Organisms and their environment Flashcards
Define food chain
The transfer of energy from one organism to the next, beginning with a producer
Define trophic level
The position of an organism in a food chain, food web, pyramid of numbers or pyramid of biomass
Why is the transfer of energy from one trophic level to the next inefficient?
Because of egestion, excretion, respiration and production of inedible bones and shells
Define food web
A network of interconnected food chains
Define Producer
An organism that makes its organic nutrients usually from energy from sunlight through photosynthesis
Define Consumer
An organism that gets its energy by feeding on other organisms
Define Herbivores
An animal that gets its energy by eating plants
Define Carnivores
An animal that gets its energy by eating other animals
Define Decomposer
An organism that gets its energy from dead or waste organic material
Why is the pyramid of biomass better than the pyramid of numbers?
- Pyramids of biomass take into account the size of organisms
- Less misinterpreted
- Range of numbers may be enormous
What is the importance of the water cycle?
Living organisms require water- provides organisms with a constant supply of water
How is nitrogen fixed?
By lightning and bacteria -root nodules of certain plants (peas, beans, clover – leguminous plants) take N2 gas and change it into nitrates in the soil
What produces ammonium ions?
Decomposers break dead matter down into ammonium ions
What converts ammonia into nitrites and nitrates
Nitrifying bacteria
What absorbs nitrate ions?
Plants
What release nitrogen back into the atmosphere?
Denitrifying bacteria
What is deamination?
Removal of the amine group in an amino acid
What is nitrogen fixation?
is when N2 and H2 combine to form ammonium ions then nitrate if oxygen is present
What are legumes used for?
To avoid using so much nitrogen- containing fertiliser so therefore it is less expensive
What is nitrification?
When ammonium ions are produced by the decomposition of amino acids and are oxidised first to nitrite then to nitrate
What is denitrifying?
When nitrate is converted to nitrogen gas
Define population
A group of organisms of one species living in the same area at the same time
Define Ecosystem
A unit containing the community of organisms and their environment interacting together
Define community
All of the populations of different species in an ecosystem
What is population growth controlled by?
Food supply
Predation and disease
Why has the population size increased significantly?
Because of improved technology leading to an abundance of food and improved medication and health care
Describe the sigmoid growth curve?
Log phase
Exponential phase
stationary phase
death phase
