Everything

Question 1

How does negative feedback occur?

Answer 1

When the output of a process inhibits or reverses the same process and maintains equilibrium

Question 2

How does positive feedback occur?

Answer 2

When the output of a process accelerates that same process and deviate away from equilibrium

Question 3

What is resilience?

Answer 3

It is the ability to withstand disturbances/ tendency to maintain stability

Question 4

Describe two characteristics of soil with high primary productivity

Answer 4

Balanced composition of sand slit and clay
Allow good drainage/ permeability
Provide sufficient air space/ porosity for root growth

Question 5

Outline two conservation techniques that could be used to reduce soil erosion

Answer 5

Contour ploughing with furrows at right angles to the slope
Wind reduction techniques eg. wind shelter breaks to prevent wind erosion
Terrace farming involves creating steps on a hillside

Question 6

What is succession

Answer 6

It is the process of changes in community/ ecosystem over time

Question 7

What is zonation

Answer 7

It is the process of changes over an environmental gradient/space

Question 8

Describe two water management strategies that can reduce water scarcity

Answer 8

Desalination to increase water supply
Use of water saving agricultural strategies (drip irrigation)
Reduce production of crops with high water demand

Question 9

Outline two reasons why loam soils are the most productive for plant growth

Answer 9

Good balance of sand and clay
Has good drainage (compared to clay)
Allows aeration (compared to clay)
Retains nutrients (compared to sand)

Question 10

Outline how soil can be viewed as an ecosystem

Answer 10

Soil is an open system with inputs (water) and outputs (nitrogen) and storages (nitrates,water) and flows(leaching, decomposition)
Like an ecosystem soil is a community of living/biotic (bacteria, fungi) and abiotic elements (clay,slit,water,heat)
…with the many complex interactions (mineral cycling, leguminous plants)

Question 11

Outline the mechanism of natural selection

Answer 11

It acts on the genetic variation of a population
Formed by mutations in previous generations
When conditions change some individuals will be fitter than others
Thus will survive and reproduce in higher rates
Inheriting these advantageous traits to their offsprings
Hence the frequency of that advantageous character will increase in the population

Question 12

State one strength and one weakness of using the ecological footprint as a model for measuring sustainability.

Answer 12

Strengths:
good visualising tool/easily understood by non-specialists;
iconic symbol for raising awareness
(widespread use so) easy to compare with other areas
Weaknesses:
calculations are complex/all models are simplifications
less reliable at local level / not everyone in the region has the same lifestyle
land has more than one function

Question 13

Identify four strategies that can be used in the sustainable management of wild fisheries.

Answer 13

a. use of quotas / international regulations against overfishing
b. restrictions on time/season/size/age allowed to fish
c. monitoring illegal fishing through technology
restrictions/bans on types and size of fishing gear
e. campaigns to reduce consumption of wild caught fish

Question 14

Evaluate the sustainability of two water management strategies to improve access to freshwater resources in a society

Answer 14

Example 1: Rainwater harvesting;
Positive:does not impact natural water cycle / replenishment rate / impossible to reduce natural income; free natural capital; useful for watering plants/irrigation / washing / fire protection / (thus) reduces consumption of groundwater/other freshwater resources;

Negative:availability restricted temporally and spatially (unequal distribution of rain /unpredictable supply);usually not safe for drinking; can’t satisfy needs of irrigation of commercial agriculture

Example 2: Desalinization;
Positive:sustainable if energy required produced by photovoltaic cells; sea water is more available than freshwater; provides accessible/safe drinking/irrigation water; salt may be used for producing useful chemical products (sodium hydroxide, hydrochloric acid);reduces pressure on freshwater reserves that need protection;

Negative:requires huge amounts of energy / increase GCC if fossil fuel used; not available in landlocked countries; building of facilities result in environmental damage/pollution; disposing of salt (brine) poses environmental hazards/pollutes ocean / salt is contaminated so can’t be eaten; high cost to build and operate that may be economically unsustainable

Question 15

With reference to Figure 3(c), explain three ways in which Hurricane Maria has affected ecosystem services provided by Dominica’s forests.

Answer 15

a. reduction in photosynthesis so less oxygen produced
b. loss of habitat for species (reducing biodiversity)
c. less uptake of water by plants resulting in increased flooding
d. loss of habitat reduces food supply / loss of trees reduces food source

Question 16

Distinguish between two named biomes and the factors that cause their distribution

Answer 16

e.g. tundra vs tropical rainforest:

Distinguishing features [3 max]:tundra has lower insolation / TRF has the highest insolation of all biomes;TRF has constant insolation throughout the year / tundra has long, dark winters; tundra has lower mean annual temperature / TRF has warmer temperatures; tundra has 6–10 months of freezing temperatures / TRF has constant warm temperatures;TRF has the largest annual precipitation compared to any biome / tundra precipitation is as low as in deserts;TRF has almost constant precipitation throughout the year; tundra precipitation mostly in form of snow / tundra has a characteristic layer of frozen ground below the surface/permafrost;TRFs have the highest biodiversity of all biomes;

Explanation of distribution: [2 max]tundra found at the poles, while TRFs at the tropics (above and below the equator);Hadley cell rises at the Equator causing huge precipitation (low pressure zone) / as warm air cools and its moisture condenses; tundra is found in the low pressure area of polar cell / at a region where there is net loss of solar energy (causing freezing temperatures) / alpine tundra found on mountaintops, where temperatures are below 0 most time of the year due to high altitude

Question 17

Evaluate one method for measuring primary productivity in a named ecosystem

Answer 17

Alternative 1:

Method: light and dark bottle for an aquatic ecosystem; measure dissolved oxygen at start and end of experiment; compare measurements in a transparent (with light) and opaque (without light) bottle
containing sample of water from ecosystem; net productivity is equivalent to change in dissolved oxygen in light bottle; gross productivity is equivalent to change in dissolved oxygen in light bottle plus the loss of dissolved oxygen in the dark bottle (due to respiration);measurements taken for a set period of time, eg one week

Evaluation:
simple, easy to conduct method;
ethical method – samples can be returned to ecosystem;
difficult to isolate primary producers from consumers in ecosystem sample;
only collecting productivity for submerged subset of ecosystem;
measurements dependent upon temperature;
quality of measurements depends on precision of instruments;

Question 18

Outline how a positive feedback loop can impact an ecosystem.

Answer 18

positive feedback loops (destabilizing) amplify changes in an ecosystem;

feedback refers to the return of part of the output from a system as input so as to affect succeeding outputs;

this drives the system towards a tipping point where a new equilibrium is adopted;

this new equilibrium may be an alternative stable state / involve collapse of original system;

Question 19

Outline, using examples, the differences between primary and secondary pollution.

Answer 19

Primary pollution:is active upon emission of pollutant;
eg carbon dioxide/lead/nitrates/phosphates/heat/light;

Secondary pollution:occurs when primary pollutants undergo some kind of physical or chemical change;
eg. nitrogen/sulphur oxides combining with water to form nitric acid/sulphur acid/acid rain;
nitrogen oxides/VOCs combining to form tropospheric ozone/photochemical smog;

Question 20

Explain the causes and effects of acid deposition on natural ecosystems.

Answer 20

Causes:
burning of fossil fuels releases NOx/SOx;
the sources of these are mainly coal-burning industries/transportation/electricity generation;
emissions from livestock/use & production of inorganic fertilizers also contribute;
volcanic eruptions can also cause acid rain/release oxides of N/S;

Effects:direct adverse effect of acidity on living organisms eg kills lichens / plankton / fish / soil microbiota;
causing leaf-fall/thinning of waxy cuticle/reduced immunity to disease/root damage in terrestrial plants;
leading to reduced primary production/plant growth;
indirect toxic effect by changing chemistry of soil/water;

Question 21

Explain how regional differences in the hydrological cycle influence the formation of different biomes.

Answer 21

in certain tropical regions there is high transpiration/precipitation;
…allowing for high productivity/tropical rainforests;

in other tropical regions evaporation exceeds precipitation;
…so, water is limiting for growth leading to vegetation of desert biomes;

in polar regions large proportion of water is frozen/stored as ice/glaciers;
…so unavailable to plants resulting in limited vegetation of tundra;

in mid-latitudes there is moderate transpiration/precipitation;
…allowing for moderate plant growth of temperate grasslands/forests;

Question 22

In 2016, the Earth’s atmospheric levels of carbon dioxide reached 400 ppm. Suggest the potential impacts of high levels of greenhouse gases on human societies in different locations.

Answer 22

Impacts may include:

increased mean global temperature causing increased use of A/Cs (especially in developed countries);

greater frequency/intensity of extreme weather events causing damage to infrastructure
(especially in cities);

long-term changes in climate/weather patterns requiring cultural changes/adaptation insocieties;

ocean acidification killing plankton/reducing fisheries (especially significant for coastal populations);

melting permafrost increasing productivity/arable land/water availability (for tundra populations);

decreased water availability/desertification leading to migration/relocation (especially for tropical populations);

biome shifts reducing/enhancing crop productivity (especially significant in crop-growing areas);

biodiversity loss reducing aesthetic value of ecosystems (significant for tourism-dependent societies);

disruption of ecosystem services causing increased flooding (particularly in high rainfall locations);

rise in sea level causing coastal erosion (especially significant to areas dependent on coastal tourism);

coastal inundation causing salinization of underground aquifers/soils (especially for coastal populations);

wider spread of tropical diseases (especially significant for previously sub-tropical areas)

Question 23

Outline how urbanization might impact two of the storages

Answer 23

reduction in biomass storage due to deforestation;

reduction of groundwater storage due to impermeable surfaces/urban withdrawal;

increase in lake/river/ocean storage due to deforestation/increase of impermeable surfaces;

less snow due to urban heat island effects;

increased sediment/pollution in lakes/rivers/oceans/groundwater due to construction/industrialized activities;

Question 24

Runoff from agricultural land can result in excess nutrients entering water bodies. Outline one indirect measure of organic pollution.

Answer 24

Alternative 1:

Named measure [1 max]:
-biochemical oxygen demand;

Methodology [2 max]:
-measure the initial dissolved oxygen;
-keep a sample in the dark for five days and measure DO again;
-take the difference of the two measurements;

Question 25

Outline two reasons why the value of resources like Uranium can change over time

Answer 25

value of resources change over time due to changing needs/shifting cultural values/technological development/accessibility;

as technology made it possible to use uranium for nuclear energy, demand (and price) ofUranium increases;

as countries seek alternatives to fossil fuels / more nuclear power stations opened so uranium increases in value;

adoption of ecocentric values e.g. Sweden, reduces demand for uranium so price falls;

Question 26

State two factors that are used to determine the conservation status of a species.

Answer 26

population size;

rate of pop increase/decrease;

degree of specialization;

distribution;

reproductive potential and behaviour;

geographic range;

habitat quality/fragmentation;

trophic level;

probability of extinction;

Question 27

Discuss how solid domestic waste disposal options could be used to reduce the threats to marine organisms.

Answer 27

Recycling can reduce plastics entering waterways;
…but is costly/depends on changing lifestyles;

Landfill can reduce wastes entering waterways;
…but can still lead to leaching of toxins into aquatic environments;

Incineration can reduce wastes entering aquatic environments;
…but may cause air pollution and deposition/acidification of marine environments;

Composting can reduce organic waste polluting waterways;
…but is only suitable for biodegradable waste;

Littering laws can reduce waste entering marine systems
…but need appropriate penalties/monitoring etc;

Conclusion e.g. recycling is probably the most reliable protection of marine organisms against plastic waste;

Note: Award [3] max if neither counterarguments nor conclusion are presented I.e. response must include at least one or the other to fullfil the ‘Discuss’ command term.