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Systems and Models
1.1.1 Outline the concept and characteristics of Systems A system is an assemblage of parts and the relationships between them, which together constitute an entity or whole. The interdependent components are connected through the transfer of energy and matter. Four things can characterize systems:
- Storages (of matter or energy)
- Flows (inputs and outputs)
- Processes (transfers and transformations of matter and energy)
- Feedback mechanisms (negative and positive feedback) 1.1.2 Apply the systems concept on a range of scales The systems concept can be applied across a range of scales such as ecosystems as small as a garden or as large as a biome, and even can be applied to look at the entire world as a system. 1.1.3 Define the terms open system, closed system and isolated system Open System: Both matter and energy is exchanged across the boundaries of the system, open systems are organic and so must interact with their environment Closed System: Energy but not matter is exchanged across the boundaries of the system. Matter is usually recycled within the system. Isolated System: Neither energy nor matter is exchanged across the boundary of the system. These systems do not exist naturally, although it is possible to think of the entire universe as an isolated system
1.1.4 Describe how the first and second laws of thermodynamics are relevant to environmental systems The first law of thermodynamics states that energy can neither be created nor destroyed, it can only change forms. This means that the total energy in any system is constant and all that can happen is change in the form that they energy takes. This law is also referred to as the “law of conservation of energy” The second law of thermodynamics states that the energy goes from a concentrated form into a dispersed form and the availability of energy to do work therefore diminishes and the system becomes increasingly disordered. The transformation and transfer of energy is not 100% efficient, in any energy conversion there is less usable energy at the end of the process. 1.1.5 Explain the Nature of Equilibrium Steady State Equilibrium: The common property of more open systems. There is a tendency in natural systems for the equilibrium to return after a disturbance such that fluctuations in the system are around a fixed path. Static Equilibrium: There are no inputs or outputs of matter or energy and no change in the system over time; therefore there are no fluctuations and the system state remains constant. Stable Equilibrium: If a system returns to the original equilibrium after a disturbance it is said to be stable Unstable Equilibrium: If a system does not return to the same equilibrium but rather forms a new equilibrium are described as unstable 1.1.6 Define and explain thee principles of positive and negative feedback Positive Feedback: occurs when a change in the state of the system leads to an additional and increased change Negative Feedback: work by reducing the effect of one of the system’s components. This is a selfregulating method of control leading to the maintenance of a steadystate equilibrium
2.1.3 Identify and explain trophic levels in food chains and food webs Ecosystems contain many interconnected food chains. Generally a food chain will start with the autotroph trophic level, then to primary consumer, then to secondary consumer and so forth. 2.1.4 explain the principles of pyramids of numbers, biomass and productivity Pyramid of Numbers: A number pyramid represents the number of producers and consumers coexisting in an ecosystem can be shown by counting the number of organisms in an ecosystem and constructing a pyramid.
Pyramid of Biomass A biomass pyramid quantities the amount of biomass present at each trophic level at a certain point in time and represents the standing stock of each trophic level measured in units such as grams of biomass per meter squared. Pyramid of Productivity A pyramid of productivity takes into account of the rate of production over a period of time because each level represents energy per unit area per unit time (rate of change) 2.1.6 define the terms species, population, habitat, niche, community and ecosystem Species: a group of organisms that interbreed and produce fertile offspring Population: a group of organisms of the same species living in the same area at the same time Habitat: refers to the environment in which a species normally lives Niche: best described as where, when and how an organism lives, essentially what defines the species Community: a group of populations living and interacting with each other in a common habitat Ecosystem: a community of interdependent organisms (biotic) and their physical environment (abiotic) 2.1.7 Describe and explain population interactions Intraspecific Competition: competition within a species (occupy the same niche) Interspecific Competition: competition between species (niches overlap) Predation: occurs when one animal hunts and kills another animal Parasitism: an organism (the parasite) benefits at the expense of another (the host) from which it derives food Mutualism: a relationship in which two organisms live together and a symbiotic relationship in which both species benefit is developed
Biomes
2.4.1 define the term biome A biome is a collection of ecosystems sharing similar climatic conditions. A biome has distinctive abiotic factors and species that distinguish it from other biomes.
Decomposers: obtain their food and nutrients from the breakdown of dead organic matter, and they break down tissue, they release nutrients ready for reabsorption by producers 2.5.2 Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations Photosynthesis: the process by which green plants convert light energy from the sun into usable chemical energy stored in organic matter
- Inputs = sunlight, carbon dioxide and water
- Processes = chlorophyll traps sunlight, the energy is used to split water, hydrogen from water is combined with CO2 to produce glucose
- Outputs = glucose used as an energy source for the plant and oxygen is released into the atmosphere
- Transformations = light energy is transformed to stored chemical energy Cellular Respiration: releases energy from glucose and other organic molecules inside all living cells
- Inputs = glucose and oxygen
- Processes = oxidation processes inside cells
- Outputs = release of energy for work and heat
- Transformations = stored chemical energy to kinetic energy and heat 2.5.3 Describe and explain the transfer and transformations of energy as it flows through an ecosystem CARBON CYCLING Carbon dioxide is fixed by autotrophs These organism respire and return some carbon into the atmosphere or assimilate into into their bodes as biomass When organisms die they are consumed by decomposers, which return carbon to the atmosphere when they respire Deforestation releases large amounts of carbon dioxide into the atmosphere Oil and gas were formed when marine organisms died and fell to the bottom of the ocean, when these fuels are burned they release large amount of carbon into the atmosphere
NITROGEN CYCLE
There is four types of bacteria that drive the nitrogen cycle:
- Nitrogenfixing bacteria are species in root nodules derive the soar’s they need from plants, and the plants gain useable nitrogen that has been fixed into nitrates
- Decomposers produce ammonia and ammonium compounds which is then fixed by the nitrogenfixing bacteria
- Nitrifying bacteria found in the soil oxidize the ammonia first into nitrites then into nitrates
- Denitrifying bacteria return nitrogen to the atmosphere
Changes
2.6.1 explain the concepts of limiting factors and carrying capacity Limiting Factors include temperature, water and nutrient availability Carrying Capacity is the maximum number of organisms that an area or ecosystem can sustainably support over a long period of time 2.6.2 Describe and explain S and J population curves The S Curve has three stages:
- Exponential Growth stage – in which the population grows and an increasingly rapid rate because there are no limiting factors, no competition and plentiful resources
- Transitional phase – where the population growth slows considerably but it continues to grow because there is an increase in competition and in predators
- Plateau Phase – in which the number of individuals stabilizes and the population growth stabilizes because the available space and resources decrease The J curve is a population growth curve, which shows only exponential growth. Growth is initially slow and becomes increasingly rapid and usually results in a population crash when carrying capacity is reached.
2.6.3 describe the role of density dependent and independent factors and internal and external factors Density Dependent Factors: some limiting factors are related to population density such as competition for resources, space and predation. As a population grows in size, the availability of resources per organism decreases. Density Independent Factors: can operate alongside densitydependent factors. These are generally abiotic such as climate change or geophysical events such a volcanic eruptions. These events increase death rate and reduce birth rate. Internal and External Factors: internal factors include density dependent fertility or size of breeding territory while external factors include predation or disease 2.6.4 describe the principles associated with survivorship curves including K and R strategists K Strategists: Tend to be limited by the carrying capacity of an environment Dominate species Slow development Delayed reproduction Longer living Larger size Less productive R Strategists: tend to have a fast rate of increase Initial colonizers Large numbers
3.1.1 Describe the nature and explain and implications of exponential growth in human populations The world’s population is growing very rapidly in an exponential manner. The impact of this is that a huge amount of resources are needed to look after the increasing number of people. Humans are K strategists, so exponential growth does not match with our type of species, as we will eventually reach carrying capacity 3.1.2 Calculate and explain the values of crude birth rate, crude death rate, fertility, doubling time and natural increase rate Birth Rate: Crude Birth Rate = total number of births total population x 100 Fertility: Changes in fertility are a combination of both socialcultural and economic factors like level of education, family planning and economic prosperity The age specific birth rate shows the number of births per 1000 women of a specific age Age specific birth rate = total number of births 1000 women of any specified age x 100 Doubling Times: The doubling time refers to the length of time it takes for a population to double in size assuming its natural growth rate remains constant Doubling Time ( years )=
percentage growthrate Death Rate: Death rate can vary for many reasons such as age structure, social class and occupations Crude De ath Rate = total number of deaths total population x 100 3.1.3 Analyze age/sex pyramids and diagrams showing demographic transition models
Population pyramids represent any measurable characteristic of the population. Population pyramids tell us a great deal of information about the age and sex structure of a population: A wide base indicates a high birth rate Narrowing base suggests falling birth rate Straight sides reveal low death rates Concave slops characterize high death rates
Energy Resources
3.3.1 Outline the range of energy resources available to society Energy can be generated from both renewable and nonrenewable resources. Renewable energy resources are sustainable because there is no depletion of natural capital. Some of these include solar, hydroelectric, geothermal and biomass Nonrenewable energy supplies cannot be replenished at the same rat they are used resulting in a depletion of the stock. Some of these include fossil fuels and nuclear power. Only about 9% of the world’s energy supply comes from renewable resources. 3.3.2 evaluate the advantages and disadvantages of two contrasting energy sources Fossil Fuels (nonrenewable) Advantages: they are cheap and plentiful and technology has been developed to allow for safe extraction and to control pollution Disadvantages: they are unsustainable because it implies liquidation of a limited stock of the resource and they contribute to climate change by adding carbon dioxide to the atmosphere
Primary Productivity Low High intermediate 3.4.3 Outline the processes and consequences of soil degradation Soil degradation is the decline in quantity and quality of soil. It includes:
- Erosion by wind and water
- Acidification is change in the chemical composition of the soil, which may trigger the circulation of toxic materials
- Atmospheric persistent organic pollutants may render soils less suitable to sustain the original land cover and use
- Can cause desertification (spread of desert conditions into previously productive areas)
- Overgrazing can severely reduce the vegetation cover and leave the surface vulnerable to erosion 3.4.4 Outline Soil conservation measures Farmers are encouraged towards more extensive management practices Mechanical methods include contour ploughing to prevent the movement of rainwater to stop erosion Preventing erosion by different cropping techniques such as maintaining a crop cover and planting grass for protection For soils that have been affected by salt, farms can flush the soil with water to leach the salt away, or apply chemicals that replace the sodium ions
Water Resources
3.6.1 describe the Earth’s Water Budget
Only a small portion of the Earth’s water is fresh water and around 70% of this is trapped in icecaps and glaciers The different forms of water are fully replenished during the hydrological cycle but at very different rates called turnover times Polar ice caps, oceans, groundwater, lakes and glaciers have the largest turnover times which is a problem since they make up a large portion of available fresh water The degree to which water can be seen as renewable or nonrenewable depends on where it is found in the hydrological cycle and how long it takes to replenish
Nature Of Pollution
5.1.1 define the term pollution Pollution is defined as the contamination of the Earth and atmosphere to such an extent that normal environmental processes are adversely affected. Pollution can be natural or anthropogenic It can be deliberate or accidental It includes the release of substances, which harm the sustainable quality of air, water and soil 5.1.2 Distinguish between the terms point source pollution and nonpoint source pollution Point Source Pollution: refers to discrete sources of contaminants that can be represented by single points and the source of the pollution can be tracked. NonPoint Source Pollution: refers to more dispersed sources from which pollutants originate and enter the natural environment Pointsource pollution is generally more easily managed as it can be localized and controlled 5.1.3 State the major sources of pollutants Major sources of pollution include the combustion of fossil fuel, domestic and industrial waste, manufacturing and agricultural systems. Some of the more significant sources include: 27% comes from mining and quarrying 20% comes from agriculture organic wastes 17% comes from industry
The main source of anthropogenic eutrophication is from nitrous oxides from fossil fuel combustion and the percolation of nitrogen fertilizers into the water A number of changes may occur as a result of eutrophication:
- Turbidity increases of the water
- Net primary productivity increases
- Dissolved oxygen in water decreases 5.4.2 evaluate the impacts of eutrophication Loss to farmers: an economic loss for farms such that when farmers apply fertilizers to stimulate crop growth and it runs off, it reduces these benefits to the soils Health concerns: A concern for health related to increase rates of stomach cancer caused by nitrates from drinking water and blue baby syndrome caused by insufficient oxygen in the mother’s blood 5.4.3 Describe and evaluate pollution management strategies with respect to eutrophication Altering Human Activities
- Avoid using nitrogen fertilizers when soils are wet
- Maintain crop cover to conserve nitrogen
- Give preference to crops that conserve nitrogen in the soil
- Do not apply nitrogen to areas near water or sloped areas Clean Up Strategies
- Adding a chemical which causes phosphates to precipitate and therefore allow for easy removal
- Remove nutrient enriched sediments by mud pumping
- Remove biomass
Global Warming
6.1.1 describe the role of greenhouse gases in maintaining mean global temperature Shortwave ultraviolet light from the Sun is reflected from the surface of the Earth as infrared light (which has a longer wavelength) Atmospheric gases (greenhouse gases) are transparent to shortwave radiation but they can trap or reflect back outgoing longwave radiation Greenhouse gases include water vapor, carbon dioxide, nitrous oxide and ozone 6.1.2 describe how human activities add to greenhouse gases Human activities have increased the level of greenhouse gases in the atmosphere. Some of the activities include:
- Burning fossil fuels and releasing carbon dioxide
- Deforestation removes a carbon sink
- Increased cattle ranching had leas to increased methane levels
- Rice farming in paddy fields creases anoxic conditions leading to methane release 6.1.3 discussion qualitatively the potential effect of increased mean global temperature Environmental Features Ice and snow: retreat of polar ice caps and glaciers Coastline: increase in sea level causing flooding Ecosystems: change in biome distribution and species composition Societal Features Water resources: severe water shortages Coastal Occupation: relocation due to flooding and storms Human Health: increased disease 6.1.4 discuss the feedback mechanisms that would be associated with an increase in mean temperature Positive feedback with regards to climate change usually refers to one a change in one environmental factor results in a successive change to stimulate more climate change. Negative feedback however in the instance of global warming usually signifies a dampening effect of global warming, or something that is slightly reversing the effect of global warming. Positive Feedback Example Negative Feedback Example 6.1.5 describe and evaluate pollution management strategies to address the issue of global warming National and International Methods Temperature increases leading to ice caps melting Decreases the Earth’s albedo, thus increasing temperature Melting of polar ice caps Surface temperature increases slightly Increased evaporation from the oceans More low clouds in the atmosphere Reflects more light back into space Surface temperature decreases slightly
