Topic 2: Ecosystems and ecology Flashcards
Outline the factors that contribute to total biodiversity of an ecosystem
biodiversity includes the diversity of species, habitat and genes;
species diversity involves both the variety/number of species/richness and their relative proportions/evenness;
habitat diversity refers to the range of different habitats in an ecosystem or biome;
…which may vary due to environmental gradients/changing abiotic conditions/altitude/latitude/major disturbances (volcanic activity/landslides, etc);
habitat/niche diversification promotes species diversity;
genetic diversity refers to the range of genetic material/genes in a population/species;
…which is influenced by mutation/sexual reproduction/natural selection/speciation;
high primary productivity/insolation/precipitation/optimum abiotic conditions promote biodiversity;
succession promotes greater biodiversity by increasing length/branching of food chains / because it leads to improved abiotic conditions.
Define net primary productivity
the gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).
Distinguish between zonation and succession.
succession is the process of changes in community/ecosystem over time, whereas zonation is the process of changes over an environmental gradient/space;
Define the term carrying capacity.
the maximum number of individuals/load of a species that can be sustainably supported by a given area/habitat/environment
Distinguish between the terms niche and habitat with reference to a named species.
habitat is the kind of (biotic and abiotic) environment in which a species normally lives;
eg lions are found in tropical grasslands;
whereas its niche refers to all its interactions with its (biotic and abiotic) environment;
eg the prey that it eats / its vulnerability to parasites / access to fresh water;
habitat may be shared by many species / niche is more limited to a single species;
eg different cat species inhabit tropical grasslands but only lions hunt in groups and so tend to take larger prey.
Describe the role of primary producers in ecosystems
producers are plants that convert light energy into chemical energy by photosynthesis;
photosynthesis/primary producers convert carbon dioxide and water into glucose/sugar and oxygen;
this conversion/glucose forms the raw material of biomass/the basis of food chains;
producers (thereby) provide food for consumers/energy in a form that can be passed along food chains;
the production of oxygen by producers is vital for the majority of ecosystems;
the absorption of CO2 maintains a balance of CO2 in atmosphere/reduces global warming;
primary producers may alternatively generate biomass through chemosynthesis;
chemosynthetic bacteria use chemical energy to produce food without using sunlight;
plants may also provide other resources/services for ecosystem eg habitats/soil conservation/cycling of matter;
Discuss strategies that can be used to improve the sustainability of food production systems.
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understanding concepts & terminology of terrestrial and aquatic food production systems; sustainability; MSY; ecological footprint; natural income & capital; quotas; harvesting methods; organic farming; pest management; integrated aquaculture; monoculture v polyculture; food choice; social equality; soil degradation; water pollution; soil conservation strategies;
breadth in addressing and linking technological and management strategies of terrestrial and aquatic food production systems with aspects of sustainability in terms of yield, environmental impacts, conservation, climate change, economics, food choices and social development and in the context of a range of geographical locations, social settings and EVSs.
examples of named food production systems and strategies;
balanced analysis evaluating a range of strategies in a range of food production systems (and social contexts) and how effective they each may be in improving sustainability along with their limitations and counterarguments;
a conclusion that is consistent with, and supported by analysis and examples given eg the strategies which can be employed to improve the sustainability of a food production system may be viewed differently by various EVSs and it may take a more anthropocentric approach to balance the success of ecocentric strategies such as diet change and education about this, with the careful, monitored implementation of technological strategies such as the use of genetically modified organisms.
State one method to determine the population size of the Keen’s mouse.
capture–mark–release–recapture / Lincoln index;
calculate the Simpson’s diversity index (D)
check notes
Explain how the level of primary productivity of different biomes influences their resilience
esilience is the ability to withstand disturbances / tendency to maintain stability/avoid tipping points;
generally, biomes with higher primary productivity (e.g. rainforests/estuaries/wetlands) are more resilient than those with lower productivity (e.g. tundra/deserts);
more productive biomes can support more species/diversity;
diversity increases resilience because loss of one species is more easily replaced by others;
more productive biomes support more branching food chains / greater complexity of interrelationships;
…that allows for more negative feedback mechanisms/shifting feeding habits maintaining stability/providing more resilience;
more productive biomes produce larger biotic storages;
larger storages are less likely to be eliminated/reduced beyond a tipping point so contribute to greater resilience;
larger storages provide higher maximum sustainable yields so are less prone to overharvesting;
higher productivity entails faster plant growth, thus more effective regeneration after a disturbance;
oceanic biomes have low productivity per unit area but their large size increases their resilience;
coral reefs have high productivity but narrow niche requirements give them low resilience;
Evaluate one method for measuring primary productivity in a named ecosystem
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;
Alternative 2:
Method:
three comparison plots, one covered in opaque plastic for terrestrial ecosystem;
measure dry biomass at start and end of experiment;
compare measurements from an open (with light) and covered (without light) plot in ecosystem;
net productivity is equivalent to change in biomass in open plot;
gross productivity is equivalent to change in biomass plus the loss of biomass in the covered plot (due to respiration);
measurements taken for a set period of time, eg one week;
Evaluation:
easy to isolate primary producers in ecosystem sample;
difficult to collect all biomass;
ethical problems as samples need to be killed to measure dry biomass;
measurements dependent upon temperature;
productivity easier to measure in simpler systems;
difficult to measure with larger producers/trees;
Discuss how human activities impact the flows and stores in the nitrogen cycle.
understanding concepts and terminology of systems approach; flows and (biotic and/or abiotic) stores in nitrogen cycle; atmospheric content; farming practices (aquatic and terrestrial); soil; eutrophication; urbanization, deforestation; transportation; forest fires; use of fossil fuels;
breadth in addressing and linking climate change; photochemical smog; secondary pollutant; acid deposition; scrubbers/catalytic converters; renewable vs. non-renewable energy sources; population growth; EVSs; sustainable development;
examples of farming practices (aquatic and terrestrial) which affect nitrogen flows; eutrophication/pollution management strategies; specific human activities causing atmospheric pollution;
balanced analysis discussing activities which increase nitrogen flows and stores, as well as decreasing or managing these flows and stores;
a conclusion that is consistent with, and supported by, analysis and examples given eg probably the greatest human disturbance to steady state equilibrium in the nitrogen cycle is the increase of inorganic stores such as nitrogen oxides in the atmosphere and nitrates in aquatic systems.
state the type of biotic interaction that occurs
competition / inter-specific competition;
competition for nesting sites/food (where their distributions/habitats overlap ie altitudes 600–800 m);
resource partitioning;
Distinguish between two named biomes and the factors that cause their distribution.
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;
Discuss the role of feedback mechanisms in maintaining the stability and promoting the restoration of plant communities threatened by human impacts.
understanding concepts and terminology of negative and positive feedback, steady state and dynamic equilibria, tipping points, resilience, sustainability, colonization, pioneer communities, succession, biodiversity, variety of nutrient and energy pathways, human threats e.g. climate change, eutrophication, deforestation, land degradation, marine pollution, toxic pollution of lakes;
breadth in addressing and linking negative feedback with stability, steady state, resilience in natural systems mitigating adverse impacts; and positive feedback with dynamic equilibria, growth, succession in restoration as well as amplifying/exacerbating human disturbance and destabilization of systems, etc.;
examples of organisms, feeding and non-feeding relationships, abiotic & biotic interactions generating negative feedback loops in natural systems and positive feedback promoting population growth, succession (i.e. earlier successional stages modifying environment to allow more and more colonization of later stages), and human impacts leading to positive feedback through e.g. agriculture, unsustainable exploitation, overharvesting, eutrophication, global warming, etc.;
balanced analysis of the extent to which feedback mechanisms maintain stability and promote restoration in face of human impact with counter examples of positive feedback leading to greater destabilization, or to a new equilibrium (past a tipping point), etc.;
a conclusion that is consistent with, and supported by, analysis and examples given e.g. “generally, negative feedback is significant in maintaining stability, while positive feedback promotes restoration of plant communities. However, human impacts frequently drive systems beyond their tipping point, and then positive feedback drives the system even further from its naturally stable equilibrium”;
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