Unit 7 - Energy + Ecosystems Flashcards
What is the definition of an ecosystem?
The community and the non-living components of its environment.
How does energy enter an ecosystem and what is it converted to?
During photosynthesis plants synthesis organic compounds (e.g. glucose from carbon dioxide using light energy). The energy is stored within these organic compounds.
What are the organic compounds produced in photosynthesis used for in the plant?
Most of the sugars made by plants are used in respiration. The rest make other biological molecules (B-glucose which makes cellulose, phospholipids for cell membrane and amino acids for proteins + enzymes) which form the biomass of the plant.
What is biomass?
Biomass is the mass of organic molecules. It can be represented as dry biomass or mass of carbon.
What is dry biomass and how would you measure it?
It is the mass of organic material with all the water removed. Biomass is not measured as wet/fresh mass because the amount of water can vary.
To measure it:
1) Heat the organism in an oven to evaporate the water but not so hot it would burn it (<100)
2) Measure the mass of the organism after a given period of time
3) Reheat and find mass again
4) Repeat until a constant mass is reached (shows all the water has been removed)
What are the units of biomass?
Mass per unit area per unit time
What is a calorimeter and how does it work?
A calorimeter is used to estimate the energy in biomass in joules.
1) The sample of living tissue is burnt in a combustion chamber
2) The heat energy released is transferred to a known volume of water surrounding the tissue
3) The increase in temperature of the water is measured and used to calculate the chemical energy in the biomass.
Equation of energy released?
Energy released (J) = volume of water (cm3) x temperature increase x specific heat capacity of water (4.18J)
Cons of simple calorimeter?
-Heat energy can escape to the surrounding and does not enter the water
-Heat energy can escape from the water due to the calorimeter not being insulated.
Features of an enclosed calorimeter which allow to produce accurate measurements?
-The container is insulated preventing loss of heat by conduction
-The stirrer ensures the heat energy is evenly distributed
-Water has a high specific heat capacity
Definition of GPP (gross primary production)
GPP is the chemical energy store in plant biomass, in a given area or volume in a given time.
(The greater the rate of photosynthesis the greater the GPP as more organic molecules are formed)
Why is only 2% of the light energy from the sun converted to biomass (GPP) in photosynthesis?
Some light is reflected off the chlorophyll, some misses the chlorophyll and some is the wrong wavelength for photosynthesis.
Definition of NPP (net primary production)?
NPP is the chemical energy store in plant biomass after respiratory losses to the environment.
Equation for NPP?
NPP=GPP-R
R = respiratory losses
How can energy be lost between tropic levels?
-Energy is lost as heat due to respiration of organic molecules
-Some organic molecules are not absorbed and are lost in faeces (egestion)
-Some organic molecules are exerted in urine
-Not all the organisms is eaten (bones)
Why is there less energy transferred between producer and primary consumer than primary and secondary consumer?
Producers contain a lot of cellulose which is difficult to digest, so less absorbed and more energy is lost in egestion/faeces.
Definition of net production of consumers (N)?
N is the chemical energy stored as biomass in a consumer which is available to the next tropic level.
What is the equation for N?
N = I - (F + R)
I is the chemical energy in ingested food
F is the chemical energy lost in faeces an urine
R is the energy lost in respiration
What are farming methods used for?
To increase the efficiency in food chains and increase the store of chemical energy in the biomass of crops or livestock (NPP or N). This increases yield, meaning more energy for human consumption and profits.
How can you increase the productivity in plants (producers)?
GPP is increased by increasing the rate of photosynthesis:
-increasing light intensity (electric lighting)
-increasing temperature (electric heaters)
-increasing carbon dioxide concentration (CO2 tanks)
How can you increase the productivity in livestock (consumers)?
By reducing the energy lost through respirations, the value of net production (N) increases and minimise energy lost to farces and urine.
-Movement can be restricted, so less respiration occurs for muscle contraction
-Animals can be kept indoors or in heated rooms so less respiration occurs to release heat to maintain body temp
-Animals are fed a high calorie controlled diet designed for maximum absorption and minimum faeces production.
How can you simplify food webs and how does it increase energy for human consumption?
Simplifying food webs removes food chains not including humans. This increases the proportion of energy transferred to humans.
Use chemical control:
-Use an insecticide to kill pests directly
-Use a herbicide to kill weeds which removed inter specific competition for the crop for abiotic factors
Use biological control:
-adding a predator of the pest to the ecosystem which eat the pests.
