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Unit – V – ECOSYSTEM AND BIODIVERSITY
Chapter – XXI – CONCEPT OF AN ECOSYSTEM
Ecology
Ecology generally is defined as the interactions of organisms with one another and with the
environment in which they occur. We can study ecology at the level of the individual, the population,
the community, and the ecosystem.
Components of an Ecosystem
ABIOTIC COMPONENTS
Sunlight
Temperature
Precipitation
Water or moisture
Soil or water chemistry (e.g., P, NH4+)
BIOTIC COMPONENTS
Primary producers
Herbivores
Carnivores
Omnivores
Detritivores
All of these vary over space/time
By and large, this set of environmental factors is important almost everywhere, in all ecosystems.
Functional group
A functional group is a biological category composed of organisms that perform mostly the same
kind of function in the system; for example, all the photosynthetic plants or primary producers form a
functional group. Membership in the functional group does not depend
very much on who the
actual players (species) happen to be, only on what function they
perform in the ecosystem.
Biotic factor in an eco system
A biotic factor is any living component that affects another organism, including animals that
consume the organism in question, and the living food that the organism consumes. Each biotic factor
needs energy to do work and food for proper growth. Biotic factors include human influence.
Abiotic factor in an ecosystem.
Abiotic factors are non-living chemical and physical parts of the environment that affect living
organisms and the functioning of ecosystems.
Food chain
A food chain is the sequence of who eats whom in a biological community (an ecosystem) to
obtain nutrition.
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Food web
A food web is a system of interconnected and interdependent food chains. It can also be defined as a
network of food relationships through which nutrients and energy are passed from one living organism
to another.
Lizard
Gross Hopper
Grass
Hawk
Rabbit
Mouse
Snake
A typical Example of a food Web
Factors of an ecosystem
The mutual and reciprocal influence between the living organisms and their non-living
environment for the continued survival and maintenance of life processes is the dynamic feature of an
eco system. An ecosystem basically involves energy flow and nutrient cycling between its various
components in a typical environment.
Basically each ecosystem is composed of two components, namely abiotic factors and biotic factors.
a) The abiotic factors include non-living substances of the environment like water, inorganic
substances like minerals like calcium, the organic constituents like protein, carbohydrates
and lipids that are synthesized by the biotic community of an ecosystem. The sustained
survival of biotic factors depends on the abiotic factors of an environment.
b) The biotic factors include the living organisms that live in specific environment and they are
grouped into three main categories namely, producers, consumers and decomposers.
c) The producers are the organisms that are capable of manufacturing their own source of food.
These producers are dependent on the light as abiotic factor for generation of chemical
energy In the form ATP molecules. A specific portion of the generated energy is utilized by
the producers for the process of growth and other cellular activities. The remaining quantity
of energy is stored in the chemical bonds for future utilization.
d) The organisms which depend on and eat other organisms for their food are called as
consumers. Consumers are of two types: The animals which directly eat the green plants are
called herbivores and the animals that eat the other animals are called carnivores.
e) The consumers are further classified into primary, secondary and tertiary consumers. The
animals that directly feed on producers are (green plants) are primary consumers. Rabbits
and deer are primary consumers. The animals that eat and feed on the primary consumers are
known as secondary consumers or primary carnivores. Fox and Wolf are primary carnivores.
The animals that eat the secondary consumer or the primary carnivores are called tertiary
consumers or secondary carnivores.
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f) The heterotrophic organisms that decompose and breakdown the dead and waste matter are
called decomposers. Fungi and certain bacteria some important examples of decomposers.
It is movement of chemical elements from the environment into living organisms and from them
back into the environment, as the organisms live, grow, die and decompose. Autotrphic plants obtain a
number of inorganic nutrients from the environment, which become a component of organic matter.
From autotrophs, nutrients go to other living constituents, and again to the environment with the help
of decomposers.
Principle of energy or nutrient cycling in an eco system through a diagram.
Solar
Energy
By Sun
GREEN PLANTS
HERBIVORES
DECOMPOSERS
PARASITES
CARNIVORES
SAPROPHYTES
NUTRIENTS
TRANSFORMERS
NON- LIVING OR
ABIOTIC
LIVING BIOTIC COMPONENTS
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Chapter – XXII – STRUCTURE AND FUNCTION OF AN ECOSYSTEM
Structure of an Ecosystem
The composition of biological community including distribution in space sped number,
biomass and life history etc.
The distribution and quantity of non-living materials.
Gradient of conditions of existence.
Function of an Ecosystem
(i) The rate of biological energy flow.
(ii) Rate of material or nutrient cycles and
(iii) Regulation of environment by the organism and regulation of organisms by environment.
Structure and function of an eco system
Structure of Ecosystem
An ecosystem has two major components:
(a) Abiotic Component
1. Components, those are non-living are called abiotic components.
2. They have a strong influence on the structure, distribution, behaviour and interrelationship of
organisms.
Abiotic components are mainly of two types:
(i) Climatic factors: which include rain, temperature, light, wind, humidity pH, organic inorganic
components, minerals etc?
(ii) Edaphic factors: Which includes pH, organic, inorganic components, minerals etc?
(b) Biotic Component
1. The living organisms including plants, animals and microorganisms (Bacteria and fungi)! that are
present in an ecosystem form the biotic components.
2. On the basis of their role in the ecosystem the biotic component can be classified into three main
groups.
(i) Producers
(ii) Consumers
(iii) Decomposers or Reducers
(i) Producers:
1. Autotrophic plants are main producers.
2. These are capable of synthesize food from non-living components.
3. In this chemosynthesis bacteria also included.
4. As the green plants manufacture their own food they are known as Autotrophs.
(ii) Consumers
1. The animals lack chlorophyll and are unable to synthesise their own food.
2. Therefore, they depend on the producer, for their food. They are known as heterotrophs. The
consumer's are of four types, namely:
(a) Primary Consumers (Herbivores)
1. These are the animals, which feed on plants or the producers. They are called herbivores. Examples:
Rabbit, dear, goat, cattle, grasshopper etc.
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(b) Secondary Consumers or Primary Carnivores
2. The animals, which feed on the herbivores, are called the primary carnivores. Examples: Cats, dogs,
fox, snakes etc.
(c) Tertiary Consumers or Secondary Carnivores
1. These are the large carnivores which feed on the secondary consumers. Examples: Wolves.
(d) Quaternary Consumers or Omnivores
2. These are the largest carnivores, which feed on the tertiary consumers and are not eaten up by any
other animal.
Examples: Lions and tigers.
(iii) Decomposers or Reducers
1. Bacteria and fungi belong to this category. They breakdown the dead organic materials of producers
and Consumers for their food and release to the environment the simple inorganic and organic
substances product as byproducts of their metabolisms
2. The producers resulting in a cycling exchange of materials between the biotic community and the
abiotic environment of the ecosystem reuse these simple substances.
3. The decomposers are known as saprophytes.
On the nourishment standpoint, biotic components may be divided into two groups:
a) Autotrophic Components or Producers
The producers, which are mainly autotrophic green plants and certain photosynthetic or
chemosynthetic bacteria, which can convert the light energy of sun into potential chemical energy in
the form of organic compounds, needed by plant for their development.
Thus producers stand as intermediaries between the inorganic and organic world. They obtain
C02 from the atmosphere and release 02instead. About 99 percent of living mantle of earth is a
producer. They produce oxygen as a byproduct of photosynthesis, needed by all living organisms for
respiration.
b) Heterotroph Components or Consumers
These are mainly animals, including man, which have an intake of organic material as food,
which is provided in the first instance by autotrophs. In heterotrophic components, utilisation,
rearrangement and decomposition of complex materials predominate. The consumers are further
subdivided into two groups:
(A) Macro consumers:
These consist of relatively larger consumers. They all phagotrophs which include chiefly
animals that ingest other organic and particulate organic they are of two types:
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(i) Herbivores:
They are primary consumers and feed on the plants. Depending upo nature of plant part eaten
by them, they can be of different types like root f' sucking animals, bark feeders and eaters etc. They
may be large cattle, goats etc.
(ii) Carnivores:
They are secondary and tertiary consumers. They feed on flesh of animals. The carnivores,
which feed on secondary consumers, are known as consumers and so on. The carnivores, which are not
further preyed upon are c top carnivores, e.g., tiger.
(B) Micro Consumers:
These are minute to small and microscopic animals. They three types:
(i) Parasites:
A parasite is an organism that lives on or in the body of another deriving benefit at the expense
of the latter. The organism, which harbours the is called the "host." The parasite is always benefitted in
this association and then injured or harmed.
(ii) Detritivores and scavengers:
Detritivores like earthworms feed on organic whereas, scavengers like vultures feed on dead
bodies.
(iii) Decomposers:
These are saprotrophs and include chiefly bacteria, actinomycetes fungi.
ECOSYSTEM
BIOTIC FACTORS
ABIOTIC FACTORS
1. Light
2. Temperature
3. pH
4. Pressure
Producers
PRIMARY
(Herbivores)
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SECONDARY
(Primary Carnivores)
Consumers
Decomposers
TERTIARY
(Secondary Carnivores)
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Nutrient cycling in a typical ecosystem
A nutrient cycle (or ecological recycling) is the movement and exchange
of organic and inorganic matter back into the production of living matter. The process is regulated
by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within
ecosystems. Ecosystems are interconnected systems where matter and energy flows and is exchanged
as organisms feed, digest, and migrate about. Minerals and nutrients accumulate in varied densities and
uneven configurations across the planet. Ecosystems recycle locally, converting mineral nutrients into
the production of biomass, and on a larger scale they participate in a global system of inputs and
outputs where matter is exchanged and transported through a larger system of biogeochemical cycles.
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Particulate matter is recycled by biodiversity inhabiting the detritus in soils, water columns,
and along particle surfaces (including 'aeoliandust'). Ecologists may refer to ecological recycling,
organic recycling, biocycling, cycling, biogeochemical recycling, natural recycling, or just recycling in
reference to the work of nature. Whereas the global biogeochemical cycles describe the natural
movement and exchange of every kind of particulate matter through the living and non-living
components of the Earth, nutrient cycling refers to the biodiversity within community food web
systems that loop organic nutrients or water supplies back into production. The difference is a matter
of scale and compartmentalization with nutrient cycles feeding into global biogeochemical
cycles. Solar energy flows through ecosystems along unidirectional and noncyclic pathways, whereas
the movement of mineral nutrients is cyclic. Mineral cycles include carbon cycle, sulfur
cycle, nitrogen cycle, water cycle, phosphorus cycle, oxygen cycle, among others that continually
recycle along with other mineral nutrients into productive ecological nutrition. Global biogeochemical
cycles are the sum product of localized ecological recycling regulated by the action of food webs
moving particulate matter from one living generation onto the next. Earths ecosystems have recycled
mineral nutrients sustainably for billions of years.
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Chapter – XXIII – ENERGY FLOW IN THE ECOSYSTEM
Food chain
A food chain is a linear sequence of links in a food web strating from a tropic species that eats
no other species in the web and ends at a tropic species that is eaten by no other species in the web.
Types of food chain
The sequence of eating and being eaten in an ecosystem is known as the food chain. It is the
path of transfer of food energy from the producers through a series of organisms i.e herbivores to
carnivores to decomposers. There are three basic types of food chain as discussed below:
1.
Grazing food chain
2.
Detritus food chain
3.
Parasitic food chain
Grazing Food Chain
Grazing food chain: The primary producers are the living green plants which are grazed on by
grazing animals. It is found in aquatic and grassland ecosystem.
Detritus food chain
Detritus food chain: This type of food chain starts from dead organic matter and so it is less
dependent on solar energy. The dead organic matter is broken down into simple nutrients by
microorganisms like fungi and bacteria. This type of food chain is found in forest ecosystem.
Dead organic matter→ Detritivores→Predators
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Parasitic food chain
Parasitic food chain: In this type of food chain either the producer or the consumer is
parasitized and therefore the food passes to the smaller organism. The energy transfer through this
kind of food chain is not significant.
Producer→ Herbivores→ Parasite→ Hyperparasites
Trees→ Fruit eating birds→ Lice and bugs→ Bacteria and fungi
Significance of Food Chains and Food webs
1.
2.
3.
4.
They help in maintaining the ecological balance.
They help in understanding the feeding relations among organisms.
Energy flow and nutrient cycling take place through them.
It explains the concept of biomagnification.
Detritivores
They are basically organisms that eat organic matter, while helping the matter decompose. an
example of a detritivore would be a worm, as they eat decomposing matter and help make healthy and
rich soil. A detritivore is an organism that feeds on decaying material, and takes it in to digest it (like
humans do). Examples include earthworms, dung beetles, maggots etc
Detritivores (also known as saprophages, detrivores or detritus feeders) are organisms that recycle
detritus (decomposing organic material), returning it into the food chain. Earthworms are a wellknown example of detritus feeders, eating rotting plant leaves and other debris. Some detritus feeders,
such as dung beetles, eat feces, which often contains a considerable nutrient load. The detritus may
already have been partially or fully decomposed by decomposers. Groups of detritivorous animals
include: millipedes, woodlice, dung beetles, dung flies and burying beetles.
General Principles Associated with Ecological Succession
1.
The physical environment determines which communities can exist in a particular place.
2.
Succession is community controlled, i.e., succession is caused by modification of the
surrounding physical environment by the existing community, i.e., a successional community
will alter the environment so that the environment is then more favorable for a different
community than the existing one.
3.
Ecological succession is directional - and therefore predictable.
4.
Succession ends in a stabilized community and ecosystem called the ecological climax. It is in
equilibrium with the physical environment of that particular area and perpetuates itself.*
* Usually an external disturbance to the area, e.g., fire, puts the area back into an earlier
successional stage. This tendency for the ecosystem to reach a stage where it stays in
equilibrium is an example of Homeostasis – developing and maintaining stability.
5.
High diversity produces stability.
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Types of Ecological Succession
1. Primary Succession begins on an area that has not been previously occupied by a community, e.g.,
newly exposed rock. There is no soil. Soil is a combination of broken down rock plus organic matter
(humus* and small, living organisms). (Humus is accumulated, decomposed plant and animal
material. Primary succession takes place very slowly with a low rate of production of biological
material.
2. Secondary
Succession begins
on
an
area
where
a
community has previously
existed. Secondary succession usually begins on an already established soil. Secondary succession
has a higher level of production of biological material at a faster rate than primary succession.
Types of Ecological pyramids.
The ecological pyramids are of three types: (i) Pyramid of energy (ii) Pyramid and (iii)
Pyramid of numbers.
1. The Pyramid of Energy
The energy pyramids give the best picture of the overall nature of the ecosystem.
Here there will be gradual decrease in the availability of energy from the autotrophs higher
trophic levels. In other words, there is decrease in energy flow from autotrophs on\ at
successive
trophic levels.
In the course of energy flow from one organism to the other, is considerable loss of energy in the form
of heat. More energy is available in the autotrophs t in the primary consumers. The least amount of
available energy will be in the tertiary consumer. Therefore, shorter the food chain, greater is the
amount of energy available at the top.
1. The energy pyramid always upright and errect.
2. It shows the rate of energy flows at different trophic levels.
3. It shows that energy is maximum at producer level and minimum at the carnivores' level.
4. At every successive trophic level there is a loss of energy in the form of heat, respiration etc.
2. The Pyramid of Biomass
They are comparatively more fundamental, as they, instead of the geometric factor, show j the
quantitative relationships of the standing crops. Here there will be gradual decrease in the biomass
from the autotrophs to the higher trophic levels. This may be illustrated by studying the trophic levels
in a pond.
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The biomass in autotrophs like algae, green flagellates, green plants etc. is the maximum. The biomass
is considerably less in the next trophic level occupied by secondary consumers like small fishes. The
least amount of biomass is present in the last trophic level.
1. This pyramid shows the total biomass at each trophic level in a food chain.
2. Pyramid in erect.
3. It indicates a decrease in the biomass at each trophic level from the base to apex of pyramid.
Example: Total biomass than herbivores, which is again more than carnivorous.
3. The Pyramid of Numbers
They show the relationship between producers, herbivores and carnivores at successive trophic
levels in terms of their number. Here there will be a gradual decrease in the number of individuals
from the lower to the higher trophic levels. This may be studied by taking the example of trophic
levels in grassland.
The grasses occupy the lowest trophic level and they are abundantly present in the grassland
ecosystem. The deers occupy the second level; their number is less than compared to the grasses.
The wolves, which feed upon the deers, are far less in number when compared to the number of deers.
The lions, which occupy the next trophic level, feed upon wolves, and the number of individuals in the
last trophic level is greatly reduced.
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In the parasitic food chain, the pyramid of numbers is founds to be inverted. Here, a single plant or tree
might support varieties of herbivore. These herbivores like birds in turn, support varieties of parasites
like lice, bugs that outnumber the herbivores.
Subsequently each parasite might support a number of hyperparasites like bacteria and fungi,
which will outnumber the parasites. Thus from the producer level onwards, towards the consumers, in
the parasitic food chain there is a gradual increase in the number of organisms, instead of the usual
decrease.
As a result of this, the pyramid becomes inverted in the parasitic food chain. There is a gradual
increase in the numbers of individuals from autotrophs to the higher trophic levels.
1. It shows the number of organism at different levels.
2. The pyramid is errect.
3. The smaller animals are preyed upon larger animals and smaller animals increase faster in number
of organism at each stage of food chain, makes a triangular figure that is known as pyramid of number.
Energy flow in an ecosystem
The energy flow in the ecosystem isunidirectional. Sun is the main source of energy. The
amount of energy received differs in amount as it depends upon the slope, cloud, latitude and
pollutants present in the atmosphere. The energy received in the Varanasi of India is three times more
than the energy received in the Britain. Some part of the energy is used by the producers. The rest is
dissipated. The efficiency to conserve energy is around 1 percent in the grasslands and savannah. It is
also similar in the mixed forests. It is higher in the modern crops and sugarcane field. It ranges from
the 5 to 10 percent. The autotrophs are also known as the producers. They make the food by
the process of photosynthesis from the inorganic materials. They not only make their food but also for
the other organisms. They absorb the energy from sun and convert into the chemical energy. They
release oxygen. The organic compounds release energy during respiration. The organic compounds
which are formed play an important role in the building of bodies and help in the release of energy
which helps to overcome the entropy. The energy is dissipated as a heat. There are herbivorous which
feed on the plants. They are not able to eat the whole of plant. There is a non usage of food
energy which passes into the decomposers.
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The phytoplankton in the aquatic food chain is mainly eaten by the herbivore.
The herbivores act on the ingested food which gets aggregated. It releases the energy later on and
helps in the respiration. The energy lost in this case is not much and the remaining is used to overcome
the entropy. The fraction of assimilated food is used for the body building. The primary carnivore feed
on theherbivore which is feeded by the secondary carnivore. In the food chain when the food is broken
energy is released. The small part of energy is utilized and so the rest of energy is dissipated.
The energy transfer from the one trophic level to the other decreases in the amount.
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Chapter – XXIV – TYPES OF ECOSYSTEM
Lentic and Lotic Ecosystems
We all depend on water for our survival. Pennsylvania is home to thousands of kinds of
organisms that depend on freshwater ecosystems for their survival, too. The freshwater aquatic biome
contains both lentic ecosystems and lotic ecosystems. There are many examples of both in
Pennsylvania.
Lentic Ecosystems: Standing Water
Some examples of lentic ecosystems are lakes, ponds, swamps, marshes, and vernal pools.
Lentic ecosystems take many forms, from small, temporary pools to large lakes. Some lentic
ecosystems are fresh water with low salt content, and others have a higher salt content (Example: The
Great Salt Lake in Utah). Lentic ecosystems such as lakes can be formed by glaciers, volcanoes, and
shifting of tectonic plates, and some are man-made. Some, such as vernal pools, are only temporary
during a rainy or wet season. Lentic ecosystems have layers from top to bottom that support different
organisms, depending on factors such as the amount of light and temperature. Algae and aquatic plants
produce food for other organisms in the ecosystem. Many tiny invertebrates, called zooplankton, live
in lentic waters. They feed on algae and plants and provide food for other organisms such as snails and
insects like water striders. The kinds of fish and other vertebrates depends on many factors, such as the
salt content, amount of light, and depth of the water. There are many species of lentic vertebrates,
including salamanders, frogs, alligators, and many kinds of birds.
Lotic Ecosystems: Flowing Water
Examples of lotic ecosystems are rivers, streams, creeks, brooks, and springs. Pennsylvania has
about 45,000 miles of flowing water. Lotic ecosystems can have many forms, from a tiny spring to a
wide, rushing river. A spring is a place where water flows from underground to above ground. They do
have some common characteristics. They always flow in one direction. They often begin in the
mountains, formed by snowmelt and rain, and they flow downward over the land. They tend to last
hundreds of thousands of years, but some smaller ecosystems such as creeks may dry up each year as
the seasons change. The types of organisms that live in lotic ecosystems depend on how fast the water
is flowing, the amount of light, and the temperature. Organisms in lotic systems must be adapted to
handle the high oxygen content, which is caused by the flowing water. Lotic systems have a low salt
content. Animals must be able to prevent excess water from building up in their bodies. Algae and
plants provide energy for animals in lotic ecosystems. Many invertebrates, such as insects, snails, and
crayfish, depend on the flowing water to bring them oxygen and nutrients. Fish that live in lotic
ecosystems must be adapted to survive in flowing water. Many lotic systems connect to each other and
form a path to the ocean (example: spring → stream → river → ocean), so some fish species spend
part of their lives in freshwater and part in the ocean. Other vertebrates spend part of the time on land
and part in the water, such as species of amphibians, reptiles, mammals, and birds. Specific examples
include: frogs, salamanders, snakes, turtles, beavers, and river otters.
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The small, shallow, and standing water body of a fresh water environment is called a pond. Several
rooted plants dominate at the bottom of the ponds. Based upon the penetration of light and depth, three
different zones are recognized in a pond.
Littoral zone
It refers to the upper and shallow water surface with plenty of light source and rooted plants.
Limnetic zone
It refers to the open water zone that reaches the depth where light effectively penetrates. The
lower limit of the zone represents the compensation level at which photosynthetic rate becomes
equivalent to the rate of respiration of aquatic plants. Planktons are dominated in this zone.
Profundal zone
It refers to the deep water at the bottom layer where the effective penetration of light is very
much limited. The flora consists of producers such as phytoplanktons, lfloating plants, submerged
plants and rooted plants. The fauna includes consumers such as zooplanktons, several arthropods,
molluses, fishes and amphibians.
Estuary ecosystem
An estuary is a partially enclosed body of water along the coast where freshwater from rivers
and streams meets and mixes with salt water from the ocean. Estuaries and the lands surrounding them
are places of transition from land to sea and freshwater to salt water. Although influenced by the tides,
they are protected from the full force of ocean waves, winds, and storms by such land forms as barrier
islands or peninsulas.
Estuarine environments are among the most productive on earth, creating more organic matter
each year than comparably-sized areas of forest, grassland, or agricultural land. The tidal, sheltered
waters of estuaries also support unique communities of plants and animals especially adapted for life at
the margin of the sea.
Many different habitat types are found in and around estuaries, including shallow open waters,
freshwater and salt marshes, swamps, sandy beaches, mud and sand flats, rocky shores, oyster reefs,
mangrove forests, river deltas, tidal pools, and seagrasses.
Estuaries provide us with a suite of resources, benefits, and services. Some of these can be
measured in dollars and cents, others cannot. Estuaries provide places for recreational activities,
scientific study, and aesthetic enjoyment. Estuaries are an irreplaceable natural resource that must be
managed carefully for the mutual benefit of all who enjoy and depend on them.
Thousands of species of birds, mammals, fish, and other wildlife depend on estuarine habitats
as places to live, feed, and reproduce. And many marine organisms, including most commerciallyimportant species of fish, depend on estuaries at some point during their development. Because they
are biologically productive, estuaries provide ideal areas for migratory birds to rest and re-fuel during
their long journeys. Because many species of fish and wildlife rely on the sheltered waters of estuaries
as protected spawning places, estuaries are often called the "nurseries of the sea."
Estuaries have important commercial value and their resources provide economic benefits for
tourism, fisheries, and recreational activities. The protected coastal waters of estuaries also support
important public infrastructure, serving as harbors and ports vital for shipping and transportation.
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Estuaries also perform other valuable services. Water draining from uplands carries sediments,
nutrients, and other pollutants to estuaries. As the water flows through wetlands such as swamps and
salt marshes, much of the sediments and pollutants are filtered out. This filtration process creates
cleaner and clearer water, which benefits both people and marine life. Wetland plants and soils also act
as natural buffers between the land and ocean, absorbing flood waters and dissipating storm surges.
This protects upland habitat as well as valuable real estate from storm and flood damage. Salt marsh
grasses and other estuarine plants also help prevent erosion and stabilize shorelines.
Pond as an ecosystem.
Ecosystem ponds can be easy to understand if you have a good grasp of what components go
into a basic, functioning ecosystem. An ecosystem pond works with Mother Nature to provide food,
shelter, and safety to the wildlife around it. It also provides you with an all-natural, low-maintenance
piece of paradise. It’s important to remember, however, that every piece of the ecosystem puzzle must
be present in order for a true ecosystem to be in place. Eliminate one of these elements and you’ve got
an unbalanced ecosystem that won’t be so low-maintenance anymore. Check out the things you’ll need
to get your ecosystem pond fired up:
Circulation System is really just a fancy way of saying “pumps and plumbing.” The proper size pump
and pipe diameter are extremely important for the aesthetics of a water feature. More importantly, an
efficient circulation system keeps the water moving and provides the necessary oxygen levels for
healthy fish and plants.
Proper Filtration System includes the use of both a biological and a mechanical filter. A biological
filter provides surface area for beneficial bacteria to colonize and remove excess nutrients from the
water. A mechanical filter will not only pre-filter the water and house the pump; it will also skim
debris from the water’s surface to prevent the accumulation of organic materials on the pond floor.
Fish are an integral part of any ecosystem. Unfortunately, fish are often seen as creating a maintenance
nightmare. Contrary to popular belief, fish will actually reduce pond maintenance, as they graze on
string algae and bottom feed from the pond floor.
Roots are Mother Nature’s true filters. Plants are great for adding character to a pond by providing
color and texture, but from a filtration perspective, they’re second to none. Thriving from the excess
nutrients in a pond and depriving algae of its food source, the aquatic plants in a water garden, given
proper coverage, are critical for the overall health of the ecosystem.
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Characteristics of marine ecosystem
Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately
97% of the planet's water. They generate 32% of the world's net primary production.[1] They are
distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in
the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine.
Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among
different marine ecosystems.[2]
A classification of marine habitats.
Marine ecosystems can be divided into many zones depending upon water depth and shoreline
features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and
tuna live. The benthic zone consists of substrates below water where many invertebrates live.
Theintertidal zone is the area between high and low tides; in this figure it is termed the littoral zone.
Other
near-shore
(neritic)
zones
can
include estuaries,salt
marshes, coral
reefs, lagoons and mangrove swamps. In the deep water, hydrothermal vents may occur
where chemosynthetic sulfur bacteria form the base of the food web. Classes of organisms found in
marine
ecosystems
include brown
algae, dinoflagellates, corals, cephalopods, echinoderms,
and sharks. Fishes caught in marine ecosystems are the biggest source of commercial foods obtained
from wild populations.
Environmental problems concerning marine ecosystems include unsustainable exploitation of
marine resources (for example overfishing of certain species), marine pollution, climate change, and
building on coastal areas. Marine ecosystem is a study involving the interconnections of marine
organisms in relation to their environment. Marine ecosystem which occupies 70% of the earth’s
surface, represents the largest habitat in which life first originated.
Characteristics:
(i) Light: Light regulates the pattern of distribution of marine animals and it contributes to the
organic production. The autotrophic producers utilize the light energy for the photosynthetic
production of food for consumers of marine ecosystem. The light penetration depends on the
intensity of light and turbidity of water.
Marine ecosystem exhibits the stratification similar to ponds and lakes. Based on the depth of light
penetration, the marine habitat is divided into three layers. These include upper euphotic zone,
middle disphotic zone and the lower aphotic zone.
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(a) Euphotic zone or upper layer extends rom surface level upto 80 metres of depth. Light
penetration is higher in this zone and also abundant producers are found.
(b) Disphotic zone or the middle layer extends from 80 metres to 200 metres. This zone is
characterized by the presence of diffused light and negligible amount of producers.
(c) Aphotic zone or bottom layer extends below the depth 200 metres. This zone is characterized
by the complete absence of light and producers.
(ii) Salinity: Marine ecosystem possesses high salinity. It is about 35%. The salinity of marine
ecosystem varies from place to place due to the dissolved salts such as chlorides of sodium, potassium,
calcium and magnesium.
(iii) Currents and Tides: Sea water which never remains static, is characterized by everlasting waves,
currents, and tides. These are directly influenced and controlled by wind action, cosmic forces, and
water densities. Water currents mostly occur at the surface and at great depths of sea water. The tidal
currents caused by the vertical movements of water and gravitational force enable the uniform
distribution of O2 and also help in the dispersal of planktons and other marine organisms
(iv) The temperature of an ocean ranges from about 2°C in the polar regions to 32°C in the tropical
regions. The annual variations in temperature in a marine ecosystem will not exceed more than 6°C
Features of terrestrial ecosystem
A terrestrial ecosystem is an ecosystem found only on a landform. Four primary terrestrial
ecosystems exist: tundra, taiga, temperate deciduous forest, and grassland.
A community of organisms and their environment that occurs on the land masses of continents
and islands. Terrestrial ecosystems are distinguished from aquatic ecosystems by the lower availability
of water and the consequent importance of water as a limiting factor. Terrestrial ecosystems are
characterized by greater temperature fluctuations on both a diurnal and seasonal basis than occur in
aquatic ecosystems in similar climates. The availability of light is greater in terrestrial ecosystems than
in aquatic ecosystems because the atmosphere is more transparent than water. Gases are more
available in terrestrial ecosystems than in aquatic ecosystems. Those gases include carbon dioxide that
serves as a substrate for photosynthesis, oxygen that serves as a substrate in aerobic respiration, and
nitrogen that serves as a substrate for nitrogen fixation. Terrestrial environments are segmented into a
subterranean portion from which most water and ions are obtained, and an atmospheric portion from
which gases are obtained and where the physical energy of light is transformed into the organic energy
of carbon-carbon bonds through the process of photosynthesis.
Terrestrial ecosystems occupy 55,660,000 mi2 (144,150,000 km2), or 28.2%, of Earth's
surface. Although they are comparatively recent in the history of life (the first terrestrial organisms
appeared in the Silurian Period, about 425 million years ago) and occupy a much smaller portion of
Earth's surface than marine ecosystems, terrestrial ecosystems have been a major site of adaptive
radiation of both plants and animals. Major plant taxa in terrestrial ecosystems are members of the
division Magnoliophyta (flowering plants), of which there are about 275,000 species, and the division
Pinophyta (conifers), of which there are about 500 species. Members of the division Bryophyta
(mosses and liverworts), of which there are about 24,000 species, are also important in some terrestrial
ecosystems. Major animal taxa in terrestrial ecosystems include the classes Insecta (insects) with about
900,000 species, Aves (birds) with 8500 species, and Mammalia (mammals) with approximately 4100
species.
Organisms in terrestrial ecosystems have adaptations that allow them to obtain water when the
entire body is no longer bathed in that fluid, means of transporting the water from limited sites of
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acquisition to the rest of the body, and means of preventing the evaporation of water from body
surfaces. They also have traits that provide body support in the atmosphere, a much less buoyant
medium than water, and other traits that render them capable of withstanding the extremes of
temperature, wind, and humidity that characterize terrestrial ecosystems. Finally, the organisms in
terrestrial ecosystems have evolved many methods of transporting gametes in environments where
fluid flow is much less effective as a transport medium.
The organisms in terrestrial ecosystems are integrated into a functional unit by specific,
dynamic relationships due to the coupled processes of energy and chemical flow. Those relationships
can be summarized by schematic diagrams of trophic webs, which place organisms according to their
feeding relationships. The base of the food web is occupied by green plants, which are the only
organisms capable of utilizing the energy of the Sun and inorganic nutrients obtained from the soil to
produce organic molecules. Terrestrial food webs can be broken into two segments based on the status
of the plant material that enters them. Grazing food webs are associated with the consumption of living
plant material by herbivores. Detritus food webs are associated with the consumption of dead plant
material by detritivores. The relative importance of those two types of food webs varies considerably
in different types of terrestrial ecosystems. Grazing food webs are more important in grasslands, where
over half of net primary productivity may be consumed by herbivores. Detritus food webs are more
important in forests, where less than 5% of net primary productivity may be consumed by herbivores.
There is one type of extensive terrestrial ecosystem due solely to human activities and eight
types that are natural ecosystems. Those natural ecosystems reflect the variation of precipitation and
temperature over Earth's surface. The smallest land areas are occupied by tundra and temperate
grassland ecosystems, and the largest land area is occupied by tropical forest. The most productive
ecosystems are temperate and tropical forests, and the least productive are deserts and tundras.
Cultivated lands, which together with grasslands and savannas utilized for grazing are referred to as
agroecosystems, are of intermediate extent and productivity. Because of both their areal extent and
their high average productivity, tropical forests are the most productive of all terrestrial ecosystems,
contributing 45% of total estimated net primary productivity on land.Only animals that is capable of
living in the landforms live here.
Terrestrial ecosystem refers to the interaction of living organisms in relation to thye land.
Although land constitutes about 30% of earth’s surface, it is characterized by diversified climatic,
abiotic and biotic factors. Terrestrial ecosystems can be categorically distinguished from aquatic
ecosystems. While aquatic ecosystem is a single phase system, whereas terrestrial ecosystem is a three
phase system in which atmosphere, soil and biotic community form the characteristic functions.
Characteristics:
 Due to limited availability of water, dryness and scarcity of water are the common features of this
typical ecosystem.
 Living organisms tend to suffer from dehydration problem due to the prevalence of acute water
scarcity and high temperature
 Temperature fluctuations are very higher and intensity of light is also high.
 Atmospheric air provides the source of O2 and CO2 at a constant level.
 The discontinued land surface contains various types of geographical barriers in the form of
mountains, valleys, lakes, rivers and seas.
 Soil surface is enriched with essential types of nutrient elements for the generation of energy.
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Chapter – XXV – INTRODUCTION TO BIODIVERSITY
The threats to biodiversity
Biological diversity refers to the variety and variability among living organisms and the
ecological complexes in which they occur. Diversity can be defined as the number of different items
and their relative frequency. For biological diversity, these items are organized at many levels, ranging
from complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the
term encompasses different ecosystems, species, genes, and their relative abundance (Office of
Technology Assessment, 1987). Or to paraphrase: number and variety of species, ecological systems,
and the genetic variability they contain.
Extinction is a natural event and, from a geological perspective, routine. We now know that
most species that have ever lived have gone extinct. The average rate over the past 200 my is 1-2
species per year, and 3-4 families per my. The average duration of a species is 2-10 million years
(based on last 200 million years). There have also been occasional episodes of mass extinction, when
many taxa representing a wide array of life forms have gone extinct in the same blink of geological
time. [see last Fall's lecture on the Emergence Of Complex Life]
In the modern era, due to human actions, species and ecosystems are threatened with
destruction to an extent rarely seen in earth history. Probably only during the handful of mass
extinction events have so many species been threatened, in so short a time.
First, we can attribute the loss of species and ecosystems to the accelerating transformation of
the earth by a growing human population (GCII). As the human population passes the six billion mark
, we have transformed, degraded or destroyed roughly half of the word's forests (GCII). We
appropriate roughly half of the world's net primary productivity for human use (GCII). We appropriate
most available fresh water (GCII), and we harvest virtually all of the available productivity of the
oceans (GCII). It is little wonder that species are disappearing and ecosystems are being destroyed.
Over-hunting has been a significant cause of the extinction of hundreds of species and the
endangerment of many more, such as whales and many African large mammals. Most extinctions over
past several hundred years are mainly due to over-harvesting for food, fashion, and profit.
Commercial hunting, both legal and illegal (poaching), is the principal threat. Snowy egret, passenger
pigeon, heath hen are USA examples. At $16,000 per pound, and $40,000 to $100,000 per horn, it is
little wonder that some rhino species are down to only a few thousand individuals, with only a slim
hope of survival in the wild. The pet and decorative plant trade falls within this commercial hunting
category, and includes a mix of legal and illegal activities.
Habitat loss/degradation/fragmentation is an important cause of known extinctions. As
deforestation proceeds in tropical forests, this promises to become THE cause of mass extinctions
caused by human activity.
All species have specific food and habitat needs. The more specific these needs and localized
the habitat, the greater the vulnerability of species to loss of habitat to agricultural land, livestock,
roads and cities. In the future, the only species that survive are likely to be those whose habitats are
highly protected, or whose habitat corresponds to the degraded state associated with human activity
(human commensals).
Habitat damage, especially the conversion of forested land to agriculture (and, often,
subsequent abandonment as marginal land), has a long human history. It began in China about 4,000
years ago, was largely completed in Europe by about 400 years ago, and swept across USA over the
past 200 years or so. Viewed in this historical context, we are now mopping up the last forests of
Pacific Northwest.
In the new world tropics, lowland, seasonal, deciduous forest began to disappear after 1500
with Spanish and Portuguese colonization of the New World. These were the forested regions most
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easily converted to agriculture, and with a more welcoming climate. The more forbidding, tropical
humid forests came under attack mainly in 20th C, under the combined influences of population
growth, inequitable land and income distribution, and development policies that targeted rain forests as
the new frontier to colonize.
Tropical forests are so important because they harbor at least 50%, and perhaps more, of
world's biodiversity. Direct observations, reinforced by satellite data, documents that these forests are
declining. The original extent of tropical rain forests was 15 million km2. Now there remains about
7.5-8 million km2, so half is gone. The current rate of loss is estimated at near 2% annually (100,000
km2 destroyed, another 100,000 km2degraded). While there is uncertainty regarding the rate of loss,
and what it will be in future, the likelihood is that tropical forests will be reduced to 10-25% of their
original extent by late 21st C. Habitat fragmentation is a further aspect of habitat loss that often goes
unrecognized. The forest, meadow, or other habitat that remains generally is in small, isolated bits
rather than in large, intact units. Each is a tiny island that can at best mai ntain a very small population.
Environmental fluctuations, disease, and other chance factors make such small isolates highly
vulnerable to extinction. Any species that requires a large home range, such as a grizzly bear, will not
survive if the area is too small. Finally, we know that small land units are strongly affected by their
surroundings, in terms of climate, dispersing species, etc. As a consequence, the ecology of a small
isolate may differ from that of a similar ecosystem on a larger scale.
Habitat loss, environmental pollution, poaching of wild life and extinction of species are the main
threats to biodiversity.
Conflicts between man and wildlife are enormously increased by several factors such as illegal
poaching, deforestation, forest fire, loss of ecosystems and food scarcity. The species which face a
high risk of extinction in near future are called endangered species. The Plants and animals that are
very much restricted to a small area and are not found elsewhere in the world are called endemic
species.
Biodiversity represents the natural and biological assemblage of the earth. It possesses the
unique feature of exhibiting varieties of species of plants and animals. Diversified and more complex
organizational levels of living organisms on earth are the distinct manifestations of biodiversity. The
ecological contribution of biodiversity In terms of valuable uses, could never be measured due to its
vast diversification and magnification on this global system. Biodiversity is closely associated with the
ecological interactions of flora and fauna which in turn, result in a typical ecological stability and
environmental quality. Environmentalists have geared up their intensive efforts that are mostly
oriented towards the conservation of biodiversity for the sake of continued survival of living
organisms on the earth. Various aspects of biodiversity can be focused as given below.
Levels of biodiversity
There are three levels of biodiversity. They are, Genetic biodiversity which refers to the genetic
constitution of a species. Next one is species diversity, which is the variety of species located within a
particular region. The third one is the eco system diversity which refers to the existence of some
different habitats with their specific groups of animals and plants.
Ecosystem diversity at community level exhibits three types. They are:
a) Alpha diversity: It refers to the diversity of organisms that share the common habitat and community.
This type of diversity is well represented by the combination of species richness and evenness within a
habitat.
b) Beta diversity: It refers to the diversity of species in between communities. Due to environmental
differences such as altitude and moisture, the species composition of communities greatly differs. Beta
diversity is mostly contributed by the greater or larger differences of species between communities.
c) Gamma diversity: It refers to the diversity of the habitats over the total geographical area.
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Ecosystem diversity possesses the unique features of illustrating the number of niches, trophic levels,
and various types of ecological processes which maintain energy flow and recycling of nutrients.
Diversity of species is the proper measure by which an ecosystem diversity can be well assessed and
evaluated.
Values of biodiversity
Man has rightly understood the values of biodiversity for very long time back and has also learnt
the skill of exploiting the uses and values of biodiversity for his continued survival and
sustenance on earth. All the existing scientific and developmental activities that are closely associated
with agriculture, live-stock, forestry and fishery are greatly influenced by the several ecosystems that
are rich in biodiversity and they contribute to more than one third of our national income.
1. Social Values: The loss of biodiversity bears a direct influence on the cultural and social values of
a country, when the loss of biodiversity is caused by the drastic alterations in an energy flow and
biogeochemical cycles. Several man-made activities in combination with natural disturbances such
as fire, trees fall and defoliation of trees lead to the critical problem in biodiversity which in turn,
affect the social values of mankind. Massive release of radiations and oil spillage in the sea cause
changes in the habitat quality that may also contribute the changes in social value.
2. Ethical Values: Ethical values play an important role for the continued maintenance of
biodiversity, because loss of biodiversity could not be reconstructed or restored. We have to
preserve all living and nonliving things on earth and take care of the existence of biodiversity.
3. Aesthetic Values: Wild life, bird watching, pet keeping and gardening are some of the prominent
examples of aesthetic values that are exhibited by biodiversity to a great extent. Eco tourism is a
evidential proof for the aesthetic value of biodiversity.
4. Option Values: This refers to the value of treasure that is found in the natural biological resources
in this biosphere for future applications. Option values should involve constant and continuous
explorations on the diversified species to unravel their characteristic features that may be highly
beneficial to the human society in future.
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