food production

Question 1

advantages of organic fertilisers

Answer 1

• improves soil structure
• greater range of minerals
• releases minerals over a longer period of time
• cheaper- available on farm

Question 2

disadvantages of organic fertilisers

Answer 2

• slow- has to decompose first
• bulkier- harder to apply
• may contain pests

Question 3

advantages of inorganic fertilisers

Answer 3

• mineral ions released immediately- fast acting
• contents known
• easy to apply

Question 4

disadvantages of inorganic fertilisers

Answer 4

-can lead to eutrophication

Question 5

nitrogen fixing plants

Answer 5

legume crops used- have nitrogen-fixing bacteria in nodules on their roots, convert nitrogen gas in air to ammonium ions
passed to plants- use to make proteins
when crop is ploughed- protein decomposed and ammonium us released into soil- converted to nitrate by nitrifying bacteria

Question 6

how do pesticides improve yield from crops and livestock

Answer 6

herbicides- plant pests
insecticides- insects
fungicides- fungi
molluscicides- molluscs(slugs/snails)

damage ecosystem- molecules passed higher up in food chain- concentrated in tissues of top carnivores

Question 7

how does biological control reduce the numbers of pests

Answer 7

uses predator species

Question 8

biological control agents

Answer 8

natural predator- ladybirds control aphid population in orange groves

herbivore- moth eat prickly pear cactus Australia

parasite- wasp encarsia lay eggs in whitefly eggs and reduces population

pathogenic microorganism- myxomatosis virus on rabbit pop in aus

sterile males- mate with females- no offspring- reduce pet numbers

pheromones- sex hormones released- males and females collected and destroyed reducing reproductive potential of pop

Question 9

advantages and disadvantages of pesticides

Answer 9

• reduces pest pop instantly
• kills whole pop
• cost
• not specific
• pest can become resistant
• chemical concentrates in organisms higher in food chain

Question 10

advantages and disadvantages of bio control

Answer 10

• organism introduced once
• one cost
• specific
• pest not resistant
• no effect on other animals in food chain
• time to reduce pop
• not all killed
• expensive repopulating

Question 11

cooling jacket

Answer 11

removes heat energy, stopping fermenter overheating and enzymes denaturing

Question 12

air filter

Answer 12

filters coming in air, maintains sterile conditions

Question 13

stirrers

Answer 13

keeps broth well stirred to oxygenate fermenter and prevent microorganisms settling

Question 14

growth medium

Answer 14

contains glucose and amino acids for microorganism growth

Question 15

super-heated steam

Answer 15

applied before fermenter used, kills unwanted microorganisms, leaves only water with no residue

Question 16

fish farming

Answer 16

farmers feed fish high lipid and protein diet- promote rapid growth
regular feeding with small amounts- most is eaten

Question 17

what happens if you put several species in one pond?

Answer 17

• interspecific competition- different species compete for food, some species wiped out
  predation- carnivorous species prey on other fish
  solution; place different species in different ponds, cover over ponds- reduce predation from birds

Question 18

what happens if you put too many individuals in one pond?

Answer 18

-intraspecific competition- larger individuals will out-compete smaller for food or pray on smaller
infectious diseases- parasites and pathogens spread quickly if too close

solution; separate by age and size, remove dead or infected quickly and add antibiotics to water to kill bacteria

Question 19

how do fish farms affect environment

Answer 19

• escape and out-compete or interbreed with local species reducing biodiversity and upset local ecosystem
• parasites or pathogens introduced into ecosystem by farmed fish
• excess feed and waste- eutrophication