food sources, so fewer species live there
- CFarmers always spray every insect from every one of the fields they own
- DA single crop produces much less oxygen than a mixture of crops would
12.Draining a peat bog releases carbon dioxide into the atmosphere.
Easy
True or false?
13.A government plans to replace an area of rainforest with oil palm plantations. Which statement describes both a benefit and a cost?
Hard
- AIt would remove habitat and release stored carbon, and it has no benefits to people
- BIt would bring jobs and income and have no effect on wildlife or the climate
- CIt would protect the soil and increase the variety of species living there
- DIt could bring jobs and export income, but it removes habitat and releases stored carbon
14.Put these events in order to show how deforestation can lead to flooding.
Medium
- Water and soil run quickly into the river
- Trees are cut down on a hillside
- The river silts up and floods the land nearby
- Less rainwater is absorbed and roots no longer hold the soil
15.Which best explains why a growing human population puts pressure on wildlife?
Easy
- AMore land is needed for housing and farming, and more waste is made
- BMore people means that more animals are born to replace the ones lost
- CWildlife needs fewer resources whenever more people are living nearby
- DWildlife stops competing with people for space once farms are built
16.Complete the sentence about forests.
Easy
Cutting down large areas of forest is called ____.
17.What is eutrophication?
Easy
- AThe build-up of poisons in animals at the top of a food chain
- BThe warming of a lake caused by a long spell of hot weather
- CToo many nutrients in water, which leads to a bloom of algae
- DThe loss of oxygen from the air above a polluted city
18.Put the stages of eutrophication in order.
Medium
- Decomposers multiply and use up the dissolved oxygen
- Fertiliser runs off fields into a lake
- Fish and other animals die from lack of oxygen
- Algae grow rapidly and form a bloom on the surface
- Light is blocked and plants below the surface die
19.Why do fish die in a lake with severe eutrophication?
Easy
- AThe fish eat so many algae that they cannot digest them
- BThe extra nutrients make the water too acidic for fish to live in
- CFish cannot swim through water that contains any algae at all
- DDecomposers use up the dissolved oxygen as they break down dead material
20.Why do aquatic plants at the bottom of a lake die during an algal bloom?
Hard
- AThe algae take in all of the carbon dioxide before it reaches the plants
- BThe plants are poisoned by the nitrates that run off from the fertiliser
- CSurface algae block the light, so the plants cannot photosynthesise
- DThe algae grow roots that crowd the plants out of the sediment below
21.Which action would help to reduce eutrophication in a nearby river?
Easy
- AAdding much more fertiliser so that the crop plants grow stronger roots
- BUsing less fertiliser and leaving plant strips between fields and the river
- CClearing away every one of the plants growing along the river banks
- DWarming the river water so that the algae decompose much more quickly
22.Why is plastic waste in the sea a problem for wildlife?
Easy
- AAnimals swallow it or get tangled in it, and it breaks down very slowly
- BIt rots away quickly and uses up nearly all of the oxygen in the water
- CIt warms the sea so much that no animals at all are able to live in it
- DIt dissolves in the seawater and turns the whole sea into poison for fish
23.What is bioaccumulation?
Easy
- AThe build-up of a harmful substance in an organism over time
- BThe growth of algae when too many nutrients enter a lake or pond
- CThe increase in the number of different species living in an area
- DThe spread of a disease from one population to another nearby
24.Why does a heron have a higher concentration of mercury than the plankton in the same lake?
Easy
- AIt absorbs the mercury directly from the air around it through its feathers
- BIt eats many contaminated fish, and the mercury is stored, not broken down
- CIt lives for much longer than plankton, so it makes more mercury itself
- DMercury is only ever made inside the bodies of large animals
25.In an invented example, a poison rises ten-fold at each step of a food chain: plankton → small fish → large fish → heron. The plankton contain 0.2 units. How many units are in the heron?
Hard
26.The pesticide DDT builds up along food chains and thinned the eggshells of some birds of prey.
Medium
True or false?
27.Explain why a top predator is at greater risk from a persistent poison than a producer is.
Medium
28.In the food chain algae → shrimp → small fish → seal, which organism would be expected to hold the highest concentration of a persistent poison?
Easy
- AThe algae
- BThe shrimp
- CThe seal
- DThe small fish
29.Which pair of gases are greenhouse gases?
Easy
- AOxygen and nitrogen gases
- BArgon and helium gases
- COxygen and hydrogen gases
- DCarbon dioxide and methane
30.Put these steps of the enhanced greenhouse effect in order.
Medium
- The Earth gives out long-wave heat radiation
- More greenhouse gases means more heat is trapped and the planet warms
- Short-wave radiation from the Sun passes through the atmosphere
- Greenhouse gases absorb some of this heat
31.Which human activities increase the amount of carbon dioxide in the atmosphere? (select all that apply)
Medium
- ABurning petrol in cars
- BClearing and burning forests
- CPlanting new woodland
- DUsing solar panels
- EBurning coal in power stations
32.Which is a major source of the greenhouse gas methane?
Medium
- APhotosynthesis in leaves
- BEvaporation from the oceans
- CCattle and rice paddies
- DWind turbines
33.As temperatures rise, many mountain plants and animals move uphill. Why are mountain species at particular risk?
Hard
- AThey can run out of higher ground, so their habitat disappears
- BMountain air contains more greenhouse gases than lowland air does
- CMountains become colder as the climate warms, so species die out
- DThey are unable to survive at any height once temperatures rise
34.Global warming is caused mainly by the hole in the ozone layer.
Medium
True or false?
35.Describe two ways that rising temperatures could reduce biodiversity.
Hard
36.What is overfishing?
Easy
- ACatching only the smallest fish in a population
- BFishing in water that is polluted with fertiliser
- CReleasing too many young fish back into the open sea
- DCatching fish faster than the stock can replace them
37.Why does a larger mesh size in a fishing net help to conserve fish stocks?
Easy
- AMore fish are caught each time the net is used
- BYoung fish can escape and grow up to breed
- CThe net floats higher and avoids catching other species
- DAdult fish can escape and are caught later in the year
38.In a simple model a stock of 10 000 fish adds 12% new fish each year. A fleet catches 1500 fish during the year. How many fish are in the stock after one year?
Hard
39.What is the purpose of a fishing quota?
Easy
- ATo make sure that all of the fish caught are the same size
- BTo limit the number or mass of fish that may be caught
- CTo increase the price of fish in the shops
- DTo stop fishing boats leaving harbour at night
40.Match each conservation measure to what it does.
Medium
- Fishing quota
- Minimum mesh size
- Protected breeding area
- Seed bank
- Stores seeds in case wild plants are lost
- Limits how many fish can be caught
- Lets the stock recover with no fishing at all
- Lets young fish escape to breed later
41.Which practices help to make forestry sustainable? (select all that apply)
Hard
- AReplanting new trees
- BCutting down only old trees
- CClear-felling whole hillsides
- DProtecting young trees
- ERemoving every tree from stream banks
42.What is conservation?
Easy
- AUsing up natural resources as quickly as possible
- BBreeding only the largest animals in a species
- CMoving all wild animals into zoos
- DProtecting and managing species and their habitats
43.Which strategy involves breeding endangered animals in zoos and later releasing some into the wild?
Medium
- ACaptive breeding and reintroduction
- BSelective breeding of farm animals
- CSetting fishing quotas for boats
- DBuilding a seed bank for crops
44.Why might a green bridge be built over a motorway?
Medium
- ATo make the road surface last for longer
- BTo stop rain washing soil into nearby rivers
- CTo let animals cross the road between habitats
- DTo increase the speed that traffic can travel
45.What is the main purpose of a seed bank?
Medium
- ATo sell rare seeds to farmers to raise money for zoos
- BTo grow seeds into crops in large factories all year
- CTo keep seeds well away from the animals that eat them
- DTo store seeds so lost wild plant species can be regrown
46.Which definition of sustainability is best?
Easy
- AUsing resources as fast as possible so that people today benefit the most
- BProtecting nature by stopping people from using any resources at all
- CMeeting the needs of people today without harming those of future generations
- DProducing as much food as possible in the shortest possible time
47.A town council can build 200 houses on a wetland that supports rare birds, or on a former factory site that needs an expensive clean-up. Which approach best evaluates the choice?
Hard
- AChoose the cheaper option because money is the only fair measure
- BWeigh the benefits and costs to people and wildlife, using evidence
- CChoose the wetland because it is nearest to where people want to live
- DChoose whichever option most of the council members like the best
48.Protecting a species always means banning all human activity in its habitat.
Medium
True or false?
49.A national park bans farming inside its boundary. Evaluate this decision by giving one benefit and one cost.
Hard
50.Four identical bottles of pond water receive 0, 1, 2 and 4 mL of fertiliser solution. What is the independent variable?
Easy
- AThe volume of fertiliser solution added
- BThe number of algal cells counted in each bottle
- CThe volume of pond water in each of the bottles
- DThe temperature of the room that the bottles are in
51.In the same investigation, which should be kept the same for every bottle?
Medium
- AThe volume of pond water, the light and the temperature
- BThe volume of fertiliser solution added to each bottle
- CThe number of algal cells counted at the end of the test
- DThe colour of the water at the end of the ten days
52.
Mean algal counts after 10 days in an experiment with sealed bottles:
Fertiliser added (mL) Algae (thousand cells per mL)
0 2
1 5
2 11
4 20
Which conclusion is best supported?
Hard
- AFertiliser has no effect at all on how fast algae grow in pond water
- BMore fertiliser gave more algae in these bottles, but a real lake may differ
- CFertiliser added to a real lake will always kill all of the fish living in it
- DAlgae grow much better in pond water that contains no fertiliser at all
53.Three repeats with 4 mL of fertiliser gave 18, 20 and 22 thousand cells per mL. What is the mean?
Medium
54.Suggest what extra evidence you would need before claiming that fertiliser run-off is causing fish to die in a real lake.
Hard

Lernnotizen

## The big idea - **Relationships** and **consequences**: human choices change ecosystems, and those changes affect people too. ## Biodiversity - **Biodiversity** is the variety of species. It gives **ecosystem services** such as pollination, clean water and medicines. - Causes of species loss: habitat loss, climate change, pollution, overhunting, invasive species. ## Habitat loss - **Deforestation** removes habitat, causes erosion and flooding, and adds carbon dioxide. A **monoculture** supports few species. Draining peat releases carbon. ## Pollution - **Eutrophication**: nutrients, then algal bloom, then plants die, decomposers use up oxygen, then fish die. - **Bioaccumulation**: persistent poisons such as DDT and mercury become more concentrated at each step of a food chain. ## Climate change - Burning fossil fuels and clearing forests release carbon dioxide, and farming releases methane. More heat is trapped, so habitats shift and some species decline. ## Conservation - **Overfishing** is controlled with quotas, mesh size and breeding areas. Conservation uses reserves, captive breeding, seed banks and corridors. - **Sustainability** means meeting today's needs without harming the future. Evaluate **trade-offs** with evidence over the short and long term. ## Think like a scientist - In the fertiliser test, the volume of fertiliser is the independent variable and algal count is the dependent variable. Sealed bottles do not prove what happens in a real lake.

Biodiversity: The variety of living things in a habitat, an ecosystem or on Earth, often measured as the number of species.
Ecosystem service: A benefit people get from ecosystems, such as pollination, clean water, fertile soil and medicines.
Extinct: A species is extinct when no individuals are left alive.
Deforestation: The clearing of large areas of forest.
Monoculture: A single crop grown over a large area, which supports few species.
Eutrophication: Too many nutrients in water, causing an algal bloom, loss of oxygen and the death of aquatic organisms.
Persistent poison: A harmful substance that is not broken down or removed from the body, such as DDT or mercury.
Bioaccumulation: The build-up of a persistent poison in an organism, becoming more concentrated at each step of a food chain.
Greenhouse gas: A gas, such as carbon dioxide or methane, that absorbs heat in the atmosphere.
Climate change: Long-term warming and other changes caused by the enhanced greenhouse effect.
Overfishing: Catching fish faster than the population can reproduce.
Quota: A limit on the amount of fish or other resource that may be taken.
Conservation: Protecting and managing species and their habitats.
Sustainability: Meeting the needs of people today without harming the ability of future generations to meet theirs.
Trade-off: A decision in which a benefit in one area has to be weighed against a cost in another.

Karteikarten

What is biodiversity?

The variety of living things in a habitat, an ecosystem or on Earth, often measured as the number of species.

Name three ecosystem services.

For example: pollination of crops, clean water, fertile soil, food, medicines, flood control.

List five human causes of species loss.

Habitat loss, climate change, pollution, overhunting or overfishing, and invasive species.

Give four effects of deforestation.

Loss of habitat, soil erosion, more flooding and more carbon dioxide in the air.

What is a monoculture and why is it bad for wildlife?

A single crop over a large area. It offers few habitats and foods, so few species live there, and pests spread quickly.

Why are peat bogs important?

They store large amounts of carbon and support specialist species. Draining them releases carbon dioxide.

Describe the stages of eutrophication.

Nutrients run off into water, algae bloom, light is blocked and plants die, decomposers use up oxygen, and fish die.

What is a persistent poison?

A harmful substance that is not broken down or removed from the body, such as DDT or mercury.

What is bioaccumulation?

The build-up of a persistent poison in an organism, becoming more concentrated at each step of a food chain.

Why are top predators most at risk from persistent poisons?

They eat many contaminated prey, so the poison is concentrated at each step up the food chain.

Name two greenhouse gases and a source of each.

Carbon dioxide from burning fossil fuels and clearing forests. Methane from cattle, rice paddies and landfill.

Explain the enhanced greenhouse effect.

More greenhouse gases absorb more of the heat the Earth gives out, so less escapes and the planet warms.

How can climate change harm biodiversity?

Habitats shift, so species that cannot move or adapt decline. Corals bleach, sea ice melts and timing of food supplies can be upset.

What is overfishing?

Catching fish faster than the population can reproduce.

Name three ways to make fishing sustainable.

Quotas, a minimum mesh size so young fish escape, and protected breeding areas.

Give three conservation strategies.

For example: reserves and national parks, captive breeding and reintroduction, seed banks, wildlife corridors, laws on trade.

What is sustainability?

Meeting the needs of people today without harming the ability of future generations to meet theirs.

How do you evaluate a trade-off?

Weigh the benefits and costs for people and wildlife, use evidence, and consider both the short and long term.

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Woodland	Number of tree species
A	3
B	7

Fertiliser added (mL)	Algae (thousand cells per mL)
0	2
1	5
2	11
4	20