topic 9

Question 1

why is only around 10% of the biomass at one level transferred to the next

Answer 1

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

Question 2

positive interactions of humans with ecosystems

Answer 2

• 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

Question 3

negative interactions of human with ecosystems

Answer 3

• 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

Question 4

benefits of hedgerows and field margins where only one crop type is grown

Answer 4

maintains biodiversity because the hedgerows provide habitat for many organisms + fuel margins give areas where wild flowers and grasses can grow

Question 5

factors affecting levels of food security

Answer 5

• 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

Question 6

optimum decay conditions

Answer 6

• more oxygen available means aerobic respiration, so heat is produced
• increasing temp then increases rate of decay

Question 7

the water cycle

Answer 7

• 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

Question 8

why is nitrogen not used directly by plants

Answer 8

nitrogen gas in the atmosphere is too unreactive

Question 9

indicator species for polluted water

Answer 9

bloodworms/sludgeworms

Question 10

indicator species for clean water

Answer 10

• 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

Question 11

indicator species for air quality

Answer 11

• 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

Question 12

factors affecting rate of decomposition

Answer 12

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

Question 13

using a belt transect

Answer 13

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

Question 14

eutrophication

Answer 14

• 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)

Question 15

harm of open water fish farming in holding nets

Answer 15

• 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

Question 16

harm of farming fish in large tanks

Answer 16

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

Question 17

examples of conservation schemes

Answer 17

• 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

Question 18

benefits of maintaining biodiversity

Answer 18

• protecting the human food supply (overfishing)
• minimises damage to food chains
• providing future medicines
• ecotourism
• providing new jobs - restoration schemes, ecotourism

Question 19

the carbon cycle

Answer 19

• 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

Question 20

desalination (two methods)

Answer 20

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

Question 21

what are the four bacteria types involved in the nitrogen cycle

Answer 21

decomposers
nitrifying bacteria
nitrogen-fixing bacteria
denitrifying bacteria

Question 22

nitrogen fixation

Answer 22

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

Question 23

nitrogen fixing bacteria in plants

Answer 23

• 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

Question 24

decomposers in the nitrogen cycle

Answer 24

• they decompose proteins and urea and turn them into ammonia
• ammonia forms ammonium ions in solution that plants can use

Question 25

nitrifying bacteria

Answer 25

one type turns ammonia in decaying matter into nitrites and another turns those into nitrates

Question 26

denitrifying bacteria

Answer 26

turns nitrates back into N2, not beneficial to living organism
often found in waterlogged soils

Question 27

methods used by farmers to increase nitrates in the soil

Answer 27

• crops are harvested so nitrogen they contain isn’t returned to the soil, leading to poor crop growth and deficiency diseases

• crop rotation - different crops are grown yearly, in a cycle
nitrogen fixing crop (legume) which returns nitrates to the soil for next years crop

• fertilisers - animal manure/compost recycles nutrients left in waste and returns them to the soil through decomposition
• artificial fertilisers can also be used - but pricey

Question 28

issues with indicator species

Answer 28

• tells you if an area is polluted or not but not HOW polluted it is
• counting the no. of a species in multiple areas gives you numerical, comparable values so you can roughly compare pollution

Question 29

non-living indicators

Answer 29

• dissolved oxygen meters + chemical tests - accurately measure the amount of dissolved oxygen in water
• electronic meters and various laboratory tests - accurately measure conc. of sulfur dioxide in the air