18. Organisms and their environment Flashcards
Source and transfer of energy
Sun is the principal source of energy input to biological systems
flow of energy through living organisms- light energy from the Sun and chemical energy in organisms, and its eventual transfer to the environment
Describe a food chain and a food web
showing the transfer of energy from one organism to the next, beginning with a producer.
a network of interconnected food chains and interpret food webs.
Describe a producer and a consumer
an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis
an organism that gets its energy by feeding on other organisms
consumers may be classed as primary, secondary, tertiary and quaternary according to their position in a food chain
Describe a herbivore, a carnivore and a decomposer
an animal that gets its energy by eating plants
an animal that gets its energy by eating other animals
an organism that gets its energy from dead or waste organic material
Describe a trophic level
the position of an organism in a food chain, food web or ecological pyramid
advantages of using a pyramid of biomass rather than a pyramid of numbers to represent a food chain
advantages of using a pyramid of energy rather than pyramids of numbers or biomass
structure and use of all pyramids
- quantity of biomass- size of each organism- better idea of quantity of energy at each level
- quantity of energy at each trophic level- informative
pyramid of number- size of bar of producer can vary- no. og organism at each trophic level is shown by area of bar.
pyramid of biomass- always pyramid- shows relative quantity of biomass at each trophic level.
pyramid of energy- always pyramid- shows relative quantity of energy
in a pyramid of numbers one large individual is shown in the same way as one very tiny individual ; biomass indicates how much food there is, available, biomass is an indicator of the energy available ; pyramid of biomass is pyramid shaped whereas a pyramid of numbers is not always
Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants and why food chains usually have fewer than five trophic levels
the transfer of energy from one trophic level to another is often not efficient
energy is lost (from the food chain as it is transferred from one trophic level to the next) / energy decreases up the trophic levels ;
only 10% energy transferred ; ora
energy is lost as heat / in respiration / in (named) metabolic
processes / movement ;
not all organisms (in one trophic level) are eaten ;
not all nutrients in the organisms are, eaten / digested / absorbed ;
some energy is lost in, excretion / urine / faeces ;
some energy is transferred to decomposers ;
(small) total percentage reaching x no. trophic level ;
not enough energy in x no. trophic level to support another level;
Describe the carbon cycle
photosynthesis-air to plant
respiration- animal & decomposer to plant
feeding- plant to animal
decomposition- plant & animal (die) to decomposer
formation of fossil fuels and combustion- plant to fossil fuel to air (plants die and no decomposers present)
A- air to plant to animal to air
D- air to plant to decomposers to air
No D- air to plant to fossil fuel to air
Describe the nitrogen cycle
- decomposition of P&A- protein to ammonium ions
- nitrification- ammonium ions to nitrate
- absorption of nitrate ions by plants- nitrate to AA
- production of amino acids and proteins- AA to protein synthesis
- feeding and digestion of proteins
- deamination- protein to waste which is decomposed
- nitrogen fixation by lightning and bacteria- N2 to nitrate
- denitrification- nitrate ions to N2
roles of microorganisms in the nitrogen cycle
decomposition- P/A protein after dead to ammonium
nitrification- ammonium ions to nitrate- nitrifying bacteria
nitrogen fixation- N2 gas to nitrate or ammonium ions
denitrification- nitrate ions to N2 gas in anaerobic conditions when soil is poorly aerated not much O2 by denitrifying bacteria
Nitrogen-fixation
Lightning- makes some of N2 react with O2, forming nitrogen oxides which dissolve in rain and are washed into soil where they form nitrates.
N2-fixing bacteria- live in soil or root nodules where they convert N2 from air spaces and combine it with other substances to make ammonium ions and their compounds.
Artificial fertilisers- N2 and H2 react together in industrial chemical processes to form ammonia to make ammonium compounds and nitrates which are sold as fertilisers.
Describe a population, a community and an ecosystem
population- a group of organisms of one species, living in the same area, at the same time
community- all of the populations of different species in an ecosystem
ecosystem- a unit containing the community of organisms and their environment, interacting together
factors affecting the rate of population growth for a population of an
organism
food supply, competition, predation and disease
sigmoid curve of population growth for a population growing in an
environment with limited resources
lag- small & grows very slowly (adapting to environment)
exponential (log)- grows at maximum rate birth rate exceeds death rate ( food supply increases )
stationary- constant birth rate= death rate ( some limiting factors)
death- falls; death rate exceeds birth rate ( food supply decreases)
