Chapter 13 - Energy + Ecosystems - (13.2) Energy transfer + Productivity Flashcards
What is the source of energy for all organisms?
The sun
How is the energy from the sun distributed to organisms?
Only around 1% of energy from the sun is captured by green plants in which it is made avaliable to other organisms in the food chain.
Organsims take in turns to pass small fractions of energy that they recieve to the next successive stage.
What do plants do with this energy?
Plants normally convert around 1 to 3 % of the suns energy into organic matter.
What is organic matter?
Organic matter contains carbon compounds and consists of mainly living organisms in the soil which can be dead or alive
Why is only a small percentage of the suns energy converted to organic matter by photosynthesis?
Roughly 90% of the suns energy is reflected back into space by clouds and dust or it is absorbed by the atmosphere.
Not all wavelengths of light can be absorbed by chlorophyll which is needed for photosynthesis so will be reflected elsewhere.
Light may miss chlorophyll molecule and therefore will not be absorbed.
May be a limiting factor such as carbon dioxide so light cannot be used then.
What is GPP?
GPP stands for Gross Primary Production.
It is the total quantity of the chemical energy store in plant biomass in a given area or volume.
However, plants use around 20-50% of this energy for respiration.
What is NPP?
NPP is stands for Net Primary Productivity.
It is the chemical energy store which is left after the losses to respiration have been taken into account.
What is NPP used for?
NPP is available for plant growth and reproduction.
It is available for other tropic levels in the ecosystem, such as consumers and decomposers.
Less than 10% of this energy is used by primary consumers for growth.
Secondary and tertiary consumers are more efficient, they transfer around 20% of energy from their prey into their own body.
If only a low percentage of energy is transferred at each stage, what are the factors that this is due to?
Some of the organisms is not fully consumed.
Some parts are consumed but not all can be digested and therefore will be lost by faeces.
Some energy is lost through urine (excretory materials).
Some energy is lost by heat, from respiration or to the environment.
These heat losses are high in mammals due to their body temperature being high. This is because a lot of energy is needed to maintain their body temperature.
How do you calculate the net production of consumers?
N = I - (F+R)
Why is there inefficient of energy transfer between trophic levels?
Give three examples why:
Most food chains have only four to five trophic levels because insufficient energy is available to support a large enough breeding population at trophic levels higher than these
The total mass of organisms in a particular place (biomass) is less at higher trophic levels
The total amount of energy available is less at each level as one moves up a food chain
