Topic 9 - Ecosystems and Material Cycles✅

OK PURR LOWK ATE THAT UP THIS TOPIC IS DONEZO GCSE Biology Edexcel Topic 9 – Ecosystems and material cycles

Describe the different levels of organisation in ecosystems

• All the organisms and the environment they live in form an ecosystem

• All the organisms that live in an ecosystem form a community

• The community is made up of populations of different species

• Each population lives in a different habitat in the ecosystem

Explain how communities can be affected by abiotic factors

• Water – if there is a drought or a flood then it will cause species to die out

• Temperature – if the species are not at the optimum temperature to survive, they won’t be adapted well, and will die

• Light – plants need enough light to photosynthesise

Explain how communities may be affected by biotic factors

• Competition – when organisms need the same resources at the same time they will struggle against other organisms. An increase or decrease in population results in change of competition

• Predation – if there are lots of predators, number of prey will decrease. And if there is not many predators, number of prey will increase

Describe the importance of interdependence in a community

• Interdependence is important because certain species depend on others for food, shelter, pollination etc

• This means that a change in the population of one species will have a great knock-on effect on other species in the same community

Describe how the survival of some organisms is dependent on other species

• Parasitism is when one species benefits, and the other is harmed

  • e.g. fleas and humans – the fleas feed off the humans, but the human skin gets irritated from the fleas sucking its blood

• Mutualism is when both species benefit from the relationship

  • E.g. ants and acacia trees – ants kill caterpillars (which harm acacia trees as they eat leaves), and the acacia tree grows thorns to provide homes for some species of ant

Explain how some energy is transferred to less useful forms at each trophic level

why energy is lost between trophic levels:

• not all of the material ingested by an organism is absorbed

• some is egested as faeces

• some energy is transferred from organisms to the surroundings as heat

• some energy is used for movement and reproduction

• lots of energy is used for respiration
  

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  impact of energy losses:

• limits the length of food chains

• fewer organisms at each trophic level

• gives triangular shape to pyramid of biomass

Calculate efficiency of energy transfers between trophic levels

(energy transferred to next level / energy available at previous level) x 100

Explain the positive and negative impacts of fish farming

• pros:

  • easy access to fishmeets the demand of fish,

  • reduces overfishing of wild fish,

  • reliable income for fish farmers

• cons:

  • loss of biodiversity,

  • increased chance of disease as fish are kept in cramped conditions,

  • uneaten food and faeces can contaminate surrounding water

Explain the pos. and neg. impacts of introduction of non-indegenous species

• pros:

  • new species can be introduced to reduce a predator. E.g. cane toads introduced to kill crop-destroying beetles

• cons:

  • new species can flush out native ones if they bring disease.

  • they compete with the native species for food, water, light and space which can result in one dying out.

Explain the pos. and neg. impacts of eutrophication

• Water becomes anoxic so aquatic animals die due to oxygen depletion,

• water bodies smell and look unpleasant due to algae,

• fishing industry fails as there is less fish in the rivers because of lack of oxygen

Explain the benefits of maintaining local and global biodiversity

• Maintaining biodiversity is good because it keeps the ecosystem stable and reliable.

• Biodiversity supports fishing and tourism industries which boost the economy.

• Biodiverse ecosystems help humans, as a lot of plants and animals provide food and medicine to humans

Explain the impacts of reforestation

• restores habitats for wildlife that may have lost homes because of deforestation.

• Helps fight against climate change (more trees = more carbon absorbed, and more oxygen emitted)

Explain the impacts of conservation of animal species

• Conservation of animal species helps prevent extinction.

• When animals go extinct there are big effects on the ecosystem; one species can destabilise it all.

• Additionally, maintaining animal diversity means that there is genetic diversity within populations.

  • Genetic diversity means if disease comes or the environment changes, at least some of the species will survive.

    • Therefore means the population won’t die out and over time leads to natural selection

Describe biological factors affecting levels of food security (3)

• New pests and pathogens

  • these can destroy crops and result in low food security

• Increased animal farming + meat and fish consumption

  • when more meat and fish are consumed, food resources that are already in low amounts become even more scarce, as the demand for them increases.

• Increased population

  • when the population gets bigger, more food is required.

  • Countries often do not have the resources for this and this can lead to low food security

Effects of temperature on rate of decomposition

 

• Higher temperature increases decomposition rate as the enzymes work faster

• If the temp is too high then the enzymes to work at a slower rate

• Cold temps slow down rate of decomposition because enzymes work slowly

Effects of water content on rate of decomposition

• Decay takes place faster in moist environments because the microorganisms involved in decay need water to survive

• More water --> decomposition happens faster

 

 

Effects of oxygen availability on rate of decomposition

• When there is a plentiful supply of oxygen, decomposition rate is faster

• This is because decomposers respire aerobically

 

What affects rate of decomposition in compost specifically

• If more oxygen is available decomposers respire aerobically, producing heat

• Increased temperature increases the rate of decay so the compost is made quicker

What is an indicator species

• Organisms whose presence or absence serve as an indicator of pollution

 

What is the indicator species for very polluted water

• Bloodworm

• Sludge worm

What is the indicator species for clean water

• Freshwater shrimps

• Stonefly

What is the indicator species for clean air

• Bushy lichen

  • Lichen only grows when there is a lack of sulfur dioxide, so if there is lichen, it means the air is clean

• Blackspot fungus

  • Found on rose leaves

  • Also sensitive to levels of sulfur dioxide

Explain how nitrates are made available for plant uptake

• Nitrogen gas in the atmosphere is too unreactive, so it cannot be used directly by plants

• Nitrogen-fixing bacteria, present in the root nodules of legume plants, convert nitrogen gas into nitrates

• Lightning can also convert nitrogen gas into nitrates

• Plants absorb nitrates through active transport

Why is the carbon cycle important

• allows the movement of carbon between global reservoirs including the atmosphere, ocean, soil and biomass

• the balance of carbon is essential due to the role that carbon plays in sustaining life

• global warming is an example of the effect of disrupting the carbon balance

Steps of the carbon cycle

• Carbon dioxide is removed from the air by photosynthesis in green plants an algae, which use it to make carbohydrates proteins and fats

• When these organisms are eaten, carbon moves up the food chain

• Carbon dioxide is returned to the atmosphere when plants, algae and animals respire

• Carbon dioxide is returned to the air when wood and fossil fuels are burned (combustion) as they contain carbon from photosynthesis

What is the role of decomposers in the carbon cycle

• Decomposers respire when they return mineral ions to the soil

• When they respire, carbon dioxide is returned to the atmosphere

Why is the water cycle important

• all life depends on water so the water cycle is a fundamental process

• distributes fresh water globally

• provides us with clean water for drinking

• provides with water needed for photosynthesis

Steps of the water cycle

• The sun's energy causes water to evaporate from the sea and lakes, forming water vapour.

  • Water vapour is also formed as a result of transpiration in plants.

• Water vapour rises and then condenses to form clouds.

• Water is returned to the land by precipitation (rain, snow or hail)

• this runs into lakes to provide water for plants and animals.

• This then runs into seas and the cycle begins again.

Describe desalination

• In areas of drought, we can harness the water cycle to produce potable water

• Desalination is performed by reverse osmosis

• It removes salt and minerals from seawater to make it drinkable

How to calculate rate changes in decaying materials (method)

• Make a solution of milk and phenolphthalein indicator

• Add sodium carbonate to make the solution alkaline and pink

• Place the tube in a water bath

• add lipase and begin a stop watch

• See how long it takes for the pink colour to disappear

• Repeat at different temperatures

• The temperature that it disappears the quickest is when the decomposition rate is highest

Core Practical: organisms and field work techniques METHOD

• Place two measuring tapes across an area like two axes of a graph.

• Then use a random number generator to make random coordinates.

• Place the quadrants in the random area and count the number of organisms there

• Repeat for reliability

• Multiply the number of organisms by the total area to get an estimate

Explain how eutrophication can cause populatons to decrease

• Eutrophication causes oxygen levels in bodies of water to decrease because nitrate levels increase

• This reduces animal population because they need oxygen for respiration and survival

• With less oxygen, algae overgrows, blocking sunlight

• This reduces plant population because they can’t photosynthesise

9.15 Explain how nitrates are made available for plant uptake

the use of fertilisers, crop rotation

and the role of bacteria in the nitrogen cycle

Nitrogen cycle:

1. Nitrogen in atmopshere (78%)

2. Nitrogen fixation (nitrogen to ammonia)

   • nitrogen fixing bacteria in root nodules of leguminous plants

   • nitrogen fixing bacteria in the soil

   • lighting (breaks down nitrogen molecules so they combine with oxygen to form nitrates)

3. ammonia converted into nitrites then nitrates by nitrifying bacteria

4.  denitrifying bacteria in anaerobic conditions turn nitrates into nitrogen gas

5.  uptake of nitrates by plants to be used to synthesize plant proteins

6. animals feed on the plants and digest the proteins, the nitrates are used for animal protiens

7. urea in waste and dead remains of plants/animals are broken down by decomposers back into ammonia

 

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roles of bacteria:

• nitrogen-fixing bacteria- turns nitrogen gas into ammonia

• nitrifying bacteria- turns ammonia into nitrites, then into nitrates

• decomposers- release ammonia by breaking down urea (in waste) and proteins (in dead plants/animals)

• denitrifying bacteria- turns nitrates into nitrogen gas
  

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Fertilisers and crop rotation

• fertilisers added to soil- animal manure or compost (decomposed organic matter).

  • Nitrogen compounds released into the soil as these decompose

• artificial fertilisers- contain nitrates

• crop rotation- different crops are grown in the same field each year in a cycle, including a nitrogen-fixing crop. To keep the soil healthy and increasing ammonia in the soil (which gets converted into nitrates). nitrates make amino acids which are needed for growth

Explain how nitrates are converted to nitrogen gas

• Decomposers break down the bodies of dead organisms, urine and faeces

• They convert nitrogen into ammonia, then nitrifying bacteria turns ammonia into nitrates

• Denitrifying bacteria in the soil breaks down nitrates, returning nitrogen gas into the air

Describe how carbon is cycled through the abiotic components of an ecosystem

• Burning fossil fuels release carbon dioxide into the atmosphere

• Oceans absorb carbon dioxide

• Carbon dioxide can be stored in rocks, which is released when these rocks are eroded

Describe how carbon ix cycled through the biotic features of an ecosystem

• During photosynthesis, plants take in carbon dioxide from the atmosphere

• During respiration plants release carbon dioxide into the atmosphere

• Animals release carbon dioxide when they respire

• Animals ingest carbon compounds when they eat plants or animals

• Decomposers release carbon dioxide during respiration

• Decomposers break things down