Download Environment Module 2_Ecological concepts

Ecological Concepts-2
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Outline

Ecotone

Niche

Biome

Biosphere

Ecosystem Productivity

Ecosystem Stability

Modification of Ecosystem

Evolution of Species

Neo-Darwinism

Succession- Ecological Succession

Primary and Secondary Succession

Autogenic and Allogenic Succession

Autotrophic and Heterotrophic Succession
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Outline

Sere

Trophic Level

Energy Flow in Ecosystem

Food Chain

Food Web

Ecological Pyramids- Pyramid of numbers, biomass and energy

Pollutants and Trophic Level

Bioaccumulation and Biomagnification

Biotic Interaction

Types of Biotic Interaction

Eutrophication, Harmful Algal Blooms & Coral Bleaching

Ecological efficiency

Questions
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Ecotone/ Eco clines

Transition zone or junction between two diverse ecosystems along with biotic communities and
abiotic condition change.

It may be very narrow or quite wide.

Zone of tension, having conditions intermediate to adjacent ecosystems.

Progressive increase in species composition of incoming community and decrease in species of
outgoing community.

Well developed ecotones contain some organisms entirely different from adjoining communities.
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Ecotone/ Eco clines

Edge effect- Sometimes number of species and population density of some of species is much
greater in ecotone than adjoining areas. Organism which occur primarily or most abundantly in
this zone are known as edge species. i.e. Density of birds is greater in mixed habitat of ecotone
between forest and desert.
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Niche

Unique functional role and position of species in its ecosystem including
• where it lives,
• what resources it uses,
• how and when it uses resources,
• how it interacts with other species.

No two species have exact identical niches.

Greater diversity of niche => More ecosystem stability as large number of pathways for flow
of energy and less fluctuation of species population.
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Niche

Forest can support large number of plant species as they occupy different niches. Like tall trees, short
trees, shrubs, bushes, grasses- because of their varying heights their requirements for sunlight and
nutrients differ and so they can survive together (reduced competition)

Most important resources in niches of plants is moisture, nutrient- phosphorus and nitrogen,

While for animals, it is food and shelter.

There are different types of niches like Habitat niche, Food niche, Reproductive niche, Physical and
chemical niche.
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Niche
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Biome

Terrestrial part of biosphere
is divisible into enormous
region called biome, which
are characterised by climate,
vegetation, animal type and
soil type.

Most important climatic
factors are temperature and
precipitation. (Heat and
Moisture).
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Biomes
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Biosphere

Biosphere is part of earth where life can
exist. It represents highly integrated and
interacting
zone
comprising
of
atmosphere,
hydrosphere
and
lithosphere.

Biosphere is absent at extremes of North
and South poles, highest mountains and
deepest oceans, since existing hostile
conditions.

Energy required for life within
biosphere comes from Sun and nutrients
come from air, water and soil.
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Ecosystem Productivity
 Growth of energy or organic matter per unit time by autotrophs at
trophic level through photosynthesis

Depending factors Availability of solar radiation at trophic level;
 Efficiency of plants to convert solar energy into chemical energy;
 Availability of moisture

Net Primary Productivity= Gross Primary Productivity (total) – Loss through respiration

NPP= usable amount of energy at trophic level
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Ecosystem Productivity

NPP decreases as one moves from equator to pole
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NPP decreases with increase in size of animals

NPP of terrestrial ecosystem is generally greater than NPP of aquatic ecosystem
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Order of NPP of terrestrial ecosystem–
1. Swamp and Marsh-Tropical Forest
2. Temperate Forest
3. Tropical Savannah
4. Agricultural Land
5. Temperate Grassland
6. Extreme Desert-Rocks-Ice

Order of NPP of aquatic ecosystem1. Attached algae & Estuaries- Coral Reef
2. Continental Shelf
3. Open Sea
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Ecosystem Stability

Ecosystem stability is the ability of ecosystem to maintain its structure and function
over long periods of time and despite disturbances.

Ecosystem structure includes
physical and geological structures of landscape,
number and diversity of species present,
population of size of those species,
ways in which population interact.
1.
2.
3.
4.

Ecosystem function refers to processes such as water and nutrient cycling and biomass
productivity that ecosystem provides.
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Ecosystem Stability

Increase in one species is compensated by decrease in
other species thus productivity is maintained.

“Homeostasis”- Self regulating, natural ecosystem
adjust changes to itself.

Increase in stability => with increase in diversity and
complexity of ecosystem

Increase in stability => Decrease in competition as
different resources can be used or use of same resources
but at different time.
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Modification of Ecosystem

Destruction of natural/ original/ native species and introducing alien species
which come in direct competition or bring diseases.

Climate Change

Chemical Fertilizers

Atmospheric Pollution

Depletion of Species

Urbanization, Industrialization, Deforestation, Irrigation

Overexploitation of resources
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Evolution of Species
Speciation
Natural
Selection
 Progressive
evolution of
Species
1. Genotype
2. Phenotype
 Neo-Darwinism
Origin, growth and development of species
through time
Mutation
Changes
Reproductive
Isolation
Ecological
Isolation
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Geographical
Isolation
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Evolution of Species

Mutation- Spontaneous and abrupt evolution cause new gene to arise in population

Reproductive Isolation- no exchange of specific gene from parent to off spring;
Sexually receptive at different times;
not attracted towards each other;
Pollination mechanism fails;
Not matching reproductive organs.





Ecological Isolation- When ecologically-based divergent selection creates reproductive
barriers between populations

Geological Isolation- population of animals, plants, or other organisms that are separated
from exchanging genetic material with other organisms of the same species. Typically
geographic isolation is the result of an accident or coincidence
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Neo-Darwinism

Organisms produce more offspring than it can be supported by environment

Members of same species shows variation because of either mutation (cause new gene to
rise) or recombination (sexually reproducing population; meiosis and fertilization produce
new combination of genes every generation)

Only those genes that help organisms to adopt its environment are selected through natural
selection.

Those offspring which are suited to their immediate environment have more chance of
surviving, reaching reproductive age and passing on suitable adaption.

Evolution thus results in adaption and diversity of species.
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Neo-Darwinism
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Succession

When ecosystem undergoes succession there is change in structure and productivity of ecosystem.
Structure of ecosystem refers to complexity and diversity of ecosystem.

Plant succession which is limited by water availability known as Xerarch succession on terrestrial
ecosystem with low moisture.

While, succession in aquatic ecosystem with high moisture known as Hydrarch succession.

Succession will increase soil structure, composition and maturity which intend to increase relative
stability of ecosystem.
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Ecological Succession

Entire process of directional and sequential change of biotic and abiotic component of ecosystem over
period of time.

Succession occurs when series of communities replace one another due to large scale destruction either
natural or manmade.

Succession is progressive series of changes which leads to establishment of relatively stable climax
community.

Succession is characterised by increased productivity, shift of nutrients from reservoirs, increased diversity,
increased niche development and gradual increase in complexity of food webs.
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Ecological Succession
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Primary Succession

Primary succession occurs on new site like bare or unoccupied areas, rocks, newly formed deltas, sand
dunes, emerging volcano islands, glacial moraines (muddy area exposed by retreating glacier)

Pioneer species- like microbes, lichens and mosses which invade first and colonise area.
1. These species are having high growth rate but short life span.
2. Pioneers take long time as soil has to be formed and over few generations of pioneers, they alter
habitat condition and made it conducive to establishment of additional organisms.

Serial species- Transitional species which succeeds pioneers and further helps in development of habitat
condition.
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Primary Succession

Community of organisms continues to develop, it becomes more diverse and
competition increases, but at same time new niche opportunities develops.

Pioneer species disappear as habitat conditions change and invasion of new species
progresses, leading to replacement of preceding community.

Climax Species- Final stage of succession, more stable, mature and complex species
which are having long life span and slow growth rate.
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Secondary Succession

Occurs when plants recognise an area in which climax community has been disturbed.
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Complete or partial destruction of existing community- mature or intermediate
community may be destroyed by natural events like floods, hurricane, forest fire or by
human interventions like harvesting, deforestation, overgrazing etc.

Difference between primary and secondary succession is, secondary succession starts
on well developed soil already formed at site. Thus, secondary succession is relatively
faster as compared to primary succession.
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Autogenic and Allogenic Succession

Autogenic succession- Succession is brought about by living inhabitants
of that community itself.

Allogenic succession- Succession is brought about by outside forces.
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Autotrophic and Heterotrophic Succession

Autotrophic succession- Succession in which initially green plants
(autotrophs) are much greater in quantity.

Heterotrophic succession- Succession in which initially heterotrophs are
greater in quantity.
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Sere

Transitional stages of sequential change from one vegetation community to another.

The whole sequence of communities that replace one another in a given area

Maximum growth and development.

Most adjustable and adaptable.
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Trophic Level

Trophic level of an organism is the position it occupies in food chain.

It is point where food energy is transferred from one group of organisms to other.

Trophic level interaction deals with how members of ecosystem are connected based on
nutritional needs.
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Energy Flow in ecosystem

Flow of energy from producers to top consumers is called energy flow.

Energy flow is unidirectional- always flows from lower to higher trophic level.

Loss of some energy in form of unusable heat at each trophic level so that energy level decreases from
first trophic level upwards.
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Food Chain

The chain of transfer of food energy from one group of
organisms to other group in ecosystem.
1.
Grazing food chain- begins with plants at base
2.
Detritus food chain- starts from dead organic matter
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Food Web

Food web is when food chain
is complicated by several
overlapping
and
interconnected layers.

Food web illustrates, all
possible transfers of energy
and nutrients among organisms
in ecosystem.

Richer the biodiversity, the
longer and more complicated
food chains and webs.
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Ecological Pyramids- Pyramid of numbers

Number of individuals in each trophic level is considered.

Can be upright (Grassland ecosystem) or inverted (Tree ecosystem)
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Ecological Pyramids- Pyramid of Biomass
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Total dry weight of all organisms at each trophic level at particular time is considered

Biomass is measured in g/m2.

Can be upright or inverted
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Ecological Pyramids- Pyramid of Energy

Energy pyramid reflects law of thermodynamics, with conversion of solar
energy into chemical energy and heat energy being depicted at each transfer
to another trophic level. Most suitable pyramid to compare functional roles
of trophic level.

Energy pyramid is always upward with large energy base at bottom.

Energy pyramid helps to explain phenomenon of biological
magnification- tendency of toxic substances to increase in concentration
progressively at higher levels of food chain.
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Ecological Pyramids- Pyramid of Energy
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Ecological efficiency
• The % of energy transferred
from one trophic level to next
varies between 5-20 % and is
called ecological efficiency
• An average figure of 10% is used
known as ten percent law-total
energy content of a trophic level
in an ecosystem is only about
1/10th that of preceding level
• Lost energy is used to catch ,
eat, digest, respiration, feces
etc.
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Pollutant and Trophic Level

Non-degradable pollutants (POPs) like chlorinated hydrocarbons which
can not be metabolised by living organisms, move through various trophic
level in an ecosystem.

Movement of these pollutants involves two processes:
1.
Bioaccumulation
2.
Biomagnification
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Bioaccumulation and Biomagnification

Bioaccumulation- refers to how pollutants enter food chain; there is an
increase in concentration of pollutants from environment to first organism
in food chain.

Biomagnification- refers to tendency of pollutants to concentrate as they
move from one trophic level to next level.

In order for biomagnification to occur, pollutants must be long-lived,
mobile, soluble in fats, biologically active.
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Biotic Interaction

Amensalism- (antibiotics) One species harm other species without itself getting
affected. i.e. Bread mold fungi Pencillium produce penicillin, an antibiotic that inhabit
growth of variety of bacteria, thus penicillium benefits from having greater availability of
food as bacteria is removed.

Predation- Predator capture, kill and eat the prey. i.e. Leopard, Tiger, Cheetahs as
predator having speed, teeth and claws to hunt.

Parasitism- One species is harmed while other is benefits. i.e. Parasites like bacteria,
fungi, virus, roundworm live on host for food, nourishment and shelter while host is
harmed.

Neutralism- No net benefit or harm to either species. They do interact but do not
affect each other. Relationship between two species inhabiting same space and using
same resources but have no effect on each other.
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Biotic Interaction

Competition- Both species are harmed to some extend. Within species or interspecies competition for food, shelter, water, mate, space, resting site.

Commensalism- One species benefits, while other is unaffected. i.e. Fish Remora
attached to Shark. Remora is benefited as it gets protection, free ride and meal (shark
left over food), while Shark is unaffected. Epiphytes- ferns, mosses, orchids.

Mutualism- Both species benefit. Symbiotic- intimate relationship. i.e. Termites
and Protozoa, Termites eat food but can’t digest while Protozoa digests and convert
into sugar and uses sugar. Pollination mutualism, where pollinator gets food and
plant has its pollen transferred for reproduction.
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Eutrophication

Syndrome of ecosystem, response to addition of artificial or natural substances such as
nitrates and phosphates through fertilizers, sewage etc. that fertilize aquatic ecosystem.

Growth of green algae- physical identification of Eutrophication

Some algae and blue-green bacteria thrive on excess ions and population explosion covers
almost entire surface layer is known as algal bloom. This growth is unsustainable.

Algal bloom covers surface layer and restricts penetration of sunlight; Oxygen level is
reduced due to population explosion; New anaerobic conditions can promote growth of
bacteria Clostridium botulinum which produces toxins– All these conditions leads to
change in animal and plant population and degradation of aquatic ecosystem and habitat
quality.
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Eutrophication

Algal bloom covers surface layer and restricts penetration of sunlight;
Oxygen level is reduced due to population explosion; New anaerobic
conditions can promote growth of bacteria Clostridium botulinum
which produces toxins– All these conditions leads to change in animal and
plant population and degradation of aquatic ecosystem and habitat quality.

Effects of Eutrophication Change in Ecosystem
 Decreased Biodiversity
 New species invasion
 Toxicity
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Harmful Algal Bloom

When environmental conditions are favourable to development of algae and
phytoplanktons, they can be multiplied rapidly and results in algal bloom.

Bloom often results in colour change in water. Algal bloom can be any colour, but
common ones are red or brown. These blooms are commonly referred as “Red
Tides”.

Most algal blooms are not harmful but some produces toxins and do affect aquatic
organisms and humans. Toxins may affect surrounding air difficult to breathe.
These known as Harmful Algal Blooms (HABs).
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BOD,COD,DO
1.
Biochemical oxygen demand (BOD, also called biological oxygen demand) is the amount of
dissolved oxygen needed (i.e., demanded) by aerobic biological organisms to break down
organic material present in a given water sample at certain temperature over a specific time
period
2.
Chemical oxygen demand (COD) is measure the amount of organic compounds in water.
• Most applications of COD determine the amount of organic pollutants found in surface water
(e.g. lakes and rivers) or wastewater, making COD a useful measure of water quality.
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BOD,COD,DO
3.
Dissolved oxygen measures the amount of gaseous oxygen (O2) dissolved in an aqueous solution.
• Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a
waste product of photosynthesis.
• Total dissolved gas concentrations in water should not exceed 110 percent. Concentrations above this
level can be harmful to aquatic life. Fish in waters containing excessive dissolved gases may suffer from
"gas bubble disease"; however, this is a very rare occurrence. The bubbles or emboli block the flow of
blood through blood vessels causing death. External bubbles (emphysema) can also occur and be seen
on fins, on skin and on other tissue. Aquatic invertebrates are also affected by gas bubble disease but at
levels higher than those lethal to fish.
• Adequate dissolved oxygen is necessary for good water quality. Oxygen is a necessary element to all
forms of life.
• Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life
forms. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress.
• The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a
few hours can result in large fish kills.
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Coral Bleaching

Bleaching of coral occurs when densities of zooxanthellae decline and/or
concentration of photosynthetic pigments within zooxanthellae fall.

Major ecological causes of coral bleaching are
 Temperature (Rise or Fall)
 Solar Irradiance
 Subaerial Exposure
 Sedimentation
 Fresh Water Dilution
 Inorganic Nutrients
 Xenobiotics- concentration of various chemical contaminants such as
Cu, herbicides and oil.
 Epizootics- Pathogens have been identified to cause translucent white
tissues, a protozoan.
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Adaptation
• Each organism is adapted to its particular environment.
• An adaptation is thus, “the appearance or behaviour or structure or mode of life of an
organism that allows it to survive in a particular environment”.
• Examples of basic adaptations that help animals and plants to survive in their respective
environments.
• Shape of bird’s beak.
• The thickness or thinness of fur.
• Presence of feathers and wings in birds.
• Evergreen and deciduous nature of trees.
• Presence and absence of thorns on leaves and stems.
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Adaptation
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Questions
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