why is only around 10% of the biomass at one level transferred to the next
not all can be eaten - eg. bone, hooves, claws and teeth
not all biomass eaten is converted into the biomass of the consumer - glucose used in respiration, urea released in urine, faeces
positive interactions of humans with ecosystems
- maintaining rainforests, stopping the destruction of habitats
- raising awareness through large-scale community projects
- reducing water pollution and monitoring changes
- protecting areas of scientific interests by not allowing people there
negative interactions of human with ecosystems
- greenhouse gases –> global warming
- introducing non-indigenous species that prey on native species
- sulfur dioxide in factories –> acid rain - affects habitats
- chemicals used in farming can leak into lakes - eutrophication
- clearing land for building - less habitats
benefits of hedgerows and field margins where only one crop type is grown
maintains biodiversity because the hedgerows provide habitat for many organisms + fuel margins give areas where wild flowers and grasses can grow
factors affecting levels of food security
- increasing birth rate and population
- diets changing to consume more meat and fish
- new pests and pathogens can destroy crops
- climate change
- conflict in certain countries
optimum decay conditions
- more oxygen available means aerobic respiration, so heat is produced
- increasing temp then increases rate of decay
the water cycle
- water vapour - suns energy causes evaporation + transpiration in plants
- water vapour rises, cooling and condensing to form clouds
- the water returns to land through precipitation and runs into lakes then into seas and the cycle repeats
why is nitrogen not used directly by plants
nitrogen gas in the atmosphere is too unreactive
indicator species for polluted water
bloodworms/sludgeworms
indicator species for clean water
• freshwater shrimps and stonefly larvae
stonefly larvae are very sensitive to oxygen concentration - raw sewage/fertilisers means increased organisms that use up oxygen
so, found in clean water
indicator species for air quality
- heavy sulfur dioxide pollution - lichen is less likely to be found/crusty lichen don’t need super clean air
- clean air - ideal environment for bushy lichen/rich variety of species
- blackspot fungus is more common on roses where it’s less polluted bc sulfur dioxide protects plants from certain fungi
factors affecting rate of decomposition
temp - chemical reactions are generally faster where it’s warm, but if its too hot then enzymes can denature
water - faster growth where there’s water bc it’s needed for respiration, also makes food easier to digest
oxygen - most decomposers respire aerobically
using a belt transect
used to study distribution along a gradient
collect data from quadrants placed in a line
repeat and then find the mean
plot graph to see if the changing abiotic factor is correlated with the change is distribution of species
eutrophication
- excess nitrates from fields can easily reach rivers and lakes bc of rain
- the excess nitrates cause algae to grow fast, blocking out light
- plants then can’t photosynthesise due to lack of light and start to die and decompose
- more food available, so microorganisms that feed on decomposing plants increase in number and use up oxygen in the water
- organisms that respire anaerobically die (eg. fish)
harm of open water fish farming in holding nets
- food is added to the nets to feed fish which can produce loads of waste –> eutrophication + death of wild species
- they can act as a breeding ground for loads of parasites - these can get out of the farm and infect wild animals
- predators are attracted to the nets, get trapped, and die
harm of farming fish in large tanks
the farms are usually low in biodiversity because there’s only one species; the tanks are kept free of plants, predators and any parasites/microorganisms are generally killed
if the fish escape into the wild, this can cause issues for wild populations of indigenous species
examples of conservation schemes
- protecting a species’ natural habitat
- protecting species’ in a safe area outside of their habitat eg. a zoo
- seed banks to store and distribute seeds of rare and endangered plants
benefits of maintaining biodiversity
- protecting the human food supply (overfishing)
- minimises damage to food chains
- providing future medicines
- ecotourism
- providing new jobs - restoration schemes, ecotourism
the carbon cycle
- photosynthesis takes CO2 FROM the air, green plants use the carbon to make fats, proteins and carbs
- eating passes the carbon compounds along the food chain
- living animals RETURN CO2 by respiration but eventually die/killed
- when they decompose the decomposers respire and RELEASE CO2
- some products are burned, combustions again RELEASES CO2
- decomposition means that nutrients can be returned to the soil
desalination (two methods)
thermal desalination - basically distillation
reverse osmosis
salt is treated to remove solids
its fed at a very high pressure
net movement of water across a partially permeable membrane from an area of low conc to an area of high conc
what are the four bacteria types involved in the nitrogen cycle
decomposers
nitrifying bacteria
nitrogen-fixing bacteria
denitrifying bacteria
nitrogen fixation
turning N2 in the air into nitrogen-containing ions in the soil which plants can use
- lightning - the amount of energy in a bolt of lightning is enough to make oxygen and nitrogen react to get nitrates
- nitrogen fixing bacteria - found in roots and soil, turns N2 into ammonia which forms ammonium ions
nitrogen fixing bacteria in plants
- nitrogen-fixing bacteria can live on root nodules of legume plants
- when they decompose the nitrogen stored in them is returned to the soil
- nitrogen-containing ions can also leak out of the nodules during plants growth
decomposers in the nitrogen cycle
- they decompose proteins and urea and turn them into ammonia
- ammonia forms ammonium ions in solution that plants can use
