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2.2 COMMUNITIES AND ECOSYSTEM (Ecological pyramids (Pyramid of Biomass…
2.2 COMMUNITIES AND ECOSYSTEM
Respiration & photosynthesis
Respiration
The conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy
glucose + oxygen = energy + water + carbon dioxide [aerobic] d
Photosynthesis
The process by which green plants make their own food from water and carbon dioxide using energy from sunlight
carbon dioxide + water + (light energy) = glucose + oxygen
Compensation point- neither adding biomass nor using it up to stay alive
fuhiigsytv
Community
A group of populations living and interacting with each other in a common habitat
Ecosystem
A community and the physical environment it interacts with
Food chains & trophic levels
Food chain
The flow of energy form one organism to the next
Shows feeding relationship between species in an ecosystem
Trophic level
Producers
Autotrophs
make food from carbon dioxide and water
Chemosynthetic organisms
make food from simple compounds (methane, hydrogen sulphide), do not require sunlight
Consumers
Carnivores
Herbivores
Omnivores
Decomposers
obtain energy from dead organisms
Detritivores
derive energy from decomposing organic material
Position that an organism occupies in a food chain
Food web
Rarely goes beyond the 4th trophic level
Ecological pyramids
graphical models of quantitative differences between amounts of living material stored at each trophic level of a food chain
Pyramid of Biomass
biomass at each trophic level
Advantages
overcomes problems of pyramids of numbers
Disadvantages
Only uses samples from populations, impossible to measure biomass exactly
Organisms killed to measure dry mass
Seasonal factors affect biomass of orgnisms
Pyramid of Numbers
the number of organisms at each trophic level in a food chain at one time
Advantages
gives a simple overview, compares changes in population numbers with time
Disadvantages
does not allow immature forms
numbers can be too great to represent accurately
all organisms included regardless of size
Pyramid of Productivity
rate of flow of energy or biomass through each trophic level
Advantages
most accurate system, shows actual energy transferred
energy from solar radiation can be added
pyramids not inverted
Disadvantages
very difficult to obtain data
difficulties in assigning a species to a trophic level (omnivore)
Bioaccumulation
The build-up of persistent/ non biodegradable pollutants within an organism or trophic level
Biomagnification
The increase in concentration of persistent/ non-biodegradable pollutants along a food chain