This document discusses ecosystems and their structure and functions. It defines an ecosystem as including all living organisms and non-living components found in a particular area, where life continues naturally without human intervention. An ecosystem structurally consists of a community of living organisms and their abiotic environment. Key components include producers, consumers, and decomposers. Energy flows through ecosystems via food chains and webs. Nutrients cycle through biogeochemical cycles like carbon and nitrogen. Ecosystems strive for homeostasis by resisting changes to their populations.

1. ARCH 5351
ECOLOGICAL ARCHITECTURE &URBANISM

2. Recall from last lesson
 Ecological Architecture Environment and its Components
 Biotic & Abiotic
 Ecology
 levels of ecological organization
 Ecosystem
 Types of Ecosystem
 components of Ecosystem
 Biosphere
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3. Ecosystem
 An ecosystem includes all living organisms and the non-living
components of the environment that are found in a particular place.
In simple words, it can be defined as a piece of land or water body
where life continues without the need of human support or
intervention.
 The simplest level of organization in any ecosystem is that of an
organism, which refers to any plant, animal or micro-organism
inhabiting an ecosystem. A population includes all the members of
the same organism that live in one place at one time. All the different
populations that live in a particular area make up a Community. The
physical location of a community is called the Habitat. An ecosystem
is in turn is a level of organization and has another higher level of
organization called Biosphere.
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4. Ecosystem
 In other words, an ecosystem is the basic functional unit of biosphere.
The major terrestrial ecosystems of the world with their groups of
climax biotic community are called ‘biomes’.
 The major terrestrial biomes are: Tundra, taiga, deciduous forests,
tropical rain forest, chapparals, savannah, grasslands and deserts.
 Extent of a biome is determined by climatic edaphic factors and
geographic and geomorphic factors.
 In this lecture you will learn about the structure and functions of
ecosystem.
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6. Ecosystem Structure
 An ecosystem can also be viewed as a piece of land or
water body where life continues naturally.
 Structurally it consists of a community of living organisms
along with their abiotic environment.
 Ecosystem structure can be described in terms of its
components, trophic organization, species composition,
stratification, consideration of size scale and boundaries
etc.
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7. Biomes 7

8. Biomes 8

9. Components of an ecosystem 9
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They are broadly grouped into:-
 Abiotic
 Physical/ Climatic factors
 Edaphic factors
 Geographic or Geomorphic factors
 Biotic components

10. Components of an ecosystem
Abiotic components (Non-living):
 Abiotic components represent the physio-chemical environment of the
earth and include different physical entities like air, water, soil etc. as well as
conditions such as temperature, light etc. these are also referred as factors
as they influence the behaviour of any individual in an ecosystem.
 The abiotic component can be grouped into following three categories:-
 Physical/ Climatic factors: Sun light, temperature, rainfall, humidity, wind
and pressure. They sustain and limit the growth of organisms in an
ecosystem.
 Edaphic factors: These are related to the structure and composition of soil
and include inorganic substances like water, carbon, sulphur, nitrogen,
phosphorus etc. as well as organic substances like Carbohydrates, proteins,
lipids and humic substances. They are the building blocks of living systems
and therefore, make a link between the biotic and abiotic components.
 Geographic or Geomorphic factors: It includes land topography, slope,
aspects (direction towards the sun), altitude, latitude etc.
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11. Components of an ecosystem
Biotic components (Living)
 Biotic components comprises the living part of
the environment, which includes the
association of a number of interrelated
populations belonging to different species in a
common environment.
 The populations are that of animal community,
plant community and microbial community.
 Biotic community is distinguished into
autotrophs, heterotrophs and saprotrophs.
 (i) Producers: The green plants manufacture
food for the entire ecosystem through the
process of photosynthesis. Green plants are
called autotrophs, as they absorb water and
nutrients from the soil, carbon dioxide from the
air, and capture solar energy for this process.
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12. Components of an ecosystem
 (ii) Consumers: They are called
heterotrophs and they consume food
synthesized by the autotrophs.
 Based on food preferences they can be
grouped into three broad categories.
Herbivores (e.g. cow, deer and rabbit
etc.) feed directly on plants, carnivores
are animals which eat other animals (eg.
lion, cat, dog etc.) and omnivores
organisms feeding upon both plants and
animals e.g. human, pigs and sparrow.
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13. Components of an ecosystem
 (iii) Decomposers: Also called
saprotrophs.
 These are mostly bacteria and fungi
that feed on dead decomposed and
the dead organic matter of plants and
animals by secreting enzymes outside
their body on the decaying matter.
 They play a very important role in
recycling of nutrients.
 They are also called detrivores or
detritus feeders.
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14. Ecosystem Function–energy Flow Through ecosystem
Food chains and energy flow are the functional properties of
ecosystems which make them dynamic.
The biotic and abiotic components of an ecosystem are linked through
them.
 Food Chain
 Transfer of food energy from green plants (producers) through a
series of organisms with repeated eating and being eaten is called a
food chain. e.g.
 Grasses → Grasshopper → Frog → Snake → Hawk/Eagle
 Each step in the food chain is called trophic level. In the above
example grasses are 1st, and eagle represents the 5th trophic level.
 During this process of transfer of energy some energy is lost into the
system as heat energy and is not available to the next trophic level.
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15. Food Chain
(1) Autotrophs: They are the producers of food for all other organisms of
the ecosystem.
(2) Herbivores: The animals which eat the plants directly are called
primary consumers or herbivores e.g. insects, birds, rodents and
ruminants.
(3) Carnivores: They are secondary consumers if they feed on
herbivores and tertiary consumers if they use carnivores as their food.
e.g. frog, dog, cat and tiger.
(4) Omnivores: Animals that eat both plant and animals e.g. pig, bear
and man
(5) Decomposers: They take care of the dead remains of organisms at
each trophic level and help in recycling of the nutrients e.g. bacteria
and fungi.
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16. Types of Food Chain
(i) Grazing food chains: which starts from the green plants that make
food for herbivores and herbivores in turn for the carnivores.
(ii) Detritus food chains: start from the dead organic matter to the
detrivore organisms which in turn make food for protozoan to carnivores
etc.
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17. Food Web
 Trophic levels in an ecosystem are
not linear rather they are
interconnected and make a food
web.
 Thus food web is a network
interconnected food chains
existing in an ecosystem.
 One animal may be a member of
several different food chains.
 Food webs are more realistic
models of energy flow through an
ecosystem.
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18. Ecological Pyramid
 Ecological pyramids are the
graphic representations of trophic
levels in an ecosystem.
 They are pyramidal in shape and
they are of three types:
 The producers make the base of
the pyramid and the subsequent
tiers of the pyramid represent
herbivore, carnivore and top
carnivore levels.
1. Pyramid of Numbers
2. Pyramid of Biomass
3. Pyramid of Energy
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19. Ecological Pyramid 19
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20. ECOLOGICAL EFFICIENCY
It is clear from the trophic structure of an ecosystem that the amount of
energy decreases at each subsequent trophic level due to two reasons:
 At each trophic a part of the available energy is lost in respiration or
used up in metabolism.
 A part of energy is lost at each transformation, i.e. when it moves
from lower to higher trophic level as heat.
 It is the ratio between the amount of energy acquired from the lower
trophic level and the amount of energy transferred from higher
trophic level is called ecological efficiency.
 Lindman in 1942 defined these ecological efficiencies for the 1st time
and proposed 10% rule e.g. if autotrophs produce 100 cal, herbivores
will be able to store 10 cal. and carnivores 1cal.
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21. BIOGEOCHEMICAL CYCLES
Bio = living, Geo = rock Chemical = element
 In ecosystems flow of energy is linear but that of nutrients is cyclical.
 This is because energy flows downhill i.e. it is utilized or lost as heat as
it flows forward.
 The nutrients on the other hand cycle from dead remains of
organisms released back into the soil by detrivores which are
absorbed again i.e. nutrient absorbed from soil by the root of green
plants are passed on to herbivores and then carnivores.
 The nutrients locked in the dead remains of organisms and released
back into the soil by detrivores and decomposers.
 This recycling of the nutrients is called biogeochemical or nutrient
cycle
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22. BIOGEOCHEMICAL CYCLES
 There are more than 40 elements required for the
various life processes by plants and animals.
 The entire earth or biosphere is a closed system i.e.
nutrients are neither imported nor exported from the
biosphere.
There are two important components of a
biogeochemical cycle
(1) Reservoir pool - atmosphere or rock, which stores
large amounts of nutrients.
(2) Cycling pool or compartments of cycle-They are
relatively short storages of carbon in the form of plants
and animals.
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23. CARBON CYCLE
 The source of all carbon is carbon dioxide present in the atmosphere. It is highly soluble in
water; therefore, oceans also contain large quantities of dissolved carbon dioxide.
 The global carbon cycle consists of following steps-
• Photosynthesis
• Respiration
• Decomposition
• Combustion
• Impact of human activities
 The global carbon cycle has been increasingly disturbed by human activities particularly
since the beginning of industrial era.
 Large scale deforestation and ever growing consumption of fossil fuels by growing numbers
of industries, power plants and automobiles are primarily responsible for increasing emission
of carbon dioxide.
 Carbon dioxide has been continuously increasing in the atmosphere due to human activities
such as industrialization, urbanization and increasing use and number of automobiles.
 This is leading to increase concentration of CO2 in the atmosphere, which is a major cause
of global warming.
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24. CARBON CYCLE 24

25. NITROGEN CYCLE
Nitrogen is an essential component of protein and required by all living organisms including human beings.
Our atmosphere contains nearly 79% of nitrogen but it cannot be used directly by the majority of living organisms.
Broadly like carbon dioxide, nitrogen also cycles from gaseous phase to solid phase then back to gaseous phase
through the activity of a wide variety of organisms.
Cycling of nitrogen is vitally important for all living organisms.
There are five main processes which essential for nitrogen cycle are elaborated below.
(a) Nitrogen fixation: This process involves conversion of gaseous nitrogen into
 Ammonia, a form in which it can be used by plants. Atmospheric nitrogen can be fixed by the following three
methods:-
(i) Atmospheric fixation: Lightening, combustion and volcanic activity help in the fixation of nitrogen.
(ii) Industrial fixation: At high temperature (400oC) and high pressure (200 atm.), molecular nitrogen is broken into
atomic nitrogen which then combines with hydrogen to form ammonia.
(iii) Bacterial fixation: There are two types of bacteria-
(i) Symbiotic bacteria e.g. Rhizobium in the root nodules of leguminous plants.
(ii) Freeliving or symbiotic e.g. 1. Nostoc 2. Azobacter 3. Cyanobacteria can combine atmospheric or dissolved
nitrogen with hydrogen to form ammonia.
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26. NITROGEN CYCLE
(b) Nitrification: It is a process by which ammonia is
converted into nitrates or nitrites by Nitrosomonas and
Nitrococcus bacteria respectively. Another soil bacteria
 Nitrobacter can covert nitrate into nitrite.
(c) Assimilation: In this process nitrogen fixed by plants is
converted into organic molecules such as proteins, DNA,
RNA etc. These molecules make the plant and animal
tissue.
(d) Ammonification: Living organisms produce
nitrogenous waste products such as urea and uric acid.
These waste products as well as dead remains of
organisms are converted back into inorganic ammonia
by the bacteria. This process is called ammonification.
Ammonifying bacteria help in this process.
(e) Denitrification: Conversion of nitrates back into
gaseous nitrogen is called denitrification. Denitrifying
bacteria live deep in soil near the water table as they
like to live in oxygen free medium. Denitrification is
reverse of nitrogen fixation.
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27. NITROGEN CYCLE 27

28. WATER CYCLE
 Water received from the atmosphere on the earth returns
back to the atmosphere as water vapour resulting from
direct evaporation and through evapotranspiration the
continuous movement of water in the biosphere is called
water cycle (hydrological cycle).
 Water is not evenly distributed throughout the surface of
the earth.
 Almost 95 % of the total water on the earth is chemically
bound to rocks and does not cycle.
 Out of the remaining 5%, nearly 97.3% is in the oceans and
2.1% exists as polar ice caps.
 Thus only 0.6% is present as fresh water in the form of
atmospheric water vapours, ground and soil water.
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29. WATER CYCLE 29

30. WATER CYCLE
 Water is not evenly distributed throughout the
surface of the earth.
 Almost 95 % of the total water on the earth is
chemically bound to rocks and does not cycle.
 Out of the remaining 5%, nearly 97.3% is in the
oceans and 2.1% exists as polar ice caps.
 Thus only 0.6% is present as fresh water in the form of
atmospheric water vapours, ground and soil water.
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31. WATER CYCLE 31
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32. HOMEOSTASIS OF ECOSYSTEM
 Ecosystems are capable of maintaining their state of equilibrium.
 They can regulate their own species structure and functional processes.
This capacity of ecosystem of self-regulation is known as homeostasis.
 In ecology the term applies to the tendency for a biological systems to
resist changes. For example, in a pond ecosystem if the population of
zooplankton increased, they would consume large number of the
phytoplankton and as a result soon zooplankton would be short supply
of food for them.
 As the number of zooplankton is reduced because of starvation,
phytoplankton population start increasing. After some time the
population size of zooplankton also increases and this process continues
at all the trophic levels of the food chain.
 Humans are the greatest source of disturbance to ecosystems.
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33. ECOSYSTEM SERVICES AND HUMAN WELLBEING
 It has been widely recognized that ecosystems are the planet’s life
support systems.
 Nature’s goods and services are the ultimate foundations of life for the
human species and all other living beings.
 Human biology has a fundamental need for food, Water, clean air,
shelter and relative climatic constancy.
 All these resources are directly or indirectly derived from ecosystems or
nature.
 Changes in the flow of these services affect health, livelihoods, income,
migration and political affairs of human society which in turn have wide
ranging impacts on human well-being.
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34. HUMAN INTERVENTION IN ECOSYSTEM
 As a result of human actions, the structure and functioning of world’s
ecosystems have changed more rapidly in the second half of the 20th century
than at any other time in human history.
 It is becoming increasingly clear that population growth and economic
development are leading rapid changes in a global ecosystems.
 In recognition of this, the United Nations undertook the Millennium Ecosystem
Assessment in order to assess the consequences of ecosystem change as
related to human well-being.
 the Millennium Ecosystem Assessment examined the state of 24 services that
make a direct contribution to human well-being.
 The assessment concludes that 15 out of these 24 services are in decline,
including provision of freshwater, marine fishery production, the number of
quality of places of spiritual and religious value, the ability of the atmosphere to
cleanse itself off pollutants, natural hazard regulation, pollination, and the
capacity of agricultural ecosystems to provide bio-control of pests.
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35. HUMAN INTERVENTION IN ECOSYSTEM
 Over the past 50 years human have changed natural ecosystems more
rapidly and extensively than in any other comparable period in human
history.
 Poverty and hunger have tended to force many rural people to do
farming on marginal drought-prone lands with poor soil fertility, and
others to move to urban slums.
 About 1 billion people are affected by land degradation such as that
caused by soil erosion, water logging or salinity of irrigated land.
 Erosion has caused substantial reductions of crop yields in Africa.
 Diminished human health and well-being tends to increase the
immediate dependence on ecosystem services and the resultant
additional pressure can damage the ecosystem’s capacity to deliver
services.
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36. HUMAN INTERVENTION IN ECOSYSTEM
 The concept of ecological footprint has been designed to measure the
extent of human pressure on the land and seas.
 Ecological footprint measures the biologically productive area that
people use for provision of renewable resources, occupy with
infrastructure, or required for absorption of Co2 wastes.
 with the modest UN projections for population growth, consumption and
climate change, by 2030 humanity will need the capacity of two Earths,
to absorb carbon dioxide waste and keep up with natural resource
consumption of ever growing human population.
 Now it depends on the people and the nations that how they respond
to such an alarming situation.
 Adopting sustainable development in future course of human
endeavour is the only solution and way forward.
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37. NEED FOR MANAGING ECOSYSTEM
 Ecosystem services are indispensable to the well-being of people
everywhere. It is also now widely recognised that adverse changes in
ecosystems have a more direct influence on human well-being among
poor populations than among wealthy populations.
 In order to achieve the goal of sustainable development and to
enhance human well-being, ecosystem services need to be conserved
by all means.
 For achieving this target, comprehensive reforms and governance,
institutions, laws and policies are required along with personal
commitment at the level of individuals to adopt an eco-friendly lifestyle.
 Reducing the present level of resource consumption, fighting inequalities
in resource access and giving top priority for managing essential
ecosystem services like provision of clean water and nutritious food are
some of the pathways to achieve sustainability.
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39. Ecosystems of Ethiopia
 Ethiopia is endowed with diverse ecosystems in which diverse flora and
fauna as well as microbial resources are found.
 The major ecosystems include:
1. Afroalpine and subafroalpine,
2. Montane dry forest and scrub, Montane moist forest,
3. Acacia-Comiphora woodland,
4. Combretum-Terminalia woodland,
5. Lowland humid forest,
6. Aquatic, wetland,
7. Montane grassland, and
8. Desert and semi desert ecosystems.
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41. THANKYOU