Chapter 13 - Energy and ecosystems Flashcards
what is the initial source of energy for organisms
sunlight
how is energy passed between organisms
biomass
what are producers
photosynthetic organisms that manufacture organic substances using light water co2 and minerals
what are consumers
organisms that get their energy from feeding on other organisms
what are primary consumers
consumers that eat producers
what are secondary consumers
those that consume primary consumers
what are saprobionts
organisms that break complex material in dead organisms down into simple molecules
what is a food chain
a feeding relationship in which producers are eaten by primary consumers they are eaten by secondary consumers who are eaten by tertiary consumers
what is each stage in a food chain called
a trophic level
what is a food web
many overlapping food chain
what is biomass
the total mass of living material in a specific area at a given time
why is it better to measure the dry mass
the presence of water in an organism varies dependent on conditions
why is such a small percentage of the suns energy used in photosynthesis
reflected by clouds
not all wavelengths of light can be used in photosynthesis
light may not fall on chlorophyll
limiting factors may reduce photosynthesis
what is gross primary production
the total quantity of chemical energy stored in plant biomass at a given Time
what is net primary production
the chemical energy that remains when the loss of energy used in respirations has been accounted for
what is the equation for net primary production
net primary production = primary production - respiratory losses
why is such a low percentage of energy transferred between trophic levels
not all of the organism is consumed
some parts are consumed but can’t be digested so are lost in faeces and urine
heat is lost through respiration
why are fertilisers needed especially in agriculture settings
normally plants would die and decompose, returning their nutrients to the soil
in agriculture the plants are removed before they can decompose so the nutrients must be returned in another way
what are natural fertilisers
consists of the dead and decaying parts of plants and animals
what are artificial fertilisers
NPK fertillisers
mined from rocks and deposits and combined to produce the right ratio for the crop
how do fertilisers increase productivity
plants grow healthier and photosynthesise more
what is nitrogen used for
dna amino acids and atp
what are some of the detrimental effects of nitrogen fertilisers
leaching, eutrophication, reduced species diversity (nitrogen favouring species out-compete others so diversity decreases )
what is leaching
the process by which nutrients are removed from the soil
describe the process of leaching
rainwater dissolved minerals and leached it into water courses and drain into fresh water lakes this can cause eutrophication and illness in humans if water is contaminated
describe the process of eutrophication
in most lakes, nitrate ions act as a limiting factor for algal growth. leaching increases the concentration of nitrate ions so they are no loner limiting. an algal bloom develops. this prevents light from reaching lower depths. plants and algae at these depths die. saprobionts break down dead plant matter. saprobionts use up oxygen and release co2. Oxygen becomes limiting for aerobic respiration and so fish and plants die. there is less competitions for anaerobic organisms who decay the material turning the water putrid
describe the phosphorus cycle
phosphate ions in rocks are released by weathering. plants absorb phosphorous through their roots. mycorrhizae increase the rate of absorptions. phosphate ions are transferred through the food chain as organisms consume one another. phosphate ions are lost from animals in waste products. when these animals and plants fie, saprobionts break down complex material into the soil to be absorbed by plants. weathering rocks releases phosphate into water sources which is taken up by aquatic producers
what is the role of mycorrhizae in the phosphorus cycle
it forms a mutualistic relationship with plants- plants benefit from the increased uptake of phosphorus and the mycorrhizae benefit form organic materials from the plant
what is denitrification
nitrates in the soil are converted into nitrogen gas by denitrifying bacteria under anaerobic conditions
what is nitrogen fixation
nitrogen gas in the atmosphere is converted into nitrogen-contaminating compounds by bacteria
what are the two microorganisms involved in nitrogen fixation
free living bacteria
reduce nitrogen gas into ammonia which they use to produce amino acods
mutualistic bacteria
what is nitrification
amino is oxidised to nitrate ions which are oxides to nitrate
why do nitrogen compounds easily leach through the soil
they are soluble
