6.3.1 Ecosystems 6.3.2 Populations and Sustainability

Question 1

decomposer

Answer 1

breaks down dead matter

Question 2

examples of decomposers

Answer 2

bacteria, fungi
detritivores: speed up decay process by breaking down matter into smaller fragments - increasing surface area

Question 3

why does decomposition release CO2

Answer 3

glucose, from digestion, is respired = releasing CO2 into the atmosphere

Question 4

saprotrophic nutrition

Answer 4

energy obtained from dead, organic matter

Question 5

autotrophic nutrition

Answer 5

nutrients obtained from photosynthesis

Question 6

importance of nitrogen for living organisms

Answer 6

make nucleic acids: DNA/RNA
make amino acids: proteins

Question 7

why is nitrogen not directly absorbed

Answer 7

N≡N bond is too strong to break (lightning can break triple bond)
N must be combined with H, O atoms to increase the ability to be absorbed

Question 8

nitrogen fixation

Answer 8

anaerobic, reduction
nitrogen-fixing bacteria use the NITROGENASE enzyme

Question 9

bacteria involved in nitrogen fixation

Answer 9

rhizobium: found in root nodules of legumes
azobacter: free in soil

Question 10

ammonification

Answer 10

decomposers break down dead matter and/or products of egestion + excretion
proteins digested as amino acids are converted into urea
bacteria use urea to respire

Question 11

bacteria involved in ammonification

Answer 11

saprotrophic micro-organisms

Question 12

nitrification

Answer 12

aerobic, oxidation
1. ammonium ions converted to nitrites
2. nitrites converted to nitrates
takes place in well-drained soils

Question 13

bacteria involved in nitrification

Answer 13

1. nitrosomonas
2. nitrobacter

Question 14

denitrification

Answer 14

anaerobic, reduction
nitrates are converted into nitrogen gas
takes place in water-logged soils

Question 15

bacteria involved in denitrification

Answer 15

pseudomonas denitrificans
use nitrates for respiration

Question 16

leghaemoglobin

Answer 16

produced by plants to absorb oxygen
oxygen is transported to mitochondria
removes excess oxygen: provides an anaerobic environment for nitrogenase

Question 17

where is leghaemoglobin found

Answer 17

root nodules

Question 18

nitrogen cycle

Answer 18

Question 19

carbon cycle

Answer 19

Question 20

succession

Answer 20

the directional change in the composition of species in a community that occupy a given area through time

Question 21

causes of succession

Answer 21

changes in the community of organisms = changes in the physical environment - allows community to become established

Question 22

established community

Answer 22

new community outcompetes former community

Question 23

succession occurs in a number of serial stages

Answer 23

at each stage, the key species that are responsible for changing the abiotic factors can be identified

Question 24

abiotic factors

Answer 24

the non-living conditions in a habitat that affect the environment

Question 25

examples of abiotic factors

Answer 25

land-based ecosystem: temperature, light, water
marine ecosystem: salinity, ocean currents.

Question 26

biotic factors

Answer 26

a living organism that affects the environment

Question 27

examples of biotic factors

Answer 27

any living organism
freshwater ecosystem: aquatic plants, fish, amphibians, algae

Question 28

pioneer community

Answer 28

a species adapted to survive in harsh/inhospitable conditions
they stabilise the environment + lead to soil development

Question 29

climax community

Answer 29

final, stable community
very little change overtime
few, dominant species

Question 30

humus

Answer 30

dead material

Question 31

primary succession

Answer 31

1. bare rock
2. pioneer community introduced
3. organisms cause erosion, provide dead material
4. intermediate species grow, reproduce, disperse seeds, die, decompose
5. intermediate species replace pioneer community

Question 32

secondary succession

Answer 32

faster than primary succession as minerals are already available in the soil
occurs on land that is clear of plants/animals - only soil remains

Question 33

deflected succession

Answer 33

when human activities halt primary succession from occurring
stops climax community forming

Question 34

human activities that cause deflected succession

Answer 34

agriculture e.g. mowing, sustainable timer production, cattle farming

Question 35

plagioclimax

Answer 35

final community in a deflected succession ecosystem
affected by grazing, burning

Question 36

beach, bare sand

Answer 36

hostile environment
very salty = low water potential
very windy
no organic matter

Question 37

mini dunes, embryo dunes

Answer 37

result of windblown sand
builds up around the base of pioneer plants
dunes increase in height as plants grow
supports primitive species e.g. maram grass

Question 38

young yellow dunes

Answer 38

increases stability
more minerals = more maram grass species growth

Question 39

old grey dunes

Answer 39

support intermediate plant species - able to outcompete pioneer plant species
increases species diversity
increase in species diversity as you move further from the sea

Question 40

why do dunes become darker as you move further away from the sea

Answer 40

soil quality improves
soil depth increases
larger root networks

Question 41

how would you measure change across a sand dune system

Answer 41

interrupted belt transects
quadrats are placed at regular intervals between 2 tape measures + number of organisms of each species is recorded
take multiple readings at each interval + calculate a mean - ensures sample is as representative as possible

Question 42

kite diagram

Answer 42

allows frequencies of different species to be recorded along the length of a transect
the higher the kite, the greater proportion of that species

Question 43

conservation

Answer 43

maintaining biodiversity by actively managing ecosystems
a dynamic process involving human action

Question 44

preservation

Answer 44

protecting an ecosystem by restricting human access and use so it remains untouched

Question 45

economic importance of conservation

Answer 45

sources of raw materials for industries; for example, timber products from natural and plantation forests for the construction and paper industries
source of natural income from exporting biological resources: timber, fish, paper products
employment for people in transport, marketing, retailing, and ecotourism provides employment for people in places with high biodiversity

Question 46

social importance of conservation

Answer 46

human communities in rural areas with little industry or commerce gain stability from the employment provided by fishing/forestry
areas set aside for forestry provide spaces for recreation. the forestry commission and private forestry owners manage their forests as an amenity for people to enjoy the visual appeal of forested areas, opportunities to take exercise and observe wildlife

Question 47

ethical importance of conservation

Answer 47

the duty that we have to conserve resources for the livelihoods and well-being of future generations
the support of indigenous peoples across the world who maintain their traditional ways of life relying on certain biological resources
e.g. the Arctic rely on seals and whales, the people of the Amazon and central Africa depend on foods that they harvest from the forests