Organisms and their environment Flashcards
The Sun is the
principal source of energy input to biological systems.
The flow of energy through
living organisms, including light energy from the Sun and
chemical energy in organisms, is eventual transfer to the environment.
A food web
is a network of interconnected food chains.
A producer
is an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis.
A consumer
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.
A herbivore
is an animal that gets its energy by eating plants
A carnivore
is an animal that gets its energy by eating other animals
A decomposer
is an organism that gets its energy from dead or waste organic material.
Advantages of using a pyramid of biomass rather than a pyramid of numbers to
represent a food chain:
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 / left ;
biomass is an indicator of the energy available ;
pyramid of biomass is pyramid shaped whereas a pyramid of numbers is not
always
A trophic level
the position of an organism in a food chain, food web or ecological pyramid.
Advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain:
it shows how much energy is available
it shows how much energy is passed through per meter square
other pyramids are not very informative, because we cannot be sure that one
gram of biomass for one species contains the same quantity of energy as one
gram of biomass of a different species.
Transfer of energy from one trophic level to another is often not efficient because
energy is lost between tropic levels. Energy is lost in respiration, movement,
muscles contraction, heat. Energy is lost in faeces, urine. Not all animal or plant is
digestible. Only 10% of the energy is transferred. As we move up the food chain
lesser and lesser energy is available to support a population. Therefore a food chain
is not longer than 5 tropic levels.
nitrogen fixation occurs by
lightning or by bacteria in root nodules, they convert
nitrogen from air into ammonia.
ammonia is converted to
nitrate ions in the process of nitrification, by nitrifying
bacteria.
the plant absorbs nitrate ions from
the soil.
plant produce amino acids and protein from
nitrate ions
animals feed and digest
protein.
deamination of protein occurs in
animals and they excrete it as urea.
bacteria decompose plant and animal proteins into
ammonium ions.
ammonium ions are converted to
nitrogen in the process of denitrification, by
denitrifying bacteria.
A population
a group of organisms of one species, living in the same area, at the same time
A community
all of the populations of different species in an ecosystem.
An ecosystem
as 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
disease
