B1. Energy Transfer in Ecosystems Flashcards
Ecosystem basics
An ecosystem includes all the… In all ecosystems, there are producers - organisms that make their own food.
An ecosystem includes all the organisms living in a particular area and all the non-living (abiotic) conditions. In all ecosystems, there are producers-organisms that make their own food.
Ecosystem basics
During photosynthesis plants use energy (from _________) and ________ _________(from the atmosphere in land-based ecosystems, or dissolved in ________in aquatic ecosystems) to make _________and other ________.
Some of the sugars produced during photosynthesis are used in ______________, to release energy for growth. The rest of the glucose is used to make other biological molecules, such as cellulose (a component of plant cell walls). These biological molecules make up the plant’s biomass- the _______ __ _________ _________. Biomass can also be thought of as the…
During photosynthesis plants use energy (from sunlight) and carbon dioxide (from the atmosphere in land-based ecosystems, or dissolved in water in aquatic ecosystems) to make glucose and other sugars.
Some of the sugars produced during photosynthesis are used in respiration, to release energy for growth. The rest of the glucose is used to make other biological molecules, such as cellulose (a component of plant cell walls). These biological molecules make up the plant’s biomass- the mass of living material. Biomass can also be thought of as the chemical energy stored in the plant.
Ecosystem basics
Energy is transferred through the living organisms of an ecosystem when organisms eat other organisms, eg, producers are eaten by organisms called primary consumers. Primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers. This is a _____ _______
Energy is transferred through the living organisms of an ecosystem when organisms eat other organisms, eg, producers are eaten by organisms called primary consumers. Primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers. This is a food chain
Measuring biomass
Biomass can be measured in terms of the ______of _______that an organism contains or the ___ _____of its ________ per _____ ____. ____ _____is the mass of the organism with the water removed. The _______ _________ of _______ ________varies, so dry mass is used as a measure of biomass rather than wet mass.
To measure the dry mass, a sample of the organism is ________, often in an ____set to a ___ ______________. The sample is then _________at ________ ___________(e.g. every day). Once the ______becomes ________you know that all the _______has been removed. The mass of ________present is generally taken to be __% of the dry mass. Once you’ve measured the dry mass of a sample, you can scale up the result to give the dry mass (biomass) of the total population or the area being investigated. So typical units for dry mass might be kg m³.
Biomass can be measured in terms of the mass of carbon that an organism contains or the dry mass of its tissue per unit area. Dry mass is the mass of the organism with the water removed. The water content of living tissue varies, so dry mass is used as a measure of biomass rather than wet mass.
To measure the dry mass, a sample of the organism is dried, often in an oven set to a low temperature. The sample is then weighed at regular intervals (e.g. every day). Once the mass becomes constant you know that all the water has been removed. The mass of carbon present is generally taken to be 50% of the dry mass. Once you’ve measured the dry mass of a sample, you can scale up
the result to give the dry mass (biomass) of the total population or the area
being investigated. So typical units for dry mass might be kg m³.
Measuring biomass - Calorimetry
You can estimate the amount of __________energy stored in biomass by __________the _________in a calorimeter (see Figure 1). The amount of heat given off tells you how much energy is in it. Energy is measured in joules (1) or kilojoules (kJ). A sample of dry biomass is burnt and the energy released is used to heat a known volume of water. The change in ________________ of the water is used to calculate the __________ _______ of the dry biomass.
You can estimate the amount of chemical energy stored in biomass by burning the biomass in a calorimeter (see Figure 1). The amount of heat given off tells you how much energy is in it. Energy is measured in joules (1) or kilojoules (kJ). A sample of dry biomass is burnt and the energy released is used to heat a known volume of water. The change in temperature of the water is used to calculate the chemical energy of the dry biomass.
Primary production
Gross primary production (GPP) is…
Approximately __% of the gross primary production is lost to the _______________ as _____when the plants ________. This is called ______________ _____(R). The remaining chemical energy is called the ___ ___________ _________(NPP).
This relationship is shown by the following formula:
Often, primary production is expressed as a rate-i.e. the total amount of…
Typical units might be kJ ha ¹yr¹ (kilojoules per hectare per year) or kJ m² yr¹ (kilojoules per square metre per year). When primary production is expressed as a rate it is called __________ ______________.
Gross primary production (GPP) is the total amount of chemical energy converted from light energy by plants, in a given area. Approximately 50% of the gross primary production is lost to the environment as heat when the plants respire. This is called respiratory loss (R). The remaining chemical energy is called the net primary production (NPP).
NPP=GPP-R
Often, primary production is expressed as a rate-i.e. the total amount of chemical energy (or biomass) in a given area, in a given time. Typical units might be kJ ha ¹yr¹ (kilojoules per hectare per year) or kJ m² yr¹ (kilojoules per square metre per year). When primary production is expressed as a rate it is called primary productivity.
Primary production - Example - Maths Skills
1. The grass in an ecosystem has a gross primary productivity of 20 000 kJ m² yr. It loses 8000 kJ m² yr as heat from respiration. Calculate the net primary productivity of the grass in this ecosystem.
- The net primary productivity in an area of tundra is 2800 kJ m² yr¹. It loses 1250 kj m’yr’ through respiration. Calculate the gross primary productivity of the area of tundra.
- net primary productivity = 20 000-8000 = 12 000 kJ m² yr
- gross primary productivity =2800 +1250 = 4050 kJ m² yr -
Primary production
The NPP is the energy available to the plant for growth and reproduction -the energy is stored in the plant’s biomass. It is also the energy available to organisms at the next stage in the food chain (the next trophic level, see. These include ___________(animals that eat the plants) and _________.
The NPP is the energy available to the plant for growth and reproduction -the energy is stored in the plant’s biomass. It is also the energy available to organisms at the next stage in the food chain (the next trophic level. These include herbivores (animals that eat the plants) and decomposers.
Net production in consumers
Consumers also store _________ _______ in their ________. Consumers get energy by __________plant material, or animals that have eaten plant material. However, not all the chemical energy stored in the consumers’ food is transferred to the next __________level-around ___% of the total available energy is _____in various ways. Firstly,… (e.g. plant roots, bones) so the energy it contains is not taken in. Then, of the parts that are ingested:
- Some are ___________, so are ________as ________. The chemical energy stored in these parts is therefore lost to the _______________.
- Some energy is also lost to the environment through ____________or excretion of _______.
The energy that’s left after all this is stored in the consumers’ biomass and is available to the next trophic level. This energy is the consumers’ net production.
The net production of consumers can be calculated using the following formula:
The net production of consumers can also be called ____________ _____________(or ___________ ______________when it’s expressed as a rate).
Consumers also store chemical energy in their biomass. Consumers get energy by ingesting plant material, or animals that have eaten plant material. However, not all the chemical energy stored in the consumers’ food is transferred to the next trophic level-around 90% of the total available energy is lost in various ways. Firstly, not all of the food is eaten (e.g. plant roots, bones) so the energy it contains is not taken in. Then, of the parts that are ingested:
- Some are indigestible, so are egested as faeces. The chemical energy
stored in these parts is therefore lost to the environment. - Some energy is also lost to the environment through respiration or excretion of urine.
The energy that’s left after all this is stored in the consumers’ biomass and is available to the next trophic level.
N=I-(F+R) Where: N = Net production, I=Chemical energy in ingested food, F=Chemical energy lost in faeces and urine, R = Energy lost through respiration
The net production of consumers can also be called secondary production (or secondary productivity when it’s expressed as a rate).
Net production in consumers - Example - Maths Skills
The rabbits in an ecosystem ingest 20 000 kJ m² yr¹ of energy, but lose 12 000 kJ m² yr of it in faeces and urine. They lose a further 6000 kJ m² yr using energy for respiration.
net productivity = 20000 - (12000 + 6000) =20000 - 18000 = 2000 kJ m² yr
Tip: Net productivity is just net production expressed as a ____, i.e. per unit time.
Tip: Net productivity is just net production expressed as a rate, i.e. per unit time.
Efficiency of energy transfer
You can use the following equation to calculate how efficient energy transfer is between one trophic level and the next
Tip: If the organisms in the previous trophic level are producers, then use ‘net primary production of previous trophic level’ rather than ‘___production of previous trophic level.
Tip: If the organisms in the previous trophic level are producers, then use ‘net primary production of previous trophic level’ rather than ‘net production of previous trophic level.
Effencieny of energy transfer - Example - Maths Skills
The net productivity of the rabbits is 2000 kJ m-2 yr -1.
The net primary productivity of the plants they were feeding on was 28 000 kJ m-2 yr-1. So the percentage efficiency of energy transfer is:
(2000 ÷ 28 000) x 100 = 7% (1 s.f.)
As you move up a food chain (from producers to consumers) energy transfer usually becomes ____efficient. For example, the efficiency of energy transfer from producer to consumer might only be _-__%, but from consumer to consumer, it might be __-__%. This is because plants (producers) contain more _______________matter than animals (consumers).
As you move up a food chain (from producers to consumers) energy transfer usually becomes more efficient. For example, the efficiency of energy transfer from producer to consumer might only be 5-10%, but from consumer to consumer, it might be 15-20%. This is because plants (producers) contain more indigestible matter than animals (consumers).
