B17 Organising an Ecosystem Flashcards
Describe the stages of the water cycle
- Most water on earth is found in oceans (salt water)
- Energy from the sun causes the water to evaporate from the sea
- Water vapour travels into the air and cools down, condensing to form clouds
- Water in clouds falls to the ground as precipitation
- Precipitation can be rain, snow, hail or sleet
- When water hits the ground, some evaporates straight back into the atmosphere, while
some passes through rocks, forming aquifers, a lot of the water forms rivers and
streams - All forms of precipitation contain fresh water i.e. no dissolved salts
How do living organisms play a role in the water cycle?
Plants take up water in their roots, and passes up the plant through the xylem, before being released as water vapour through the stomata (transpiration)
Animals take in water when drinking, and in their food. They release water in their faeces and urine, as well as while exhaling
Describe the processes that take place in the carbon cycle in short
- Starts with CO2 in atmosphere
- Plants perform photosynthesis, taking in CO2
- CO2 returns back to the atmosphere via AEROBIC RESPIRATION
Describe the carbon cycle in the long way
- Plants and algae absorb CO2 from atmosphere for photosynthesis to produce energy
- Energy used to make carbs, fats and proteins - which make up their cells
- Plants respire, so some carbon is released back into the atmosphere as CO2
- Plants are eaten by other animals and so on etc
- Carbon that was in the plant, becomes a part of the carbs, fats and proteins in the cells
of consumers - Animals respire - releasing CO2
- Animals release waste products e.g. faeces, and they also die
- Decomposers break down waste products
- Decomposers carry out respiration, and return CO2 back into the atmosphere
- If decomposition can’t occur, the carbon is slowly turned into fossil fuels
(Humans have been burning large amounts of fossil fuels recently, releasing more CO2 back into the atmosphere)
Give two examples of decomposing organisms
Bacteria and fungi
Why are decomposers very important?
They cycle CO2, and as well as returning CO2 back into the atmosphere, they also return mineral ions to the soil
Describe and explain the optimum conditions for decomposition
Warm temperature - Decomposers use enzymes to break down dead material, which work faster at warmer conditions (too hot - enzymes denature, decomposers cld die)
Amount of water - Decomposers work faster in moist conditions, as many chemical reactions in decay require water
Oxygen levels - Required for aerobic respiration (compost bins have holes and are often mixed to aerate heaps regularly)
Mixing compost breaks up clumps, increasing the surface area for decomposers to act on
Describe anaerobic decay
In absence of O2
Produces a mixture of gases including methane
Small scale biogas generators are used to provide food for homes
Why is sour milk acidic?
Decomposing bacteria use enzymes to produce acidic molecules
Describe a practical to investigate the effect of temperature on the rate of “decay” (digestion) of milk, using the enzyme lipase
- Add a fixed volume of lipase solution to a test tube (w pipette)
- Add a fixed volume of cresol red (indicator), milk, and sodium carbonate to another
test tube - Tube should be purple (Cresol red is purple in alkaline, yellow in acidic)
(NaCO3 solution is alkaline) - Place inside hot water bath at 20°C and place thermometer inside milk tube, and wait
until the temperature of the solutions is the same as the water - Use pipette to transfer fixed volume of lipase to milk tube, and start a timer
- (Lipase begins to break down lipids into fatty acids and glycerol)
- Fatty acids cause solution to become acidic
- Indicator turns yellow
- Stop timer and record results
- Repeat experiment with a range of different temperatures
Describe the results for the milk decay practical + anything else worth noting
- Use a clean test tube for the milk solution each experiment, as traces of lipase could
trigger a reaction before it’s ready - Looking for a change in colour could result in inconsistencies, (difficult to know exact
point to stop the timer) so one should share results with other groups and calculate a
mean.
RESULTS
- At low temperatures, the reaction is slow, as the enzymes work slower at low temperatures
- At warmer temperatures, reaction reaches optimum rate (optimum temperature) w the highest enzyme activity
- After optimum temperature, reaction is slower as enzymes have denatured at higher temperatures
Which type of decomposition is fastesr? (aerobic or anaerobic)
Aerobic (bacteria are able to metabolise more quickly in the presence of oxygen and heat)
