organisms and their environments
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the flow of energy:
• Starts with the sun • Green plants and algae convert light energy from the sun into chemical energy in the form of carbohydrates • Plants use the food made by photosynthesis to grow parts such as leafs, stems, fruits etc. • These parts are then eaten by animals - the chemical energy of the plant is then transferred to the animal’s body • If this animal is then eaten by a second animal, the chemical energy of the first animal is transferred to the body of the second animal
food chain
shows the direction of energy from one organism to the next
food web
network of interconnected food chains
pyramid of energy
shows the amount of energy available in the form of biomass at each trophic level
how is energy lost (herbivores)?
• Herbivores: - not all of the plant is eaten, for examplethe roots may not be eaten by the herbivore - energy is used to build inedible tissues such as wood (cellulose) or roots - energy is lost as heat during respiration (this occurs in all living organisms, including decomposers)
how is energy lost (carnivores)?
• Carnivores: - energy is lost as heat - energy is lost as excretory products (for example, urea) - energy is used to build up inedible parts such as bones
What are the 4 main reservoirs that carbon is stored in/cycles between?
• The atmosphere • The ocean • Land biomass • Fossil fuels
how is carbon dioxide returned to the air?
• respiration • combustion
how is carbon dioxide removed from the air?
• Through photosynthesis by converting carbon dioxide into carbohydrates
nitrogen fixation
nitrogen gas to ammonium ions
what are the two main ways in which nitrogen fixation happens
lightning bacteria
what do nitrogen fixing bacteria do?
they convert nitrogen gas in the air between soil particles to form ammonia which dissolves to ammonium ions
denitrification
nitrate ions to nitrogen gas
nitrification
ammonium ions to nitrate ions
how do plants absorb nitrate ions?
• Through root hair cells • Through active transport
deamination
the removal of the nitrogen-containing part of amino acids to form urea. Which is then secreted in the form of urine
decomposition
proteins to ammonium ions
population
group of organisms of one species, living in the same area at the same time
community
all the populations of different species in an ecosystem
ecosystem
unit containing the community of organisms and their environment, interacting together
Factors affecting the number of individuals within a population:
• food supply • predation • disease • competition
Factors affecting how the size of a population changes over time:
• Number of births: this increases the population size because offspring are added. • Immigration: this increases the size of the population because individuals come into the area from somewhere else. • Number of deaths: this decreases the population size because some individuals are eaten, or die of old age or illness. • Emigration: this decreases the size of the population because individuals leave the area to go somewhere else
carrying capacity
maximum number of organisms that an ecosystem can support