10.2 Flashcards
define trophic level
the position of an organism in a food chain or web which describes its feeding relationship with other organisms
what are producers
make food by photosynthesis or chemosynthesis
what are primary consumers
organisms that eat producers
what are secondary consumers
animals that feed on primary consumers
what are tertiary consumers
feed on secondary consumers (top predators)
what are the disadvantages of organisms having one food source
any event that reduces its availability can be detrimental to the species
what is the role of decomposers
break down the remains of animals and plants and return mineral nutrients to the soil
what is a pyramid of numbers
the number of organisms at each trophic level of the food chain
what is a pyramid of biomass
represents the biomass of organisms of each trophic level in a food chain
what is a pyramid of energy
represents the total energy store of the organisms at each tropic level in a food chain
why are only small proportions of energy passed on between the food chain
undigested matter goes to faeces
lost in heat energy due to respiration
waste products such as urea
what is the secondary production
the process of making new animal biomass from plant material that has been eaten
what is GPP (gross primary productivity)
the rate at which light from the sun catalyses the production of new plant material
what is NPP (net primary productivity)
the material produced by photosynthesis stored as new plant body and tissue
how do you calculate NPP
GPP-R (respiration)
what are the 2 phases involved in the cycling of nutrients in an ecosystem
biotic phase - inorganic ions are incorporated in the tissue of living things
abiotic phase - inorganic ions are returned to the non-living part of the ecosystem
what is the role of decomposers in nutrient cycles
feed on droppings and dead bodies, digest them and return nutrients back to the soil in a form which plants can use again
what are the best conditions for fast decomposition and why
warm - increase speed of chemical reactions but not too high temperatures otherwise enzymes will denature
moisture - easier to dissolve foods & prevent them from drying out
plenty of oxygen available
why is nitrogen important
needed for making amino acids and proteins
why can plants not use nitrogen from the air
it is inert thereforE unreactive
how are nitrates returned to the soil
urine contains urea which is a break down product from amino acids
proteins are passed out in faces
dead bodies made from proteins
these are then broken down to ammonium compounds which can be oxidised by nitrifying bacteria to convert them to nitrates which plants can reabsorb
what are nitrifying bacteria
bacteria which oxidise ammonium compounds to form nitrites and nitrates
what are nitrogen-fixing bacteria
bacteria in the soil that can convert nitrogen from the soil air into ammonia that is then converted into nitrates by nitrifying bacteria
what are legumes
plants such as beans, peas and clover which have nodules on their roots that are full of nitrogen-fixing bacteria
what are denitrifying bacteria
break down nitrates to power the production of ATP producing nitrogen gas as a waste product
what is a carbon sink
a reservoir where carbon is removed from the atmosphere and ‘locked up’ in organic or inorganic compounds
