🩷 3.5 - 3.5.3 Energy and ecosystems (A-level only) Flashcards
What do plants produce, beginning with B, when they photosynthesise?
Biomass.
Biomass definition.
The mass of living material.
What does an ecosystem include?
All the organisms living in a particular area and all the non-living (abiotic) conditions.
What are producers in an ecosystem?
(+ an example)
Producers are organisms which make their own food.
Example: Plants and algae produce their own food through photosynthesise.
What do plants use during photosynthesis and what do they make?
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.
What process are some of the sugars produced during photosynthesis used in?
Respiration, to release energy for growth.
After the sugars which are made during photosynthesis are used in respiration what are they used to make?
They are used to make other biological molecules, such as cellulose.
What do the biological molecules which are in plants make up?
The plants biomass which is the mass of living material.
Biomass can also be thought of as the c _ _ _ _ _ _ _ e _ _ _ _ _ s _ _ _ _ _ in the plant.
chemical energy stored.
When is energy transferred through the living organisms of an ecosystem?
When organisms eat other organisms.
What are producers eaten by?
Primary consumers.
What are primary consumers eaten by?
Secondary consumers.
What are secondary consumers eaten by?
Tertiary consumers.
Biomass can be measured as r m_ _ _ or using a cal_ _ _ _ _ _ _ _.
dry mass or using a calorimeter.
What can biomass 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 definition.
The mass of the organism with the water removed.
How do you measure the dry mass?
A sample of the organism is dried, often in an oven set to a low temperature, it is then weighed at regular intervals and once the mass becomes constant you know that all the water has been removed.
What might a typical unit for dry mass be?
kg m^-2.
The mass of carbon present is generally taken to be _ _% of the dry mass.
50%.
How can you estimate the amount of chemical energy stored in biomass? + how?
By burning the biomass in a calorimeter. The amount of heat given off tells you how much energy is in it. Energy is measured in joules (J) or kilojoules (KJ).
How is the chemical energy of the dry biomass found and calculated?
1) A sample of dry biomass is burnt and the energy released is used to heat a known volume of water.
2) The change in temperature of the water is used to calculate the chemical energy of the dry biomass.
GPP and NPP are both what?
Chemical energy stores.
What does GPP stand for?
Gross Primary Production.
What does NPP stand for?
Net Primary Production.
Gross Primary Production definition.
The total amount of chemical energy converted from light energy by plants, in a given area.
Approximately what % of the GPP is lost to the environment as heat when the plants respire?
50%
What is it called when approximately 50% of the GPP is lost to the environment as heat when the plants respire?
Respiratory loss (R).
What is the remaining chemical energy called after approximately 50% of the GPP is lost to the environment as heat when the plants respire?
The net primary production (NPP).
What is the equation which links NPP, R and GPP?
NPP = GPP - R.
Net Primary Production definition.
The energy available to the plant for growth and reproduction. The energy is stored in the plants 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.
How do consumers get energy?
They get energy by ingesting plant material, or animals that have eaten plant material.
Why is around 90% of the total available energy lost when not all the chemical energy stored in the consumers food is transferred to the next trophic level?
1) Not all of the food is eaten (plant roots/bones) so the energy it contains is not taken in. Some are indigestible, so are egested as faeces. Some is also lost to the environment through respiration or excretion of urine.
What is the energy thats left after all this is stored in the consumers biomass and is available to the next trophic level called?
This energy is the consumers net production.
What is the formula which is used to calculate the net production of consumers?
N = I - ( F + R )
N = I - ( F + R )
What does the F in this equation to calculate the net production of consumers stand for?
F = Chemical energy lost in faeces and urine.
N = I - ( F + R )
What does the R in this equation to calculate the net production of consumers stand for?
R = Energy lost through respiration.
Remember, when production is expressed as a rate it is called pro_u_ _ _ _ _ _ _.
productivity.
What can the net production of consumers also be called?
Secondary production (or secondary productivity when its expressed as a rate).
What do food chains are food webs show?
They show how energy is transferred through an ecosystem.
What do food chains show?
Food chains show simple lines of energy transfer. Each of the stages in a food chain is called a trophic level.
What do food webs show?
Food webs show lots of food chains in an ecosystem and how they overlap.
What is the role of decomposers?
They break down dead or undigested material, allowing nutrients to be recycled.
What do most farming practices aim to increase?
The amount of energy that is available for human consumption.
What are 2 farming practices which can be done to increase the amount of energy that is available for human consumption?
1) The energy lost to other organisms, e.g. pests, can be reduced.
2) The energy lost through respiration can be reduced.
What does simplifying the food web mean?
It means getting rid of pests (farmers need).
What type of pesticides can be used to reduce pest numbers?
Chemical pesticides.
What does killing insect pests mean?
If insecticides are used to kill insect pests that eat and damage crops, it means that less biomass is lots from crops, so they grow to be larger, which means NPP is greater.
What does killing weeds mean?
If herbicides are used to kill weeds, direct competition with the crop for energy from the sun is removed. It can also remove the preferred habitat or food source of the insect pests, reducing their numbers and simplifying the food web.
What does it mean if the numbers of pests is reduced due to biological agents?
Crops lose energy less energy and biomass, increasing the efficiency of energy transfer to humans.
True or false?
Parasites live in or lay their eggs on a pest insect.
True.
What are two things parasites do?
They either kill the insect or reduce its ability to function.
What are used to kill pests?
Pathogenic (disease-causing) bacteria and viruses are used.
What systems do farmers use to combine both chemical and biological methods?
Integrated systems.
What is the positive of farmers using integrated systems?
It can reduce pest numbers even more than either method alone, meaning NPP is increased even more.
What does it mean if respiratory losses are reduced?
It means that energy is transferred more efficiently.
What is one way in which farmers can increase the net production of their livestock?
By controlling the conditions that they live in, so that more of their energy is used for growth and less is lost through respiration (and activities that increase the rate of respiration).
Give two ways of how farmers might reduce the respiration rate of their livestock.
1) Decrease their movement by keeping their animals in pens so their movement is restricted = respiration rate decreased.
2) Keeping the pens indoors and keeping them warm to reduce the amount of energy used for generating body heat = respiration rate decreased.
What does it equal when farmers reduce the respiratory of their livestock by keeping them in pens?
It means that more biomass is produced and more chemical energy can be stored, increasing net production and the efficiency of energy transfer to humans.
What is the benefit of keeping animals in pens, reducing their respiratory rate?
More food can be produced in a shorter space of time, often at a lower cost.
What is the disadvantage of keeping animals in pens, reducing their respiratory rate?
Raises ethical issues.
(some people believe that the conditions intensively reared animals are kept in cause the animals pain, distress or restricts their natural behaviour, so it should not be done).
