Chapter 13 - Energy and Ecosystems Flashcards
Define Biomass
The total mass of living material in a specific area at a given time - this can be as fresh or dried mass
Define consumer
An organism that obtains their energy by feeding on other organisms rather than using the energy of the sunlight directly
Define producers
A photosynthetic organism that manufactures organic substances using the energy of sunlight directly
Define saprobionts
a group of organisms that breaks down the complex materials in dead organisms into simple ones
Define food chain
a series of feeding relationships starting with a producer and connected by arrows that show the direction of energy flow
Define food web
a series of interconnecting food chains showing more of the feeding relationships in a particular area
Define trophic level
each stage in a food chain or each level in an ecological pyramid
Give the equation which shows percentage efficiency of energy transfers
percentage efficiency = (energy available AFTER the transfer/ energy available BEFORE the transfer ) x 100
What are autotrophs?
Organisms that make their own food
What are heterotrophs?
Organisms that cannot make their own food
How come only about 10% of energy is passed to each trophic level? (give 5 reasons)
Because energy is lost as:
- uneaten parts
- decay of dead materials
- excretion
- egestion
- exothermic reactions
What is the issue with using dry biomass for investigating diversity?
It needs to have water removed, meaning the organism must be dead so there is a relatively small sample size used
Give the equation for biomass
Dry mass / area. in a given time
What is the unit for biomass?
gm-2 or gm-3
The chemical energy store of an organism can be estimated using what?
Calorimetry
Give the method for estimating the chemical energy store of an organism
Weigh a sample of dry mass
Put it in a sealed container called a bomb
Burn it in pure oxygen
Put the bomb in a water bath
Measure the temperature rise
Use specific heat capacity to calculate the energy released from the biomass
This is an estimation of the chemical energy store of the organism
Define gross primary production
The total quantity of the chemical energy store in plant biomass, in a given area and time
Define net primary production
The chemical energy store remaining after respiratory losses have been taken into account
Give the equation for calculating net primary production
Net Primary Production = Gross Primary Production - respiratory losses
Give 4 reasons why most of the sun’s energy is not converted into organic matter by photosynthesisi
- Over 90% of the suns energy is reflected back into space by clouds and dust
- Not all wavelengths of light can be absorbed and used for photosynthesis
- Light may not fall on a chlorophyll molecule
- A factor may limit the rate of photosynthesis
On average how much of the net primary production can be used by the primary consumer?
10%
On average how much of the net primary production can be used by the secondary consumer?
20%
On average how much of the net primary production can be used by the tertiary consumer?
20%
Why are energy transfers between trophic levels so inefficient? (give 4 reasons)
- Not all of the organism is consumed
- some parts of the organism cannot be digested
- some of the energy lost in excretory materials (eg urine)
- Some energy losses occur as heat from respiration which is lost to the environment
Give the calculation of net primary production when you have values for energy lost as waste and metabolic processes
Net primary production = chemical energy store in food - (energy lost as waste + energy lost in respiration)
Explain why there are usually only 4 trophic levels in each food chain
Because after that point the energy transferred by consumption is inefficient to provide enough energy to support a breeding population
How do farmers increase yield of products?
They increase the efficiency of energy transfer along the food chain.
Give 5 ways farmers can increase the efficiency of energy transfer and explain how it helps
- Use confined spaces for animas - reduced energy used for muscular contractions
- Use indoor environments - temperature can be controlled so less energy is lost keeping warm
- Control diets - ensure the food is the most beneficial and efficient to receive the most energy
- Use pesticides - reduce competition from pests and damages to plants which reduce their ability to photosynthesis
- Create a monoculture - exclude competition and predators to ensure the most beneficial environments
Define Ammonification
The process by which organic nitrogen is converted to ammonia
Define Nitrogen Fixation
The process by which atmospheric nitrogen is incorporated into organic compounds by nitrogen fixing bacteria
Define Nitrification
The process by which ammonia is oxidised to nitrite ions and then to nitrate ions by nitrifying bacteria
Define Denitrification
The process by which soil nitrites or nitrates are reduced to produce molecular N2 gas
Describe the basic process by which a nutrient is cycled around the community
The nutrient is taken up by producers as simple inorganic molecules.
The producers incorporate the molecule into their biomass
When the producer is consumed, the nutrient is passed to consumers.
When producers or consumers die or excrete waste substances, their complex molecules are broken down into simple molecules by saprobionts
What form of nitrogen can be taken up by plants?
Nitrate ions
How are ions taken up by plants?
Active transport by the roots.
How do animals obtain nitrogen?
By consuming producers
Give examples of nitrogen containing compounds
Amino acids
Urea
Nucleic acids
What type of bacteria carries out nitrification and why?
Free living nitrifying bacteria which obtain energy from carrying out the oxidation reaction
What do nitrifying bacteria need to carry out their role?
Oxygen
What are the 2 stages of nitrification
oxidation of ammonia to nitrite ions
oxidation of nitrite ions to nitrate ions
What are the main types of bacteria that carry out nitrogen fixing?
Free living nitrogen fixing bacteria
Mutualistic nitrogen fixing bacteria
What is the difference between free living nitrogen fixing bacteria and mutualistic nitrogen fixing bacteria?
Free living reduces N2 to ammonia and stores it in their biomass which is released when they die
Mutualistic reduced N2 to ammonia and lives on plants to give them nitrogen in exchange for compounds like amino acids
What bacteria cause denitrification? How are these bacteria different to nitrifying bacteria?
Denitrifying bacteria
They are anaerobic bacteria unlike nitrifying bacteria which are aerobic
What compounds is phosphate a component of?
ATP, phospholipids, nucleic acids
Where is the main reservoir of phosphate ions stored? How is this different to the nitrogen cycle?
In rocks, different because in the nitrogen cycle the main store of nitrogen is atmospheric gas
Explain how dissolved phosphate ions in water is restored to phosphate in rock
By sedimentation
Explain how phosphate ions in waste and remains is restored to phosphate in rock
By deposition
Explain how phosphate in rock is changed to dissolved phosphate ions in oceans
By erosion and use of fertilizers
How do agricultural ecosystems increase productivity?
By increasing the efficiency of energy transfer along human food chains
How do fertilisers increase productivity?
Land is used repetitively for crop production which strips it of its mineral ions. Normally mineral ions are returned to the soil by excretion of consumers and dead organisms, however since crops are harvested these excretions and organisms are not found on the soil, meaning ions are not returned. This will reduce productivity and act as a limiting factor, but fertilisers return mineral ions to the soil to increase productivity
What are the 2 types of fertilisers?
Artificial
Natural
What is the difference between artificial and natural fertilisers?
Artificial are inorganic fertilisers that gain their minerals from mining rocks
Natural are organic fertilisers that gain their minerals from decaying organisms and excretions
Which type of fertiliser is the most efficient?
A combination of 2 has proved the most useful in increasing productivity
Why are nitrogen containing fertilisers good for increasing productivity?
The plants develop earlier, grow taller and have an increased overall leaf SA which increases rate of photosynthesis which increases the size of the crop therefore increasing productivity
Name 3 detrimental effects to the environment caused by nitrogen containing fertilisers
Reduced species diversity
Leaching
Eutrophication
Explain why nitrogen containing fertilisers reduces species diversity
Because they favour fast growing plants like grass which out compete the other organisms
What is leaching ?
The process by which nutrients are removed from the soil
What causes leaching?
Rainfall
What are 2 risks associated with high nitrate levels in drinking water
Stomach cancer and prevents efficient transfer of oxygen in babies
What is eutrophication?
The process by which nutrient concentrations increase in bodies of water, leading to death of organisms
List the sequence of events that leads to eutrophication
- leaching increases nitrate concentrations meaning it is no longer a limiting factor for plant and algae growth, which grow quickly
- Upper layers of water become densely layered with algae (algal bloom) which prevents light from reaching lower levels of water
- Light is now a limiting factor on plant and algal growth in lower layers, which then die
- An increase in dead organisms causes saprobiontic bacteria to thrive as food is no longer a limiting factor
- Oxygen concentration in water decreases as bacteria use it for respiration
- aerobic organisms die due to lack of O2
- bacteria decompose more organisms which leads to more nitrate ions being released, and toxic wastes to be released
the water is now uninhabitable
List 6 causes of eutrophication
Natural fertiliser Artificial fertiliser Human sewage Ploughing old grassland Natural leaching Animal slurry
