3.2.1a Functioning Ecosystems: Energy Transfer Flashcards
how does energy enter an ecosystem?
- ultimate source of energy = sunlight
- sunlight converted to chemical energy by photosynthesising organisms and passed as food between other organisms
what is the photosynthesis equation?
carbon dioxide + water –> glucose + oxygen
define producer
plant in the food chain - make food by photosynthesis - autotrophs
define primary consumer
animals that eat the producer - heterotrophs
define secondary consumer
eat animal material - carnivores - heterotrophs
define tertiary consumer
eats secondary consumers - heterotrophs
define quaternary consumers
eats tertiary consumers - heterotrophs
define omnivore
eats both plants and meat
define herbivore
eats plants
define trophic level
position occupied by a group of organisms in a food chain
define food chain
describes a feeding relationship between organisms
define food web
many food chains linked together
define carnivore
an animal that eats other animals and therefore is a secondary and tertiary consumer
define biomass
the total mass (weight) of all living material in a specific area, habitat or region
what is the key concept of energy flow in ecosystems?
nutrients are recycled, but energy flow is unidirectional and transferred
what are food chains?
- a food chain shows how energy is passed through a series of animals
- the arrows in a food chain show the flow of energy
- as an organism is eaten, energy is transferred to the organism that it ate
what is a food web?
- within most ecosystems, organisms feed upon a variety of resources and many food chains co-exist
- linkages form between different chains creating a complex network of connections
- A food web is a complex network of inter-related food chains
what are pyramids of number?
- trophic levels are displayed as a series of steps of differing widths
- the width of each step in the pyramid is proportional to the numbers of organisms present at each level
what are pyramids of biomass?
- representation of trophic levels with ecosystems in terms of total dry mass per square meter of area (known as biomass)
- a pyramid of biomass represents the total dry mass (in grams per square meter of area) of all the organisms in each trophic level at a particular time.
what is the difference between pyramid of number vs biomass?
- the pyramid of biomass takes into account the size of organisms but it is only a ‘snapshot’ of the amount of material present at a given time
what are pyramids of energy?
- constructed using energy values determined from a given area over a specified period of time for each trophic level (usually KJ/M62/yr)
- pyramids of energy represent the flow of energy through each trophic level over a specified period of time and provide a measure of productivity
- they therefore take into account seasonal fluctuations in productivity
- rule of thumb: 10% of biomass will be passed on between each trophic level
what is the relationship between energy flow and energy loss?
- energy is transferred between trophic levels when one organism eats another
- these transfers are inefficient, and this inefficiency limits the length of food chains
- only a small proportion of the available energy is transferred from one trophic level to the next
- much energy is lost during the respiratory processes of each organism in the chain
- it is this energy loss, at each stage, which limits the length of food chains (number of trophic levels)
what is the relationship between biomass and energy losses?
- the dry mass of living material (biomass) at each stage in a food chain, is less than it was at the previous stage
- the biomass and the chemical energy contained in the biomass is reduced at each trophic level because:
- not all light energy is utilised to make biomass. Some is reflected and passes straight through the plant
- some materials and energy are always lost in the organism’s waste materials
- respiration supplies all the energy needs for living processes, including movement, growth and temperature regulation - this energy is not available to the next trophic level
- not all the individual organisms in a trophic level will get eaten by organisms in the next level up and not all parts of the organism are eaten
how much energy from the sun is utilised during photosynthesis?
1% to 5%
what are the 3 ways that light energy is wasted (not absorbed by plants)?
- the green light is reflected and lost (only red and blue regions used)
- reflection from surfaces
- passes through plant
what is the formula for calculation photosynthetic efficiency (memorise)?
photosynthetic efficiency (%) = (gross primary product / light energy input) x 100
define GPP
the rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time).
define NPP
the rate at which energy is stored as biomass by plants or other primary producers and made available to the consumers in the ecosystem
what is secondary production?
- energy flow through consumer populations takes into account the fate of the energy consumed by the organisms in the food chain.
- the energy used to make new consumer tissue is called secondary production
how can energy efficiency be calculated?
- approximately 10% of energy is passed on between each trophic level
- at the top there is no energy left to pass on
- (small no. / big no.) x 100
