energy and ecosystems Flashcards
What’s an ecosystem
Abiotic and biotic factors in a community
What’s biomass
mass of living material
How can biomass be measured?
*mass of carbon
*dry mass of tissue (mass of organism/tissue after water removed)
What’s GPP
*gross primary production
*chemical energy store in plant biomass
How is GPP measured
energy per unit area for eg J m-2 (joules per square metre)
What’s gross primary productivity
The rate in which plants are able to store chemical energy via photosynthesis
How is gross primary productivity measured
Units of energy/mass per unit area per time for example kg or j km-2 yr-1 (kilograms per square kilometre per year)
What’s net primary production
Chemical energy store in plant biomass after respiratory loses to environment
How is biomass made?
- in photosynthesis, plants make organic (carbon) compounds from atmospheric or aquatic CO2
● Most sugars synthesised are used by the plant as respiratory substrates
● Rest used to make other groups of biological molecules (eg. carbs, lipids & proteins) → form biomass
In aquatic plants how is GPP measured?
Measured units of area per unit volume for eg- kg m-3 (kilograms per cubic metre)
What are the biological molecules that are made by left over sugars that weren’t used in respiration? And what are their roles?
Starch- used as a short term energy store
Proteins- plant cells combine sugars with nitrate to form amino acids used to produce proteins
Cellulose- used for structural support in the cell wall
Lipids- plant cells convert sugars to lipids- used as long term energy stores.
If dry mass if the grass from 1m2 of a fuel is 0.2kg, grass has dry mass (biomass) of 0.2kg m-2. If grass field is 200m2, what’s the biomass of the whole field?
0.2 x 200= 40kg
Does biomass change over time? Can it be given in units of time?
Yes
Does biomass change over time? Can it be given in units of time?
Yes
if the average biomass of a group of oaks trees over the course of a year is found to be 13,000 kg, what’s the average biomass in a year?
13,000 kg y⁻¹ (this means 13,000 kg per year)
What’s a calorimeter and how’s it used?
*equipment used to estimate chemical energy in dry biomass
*sample is burnt in a calorimeter
*sample heats volume of water
*change in temp shows estimate chemical energy in sample
The total biomass of the grass that grows in a 200 m2 field is found to be 1,000 kg. Calculate the gross primary production of the grass field. Give appropriate units.
Step 1: Calculate the total yearly biomass of grass in 1 m2 of the field
1,000 ÷ 200 = 5 (kg)
Step 2: Give the appropriate units
5 kg m-2
On average, a patch of rainforest covering an area of 1 km2 is estimated to contain 1,500 kg of biomass. Calculate the gross primary production of this rainforest patch. Give your answer in g m-2.
1km2= 1,000,000 m2 (1km = 1,000 metres to get km2 times 1,000 x1,000)
1kg=1,000g
1,500kg= 1500000g (five zeros)
Gross primary production= 1500000g/1,000,000m2
Answer= 1.5 g m-2
The biomass of aquatic algae in a tank is estimated to contain a total of 5,440 joules of chemical energy. The tank has a volume of 4 m3. Calculate the gross primary production of this aquatic algae. Give appropriate units.
Step 1: Calculate the chemical energy of the biomass of aquatic algae in 1 m3
5,440 ÷ 4 = 1,360 (J)
Step 2: Give the appropriate units
Answer= 1,360 J m-3
What’s net primary production?
amount of energy available to herbivores in the plant’s biomass after plant respiratory losses
How is net primary production calculated?
Gross primary production- Respiration= Net primary production (GPP- R= NPP)
What are the units of net primary production?
*units of energy per unit area or volume, for example:
Using area: J m–2 (joules per square metre)
Using volume: J m–3 (joules per cubic metre)
What are the units of net primary productivity?
*units of energy or mass per unit area per unit time eg
mass= kg km-2 yr-1 (kilograms per square kilometre per year)
energy= mj m–2 y-1 (megajoules per square metre per year)
What are the roles of decomposers?
*they breakdown dead plant/animal material by secreting digestive enzymes onto the surface
*breakdown matter into small soluble food molecules that’s then absorbed by decomposers
How do decomposers help?
they help release organic nutrients back into environment for growth of plants and other products
How is light energy converted to chemical energy?
light energy is absorbed by chlorophyll and other pigments, and converted into chemical energy in the form of ATP and NADPH.
What’s primary production?
storing of chemical energy in the biomass of primary producers
How’s primary production measured?
mass or energy per unit area
for eg:
mass= kg ha-1 (kilograms per hectare)
energy= kj ha-1 (kilojoules per hectare)
How’s primary/secondary productivity measured?
mass or energy per unit area per unit time (years)
Why is not all the chemical energy/biomass transferred to the consumer after eating?
*Not all of the biomass of the food is eaten (e.g. the roots and woody parts of plants or the bones of animals), meaning that the chemical energy this biomass contains is lost to the environment
*Consumers are not able to digest 100% of the food they ingest, so some is always egested as faeces.
* chemical energy is lost to the environment when consumers respire (lost as heat) and during the excretion of waste products
What is net production of consumers?
energy that is left after losses is stored as new biomass to the consumer
How do you calculate net production of consumers
N= I- (F+R)
I= chemical energy in ingested food
F= energy lost to environment thru urine/faeces
R= respiratory losses
In a patch of woodland, caterpillars ingest 2,000 kJ m⁻² yr⁻¹ of chemical energy from the biomass of oak leaves. The caterpillars lose 1,200 kJ m⁻² yr⁻¹ of this energy in faeces and urine. They lose a further 600 kJ m⁻² yr⁻¹ of this energy through respiration. Calculate the net production of the caterpillars.
Step 1: Write out the equation and substitute in the known values
N = I - (F + R)
N = 2,000 - (1,200 + 600)
Step 2: Calculate the net production (N) and give appropriate units
N = 2,000 - 1,800
N = 200 kJ m⁻² yr⁻¹
Explain why these units for primary or secondary productivity are used
● Per unit area → takes into account that diff environments vary in size
○ Standardising results for comparison between environments
● Per year → takes into account effect of seasonal variation (temperature etc.) on biomass
○ More representative and enables comparison between environments
Explain why most light falling on producers is not used in photosynthesis
● Light is reflected or wrong wavelength
● Light misses chlorophyll / chloroplasts / photosynthetic tissue
● CO2 concentration or temperature is a limiting factor
Explain why energy transfer between trophic levels is inefficient
● Heat energy is lost via respiration
● Energy lost via parts of organism that aren’t eaten (eg. bones)
● Energy lost via food not digested → lost as faeces
● Energy lost via excretion eg. urea in urine
Explain how crop farming practices increase energy transfer efficiency
● Simplifying food webs to reduce energy / biomass losses to non-human food chains eg.
○ Herbicides kill weeds → less competition (eg. for light) so more energy to create biomass
○ Pesticides kill insects (pests) → reduce loss of biomass from crops
○ Fungicides reduce fungal infections → more energy to create biomass
● Fertilisers e.g. nitrates to prevent poor growth due to lack of nutrients
Explain how livestock farming practices increase energy transfer efficiency
● Reducing respiratory losses within a human food chain- more energy to create biomass
○ Restrict movement and keep warm → less energy lost as heat from respiration
○ Slaughter animal while still growing / young, when most of their energy is used for growth
○ Treated with antibiotics → prevent loss of energy due to pathogens
○ Selective breeding to produce breeds with higher growth rates
How does slaughtering animals when they’re young increase energy transfer efficiency?
young animals require less energy for maintenance compared to older animals (because they are smaller and have less developed systems) As animals grow, their energy requirements for basic metabolic processes increase. By slaughtering them before they reach full maturity, farmers can reduce the energy lost to maintenance.
young animals- higher growth rates and can convert feed into body mass more efficiently. larger proportion of the energy from their feed goes into growth rather than maintenance.
A 2 g sample of biomass was fully combusted in a calorimeter.
The volume of water in the calorimeter was 100 cm3
The increase in temperature recorded was 15.7 °C
4.18 J of energy are needed to increase the temperature of 1 cm3 of water by 1 °C
Use this information to calculate the heat energy released in kJ per g of biomass.
Show your working
3.28 / 3.3 (kJ g−1)
Explain how features of a calorimeter enable valid measurement of heat energy released
● Stirrer → evenly distributes heat energy (in water)
● Air / insulation → reduces heat loss & gain to & from surroundings
● Water → has a high specific heat capacity
Chlorella cells can divide rapidly. A culture of 2000 chlorella cells was set up in a fermenter. The cells divided every 90 minutes. You can assume there were no limiting factors and that no cells died during the 24 hours. Give your answer in standard form.
1440/90 = Divide 16 times
2000x2^16
Ans = 1.3x10^8
Explain the importance of NPP in ecosystems
● NPP is available for plant growth and reproduction
● NPP is also available to other trophic levels in the ecosystem, such as herbivores and decomposers
