biomass transfer through ecosystems Flashcards
define trophic level
each stage in a food chain
what are food chains/webs used to demonstrate?
transfer of biomass through organisms in an ecosystem
describe the first trophic level
producer - an organism that converts light energy into chemical energy via photosynthesis
why is there a limited number of trophic levels?
there is insufficient biomass and stored energy left to support further organisms
what is the role of decomposers
break down dead organisms and release nutrients back into the ecosystem
what is biomass?
mass of living material present in a particular place or organism
how would you calculate biomass at each trophic level?
biomass present x total number of organisms in trophic level
define ecological efficiency
efficiency by which biomass/energy is transferred
what makes up biomass?
cells and tissues composed of carbon compounds
what are the units for biomass on land and water?
land = gm-2
water = gm-3
how is biomass measured?
discount water and measure mass
why is it important to not consider water and use dry mass?
organisms have varied amounts of water
- makes data unreliable unless large sample is taken
what are the limitations of pyramids of biomass
fails to consider how climate plays a role in trophic level activities
how are biomass and energy linked?
light energy is captured by plants and transferred to organic compounds, forming biomass.
- so biomass can be equated to energy content
what is meant by gross primary production?
rate at which chemical energy is stored by producers
define net primary production
energy left over after respiration in plants
how is energy transferred from one trophic level to the next?
consumption
how is ecological efficiency calculated?
energy or biomass available after transfer / energy or biomass available before the transfer x 100
explain 3 reasons why 1-3% of sunlight producers receive is converted into chemical energy
- not all solar energy is used for photosynthesis - 90% is reflected, some transmitted through leaf and some is of unusable wavelength
- other factors may limit photosynthesis
- proportion of energy is lost and used for photosynthetic reactions
define primary production
generation of biomass in a producer
define secondary production
generation of biomass in a consumer
explain 4 reasons why consumers at each trophic level convert only a small amount of biomass in the trophic level to their own organic tissue.
- not all biomass of an organism is eaten - plant roots/animal bones
- some energy transferred to environment as metabolic heat as result of movement/respiration
- some parts that are eaten are indigestible
- some energy lost in excretory materials (urine)
explain why biomass decreases at each trophic level in a food chain.
- organic compounds of organisms store energy
- so biomass is equated to energy content
- small proportion of food ingested by animals is converted into new tissue - only part of biomass/energy available for next trophic level
describe how humans have manipulated energy transfer through trophic levels in the farming of plants and animals to our advantage.
- agriculture results in simple food chain of 3 or 2 trophic levels
- animal feed (producer) -> livestock (primary consumer) -> humans (secondary consumer)
- minimal energy is lost bc fewer trophic levels - as much energy as possible transferred into biomass eaten by humans
