energy transfers in eco systems Flashcards
what produces biomass
plants when they photosynthesise
what does an ecosystem include
An ecosystem includes all the organisms living in a p articular area
and all the non-living (abiotic) conditions
what are producers
organisms that make their own food,
e.g. plants and algae produce their own food through photosynthesis
during photosynthesis what do plans use
energy (from sunlight) and carb on dioxide (from the atmosphere in land-based
ecosystems, or dissolved in water in aquatic ecosystems) to make glucose and other sugars
what are some of the sugars in photosynthesis used in
respiration, to release energy for growth.
what is the rest of the glucose 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.
what can biomass also be thought of as
the chemical energy stored in the plant.
what is energy transferred through
the living organisms of an ecosystem when organisms eat other organisms,
e.g. 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
how can biomass be measured as or using
it can be measured as dry mass or using a calorimeter
what can biomass be measured in terms of
in terms of the mass of carbon that an organism
contains or the dry mass of its tissue per unit area.
what is dry mass
Dry mass is the mass of the organism with the water remove d
how do you measure the dry 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.
what is the typical unit for dry mass
kg m^-2
what can the result from the dry mass sample be scaled up to give
If needed, the result from the sample can be scaled up to give the dry mass (biomass) of the total
population or the area being investigated.
what is 50% of the dry mass made up of
carbon
how can you estimate the amount of chemical energy stored in biomass
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)
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.
what are examples of chemical stores
GPP and NPP
what is GPP
Gross primary production (GPP) is the total amount of chemical energy
converted from light energy by plants, in a given area
what happens to 50% of the GPP
Approximately 50% of the gross primary pro duction is lost to the environment
as heat when the plants respire. This is called respiratory loss (R).
what is the remaining chemical energy called
The remaining chemical energy is called the net primary production (NPP). So NPP = GPP - R
what is NPP
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
what is primary production expressed as
Often primary pro duction 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 1 y e a r1(kilojoules per hectare per year) or kj n r2y r 1.
W hen primary pro duction is expressed as a rate, it is called primary productivity.
