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Environmental systems and societies ch. 1 & 2
Terms in this set (47)
Outline the concept and the characteristics of a system
A system is an assemblage of parts and the relationships between them, which together constitute and entity or a whole.
The interdependent components are connected through the transfer of of energy and matter, with all parts linked together and affecting each other.
Systems consist of:
- feedback mechanisms
Apply the system concept on a range of scales
Systems can be applied across a range of scales, from global-scale biomes to the small scale of life contained within a bromeliad in the rainforest canopy.
Small-scale local ecosystem: small forest
A large ecosystem: a biome:
Example of a global ecosystem: Gaia
Define the terms open system,
closed system and isolated system.
- An open system exchanges matter and energy with its surroundings (for example, an ecosystem).
- A closed system exchanges energy but not matter. Strictly, closed systems do not occur naturally on Earth, but all the global cycles of matter, for example, the water and nitrogen cycles, approximate to closed systems.
-An isolated system exchanges neither matter nor energy.
Describe how the first and second
laws of thermodynamics are
relevant to environmental systems
The first law concerns the conservation of energy.
The second law explains the dissipation of energy that is then not available to do work, bringing about disorder.
The first law:Energy can't be created or destroyed; can only change forms.
The second law: Explains that, when energy is converted, it will be lost from the system due to the work done, bringing about disorder (entropy).
This means that energy and materials go from a concentrated into a dispersed form (the availability of energy to do work diminishes) and the system becomes increasingly disordered.
Both laws should be examined in relation to the energy transformations and maintenance of order in living systems.
Explain the nature of equilibria.
A steady state equilibrium is the property of most open systems. The stability of this form of equilibrium means that the system can return to the steady state following disturbance.
Static equilibrium: No inputs/outputs. No change over time. Belongs to inanimate objects.
Some systems may undergo long‑term changes to their equilibrium
while retaining an integrity to the system (for example, succession). The relative stability of an equilibrium—the tendency of the system
to return to that original equilibrium following disturbance, rather than adopting a new one.
Define and explain the principles of positive feedback and negative feedback.
Feedback refers to the return of a part of the output from a system as input, so as to affect succeeding outputs. There are two types of feedbacks:
- Negative: feedback that tends to damp down, neutralize or counteract any deviation from equilibrium, and promotes stability.
-Positive: Feedback that amplifies or increases change; it leads to exponential deviation away from an equilibrium.
Describe transfer and transformation processes.
Transfers normally flow through a system and involve a change in location.
Transformations lead to an interaction within a system in the formation of a new end product, or involve a change of state. Using water as an example, run-off is a transfer process and evaporation is a transformation process. Dead organic matter entering a lake is an example of a transfer process; decomposition of this material is a transformation process.
Distinguish between flows and storages in relation to systems.
Flows:inputs and outputs
Storages: stock held within a system
Evaluate the strengths and limitations of models.
❤️allow us to predict and simplify complex systems.
❤️inputs can be changed and outcomes examined without having to wait for real events.
❤️results can be shown to others.
💔they may not be accurate.
💔relies on the expertise of the people making them.
💔different people might interpret them differently.
💔different models may show different effects using the same data.
💔they are oversimplified which has lead to criticism.
Distinguish between biotic and abiotic (physical) components of an ecosystem.
Biotic refers to the living components within an ecosystem.
Abiotic refers to the non-living factors of the ecosystem
Define the term trophic level.
The term trophic level refers to the feeding level within a food chain. Food webs are made from many interconnecting food chains.
Identify and explain trophic levels in food chains and food webs selected from the local environment.
Producers: Autotrophs, Are at the bottom of food webs/chains. Convert abiotic components into living matter.
Primary consumers: herbivore, eat producers (2nd in food chain)
Consumer: Eat other organisms to obtain energy and matter.
Decomposers: Eat dead organisms
Top carnivores: on the top of the food chain/ trophic level, carnivores or omnivores
Explain the principles of pyramids of numbers
Pyramids are graphical models of the quantitative differences that exist between the trophic level of a single ecosystem. These models provide a better understanding of the workings of an ecosystem by showing the feeding relationship in a community.
The numbers of producers and consumers coexisting in an ecosystem can be shown by counting the numbers of organisms in an ecosystem and constructing a pyramid of number. The pyramid of numbers is therefore records the number of individuals at each trophic level.
In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends.Pyramids of numbers can sometimes display different patterns, for example, when individuals at lower trophic levels are relatively large.
Explain the principles pyramids of biomass
Pyramids of biomass represents the biological mass of the standing stock at each trophic level at a particular point in time.
Similarly to pyramids of numbers , pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass
Biomass, measured in units of mass or energy (for example, g m-2 or J m-2)
Explain the principles pyramids of productivity
Pyramids of productivity shows the flow of energy (i.e. the rate at which the stock is being generated) through each trophic level.
Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain.
Discuss how the pyramid structure affects the functioning of an ecosystem.
Because energy is lost through food chains, top carnivores are at risk from disturbance further down the food chain. If there is a reduction in the numbers of producers or primary consumers, existence of the top carnivores can be put at risk if there are not enough organisms to support them.
Top carnivores can also be put at risk though other interferences in the food chain, e.g. the use of pesticides such as DDT, which is non-biodegradable. The use of DDT resulted in bioaccumulation (The process of a potentially toxic substance being stored in an organism) which harms top organisms.
Discuss how the pyramid structure affects the functioning of an ecosystem - CASE STUDY (snow leopards)
Snow leopards have little prey to feed on (wild sheep and goats) because of overgrazing by farmers. This means they'll have to eat domestic livestock instead, which causes them to be killed by farmers. Because of problems like the one above they're endangered.
Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples.
Species: A group of organisms that can interbreed and receive fertile offspring
Population: A group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding
Habitat: The environment in which a species normally lives
Niche: Where and how a species lives - a species share of habitat and resources in it
Community:A group of populations living and interacting with each other in a common habitat.
Ecosystem: A community of interdependent organisms and the physical environment they inhabit.
Describe and explain population interactions using examples of named species.
Ecosystems contain numerous populations with complex interactions between them. They can be divided into 4 types:
Competition: When resources are limiting, populations are bound to compete in order to survive. It can either be within species (intraspecific) or between different species (interspecific). E.g: between baboons
Predation: Predation occurs when one animal (or plant) hunts and eats other animals. Snowshoe and lynx
Parasitism: is a symbolic relationship in which one species benefits at the expense of the other. E.g: tics on dogs
Mutualism: is a symbolic relationship in which both species benefit. E.g: coral reefs and lichens
List the significant abiotic (physical) factors of an ecosystem.
Ecosystems can be broadly divided into 3 types:
1. Marine - the sea, salt marshes and mangroves are all characterized by the high salt concentration of the water.
2. Freshwater - Rivers, lakes and wetlands
3. Terrestrial - land-based
Describe and evaluate methods for measuring at least three abiotic (physical) factors within an ecosystem.
1. Marine—salinity, pH, temperature, dissolved oxygen, wave action
2. freshwater—turbidity, flow velocity, pH, temperature, dissolved oxygen
3. Terrestrial—temperature, light intensity, wind speed, particle size, slope, soil moisture, drainage, mineral content
Evaluate and explain three measures for describing abiotic factors
Temperature; an electronic thermometer with probes (datalogger) is used. Can be used to measure the temperature of air, water, and soil at different depths.
For soil depths: same depth each time, must be buried deeply enough, depth needs to be checked every time it's used.
pH; measured by using a pH meter or datalogging pH probe. Freshwater is usually slightly basic to slightly acidic (depends on nearby soil, rock, vegetation). Sea water usually has a pH above 7 (alkaline).
The meter/probe must be cleaned between each reading, and reading must be taken from the same depth. Soil pH measured using a soil test kit (indicator solution added and colour compared to a chart).
Salinity; measured using electrical conductivity (with a datalogger) or density of water (high salt content=denser). Salinity usually expressed as parts of salt per thousand parts of water (ppt). Sea water usually 35ppt=35g dm^-3
❤️dataloggers can collect samples over time; more samples=more accurate results.
💔abiotic factors change each day; can't be certain that the data is representative.
Describe and evaluate methods for estimating abundance of organisms - moving organisms only
1. Capture-mark-release-recapture (Lincoln index): a method that allows you to estimate the total population size of an animal in your study area. It involves collecting a sample from the population, marking them in some way, releasing them back into the wild, then resampling some time later and counting how many marked individuals you find in the second capture. Calculations
N= (n1*n2)/ m
N= total population size
n1= animals captured on day 1
n2= animals captured on day 2
m= number of marked animals recaptured on the second day
+ quite accurate.
- animals moving in and out of the study area can cause inaccurate results.
-only an estimate, not fully accurate.
-->must be careful when marking animals; the marks must be ethical, non-harmful, and non-conspicuous (prey shouldn't be seen easier by predators, etc.).
Describe and evaluate methods for estimating abundance of organisms - non-moving organisms only
2. Quadrats: are used to limit the sampling area when you want to measure the population size of non-mobile organisms, They vary in size and should be placed at random.First you mark out an area, then place quatrats on this area.
The population density is found (number of organisms sampled divided by total area covered by quadrats). Percentage frequency (percentage of total quadrat number that the species was present in) is best used for plants as they don't move.
+ quite accurate.
+ very efficient for plants.
💔animals move and will cause the results to be inaccurate.
💔because random/stratified random sampling is used, it is a bit more time consuming.
Describe and evaluate methods for estimating the biomass of trophic levels in a community.
Biomass is the mass of organic matter in organisms of ecosystems, usually per unit area. Biomass is calculated to indicate the total energy within a living being or trophic level. Biological molecules are held together by bond energy, so the greater the mass of living material, the greater the amount of energy present.
Biomass is taken as the mass of an organism minus the water count (i.e. dry weight biomass). To obtain quantitative samples of biomass, biological material is dried to constant weight. first, the sample is weighed, and then put in a hot oven for a certain length of time, and is then reweighed afterwards and done several times until the mass remains constant. The change in weight signals how much biomass there is.
+accurate way of measuring biomass
- Time consuming
- organism must be killed - ethical issues. Can therefore not always be used
Define the term diversity.
Diversity is the function of two components: the number of different species and the relative number of individuals of each species
Apply Simpson's diversity index and outline its significance.
Simpsons diversity index is a way of measuring diversity:
Formula: D=(N(N-1))/"sum of"n(n-1)
N=total number of organisms of all species found
n=number of individuals of a particular species
"Sum of"=sum of (the little sidewards M thingy)
+ gives a good guess of the diversity and is useful to classify the diversity of different areas.
💔there are many times when species are missed and not found because of their e.g. location (insects under the bark for example). This results in the diversity being inaccurate at times.
Define the term biome.
A biome is a collection of ecosystems sharing similar climatic conditions. It has distinctive abiotic factors and species which distinguishes it from other biomes.
Biomes usually cross national boundaries (biomes do not stop at a border; for example, the Sahara, tundra, tropical rainforests).
Explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biome.
1. Tropical rainforest:
High temperatures, high precipitation and insolation, placed around the equator, little seasonal variation in sunlight and temperatures. High levels of photosynthesis and high rates of NPP, with very high diversity and productivity
Lie close to the tropics of cancer and capricorn. Vegetation is scarce but the soil is very high in nutrients, partly because there in very little precipitation and partly because the temperatures are very high in the daytime and very low at night.The insolation is very high
Distribution: most tundras are found in the north polar region.
Structure: permafrost, low scrubs and grasses.
Productivity: low because of lack of light and rainfall.
Temperature: very low (during winter months it can get to -50 degrees Celsius).
Precipitation: very low.
Insolation: very low during winter where days are shorter, but much higher during summer where the sun is out almost 24 hours a day.
4. Temperate forest:
Structure: can contain both deciduous and evergreen trees. Simple structure and not that high diversity compared to tropical rainforests.
Productivity: quite in the middle; has the second highest NPP after tropical rainforests.
Temperature: warm summers and cold winters.
Precipitation: between 500-1500 mm/yr (lower would make them turn into grasslands).
Insolation: depends on season because of the tilting of the earth.
Explain the role of producers, consumers and decomposers in the ecosystem.
Producers: Are at the bottom of food webs/chains. Convert abiotic components into living matter. Are the basis of ecosystems
Consumers: Eat other organisms to obtain energy and matter.
Decomposers: Feed on dead biomass created by ecosystem.
Describe photosynthesis in terms of inputs, outputs and energy transformations.
Photosynthesis is the process by which green plants convert light energy from the sun into usable chemical energy stored into organic matter. Photosynthesis requires carbon dioxide, water, chlorophyll and light. In terms of inputs, outputs and energy transformations, photosynthesis can be summarized as followed:
- Inputs: sunlight, carbon dioxide and water
- Processes: Chlorophyll traps sunlight, the energy is used to split water molecules: hydrogen & carbon dioxide to produce glocuse.
- outputs: Glucose used as an energy source for the plant, oxygen is released to the atmosphere though stomata
- Transformations: Light energy is transformed to stored chemical energy.
Explain respiration in terms of inputs, processes, outputs, and energy transformations.
Respiration takes organic matter and oxygen to produce carbon dioxide,water and the release of energy.
Inputs: glucose, oxygen
Processes: oxidation processes inside cells
Outputs: release of energy for work and heat
Transformations: stored chemical energy-->kinetic energy and heat.
Describe and explain the transfer and transformation of materials and energy as they cycle within an ecosystem.
1. Sunlight enter the ecosystem
2. Solar radiation is lost by reflection off leaves, the light not hitting the plants, the light being of the wring wavelengths (and therefore not absorbed). It could also be because of the transmission of light through leaves or the inefficiency of photosynthesis.
3, The energy may then exit the ecosystem through heat and respiration, re-radiation into the atmosphere
- Carbon cycle (check notes)
- Nitrogen cycle (check notes)
- Water cycle (check notes)
- Nutrient cycle: The biomass from the plants decays, creating litter (e.g. leaves) with nutrients in them. There may then be and input through rainfall nutrients in the litter will be lost in run-off. The litter will then become nutrient rich soil through degradation and mineralization. The nutrients in the soil could be increased by the input from weathered rock, as well as lost through leaching. There will then be an output from the soil as plants uptake the nutrients, and thus restarting the cycle.
Define the terms gross productivity, net productivity, primary productivity and secondary productivity.
Gross productivity (GP): The energy or biomass produced in an area during a period of time
Net productivity (NP): the gain in energy/biomass per unit area per unit time after respiratory loss
Define the terms and calculate the values of both gross primary productivity (GPP) and net primary productivity (NPP) from given data.
Gross primary productivity (GPP): the energy gain through photosynthesis into primary producers.
Net primary productivity (NPP): The gain by producers in energy after respiration. Calculations:
NPP =GPP- R
Define the terms and calculate the values of both gross secondary productivity (GSP) and net secondary productivity (NSP) from given data.
Gross secondary productivity (GSP): the energy gained through absorption in consumers. Calculations:
GSP = food eaten - feaces lost
Net secondary productivity (NSP): the gain by consumers of biomass per unit area per unti time remaining after respiratory losses. Calculation:
NSP= GSP - R
Explain the concepts of limiting factors and carrying capacity in the context of population growth.
Limiting factors are factors that limit the distribution or numbers of a particular population/ are environmental factors which slow down growth.
Carrying capacity: refers to the number of organisms or size of population that an ecosystem or area can support sustainably over a long period of time
Describe and explain S and J population curves.
1. S-Curves: Growth curves that show rapid initial growth and that slow down as the carrying capacity is reached. The initial stage is called the exponential growth stage, then comes the transitional stage ( population slows down considerably due to competition,diseases and predators , but is still growing) and finally there is the plateau stage (in which the number of individuals and population stabalizes). This is the patterns of mammals
2. J-Curves: Is a population growth curve that shows only exponential growth; it is rapid and does not slow down, but instead has a sudden decline. The exponential growth could be due to there being plentiful resources, little competition, favorable abiotic factors (e.g. temperature) and lack of preditors and disease.
Describe the role of density‑dependent and density‑independent factors, and internal and external factors, in the regulation of populations.
- Density dependent factors = factors that lower birth-rates and increase death rates as population increases (internal)
- Density independent factors = factors that affect a population irrespective of population density (external). Are generally abiotic.
According to theory, density-dependent factors operate as negative feedback mechanisms leading to stability or regulation of the population.
Both types of factors may operate on a population. Many species, particularly r‑strategists, are probably regulated by density- independent factors, of which weather is the most important. Internal factors might include density-dependent fertility or size of breeding
territory, and external factors might include predation or disease.
Describe the principles associated with survivorship curves including, K‑ and r‑strategists.
There are 2 strategies for a population to grow, either a species reproduces a lot and then leaves the babies (r-strategists) or they barely reproduce and then take care of the offspring (K-strategists).
- K-strategists: live in stable environments, they are slow-growing organisms (have few offspring). They will come later in the line of succession as they live in the stable environment. They care care of their offspring, and they are most often close to the carrying capacity of the environment and larger in size .
- r-strategists: grow and mature quickly and produce many, small offspring. They come first in the line of succession as they are initial colonizers. They will adapt (mutate) to new environments and are small in size.
- C-strategist: in between r & K strategists,
Describe the concept and processes of succession in a named habitat.
Succession is "the orderly process of change over time in a community" (the long-term change in the composition of a community) which explains how ecosystems develop from base substance over a period of time . Changes in the community of organisms cause changes in the environment.
There are various types of succession, depending on the type of environment occupied:
1) succession on bare rock is a lithosere (p.65 in book)
2) Succession in freshwater habitat is a hydrosere
3) Succession in a dry habitat (e.g. sand) is xerosere
- Primary succession: on a previously uncolonized substrate
- Secondary succession: where a previous community has been destroyed (faster than primary due to soil and seed bank)
Zonation is NOT succession, but rather the arrangement or patterning of plant communities or ecosystems into bands in response to change, over distance, in some environmental factor. The main biomes display zonation in relation to latitude and climate. Plant communities may also display it on e.g a mountain.
CASE STUDY: Mt Kinabalu in Borneo shows altitudinal zonation; tropical rainforests at the base, then tropical montane, and then alpine communities near the bare granite summit.
Temperatures at the base is about 26 degrees Celsius, but can be 0 degrees Celsius at the summit. This change in temperature is what caused the zonation.
Many ecosystems=manyhabitats=many species.
Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession.
Features of early succession:
- Organic matter: small
- Nutrients: External (from rain and feces)
- Nutrient cycles: open (comes from outside)
- Growth form: r- species (i.e. their are small species)
- Life cycles: simple
- Gross productivity: GP is low
- Respiration: R is low
- Net productivity: High, the system is growing and biomass is accumulating
Features of late succession:
- Organic matter: large
- Nutrients: internal ( the community itself produced them - plants)
- Nutrient cycles: closed (plant nutrient = back to life)
- Growth form: K- species (i.e. their are large species)
- Life cycles: complex
- Gross productivity: increased consumer community = high
- Respiration: increased consumer community is balance by respinartion. R is therefore low
- Net productivity: low, approaches zero
Describe factors affecting the nature of climax communities.
-> Climax community: A biological community of plants, animals and fungi, which have through the process of succession reached a steady state.
Features of climax communities: Greater biomes, higher levels of species, lower pH, greater habitat diversity and a steady state equilibrium
The equilibrium occurs because the climax community is composed of species best adapted to average conditions in that area.
Climatic and edaphic (soil-related) factors determine the nature of a climax community. Human factors frequently affect this process through, for example, fire, agriculture, grazing and/or habitat destruction. Interference such as these human factors mean that succession is interrupted = PLAGIOCLIMAX
Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem along an environmental gradient.
1. LINE TRANSACT: is tape measure laid out in the direction of the gradient.. All organisms touching the tape are recorded, Many line transects need to be taken into account. Can be both continuous and interrupted
2. BELT TRANSACT: This is a band of chosen width laid along the gradient. Everything within the belt is calculated. Can be both continuous and interrupted
+ valid if repeated
+ good for abiotic variables
- Placing could be bais if not random selection is not used
- could be problems with seasonal fluctuations
Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem due to a specific human activity.
Images taken from satellites from above.
+ covers large area
+ can see change over time
+ gives motivation to change (really?)
- can only see what is visible from above; not what is underground.
Describe and evaluate the use of environmental impact
Aim: establish impact of the project on environment.
Predicts impacts on: habitats, species, and ecosystems. Helps decide whether to carry the development out.
A baseline study is carried out first. It measures:
-habitat type and abundance
-list of endangered species
+can be very effective and predict negative environmental impact
- hard to put together a good baseline study
- quality of baseline study determines everything
- the complexity of natural systems makes environmental decisions more difficult.
Describe and evaluate the use of environmental impact
assessments (EIAs) - CASE STUDY
The three gorges dam is located on the Yangtze River in China, and is the largest hydroelectric dam development in the world.
Estimated that it could generate 1/8 of the country's electricity.
An EIA was done. Problems included:
-relocation of people in flooded areas
-reduced water speed because of sedimentation in areas behind the dam
-effect of landslides from the increase in geological pressure from riding water
-47 endangered species found in river
-physical barrier of dam interferng with fish spawning
-100,000 acres flooded.
Positives were seen to outweigh negatives; it was built.
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