3.5 energy transfers in and between organisms Flashcards
what is meant by food chain?
describes a feeding relationship in which the producers are eaten by the primary consumers which are eaten by the secondary consumers which are eaten by tertiary consumers which may be further eaten by quaternary consumers
what is meant by food web?
many food chains linked together
what is meant by producer?
photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide, and mineral ions
what is a primary consumer?
consumers that directly eat producers
what is a secondary consumer?
animals that eat primary consumers
what is a tertiary consumer?
animals that eat secondary consumers
what are saprobionts?
decomposers, a group of organisms that break down the complex materials in dead organisms into simple ones releasing valuable minerals and elements in a form that can by absorbed by plants and so contribute to recycling, the majority of this is done by bacteria and fungi
what is meant by trophic level?
each stage in a food chain
what is a herbivore?
an animal that eats only plants (producers) and is therefore a primary consumer
what is a carnivore?
an animal that eats only animals and is therefore a secondary consumer or higher in the food chain
what is an omnivore?
an animal that eats plants and animals and is therefore a primary consumer and a secondary or tertiary consumer
what is meant by habitat?
the place where the community is found
what is meant by ecosystem?
all the interacting biotic and abiotic factors in an area
what is meant by biomass?
the total mass of living material in a specific area at a given time
how does energy enter an ecosystem?
producers transfer the suns light energy into organic substances via photosynthesis
what do the arrows show in food chains and food webs?
the direction of energy flow
how is energy passed between the trophic levels?
one trophic level is eaten by the next trophic level
why is biomass only an estimate?
the sample may not be representative when measuring the dry mass/mass of carbon in a killed animal
how is biomass measured?
using dry mass per given area in a given time, measured in grams per square metre on land and grams per cubic metre in water
how does calorimetry work?
a sample of dry material is weighed and is then burnt in pure oxygen within a sealed chamber called a bomb, the bomb is surrounded by a water bath and the heat of combustion causes a small temperature increase, as the amount of energy needed to raise the temperature of one gram of water by one degree Celsius is known, the energy released from the mass of burnt biomass can be calculated in the units kJKg-1
where does the carbon dioxide needed by plants come from?
the atmosphere
other than respiration, what are the sugars synthesised by plants used for?
storage as starch and in cellulose cell walls
why is most of the sun’s light energy not converted into organic matter?
over 90% is reflected back into space by clouds and dust or absorbed by the atmosphere, not all wavelengths of light can be absorbed and be used in photosynthesis, light may not fall on a chlorophyll molecule, a factor e.g. carbon dioxide levels might limit the rate of photosynthesis
what percentage of the sun’s energy is captured by plants or algae?
1-3%
what is gross primary production?
the total quantity of energy that plants in an area/volume convert into organic matter (biomass) in a given time
what is net primary production?
respiration uses 20-50% of gross primary production, NPP is the energy left over to be stored
how do you calculate net primary production?
net primary production = gross primary production - respiration
what is NPP used for?
for plant growth and reproduction, it can also be passed along to other trophic levels, however less than 10% is used by primary consumers for growth, secondary/tertiary consumers transfer about 20% of energy from their prey to their own biomass
how does energy loss in food chains occur?
not all of the organism is eaten, not all is digested and lost in faeces, some lost in excretory materials such as urine, heat loss to the environment
how do you calculate the net production of consumers?
net production = chemical energy store in food - (energy lost in faeces and urine + energy lost in respiration) aka N = I - (F + R)
why can food chains only support five trophic levels?
food chains are extremely inefficient, insufficient energy available to support a large population at high trophic levels, the total biomass is less at each trophic level, therefore the amount of energy transfer is less
how can you improve the efficiency of a food chain?
reducing the number of trophic levels
what do farmers aim to do?
produce the maximum yield with the minimum input
what is the focus of intensive rearing?
to convert the smallest amount of food energy into the greatest quantity of animal mass, minimising energy loss helps this, this allows more energy taken in by the animals to be converted to body mass, this is then passed along the food chain to humans (this means more profit)
what measures may farmers take to improve the energy conversion rate in their livestock?
limit movement to reduce energy expenditure from exercise, heat the environment so energy is not wasted to maintain a stable body temperature, control diet (food that is high in fibre)
what are the pros of intensive farming?
efficient energy conversion, low cost, use of space, safety, food is essential for life
what are the cons of intensive farming?
low quality of food, disease, overuse of drugs, low animal welfare, pollution, reducing genetic diversity, use of fossil fuels
how is efficient energy conversion a pro of intensive farming?
restricting wasteful energy loss means more energy is passed to humans in the food chain
how is intensive farming low cost?
foods such as meat, eggs and milk can be produced more cheaply than by other methods, with more and more families now reliant on food banks this could be helpful
how is use of space a pro for intensive farming?
intensive rearing uses less land so less of the countryside is required for agriculture, leaving more as natural habitats
how is safety a pro for intensive farming?
small, concentrated units are easier to control and regulate, it is easier to prevent infections being introduced from the outside and to isolate animals if this happens
how is food is essential for life a pro for intensive farming?
with an ever expanding human population, there is pressure to produce more and more food intensively
how is quality of food anti intensive farming?
the taste of foods produced by intensive rearing is inferior to food produced less intensively
how is disease anti intensive farming?
large numbers of animals living in close proximity means that infections can spread easily amongst them
how is use of drugs anti intensive farming?
over use of antibiotics to prevent disease in animals has led to the evolution of antibiotic resistance, this resistance can be transferred to bacteria that cause human diseases, making their treatment with certain antibodies ineffective, other drugs may be given to animals to improve their growth or reduce aggressive behaviour, these may alter the flavour of the food or pass into the foods given to humans, effecting their health
how is animal welfare anti intensive farming?
the larger intensive farms have the resources to maintain a high level of animal welfare and are most easily regulated, however animals are kept unnaturally and this can cause stress resulting in aggressive behaviour, this may cause them to harm each other, which is why battery chickens are debeaked, restricted movement can lead to osteoporosis and joint pain, the wellbeing of animals may be sacrificed for financial gain
how is pollution anti intensive farming?
intensively reared animals produce a large concentration of waste in a small area, rivers and ground water may become polluted, pollutant gases may be dangerous and smell, large intensive farms may have their own disposal facilities that enable them to treat waste more effectively than smaller ones
how is reducing genetic diversity a con for intensive farming?
selective breeding is used to develop animals with high energy conversion rates and a tolerance of confined conditions, this reduces the genetic diversity of domestic animals , resulting in loss of genes that may later be advantageous
how is the use of fossil fuels a con for intensive farming?
high energy conversion rates are possible because fossil fuels are used to heat the buildings that house the animals, in the production of the materials in the buildings (especially cement) and in the production and transportation of animal feeds, the carbon dioxide emitted increases global warming
how could you determine the dry mass of a sample of plant material?
heat at 100 degrees Celsius to evaporate the water, weigh and heat until there is no further change in mass
what is the advantage of using dry mass and not fresh mass to compare the yield of plants?
the amount of water present will vary which decreases the reliability of using fresh mass, but not dry mass as the water is removed
what same key stages do all nutrient cycles have?
nutrient absorbed as simple inorganic molecules by the producer, producer converts it into complex organic molecules, nutrient passes on during feeding relationships, after death, consumer broken down by saprobionts, nutrients released back into the soil in its simplest form
why do living things need nitrogen?
nitrogenous bases (DNA + RNA), amino acids, protein
how do organisms get their nitrogen?
few organisms can use gaseous nitrogen as it is unreactive and not easily converted into other components, plants use nitrate ions (NO3-) from the soil, these are taken up via active transport, animals get their nitrogen from consuming plants
nitrate ions are soluble, why is this a problem?
washed away from plant roots by rain water, leaches into lakes, causes growth of algae, blocks sunlight for photosynthesis, decomposers use oxygen for respiration to break down dead plants, no oxygen for fish, fish die
how do microorganism play a huge role in cycling nitrogen?
during decomposition, microorganisms replenish the nitrate concentration in the soil.
what happens in nitrogen fixation?
nitrogen can be fixed into ammonia by humans using the haber process, this is then used in the production of fertilisers. a small amount of nitrogen is fixed into nitrate by lightning. The main way is by microorganisms that can be free living or mutualistic nitrogen fixing bacteria.
what are the same key stages in all nutrient cycles?
nutrient absorbed as simple inorganic molecules by the producer, producer converts it into complex organic molecules, nutrient passed on during feeding relationships, after death, consumer broken down by saprobionts, nutrients released back into the soil in its simplest form
what are the key stages of the nitrogen cycle?
nitrogen fixation, ammonification, nitrification, and denitrification
what is the role of free living nitrogen fixing bacteria?
reduce nitrogen gas into ammonia, then used to manufacture amino acids, nitrogen rich compounds are released from them when they die and decay
what is the role of mutualistic nitrogen fixing bacteria?
the nitrogen fixing bacteria live in colonies inside the cells of root nodules of leguminous plants such as clover or peas, the bacteria get carbohydrates from the plant and the plant acquires amino acids from the bacteria
what are rhizobium?
mutualistic nitrogen fixing bacteria
what happens in ammonification?
organic N containing compounds from dead organism are turned into ammonia by saprobionts, which goes on to form ammonium ions, animal waste (urine and faeces) also contain nitrogen compounds, these are also turned into ammonia by saprobionts and go on to form ammonium ions
what happens in nitrification?
plants can only take up nitrogen in the form of nitrate, ammonium compounds are oxidised into nitrates by nitrifying bacteria in two stages, first oxidising ammonium ions into nitrite ions (NO2-), then oxidise nitrite ions into nitrate ions (NO3-), oxidation reaction releases energy, chemosynthetic bacteria use released energy to live, this requires oxygen so air spaces are needed.
what happens in denitrification?
nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas, this happens under anaerobic conditions e.g. when the soil is waterlogged
why must phosphorus be recycled?
it is required by all living things, uses include phospholipids, nucleic acid, and ATP
