B7 - Ecology Flashcards
Why is sodium carbonate solution added to the milk sample in the decay practical?
It makes the solution slightly alkaline. This is required as when the lipase releases fatty acids, the solution becomes acidic
What is decomposition?
Decomposition is the breaking down and digestion of biological waste by decomposers
What three factors affect the rate of decay of biological material?
Temperature
Availability of oxygen
Availability of water
Describe how temperature affects the rate of decay of biological material
A higher temperature results in a faster rate of decay because the enzymes decomposers secrete break down biological material in warm conditions. HOWEVER, if the temperature is too extreme, the enzymes will denature and the decomposer may die
At low, cold temperatures, enzymes will function at a slow rate, so decomposition rate will be slow. This is why food is stored in a fridge
Describe how water availability affects the rate of decay of biological material
Rate of decay is faster if the biological material is moist. This is because many of the chemical reactions in decay require water. This means that gardeners, for example, do not allow a compost heap to dry out
Describe how the availability of oxygen affects the rate of decay of biological material
Rate of decay is faster in regions of good oxygen supply. This is because decomposers carry out aerobic respiration
State two uses of decay
As compost
In biogas generators
Describe how decay can be used as compost
Decomposed matter is used to naturally fertilise and improve soil as compost. Once the compost is spread onto the soil, it is broken down by microorganisms and detritivores. This ensures the cycling of materials that can be absorbed by plants or crops for growth
Describe how decay can be used in biogas generators
In anaerobic decay, methane gas is produced. The generator contains inlets for animal and plant waste material. This decomposes. Methane gas is then combusted as a fuel for cooking, heating or to power a turbine to produce electricity. Carbon dioxide that is produced as a bi-product of the combustion is released into the atmosphere and may be used by plants in photosynthesis. The generator also contains outlets for decomposed material that can be used as fertiliser for crops
Explain why a widespread use of biogas as a fuel may be beneficial for global biodiversity
Carbon neutral energy sources help to maintain stable levels of CO2 in the atmosphere, which may reduce the rate of global warming. This may benefit global biodiversity as it will reduce the extinction of species as a result of being unable to survive in a different climate
Suggest why milk left at room temperature becomes sour after a few days
Bacteria in the milk begin the decay process. These bacteria secrete enzymes to produce acidic molecules that make the sour milk taste acidic
What is the IV, DV and CV of the decay investigation?
IV - Temperature of water bath/electrical heater
DV - Time taken for the indicator to change colour
CV - Volumes of different solutions
How can the investigation of the decay of milk be improved?
- Use a clean test tube for the milk solution each time the experiment is repeated. This is because any traces of lipase from the previous experiment will trigger the reaction, resulting in unreliable results
- Share data with other groups of scientists and calculate a mean to reduce the effect of stopping the stopwatch too soon or too late
Decay is a slow process.
What is one disadvantage of the milk decay practical?
The decay is modelled using the enzyme lipase. This means only approximate results are retrieved
Describe how to investigate the effect of temperature on the rate of decay of fresh milk by measuring the pH change
Place 5cm³ of lipase solution into a test tube using a pipette
Place 5cm³ of milk into a different test tube and add five drops of the indicator cresol red/phenolphthalein to the milk
Pour 7cm³ of sodium carbonate solution to the milk test tube. This makes the solution alkaline, so it should turn pink or purple
Place both test tubes into a water bath set at 20 degrees Celsius and place a thermometer into the test tube containing the milk sample. Wait until the test tubes equilibrate to the conditions
Use a pipette to transfer 1cm³ of lipase solution to the test tube containing milk and stir using a glass rod
Start a stopwatch. The lipase will start to break down the fat molecules in the milk, releasing fatty acids that causes the solution to become acidic. As a result, the pH drops
At this point, the indicator will change colour. Stop the stopwatch at this time and record how long the colour change took in a table
Repeat the experiment at a range of different temperatures and carry it out three times at each temperate.
Calculate a mean time taken for the colour change to occur and calculate the rate of decay using the equation rate = 1000/time
Describe how plants are involved in the water cycle
Plants take in water for photosynthesis
Plants lose water by evaporation through transpiration
Plants form water through respiring
When plants die, decomposers release water from them. Decomposers also release water through respiration when breaking down biological matter
State the roles of microorganisms in cycling materials through an ecosystem
Role of plants in cycling carbon and water -> photosynthesis, respiration, transpiration & decay
Role of decomposers in cycling carbon and water -> aerobic respiration for decay and anaerobic respiration in biogas generators
Role of animals in cycling water -> aerobic respiration and excretion
Role of humans and human activity in cycling carbon -> combusting fossil fuels, and aerobic respiration
Is precipitation freshwater or saltwater? Explain your answer
What are the different forms of precipitation?
Freshwater. Salt cannot be evaporated
Global warming is causing ice caps to melt. Describe some of the biological consequences of melting ice caps
More extreme weather events
Sea levels may rise
Habitats will be destroyed
Reduced biodiversity
Describe how living things are involved in the cycling of carbon
Carbon is removed from the atmosphere by green plants and algae during photosynthesis
When plants and algae respire, some carbon is returned to the atmosphere
When plants are eaten by animals, some carbon becomes part of the fats and proteins in their bodies. When animals respire, some carbon is returned to the atmosphere
When plants and animals die, decomposers secrete enzymes to break them down. This uses aerobic respiration and so releases carbon dioxide into the atmosphere
Other animals and microorganisms such as detritus feeders also feed on dead remains. When they respire, carbon is returned to the atmosphere
The combustion of wood and fossil fuels by humans also releases carbon dioxide into the atmosphere
Describe the water cycle
Energy from the sun evaporates water from the land and sea, turning it into water vapour. Water vapour also comes from transpiration in plants
The warm water vapour is carried upwards as warm air rises and at high altitude it cools and condenses to form clouds
Water falls from the clouds as precipitation onto land, where it provides fresh water for plants and animals
It then drains into the sea and the process starts again
