Ecosystems 2

Question 1

Ecosystem

Answer 1

All the living organisms that interact with one another in a defined area

Question 2

Factors affecting ecosystems

Answer 2

Biotic and abiotic factors

Question 3

Biotic factors

Answer 3

Interactions between organisms
Competition for food territory and breeding partners

Question 4

Abiotic factors

Answer 4

Light
Temperature - effect enzymes in metabolic reactions can trigger migration
Water availability- lack of water leads to death
Oxygen availability- in aquatic ecosystems require fast flowing cold water containing O2
Soil factors

Question 5

Trophies levels

Answer 5

Each stage in the food chain
First tropic level= producer - light energy into chemical energy
Trophies levels after are all consumers
Rare to have more that quaternary consumer

Question 6

Biomass

Answer 6

Mass of living material present in particular place or particular organisms can be equated to energy content
To calculate biomass multiply dry mass by total number of organisms at that level g per square metre

Question 7

Efficiency of biomass and energy transfer

Answer 7

Biomass is nearly always less than tropic level below
When animals eat tropic level below only transfer small proportion into making new tissues - only this part of the biomass the next level can eat
Energy available measures in kJ per m^2 per yr

Question 8

Ecological efficiency

Answer 8

Efficiency with which biomass is transferred from one tropic level to the next
Net production = gross production- respiratory losses
Ecological eff. = energy after transfer/ energy before transfer x 100

Question 9

Consumer efficiency

Answer 9

Convert 10% of biomass to tissue because
- not all biomass is eaten leaving bones and roots
- some energy transferred to environment
-some parts are not edible sheared into faeces
- some energy is lost via urine

Question 10

Human manipulation of biomass

Answer 10

Plants and animals provided with abiotic factors required to thrive
Competition is removed and predators
Farming animals 3 tropic levels more biomass to consume
Crops only 2 tropic levels
Minimum energy is lost max biomass eaten

Question 11

Ammonification

Answer 11

Sabriobonts to undergo extra cellular digestion of nitrogen containing matter
Decomposing

Question 12

Nitrification

Answer 12

NH4- released into soil
Bacteria in the soil converts ammonia to nitrates
nitrifying bacteria (nitrosomas) oxidise ammonia to nitrites
Nitrobacter oxidise nitrites to nitrates for plants

Question 13

Denitrification

Answer 13

Bacteria in soil break down nitrates and release nitrogen into the atmosphere
Only anaerobic conditions

Question 14

Nitrogen fixing

Answer 14

Atmospheric nitrogen converted to ammonia using nitrogen fixing bacteria
Rhizobium
Using nitrogenase

Question 15

Nitrogen cycle

Answer 15

Ammonification
Denitrification
Nitrification
Nitrogen fixation

Question 16

Carbon cycle

Answer 16

Decomposers - break down dead organisms respiring CO2 into atmosphere
Dead organic matter become trapped making fossil fuels
Consumers carbon macromolecules passed from producer respire releasing CO2
Producers take CO2 from atmosphere for photosynthesis release during respiration

Question 17

Atmospheric CO2

Answer 17

Atmospheric CO2 levels are higher at night and during winter as photosynthesis levels are low
Combustion of fossil fuels once levels of CO2
Deforestation- less CO2 is removed from atmosphere
Temp increasing sea cannot dissolve CO2 as it’s too warm etc

Question 18

Primary succession

Answer 18

Occurs on areas of land taht has been newly formed eg bare rock no organic matter or soil to begin with
V slow process

Question 19

Seral stages

Answer 19

Succession steps
Pioneer community - colonisers (lichen)
Intermediate community - secondary colonisers tertiary , scrubland -> climax community dominant species

Question 20

Climax community

Answer 20

Less hostile conditions
High species diversity
Stable
Eg woodland

Question 21

Secondary succession

Answer 21

Occurs where soil is present but contains no plant or animal species
Eg bare earth after forest fire
Recolonised -> rapid process

Question 22

Pioneer species adaptions

Answer 22

Ability to produce large quantities of spores which are blown by wind
Seeds germinate rapidly
Ability to photosynthesise or produce own energy
Tolerance to extreme conditions
Ability to fix nitrogen from atmosphere

Question 23

Animal succession

Answer 23

Primary consumers first to colonise area- much slower than plant succession
Secondary consumers arrive once suitable food source established
Larger animals then colonise the area

Question 24

Deflected succession

Answer 24

Activities which prevent ecosystems reaching climax community - stopped artificially (plagioclimax)
Grazing of animals or mowing grass clearing field for crops forest clearance to promote biodiversity

Question 25

Measuring abundance of plants

Answer 25

Estimated number in population= number of individuals in sample /area of sample

Question 26

Measuring abundance of animals

Answer 26

Mark release recapture
Lincoln index = No in first x No in 2nd/ number of recaptured