[13.1] food chains and energy transfer Flashcards
definition of an ecosystem
interaction of biotic and abiotic factors within an area
definition of species
a group of organisms capable of naturally reproducing to produce viable offspring
definition of habitat
- the place where an organism normally lives
- it has biotic and abiotic features which separate it from other habitats
definition of community
the different populations of species that live in a habitat
definition of decomposers
microbes, bacteria, and fungi that obtain nutrients by breaking down dead organisms and faeces
definition of detritus feeders
organisms such as earthworms which feed on small fragments of organic debris, called detritus
what non-living material is detritus made up of?
- faeces
- fallen leaves
- remains of dead organisms
definition of niche
- the interrelationship of a species with all the biotic and abiotic factors affecting it
- the role of an organism within an ecosystem / community
definition of trophic level
the position an organism occupies within a food web
definition of autotroph / producer
- able to produce organic molecules from inorganic molecules
- the first trophic level in the food chain
definition of heterotroph
- an organism unable to synthesise its own organic molecules
- must feed on organic matter
definition of primary consumer / detritivore
an organism which consumes producers / dead matter
definition of secondary consumer
an organism which feeds on primary consumers
definition of saprotroph / saprobiont
- an organism which digests its food externally then absorbs the contents
- feeds on dead or decaying matter
what is saprotrophic nutrition?
extracellular digestion via secretion of digestive enzymes which releases inorganic ions into the soil, most of which are absorbed by saprobionts
how are producers always photoautotrophic and what is the importance of this?
they make their own food using light energy
what is the importance of producers always being photoautotrophic?
all photoautrophs use the same photosynthesis reaction, suggesting they evolved from the same ancestor
what is the role of a producer?
to absorb light energy and use it to convert atmospheric CO₂ (land plants) or aquatic CO₂ (underwater plants) to glucose and other sugars for chemical energy
what is biomass?
the mass of carbon in an organism OR the dry mass of tissue
where does biomass come from?
- light energy absorbed by producers is used to convert CO₂ to organic, C-based molecules eg. glucose
- this is either used as a respiratory substrate or to build large molecules in producers, (proteins, cellulose etc.) forming biomass
how is biomass transferred from a producer to a consumer?
- the molecules that make up biomass (proteins etc.) contain chemical energy
- when a consumer eats a plant, it takes in the plant’s biomass, digests it and builds its own molecules and therefore biomass
- chemical energy from plant’s biomass is now in animal’s biomass
what are the 2 ways of measuring biomass?
- dry pass per area per time or carbon per area per time
- calorimetry
how do you work out the dry mass of tissues?
- every organism has variable amounts of water, so you don’t want to include this in the biomass
- place your sample in the oven at a low temperature so it doesn’t burn
- weigh it at regular intervals and reheat until the weight remains constant
- units = mass / area / time
describe the process of finding the dry mass of a plant sample
- weigh crucible without sample
- place sample in crucible
- place crucible in oven
- set oven to low temp
- remove and weigh crucible, with sample, at regular intervals during the drying process
- once mass of crucible and sample stops decreasing and becomes constant, sample is fully dehydrated
- to find dry mass of sample, subtract original mass of crucible, without sample, from final constant mass
what are the limitations of meauring dry biomass? [3]
- difficulty in sampling
- variability in biomass
- destruction of samples
describe the process of calorimetry
- burning a sample releases energy, which is used to heat a known mass of water with a known shc
- use the temperature change of the water to work out the energy released from the sample
- E = m × c × θ
what are the limitations of calorimetry? [7]
- long time to fully dehydrate to find dry mass
- precise equipment is needed, which may not be available
- all of sample may not be burnt
- water may not be pure, so shc may not be 100% accurate
- more simple basic calorimetrry = less accurate estimate
- some energy released is used to heat beaker with water
- some heat released is lost to surroundings
