The document provides information on several topics related to ecosystems and human populations: 1. It defines key terms related to systems, models, and thermodynamics including open/closed/isolated systems, laws of thermodynamics, and equilibrium. 2. It outlines definitions and concepts for ecosystems like biotic/abiotic factors, biomes, trophic levels, ecological pyramids, population interactions, and succession. 3. It discusses human population dynamics including exponential growth and density-dependent limiting factors that lead to population stability through negative feedback mechanisms.

1. IB ESS/GURU
IB ESS EXAM NOTES
TOPIC 1: Systems and Models
· Systems: an assemblage of parts and their relationship forming a functioning entirety or whole
o Open systems: exchanges matter and energy
o Closed systems: exchanges only energy
o Isolated systems: neither matter nor energy and is theoretical
· Laws of thermodynamics
o 1st: energy is neither created nor destroyed, only changes forms
o 2nd: the entropy of a closed system increases; when energy is transformed into work, some
energy is always lost as waste heat
Equilibrium
oSteady-state: in open systems, continuous inputs and outputs of energy and matter, system as a
whole remains in a constant state, no long term changes.
o Static: no change over time; when the state of equilibrium is distributed, the system adapts a
new equilibrium; can’t occur in living systems
o Stable: the system returns to the same equilibrium after disturbances
o Unstable: system returns to a new equilibrium after disturbances
·Feedback
o Positive: results in a further decrease of output and the system is destabilized and pushed into a
new state of equilibrium
o Negative: tends to neutralize or counteract any deviation from an equilibrium and tends to
stabilize systems
· Transfers and transformations
o Transfers:
- The movement of material through living organisms
- Movement of material in non-living process
- The movement of energy
o Transformations
- Matter to matter
- Energy to energy
- Matter to energy
- Energy to matter
· The Gaia model

2. IB ESS/GURU
o Views earth as a living organism
o The earth has a “disease”
TOPIC 2: Ecosystems
Definitions:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Biotic factors: living components
Abiotic factors: non-living physical and chemical components
Species: a particular type of organism
Population: a group of individuals of the same species living in the same area at the same
time
Habitat: the environment where a species normally lives
Ecological niche: how an organism makes a living
Community: a group of populations living and interacting with each other in a common
habitat
Ecosystem: a community of independent organisms (biotic factors) and the physical
environment (abiotic factors) which they inhabit
Biome: a collection of ecosystems sharing common climatic conditions
Respiration: a process of breaking down food in order to release energy
Photosynthesis: a process of producers making their own food (glucose) and producing
oxygen from water and carbon dioxide
Biomass: the living mass of an organism or organisms but sometimes refers to dry mass
Gross Productivity: the total gain in energy or biomass per unit area per unit time
a. o GPP: by producers
b. o GSP: by consumers
Net Productivity: the total gain in energy or biomass per unit area per unit time after
allowing for losses to respiration
a. o NPP: by producers
b. o NSP: by consumers
Biomes:
1.
2.
3.
4.
5.
climate
latitude (distance from equator)
altitude (height above sea level)
wind and water currents
P/E ratio (precipitation over evaporation ratio)

3. IB ESS/GURU
latent heat: heat that is either taken in or produced when water changes from state to state
Different Biomes:
Tropical Rainforest – hot and wet areas with broadleaved ever green forest. Within 50 north or
south of the equator. High rainfall and high temperature, high insolation as near equator. There
are amazingly high levels of biodiversity, many species and many individuals of specie. There
are very large evergreen trees, small shrubs, orchids.It is estimated that tropical rainforest
produces 40% of NPP of terrestrial ecosystems. But the problems it has, are that 50% of human
population live near the equator, so they damage the biome, they are exploited for human
economical needs.
Desert – dry areas which are usually hot in the day and cold in the night, there are tropical,
temperate and cold deserts. It covers 20-30% of earths surface, about 300 of north or south of the
equator. Water is limited in the deserts. There are few species and very low biodiversity, there
are only the ones who adapted to the conditions. Soil can be rich, because the nutrients are not
washed away from the water. NPP is low because the amount of plants and animals are limited,
because of the water. Desertification is the human activity.
Temperate Grassland – fairly flat areas, that are covered with grass, they are located 400 – 600
from the equator, either north or south. The net productivity is not very high, because its only
grass that grows on the land, nothing else. And with that the animals that are growing are small
size as well. Humans use grass lands for the crops.
Temperate Forest - mild climate and deciduous forest. Located 400 – 600 north or south of the
equator, it has 4 seasons, there also are fewer species than tropical rainforest, it has the second
highest NPP after the tropical rainforest. Much of the temperate forests, have been cleared
because of human activities.
Arctic Tundra – Tree less plain with permafrost, cold and very low precipitation, dark nights. It
is 10% of lands surface, it is located on the arctic cap. Water is limiting but the fire can stop the
climax community forming. There are no trees but there Is a thick mat, covered by mosses and
grasses. It has very low biodiversity, and soil is poor. With that the NPP is very low, humans use
it for mining.

4. IB ESS/GURU
Ecosystem Structure:
Food chains and trophic levels
1.
2.
3.
4.
5.
6.
7.
food chain: shows a flow of energy from one organism to the next
food web: shows a complex network of interrelated food chains
trophic level: a position that an organism or a group of organisms in a community
occupies in a food chain
producers or autotrophs: which manufacture their own food from inorganic substances
consumers or heterotrophs: which feed on autotrophs or other heterotrophs to obtain
energy
decomposers: consumers that obtain energy from dead organisms
detritivores: consumers that derive their food from detritus or decomposing organic
material
Ecological pyramids
1.
Pyramid of numbers: shows the number of organisms at each trophic level in a food chain
o
advantages:


o
o easy method of giving an overview
o good for comparing changes in population numbers over different times
disadvantages:


o all organisms included regardless of their size
o numbers can be too great to represent accurately
2. Pyramid of biomass: contains the biomass at each trophic level
o advantages:
 overcomes the problems of pyramids of numbers
o
disadvantages:



3.
only uses samples from populations, so it’s impossible to measure biomass
exactly
organisms must be killed to measure dry mass
pyramid of productivity: contains the flow of energy through each trophic level; shows
the energy being generated and available as food to the next trophic level during a fixed
period of time
o
advantages:

o
shows the actual energy transferred and allows for rate of production
disadvantages:

very difficult and complex to collect energy data as the rate of biomass
production over time is required

4.
bioaccumulation and biomagnification
o
o
bioaccumulation: increase in concentration in one organism over time
§biomagnification: increase in concentration with the increase in trophic levels

5. IB ESS/GURU
5.
o trophic efficiency: only 10% of the energy is transferred to the next, so the trophic
efficiency=10%
Population Interactions
A population is a group of organisms of the same species living in the same area at the same time
and capable of interbreeding.
Population density is the average number of individuals in a stated area.
Competition
Competition between members of the same species is Intraspecific competition.
Individuals of the different species, competeting for the same resource is
called Interspecific competition.
The other outcome is that one species may totally outcompete the other, this is the principle
of Competitive exclusion.
Predation – happens when one animal, the predator, eats another animal, the prey.
Herbivory – is defined as an animal eating green plant.
Parasitism - is a relationship between two species in which one species lives in or on another
gaining its food from it.
Mutualism - s a relationship between two or more species in which both or all benefit and none
suffer.
Succession
Succession is the change in species composition in an ecosystem over time
It may occur on bare ground where soul formation starts the process or where no soil has already
formed, or where the vegetation has been removed.
Early in succession, GPP and respiration are low and so NPP is high as biomass accumulates.
Secondary succession occurs on souls that are already developed and ready to accept seeds
carried in by the wind. Also there are often dormant seeds left in the soil from previous
community. This shortens the number of seral stages the community goes through.

6. IB ESS/GURU
Changes occurring during a succession (refer to Fig. 14.4 on page 268)
the size of organisms increases
energy flow becomes more complex
soil depth, humus, water-holding capacity, mineral content and cycling increase
Biodiversity increases and then falls as the climax community is reached
NPP and GPP rise and then fall
Production: respiration ratio falls
Species diversity in successions
Early stages of succession: few species
Species diversity increases with the succession
Increase continues until a balance is reached between possibilities for new species to establish,
existing species to expand their range and local extinction
TOPIC 3: Human Population, Carrying Capacity and Resource Use
Population dynamics
Exponential growth or geometric growth
When the population is growing, and there are no limiting factors slowing the growth.
Density-dependent limiting factors (biotic factors when effects depend on the population
density)
· Negative feedback mechanism- lead to stability of the population
· Internal – factors act within species
1. Limited food supply lead to intraspecific competition
2. Lack of suitable territory
3. Survival of the fittest
· External – factors act between different species (predation and disease)
1. Predation – pray animals increase, predators increase -> pray decreases and the predators
decrease
2. Disease – at high populations spreads fast

7. IB ESS/GURU
S-curves
The visual picture of the curves
· Start with exponential growth
· Then the growth slows down
· Finally constant size
Other facts:
· Consistent with carrying capacity of the environment
· Environmental resistance
Density-independent limiting factors (abiotic factors when effects do not depend on the
population density)
· Climate
· Weather
· Volcanic eruptions
· Floods
J- curves
· “Boom and bust” – population grows exponentially and suddenly collapses
· The collapse is referred to as overshoot
· The sudden collapse usually caused by abiotic factors
· The J-curves usually occur in:
1. Microbes
2. Invertebrates
3. Fish
4. Small mammals
K-and r-selected species
K-selected species
· Long life
· Slower growth
· Late maturity
· Fewer large offspring
· High parental care and protection
· High investment in individual offspring
· Adapted to stable environment
· Later stages of succession
· Niche specialists
· Predators
· Regulated mainly by internal factors
· Higher trophic level
· Trees, albatrosses, humans

8. IB ESS/GURU
r-selected species
· Short life
· Rapid growth
· Early maturity
· Many small offspring
· Little parental care or protection
· Little investment in individual offspring
· Adapted to unstable environment
· Pioneers, colonizers
· Niche generalists
· Prey
· Regulated mainly by external factors
· Lower trophic level
· Examples: annual plants, flour beetles, bacteria
K-and r-selected species are extremes of a continuum. Many species are mixture of both
characteristics.
Demographics – study of the dynamics of the population change.
Human Development Index – measure:
1. Life expectancy
2. Well being
3. Standards of living
4. GDP
MEDC- industrialized nations with high GDPs.
LEDC- less industrialized nations with lower GDP
Population growth effects on the environment
More people- more recourses- more waste- greater impact
Factors that affect population size:
· Crude birth rate – number of births per thousand individuals in population per year
· Crude death rate – the number of deaths per thousand individuals in a population per
year.
· Immigration
· Emigration
· Natural increase rate – (crude birth rate – crude death rate) / 10, which, gives the
natural increase rate as a percentage. It excludes the effects of migration.

9. IB ESS/GURU
· Total fertility rate – the average number of children each woman has over her lifetime.
· Fertility rate – the number of births per thousand women of childbearing age. In
reality, replacement fertility ranges from 2.03 in MEDCs to 2.16 in LEDCs because of
infant and childhood mortality.
· (Fertility is sometimes considered a synonym for the birth rate)
Human population growth
Demography is the study of the statistical characteristics of human populations, e.g. total
size, age and sex composition ad changes over time with variations in birth and death rates.
· Carrying capacity – the maximum number of a species or “load” that can be sustainably
supported by a given environment, without destroying the stock
· Populations remain stable when birth rate = death rate
· The size of the population is depended on the wealth of the population
· Demand for and the exchange of the resources effects the size
· All of the above differs in MEDCs and LEDCs
Population growth and food shortages
There are two main theories relating to population growth and food supply, from Malthus
and Boserup
Malthusian theory
· Thomas Malthus – English clergyman and economist (1766 to 1834)
· Published an essay on the principle of population in 1798
· Claimed that food supply was the main limit to population growth
· Believed that human population increases geometrically, whereas food supplies grows
arithmetically, and as a result, there are much more humans than food supplies
Limitations of Malthusian theory
· Too simplistic
· Shortage of food is just one possible explanation for the slowing in population growth
· It is only poor who go hungry
· Globalization is something Malthus could not have expected
Boserup’ theory
· Ester Boserup, a Danish economist (1965)
· Increase in population would stimulate technologists to increase food production
· Rise in population will increase the demand for food and so act as an incentive to change
agrarian technology and produce more food

10. IB ESS/GURU
· Belief that “necessity is the mother of invention”
Limitations of Boserup’s theory
· Too simplistic view
· Like Malthus, his idea is based on the assumption of a “closed” community.
· Emigration and immigration are not considered
· Overpopulation can lead to unsuitable faming
Family sizes
· Appears that decision to have children is not correlated with GNP of a country nor personal
wealth:
· High infant and childhood mortality
· Security in old age
· Children are an economic asset in agricultural societies
· Status of women
· Unavailability of contraception
The ways to reduce the family size are to:
· Provide education
· Improve health
· Provide contraception
· Increase family income
· Improve resource management
Population Pyramids
These pyramids show how many individuals are alive in different age groups (five-year
cohorts) in a country for any given year. They also show the frequency of males and females.
In the pyramids, population numbers are on the x-axis and the age groups on the y-axis.
The shapes of the pyramids are following:
· Expanding (stage 1) – high birth rates; rapid fall in each upward age group due to high
death rates; short life expectancy.
· Expanding (stage 2) – high birth rates; fall in death rates as more living to middle age;
slightly longer life expectancy.
· Stationary (stage 3) – declining birth rate; low death rate’ more people living to old age.
· Contracting (stage 4) – low birth rate; low death rate; higher dependency ratio; longer life

11. IB ESS/GURU
expectancy.
Demographic transition model:
Demographic transition model describes the pattern of decline in mortality and fertility
(natality) of a country as a result of social and economic development.
This model can be described as a five-stage population model, which can be linked to the
stages of the sigmoid growth curve.
The stages are:
Pre- industrial society:
· High birth rate due to no birth control;
· High infant mortality rates;
· Cultural factors encouraging large families.
· High death rates due to disease, famine, poor hygiene and a little medicine.
LEDC:
· Death rate drops as sanitation and food improve,
· Disease is reduced so lifespan increases.
· Birth rate is still high so population expands rapidly
· Child mortality falls due to improved medicine.
Wealthier LEDC:
· Birth rats fall due to access to contraception.
· Improved health care, education and emancipation of women.
· Population begins to level off and desire for material goods and low infant death rates mean
that people have smaller families.
MEDC:
· Low birth rates
· Low death rates
· Industrialized countries
· Stable population sizes
MEDC:
· Population may not be replaces as fertility rate is low.
· Problems of aging workforce.
Food Resources

12. IB ESS/GURU
Undernourishment, malnourishment – Lack of essential nutrients like proteins, vitamins,
minerals.
Agriculture
Types of farming systems
Subsistence farming – the provision of food by farmers for their own families or the local
community
Cash cropping- growing the food for the market
Commercial farming- large, profit- making scale maximizing yields per hectare.
(monoculture)
One type of crop or animal is produced.
Extensive farming – more land with lower density of stocking or planting and lower inputs
and corresponding outputs.
Intensive farming – using the land more intensively with high levels of input and output per
unit area.
Pastoral farming – raising animals on a land which is not suitable for crops.
Arable farming is sowing crops on good soils to eat directly or to feed to animals
Mixed farming – has both animals and crops and is a system in itself where animals waster is
used to fertilize the crops and improve soil structure.
Farming’s energy budget
A system with inputs, outputs, storages and flows = marketable product sold by weight
Energy balance in farming = fuel, labor, any other energy, soil, sow the seed, harvest the
crop, prepare and package, transport, energy cost of dealing with waster products.
Grain equivalent – the quantity of wheat grain that would have to be used to produce one kg
of that product.
Rice Production in Borneo
Traditional, extensive rice production in Indonesian Borneo

13. IB ESS/GURU
- Low inputs of energy and chemicals, high labor intensity and a low productivity.
- No fertilizers and pesticides used
- Rice yield is only output (no pollution)
Intensive rice production in California
- high inputs of energy and chemicals, low labor intensity and a high productivity
- diesel and petrol
- fertilizers (N, P) Pesticides (insecticides and herbicides)
- More energy input than output
- More pollution
Fisheries – industrial hunting
According to FAO more than 70% of the world’s fisheries are fully exploited, in decline or
seriously depleted.
The global fish catch is in decline even though technology has improved.
Demand is high and rising but fisherman cannot find or catch enough fish because they are no
longer there
The tragedy of the commons - Tension between the common good and the needs of the
individual and how they can be in conflict.
Exploitation of the oceans is the tragedy of the commons
The Grand Banks off the coast of Newfoundland were once among the richest fishing grounds on
Earth. Since 1400s it’s been depleted by various countries.
The United Nations Convention on Law of the Sea (UNCLOS) – international agreement written
over decades that attempts to define the rights and responsibilities of nations with respect to the
seas and marine resources.
Maximum Sustainable Yield (MSY)
Sustainable Yield – increase in natural capital
Sustainable yield of the aquifer is the amount that can be taken each year without permanently
decreasing the amount of water stored.

14. IB ESS/GURU
SY = annual growth and recruitment – annual death and immigration
Harvesting MSY leads to population decline and thus loss of resource base and an unsustainable
industry or fishery.
Optimal Sustainable Yield (PSY) – half the carrying capacity. Safety margin than MSY ut still
may have an impact on population size with other environmental impacts.
Resources- Natural Capital
Natural Capital - Natural resources, services that support life, natural processes. The Goods and
services that are not manufactured but have value to humans.
Natural Income – (yield, harvest, services) Yield from the natural capital.
Renewable Resources – living resources that can replace or restock themselves. (Alternative
energy resources)
Non-renewable resources- exist in finite amounts on Earth and are not renewed or replaced after
they have been used or depleted. (Minerals and fossil fuels)
Replenishable Resources – replaceable but take long period of time. (Groundwater)
Sustainability – living within the means of nature, on the “interest” or sustainable natural income
generated by natural capital.
“Tragedy of commons”- many individuals who are acting in their own self-interest to harvest a
resource may destroy the long-term future of that resource so there is none for anyone.
Resource Values
Economic – marketable goods and services
Ecological- life-support services
Scientific/technological - applications
Intrinsic – aesthetic, cultural, spiritual
Urbanization – the drifts from the countryside to urban life. Urbanization might eventually
encroach on or degrade natural habitats of the cities.
Globalization- Every society on Earth is connected and unified into a single functioning entity.
(Global trade) Globalization often leads to westernization. Globalization has facilitated the
process of global agreements on global issues.

15. IB ESS/GURU
Human Carrying Capacity – Maximum number or load of individuals that an environment can
sustainably carry or support.
Ecocentric - reduce the use of non-renewable resources and minimize their use of renewable
ones.
Technocentric – human carrying capacity can be expanded continuously through technological
innovation and development.
Conventional Economists – trade and technology increase the carrying capacity.
Ecological Economists – technological innovation can only increase the efficiency with which
natural capital is used.
Reuse- object is used more than once. (Drink bottles, secondhand cars)
Recycling – objects material is used again to manufacture a ne product. (Aluminum)
Remanufacturing – object’s material is used to make a new objects of the same type. (Plastic
bottles)
Absolute Reductions – use fewer resources (energy, paper)
Ecological footprint – area of land that would be required to sustainably provide all of a
particular population’s resources and assimilate all its wastes.
Population dynamics
Exponential growth or geometric growth
When the population is growing, and there are no limiting factors slowing the growth.
Density-dependent limiting factors (biotic factors when effects depend on the population
density)
· Negative feedback mechanism- lead to stability of the population
· Internal – factors act within species
1. Limited food supply lead to intraspecific competition
2. Lack of suitable territory
3. Survival of the fittest
· External – factors act between different species (predation and disease)
1. Predation – pray animals increase, predators increase -> pray decreases and the predators
decrease
2. Disease – at high populations spreads fast
S-curves
The visual picture of the curves
· Start with exponential growth
· Then the growth slows down
· Finally constant size
Other facts:

16. IB ESS/GURU
· Consistent with carrying capacity of the environment
· Environmental resistance
Density-independent limiting factors (abiotic factors when effects do not depend on the
population density)
· Climate
· Weather
· Volcanic eruptions
· Floods
J- curves
· “Boom and bust” – population grows exponentially and suddenly collapses
· The collapse is referred to as overshoot
· The sudden collapse usually caused by abiotic factors
· The J-curves usually occur in:
1. Microbes
2. Invertebrates
3. Fish
4. Small mammals
K-and r-selected species
K-selected species
· Long life
· Slower growth
· Late maturity
· Fewer large offspring
· High parental care and protection
· High investment in individual offspring
· Adapted to stable environment
· Later stages of succession
· Niche specialists
· Predators
· Regulated mainly by internal factors
· Higher trophic level
· Trees, albatrosses, humans
r-selected species
· Short life
· Rapid growth
· Early maturity

17. IB ESS/GURU
· Many small offspring
· Little parental care or protection
· Little investment in individual offspring
· Adapted to unstable environment
· Pioneers, colonizers
· Niche generalists
· Prey
· Regulated mainly by external factors
· Lower trophic level
· Examples: annual plants, flour beetles, bacteria
K-and r-selected species are extremes of a continuum. Many species are mixture of both
characteristics.
Demographics – study of the dynamics of the population change.
Human Development Index – measure:
1. Life expectancy
2. Well being
3. Standards of living
4. GDP
MEDC- industrialized nations with high GDPs.
LEDC- less industrialized nations with lower GDP
Population growth effects on the environment
More people- more recourses- more waste- greater impact
Factors that affect population size:
· Crude birth rate – number of births per thousand individuals in population per year
· Crude death rate – the number of deaths per thousand individuals in a population per year.
· Immigration
· Emigration
· Natural increase rate – (crude birth rate – crude death rate) / 10, which, gives the natural
increase rate as a percentage. It excludes the effects of migration.
· Total fertility rate – the average number of children each woman has over her lifetime.
· Fertility rate – the number of births per thousand women of childbearing age. In
reality, replacement fertility ranges from 2.03 in MEDCs to 2.16 in LEDCs because of infant
and childhood mortality.
· (Fertility is sometimes considered a synonym for the birth rate)
Human population growth
Demography is the study of the statistical characteristics of human populations, e.g. total size,
age and sex composition ad changes over time with variations in birth and death rates.

18. IB ESS/GURU
· Carrying capacity – the maximum number of a species or “load” that can be sustainably
supported by a given environment, without destroying the stock
· Populations remain stable when birth rate = death rate
· The size of the population is depended on the wealth of the population
· Demand for and the exchange of the resources effects the size
· All of the above differs in MEDCs and LEDCs
Population growth and food shortages
There are two main theories relating to population growth and food supply, from Malthus and
Boserup
Malthusian theory
· Thomas Malthus – English clergyman and economist (1766 to 1834)
· Published an essay on the principle of population in 1798
· Claimed that food supply was the main limit to population growth
· Believed that human population increases geometrically, whereas food supplies grows
arithmetically, and as a result, there are much more humans than food supplies
Limitations of Malthusian theory
· Too simplistic
· Shortage of food is just one possible explanation for the slowing in population growth
· It is only poor who go hungry
· Globalization is something Malthus could not have expected
Boserup’ theory
· Ester Boserup, a Danish economist (1965)
· Increase in population would stimulate technologists to increase food production
· Rise in population will increase the demand for food and so act as an incentive to change
agrarian technology and produce more food
· Belief that “necessity is the mother of invention”
Limitations of Boserup’s theory
· Too simplistic view
· Like Malthus, his idea is based on the assumption of a “closed” community.
· Emigration and immigration are not considered
· Overpopulation can lead to unsuitable faming
Family sizes
· Appears that decision to have children is not correlated with GNP of a country nor personal

19. IB ESS/GURU
wealth:
· High infant and childhood mortality
· Security in old age
· Children are an economic asset in agricultural societies
· Status of women
· Unavailability of contraception
The ways to reduce the family size are to:
· Provide education
· Improve health
· Provide contraception
· Increase family income
· Improve resource management
Population Pyramids
These pyramids show how many individuals are alive in different age groups (five-year cohorts)
in a country for any given year. They also show the frequency of males and females. In the
pyramids, population numbers are on the x-axis and the age groups on the y-axis.
The shapes of the pyramids are following:
· Expanding (stage 1) – high birth rates; rapid fall in each upward age group due to high death
rates; short life expectancy.
· Expanding (stage 2) – high birth rates; fall in death rates as more living to middle age; slightly
longer life expectancy.
· Stationary (stage 3) – declining birth rate; low death rate’ more people living to old age.
· Contracting (stage 4) – low birth rate; low death rate; higher dependency ratio; longer life
expectancy.
Demographic transition model:
Demographic transition model describes the pattern of decline in mortality and fertility (natality)
of a country as a result of social and economic development.
This model can be described as a five-stage population model, which can be linked to the stages
of the sigmoid growth curve.

20. IB ESS/GURU
The stages are:
Pre- industrial society:
· High birth rate due to no birth control;
· High infant mortality rates;
· Cultural factors encouraging large families.
· High death rates due to disease, famine, poor hygiene and a little medicine.
LEDC:
· Death rate drops as sanitation and food improve,
· Disease is reduced so lifespan increases.
· Birth rate is still high so population expands rapidly
· Child mortality falls due to improved medicine.
Wealthier LEDC:
· Birth rats fall due to access to contraception.
· Improved health care, education and emancipation of women.
· Population begins to level off and desire for material goods and low infant death rates mean that
people have smaller families.
MEDC:
· Low birth rates
· Low death rates
· Industrialized countries
· Stable population sizes
MEDC:
· Population may not be replaces as fertility rate is low.
· Problems of aging workforce.
Energy Resources
· Source – sun.
· Fossil fuels are sources of stored energy from the sun
· Oil is the economy’s largest source at the moment, supplying 37% of all the energy we use.
· Coal is the next largest, supplying 25%
· Natural gas supplying 23%
How much longer for fossil fuels?
The common estimates include:

21. IB ESS/GURU
· Oil – 50 years
· Natural gas – 70 years
· Coal - 250 years
· Will eventually run out, as they are non-renewable energy sources.
Depends on:
· Our rate of use
· Technologies
· Efficiency of humans
· How successful humans are at finding new sources
· How successful humans are at finding and extracting more.
· If the wealth of humans increase
· The population of humans
· Demand increase or decrease
Evaluation of energy sources and their advantages and disadvantages
Non-renewable
Coal (fossil fuel)
From
· Fossilized plants laid down in the carboniferous period
· Mined from seams of coal which are in strata between other types of rock
· May be open cast mined (large pits) or by tunnels underground.
· Burnt to provide heat directly or electricity by burning to turbines in power stations.
Advantages
· Plentiful supply
· Easy to transport and solid
· Needs no processing
· Relatively cheap to mine and convert to energy by burning
· Up to 250 years of coal left
Disadvantages
· Non-renewable energy source
· Cannot be replaced once used (same for oil and gas)
· Burning releases carbon dioxide which is a greenhouse gas
· Some coals contain up to 10% sulfur.
· Burning sulfur forms sulfur dioxide which causes acid deposition
· Particles of soot from burning coal produce smog and lung disease.
· Coal mines leave degraded land and pollution.
· Lower heat of combustion than other fossil fuels (less energy released per unit mass)

22. IB ESS/GURU
Oil (fossil fuel)
From
· Fossilized plants and micro-organisms that are compressed to a liquid and found in porous
rocks
· Crude oil is refined by fractional distillation to give a variety of products from lighter jet fuels
and petrol to heavier diesel and bitumen.
· Extracted by oil wells.
· Many oil fields are under the oceans so extraction is dangerous
· Pipes are drilled down to the oil-bearing rocks to pump the oil out.
· Most of the world economy runs on oil either burnt directly in transport and industry or to
generate electricity
Advantages
· High heat of combustion
· Many uses
· Once found is relatively cheap to mine
· Easily converted into energy
Disadvantages
· Only a limited supply
· May run out in 20-50 years
· Gives off carbon dioxide when burned
· Oil spill danger from tanker accidents.
· Risk of terrorism in attacking oil pipes
· Greenhouse gas effect
Natural gas (fossil fuel)
From
· Methane gas and other hydrocarbons trapped between seams of rock
· Extracted by drilling like crude oil
· Often found with crude oil
· Used directly in homes for domestic heating and cooking
Advantages
· Highest heat of combustion
· Lot of energy gained from it
· Ready- made fuel

23. IB ESS/GURU
· Relatively cheap form of energy
· Cleaner fuel than coal and oil
Disadvantages
· Only limited supply of gas but more than oil
· About 70 years left (according to current usage)
· Gives off carbon dioxide but only half as much per unit of energy produced as coal
Nuclear fission
From
· Uranium is the raw material. This is a radioactive and is split in nuclear reactors by bombarding
it with neutrons
· As it splits into plutonium and other elements, massive amounts of energy are also released
· Uranium is mined
· Australia has the most known reserves
· Canada exports the most
· Other countries have smaller amounts
· About 80 years worth left to mine at current rates
· Could be extracted from sea water
Advantages
· Raw materials are relatively cheap once the reactor is built and can last quite a long time
· Small mass of radioactive material produces a huge amount of energy
· No carbon dioxide released nor other pollutants (unless there are accidents)
Disadvantages
· Extraction costs high.
· Nuclear reactors are expensive to build and run
· Nuclear waste is still radioactive and highly toxic
· Big question of what to do with it
· Needs storage for 1000s of years
· May be stored in mine shafts or under the sea
· Accidental leakage of radiation can be devastating.
· Accidents are rare but worst nuclear reactor accident at Chernobyl, Ukraine was in 1986
· Risk of uranium and plutonium being used to make nuclear weapons
Renewable

24. IB ESS/GURU
Hydroelectric power (HEP)
From
· Energy harnessed from the movement of water through rivers, lakes and dams to power
turbines to generate electricity
· Pumped-storage reservoirs power turbines
Advantages
· High quality energy output compared with low quality energy input
· Creates water reserves as well as energy supplies.
· Reservoirs used for recreation, amenity
· Safety record is good.
Disadvantages
· Costly to build
· Can cause the flooding of surrounding communities
· Dams have major ecological impacts on local hydrology
· Silting of dams
· Downstream lack of water
· Risk of flooding if dam bursts
Biogas
From
· Decaying organic plant or animal waste are used to produce methane in biogas generators or
burnt directly as dung/plant material
· More processing can give oils which can be used as fuel in vehicles instead of diesel fuel =
biofuels
Advantages
· Cheap
· Available
· If the crops are replanted, biogas can be a long-term, sustainable energy source
Disadvantages
· May be replacing food crops on a finite crop land and lead to starvation

25. IB ESS/GURU
· When burnt, it still gives off atmospheric pollutants, including greenhouse gases.
· If crops are not replanted, biomass is a non-renewable resource.
Wood
From
· Felling or copping trees.
· Burnt to generate heat and light
Advantages
· Cheap
· Available
· If the crops are replanted, biogas can be a long-term, sustainable energy source
Disadvantages
· Low heat of combustion
· Not much energy released for its mass
· When burnt, it gives off atmospheric pollutants, including greenhouse gases
· If trees are not replanted wood is a non-renewable resource.
· High cost of transportation as high volume.
Solar photo volcanic cells
From
· Conversion of solar radiation into electricity via chemical energy
Advantages
· Infinite energy supply
· Safe
· Low quality energy converted to high.
Disadvantages
· Manufacture and implementation of solar panels can be costly.
· Need sunshine, do now work in the dark
Solar-passive
From
· Using buildings or panels to capture and store heat

26. IB ESS/GURU
Advantages
· Minimal cost if properly designed.
Wind
From:
· Can be found singly, but usually many together in wind farms
Advantages
· Clean energy and supply once turbines made
· Little maintenance required
Disadvantages
· Need the wind to blow
· Often windy sites not near highly populated areas
· Manufacture and implementation of wind farms can be costly
· Noise pollution
· Some local people object to on-shore wind farms, arguing that it spoils countryside
· Question of whether birds are killed or migration routes disturbed by turbines
Tidal
From:
· The movement of sea water in and out drives turbines
· A tidal barrage is built across estuaries, forcing water through gaps
· In future underwater turbines may be possible out at sea and without dam
Advantages
· Should be ideal for an isolated country such as the UK
· Potential to generate a lot of energy this way
· Tidal barrage can double as bridge, and help prevent flooding
Disadvantages
· Very costly
· Few estuaries are suitable
· Opposed by some environmental groups as having a negative impact on wildlife
· May reduce tidal flow and impede flow of sewage out to sea
Wave
From
· The movement of sea water in and out of cavity on the shore compresses trapped air, driving a

27. IB ESS/GURU
turbine
Advantages
· Should be ideal for an island country
· These are more likely to be small local operations
· Can be done on a national scale
Disadvantages
· Construction can be costly
· May be opposed by local or environmental groups.
· Storms may damage them
Geothermal
From
· It is possible to use the heat inside the Earth in volcanic regions.
· Cold water is pumped into the Earth and comes out as steam
· Steam can be used for heating or to power turbines creating electricity.
Advantages
· Infinite energy supply
· Is used successfully in some countries, such as New Zealand.
Disadvantages
· Can be expensive to set up
· Only works in areas of volcanic activity
· Geothermal activity might calm down, leaving power station redundant
· Dangerous underground gases have to be disposed carefully
Nuclear fusion – energy can be released by the fusion of two nuclei of light elements
TOPIC 4: Biodiversity and Conservation

28. IB ESS/GURU
Background and Mass Extinctions
background extinction rate- natural extinction rate for species
E. O. Wilson- a biologist at Harvard, thinks that the current rate of extinction is 1000 times the
background rate and is caused by human activities
hotspots- areas where species are more vulnerable to extinction
Biologists thing: we are the sixth mass extinction called the Holocene extinction event
To see all 6 mass extinctions refer to the Table on page 95
The Sixth Mass Extinction
1.
2.
3.
4.
5.
6.
far greater than any in the past
already wiped out many large mammal and flightless bird species
humans alter the landscape on an unprecedented scale
previous mass extinctions were due to physical (abiotic) causes over long time spans
current mass extinction is caused by humans (biotic causes) and is accelerating
humans:
1. transform the environment
2. overexploit other species
3. introduce alien species
4. pollute the environment
5. Worldwide Fund for Nature produces periodic report called the Living Planet
Report
6. o measures trends in the Earth’s biological diversity
7. two phases to the sixth mass extinction
8. o 1. when modern humans spread over the Earth about 100 000 years ago
9. o 2. when humans became farmers 10 000 years ago
Hotspots
some regions have more biodiversity than others
in hotspots there are unusually high numbers of endemic species- those only found in that place
tend to be nearer the tropics and are often tropical forests
tend to have large densities of human habituation nearby
Keystone Species
species that have a bigger effect on their environment than others
act as keystone in an arch, holding the arch together
their disappearance can have an impact far greater than and not proportional to
their numbers or biomass
4. o could destroy the ecosystem or imbalance it greatly
1.
2.
3.

29. IB ESS/GURU
Example: elephants in the African savanna act as engineers, removing trees, after which grasses
can grow
Types of Diversity
1.
Biodiversity- the numbers of species of different animals and plants in different places
a. o can be considered at three levels:
i. Genetic diversity- the range of genetic material present in a species or a
population
ii. Species diversity- the number of different species within a given area or
habitat
iii. Habitat diversity- the number of different habitats per unit area that a
particular ecosystem or biome contains
b. Simpson’s diversity index- measure species diversity in an area
i. o Simpson’s reciprocal index- in which 1 is the lowest diversity
ii. where N = the total number of organisms of all species and n = the total
number of organisms of a particular species
How New Species Form
Charles Darwin proposed the theory of evolution which is outlined in The Origin of
Species, published in 1859
2. The theory is summarized bellow
a. o Speciation- when species are formed by gradual change over a long time
b. o when populations of the same species become separated, they cannot interbreed
and may start to diverge if the environments they inhabit change
c. o separation may have geographical or reproductive causes; humans speed up
speciation by artificial selection of plants and animals and by genetic engineering
d. o over time the population gradually changes= natural selection
e. o “the survival of the fittest”
1.
o
o
o
Physical Barriers (examples of species and speciation)
o Large flightless birds (e.g. emu, ostrich, rhea, cassowary) only found in Africa, Australia,
South America
o cichlid fish in the lakes of East Africa, Lake Victoria, Lake Tanganyika, Lake Malawi
o Llamas and camels (llamas in South America and camels in Africa and central Asia)

30. IB ESS/GURU
Land bridges: allow species to invade new areas
Continental drift: the movement of tectonic plates
Plate tectonics: the study of the movement of plates (continental drift)
Plates may either slide past each other, diverge, or converge
Factors that help to maintain the biodiversity
complexity of the ecosystem
stage of succession
(lack of) limiting factors
inertia
Factors that lead to loss of biodiversity
Natural hazards
loss of habitat
fragmentation of habitat
pollution
overexploitation
introducing non-native (exotic species)
spread of disease
modern agricultural practices
What makes a species prone to extinction?
narrow geographical range
small population size of reclining numbers
low population densities and large territories
few populations of the species
a large body
low reproductive potential
seasonal migrants
poor dispersers
specialized feeders or niche requirements
hunted for food or sport
minimum viable population size: that is needed for a species to survive in the wild is a figure that
scientists and conservationists consider
Species Examples (recovered, extinct, endangered)
o
Recovered Species
Australian saltwater crocodile

31. IB ESS/GURU
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o
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18 out of 23 were once endangered
listed as protected species in Australia in 1971
overexploited for skin (leather), meat and body parts through illegal hunting, poaching and
smuggling
restored through ranching and closed-cycle farming
Golden lion tamarin (GLT) recovered or not?
small monkey
endemic to Atlantic coastal rainforests of Brazil
omnivores
only 2% of their native habitat is left
poachers earn US$20 000 for skin
captive breeding program
some re-introduced to the wild but with only 30% of success
their future uncertain
Extinct Species
o
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o
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Thylacine (Tasmanian tiger)
life expectancy of 12-14 years
habitat: open forests and grassland
competed with dingoes on the mainland of Australia
hunted by farmers whose stock of sheep was the species’ prey
hunting, poisoning, and trapping
shooting parties organized for tourists’ entertainment
last one has been killed in 1930
now introduced dogs have taken over the ecological role of the thylacine
Dodo
large flightless bird endemic to the island of Mauritius
ground-nesting bird
1505 Portuguese sailors ate dodo as a source of fresh meat
new species introduced that ate dodo
humans killed the birds for sport
destruction of habitat
extinct by 1681
fauna impoverished by its loss
became an icon due to its apparent stupidity
Endangered species

32. IB ESS/GURU
o
o Rafflesia
 tropical parasitic plant in the forests of South-East Asia

single sexed
 pollination must be carried out when the plant in bloom
 vulnerable because they need specific conditions to survive
 deforestation and logging destroy their habitat
 now there are Rafflesia sanctuaries
TOPIC 5: Pollution Management
· Pollution: the addition of substances to the biosphere by human activity, at a rate greater than
could be rendered harmless by the env-t
- Major sources of pollution (table on p. 277)
· Combustion of fossil fuels
· Domestic waste
· Industrial waste
· Agricultural waste
- Point source pollution
· the release of pollutants from a single, clearly identifiable site(e.g factory chimney, waste
disposal pipe)
· easier to locate à easier to manage
- Non-point source pollution: the release of pollutants from numerous, widely dispersed origins
(e.g. vehicles, chemical spreads on fields)
· Difficult to locate
· General restrictions could be put to control it
Detection and monitoring of pollution
· Indicator species: species that are only found if the conditions are either polluted or unpolluted
- Biochemical oxygen demand (BOD)
· The measure of the amount of dissolved oxygen required to break down the organic material in
a given volume of water through aerobic biological activity
· Indirect pollution measurement
· Higher BODà more pollution

33. IB ESS/GURU
- Biotic index
· A 1 to 10 scale
· Gives a measure of the quality of an ecosystem by the presence and abundance of the species
living in it
· Indirect method
· Used at the same time as BOD measurements
- Three-level model of pollution management
· a model for reducing the impact of pollutants
· “replace, regulate, restore” model
· Refer to figure 15.3 on page 282
· Pollution management strategies (refer to case study on p282-283)
- Domestic Waste (Solid domestic waste or municipal solid waste)
· Makes up about 5% of total waste
· 3kg of solid waste per capita in USA
· solid waste production has risen from 300kg per year in 1985 to 500
Strategies to minimize waste
- Recycling
· Collecting and separating waste materials and processing them for reuse
· E.g. aluminum cans
o Only 5% of energy needed to recycle it
o Can be recycled indefinitely
- Disposal of waste: Landfill
· Waste buried in a suitable site
· Lined with special plastic liner to prevent leachate (liquid waste) from seeping out
· Produced methane could be used to generate electricity
- Disposal of waste: Incinerators
· Burning of waste at high temperatures
· Heat produced is used (heat-to-energy incineration)
· Smaller land area used than in landfill
· Ash from incinerators could be used in road building
· Expensive
- Disposal of waste: organic waste
· Could be composted or put into anaerobic digesters
· Produced methane could be used as fuel

34. IB ESS/GURU
Eutrophication
· The addition of excess nutrients to a freshwater ecosystem
· Could be a natural process
· Usually nitrates and phosphates from: detergents, fertilizers, sewage etc.
- The process of eutrophication
· Fertilizers wash into a river or lake
· High levels of phosphate allow faster algae growth
· Algal blooms block the sunlight
· More algaeà more food for zooplanktonàmore food for fishàless zooplankton
· Algae die and are decomposed
· Not enough oxygen in wateràfood chains collapseàorganisms die
· Dead organic material forms sediments on the river bed and turbidity increases
· A clear blue lake is left
Reduces biodiversity in slow-moving water bodies, temporary reduction in biodiversity in fastmoving waters
- Eutrophication management strategies (refer to table 15.4 on p. 287)
- Impacts of eutrophication
· Bad smell
· Rivers/lakes covered by green algal scum and duckweed
· Anaerobic water (oxygen-deficient)
· Loss of biodiversity and shortened food chains
· Death of higher plants
· Death of aerobic organisms – invertebrates, fish and amphibians
· Increased turbidity
Introduction to ozone
Found in stratosphere, where it blocks UV radiation, and troposphere
- Depletion of stratospheric ozone
· The ozone layer
o Reactive gas mostly found between 20 and 40km altitude
o Made from oxygen (O2)
o UV radiation is absorbed in its formation and destruction
o The ozone layer absorbs more than 99% of UVC radiation

35. IB ESS/GURU
· Damaging effects of UV radiation
o Mutation
o Damage to photosynthetic organisms
o Damage to consumers of photosynthetic organisms
oC
- The action of ozone depleting substances
· Liming lakes: adding powdered limestone raises the pH but the effects are short-lived
· Reducing emissions: reducing combustion of fossil fuels
o Precombustion: removing sulfur from the fuel before combustion
o “end of pipe measures”
TOPIC 6: The Issue of Global Warming
TOPIC 7: Environmental Value Systems
Environmental philosophies
o Ecocentric: life-centered, respects rights of the nature and the dependence of humans on nature
o Technocentric/Anthropocentric: human-centered, humans are not dependent on nature, but
nature is there to benefit the human kind
Technocentric worldviews
o Cornucopians: people who see the world having infinite resources to benefit humanity. Believe
that the env-tal problems could be solved with technologies, improving our living standards
o Env-tal managers(stewardship): believe that we have an ethical duty to protect the nature.
Support limited limiting resource exploitation. Believe that if we look after the planet, it looks
after us
· Nurturing vs. intervening or manipulative approaches= environmental vs. technocentric
worldviews
Ecocentric worldviews
Biocentric: all life has an inherent value, not just for humans. Some philosophies believe
that humans aren’t any more important than other species.
Soft technologists: believe in small-scale local community action and emphasize the role
of individuals making a difference
Deep ecologies: put more value on nature than humanity. Believe in biorights – universal
rights of all species and ecosystems; advocate strong policy and population change
Various environmental worldviews
o Communism and capitalism in Germany
- disregarding value of the environment and exploiting resources
o Native American
- Use low impact technologies and respect nature
- Polytheistic religion believes that animals and plants have a spirituality
o Modern Western
- view earth as a resource for humanity.

36. IB ESS/GURU
- Ecofeminists
· argue that it is the rise of male-dominated species that has led to our view of nature as a
foe
o Buddhism’s view
- believe that we are all dependent on each other and preaches that all being are equal
- believe that all living organisms share the conditions of birth, old age, suffering and
death