Ecosystem
SUPPLEMENTARY ASPECTS
A marshland
ECOTONES
A TRANSITION ZONE BETWEEN ECOSYSTEMS
Ecotone is the area of transition between two
ecosystems.
It is the area where two communities integrate
and meet
Ecotones can be local or regional
Examples of ecotones
1. Marshlands- between dry and wet ecosystems. Ex- Rann of
Kutch(Gujarat)
2. Mangroves- Terrestrial and marine. Ex-Pichavaram(TN)
3. Estuaries- saltwater and freshwater. Ex- Vembanad
lake(Kerala)
4. Grasslands- Desert and forests. Ex- Banni
grasslands(Gujarat)
Why ecotones are important
u Contain species from both adjacent ecosystems.
u High biodiversity and species richness
u Act as buffer zone between ecosystems, zone of nutrient and gene exchange
u Vulnerable to global warming and human modifications
Biodiversity in an ecotone
EDGE EFFECT
At the ‘edges of ecosystems’, that is at
ecotones,
both the number and population of species will
be higher.
This phenomenon is called edge effect
Species which are primarily at this zone are
called EDGE species
It is the change in species diversity at edge of
Since we are here,
There is another concept of ‘Edge
species’ which is easily mistaken by
students.
Let’s study that as well
EDGE Species
Evolutionarily Distinct and Globally
Endangered
They unique in its evolutionary history. They
don’t have many related species, or they
may have rare genetic features
They are at the verge of extinction too
u Long-beaked echidna
u Egg laying mammal
u Very few close relatives
u Seen in Australian continent
Purple Frog
u Ganges River Dolphin
u Endangered
u Ganga-Brahmaputra river system
u Essentially blind and use ultrasonic
radar system
Hawksbill turtle- Critically
Endangered
Ecosystem Superstars
SPECIES WHO ARE CRUCIAL TO AN ECOSYSTEM
Keystone species
u A keystone species is an organism that helps define an entire ecosystem.
u Without its keystone species, the ecosystem would be dramatically different or cease to exist
altogether.
u If such a species is removed, it is difficult for another species to fill that Niche
u Keystone species may not be the most abundant species
u Many of the keystone species are predators
Ochre Sea star
u Pacific ocean
u Help stabilize the population of seaweeds by
preying on Mussels, Sea urchins and Sea snails
u Without Sea stars, seaweed populations may
collapse
Yellowstone- before & after Wolves
Keystone species of grassland
Other major keystone species
u Tiger
u Rhino
u Lion
u Insects
A major sub group within the Keystone
species is the –
Ecosystem engineers
Beavers
An ecosystem engineer is any species that
creates, significantly modifies, maintains or
destroys a habitat.
These organisms can have a large impact on
species richness and landscape-level
heterogeneity of an area
Kelps and kelp forests
Parrotfish – eat marine algae from
reefs
Zebra mussels- an invasive engineer
Other common engineers
u Plankton
u Spiders
u Whales
u Humans
UMBRELLA SPECIES
A popular example
An umbrella species is defined as a species
whose conservation is expected to confer
protection to a large number of naturally co-
occurring species.
Tiger and Elephant reserves in India
protects large number of other species
Thus they are also Umbrella species
Dudhwa tiger reserve, U.P
But a refuge of others too..
One horned Rhino Sambhar deer
Common examples of umbrella
species
u Tiger
u Elephant
u Giant Panda
u Asiatic Lion
u One-horned Rhinoceros
Both keystone and umbrella species can
overlap.
The uniqueness of an umbrella species lies
in its large geographical range
FLAGSHIP SPECIES
A flagship species is a species selected to act
as an ambassador, icon or symbol for a
defined habitat, issue, campaign or
environmental cause.
Silent Valley (Kerala) –Lion Tailed
Macaque
Sundarbans and Bengal Tiger
INDICATOR SPECIES
An indicator species is an organism whose
presence, absence or abundance reflects a
specific environmental condition.
Indicator species can signal a change in the
biological condition of a particular ecosystem,
and thus may be used as a proxy to
diagnose the health of an ecosystem.
Lichens
u Lack of lichens indicate air
pollution
Tubifex worms
u Live in aquatic habitats
u Can tolerate poor- oxygen
conditions and high level of
organic pollutants
u It indicate stagnant water with
poor quality unfit for drinking
Frogs are indicators of chemical
pollution
u They need to maintain moist skin for breathing
u Amphibians are sensitive to even trace chemical contents in water
u Thus their presence or absence in an ecosystem is an indicator of
environmental pollution
u It is apart from their role in stabilising insect and pest populations
Bio accumulator indicator species
What is bio accumulation
and
biomagnification
Bioaccumulation is the gradual accumulation
of pesticides or other chemicals, in an
organism.
Occurs when an organism absorbs a substance
at a rate faster than that at which the substance
is lost
Biomagnification is the process by which
toxic chemicals build up within predators.
This typically occurs across an entire food
chain and affects all of the organisms but
animals higher up in the chain are more
impacted.
Molluscs- a bioaccumulation
indicator
u Molluscs like snails accumulates
poisonous chemicals and heavy
metals in their shells
u Study of mollusc shells is a good
way to measure pollution in
aquatic environment
Sentinel Species
Sentinel species are organisms, used to detect
risks to humans by providing advance warning
of a danger.
Primarily apply in the context of environmental
hazards rather than those from other sources.
Canary birds- warning CO
presence in mines
Introduced species
OR
Exotic species
An introduced species, is a species living
outside its native distributional range, but which
has arrived there by human activity, directly or
indirectly.
Non-native species can have various effects on
the local ecosystem.
Papaya- an exotic species in India
u Native to tropical America
u Introduced in India by the Portuguese
u Now India is the world’s largest producer of Papaya
fruits
Invasive Alien Species - IAS
An invasive species is an introduced
organism that becomes overpopulated and
harms its new environment.
Invasive species adversely affect habitats,
causing ecological, environmental, and
economic damage.
For millennia,
humans have served as both accidental and
deliberate dispersal agents,
beginning with their earliest migrations,
accelerating in the age of discovery, and
accelerating again with international trade.
Kudzu- once a garden plant in East Asia
Major Invasive Alien Species in India
African Apple Snail
u The most invasive among all alien fauna in India, this
mollusk was first reported in the Andaman and
Nicobar Islands.
u It is now found across the country and is threatening
the habitat of several native species.
Papaya Mealy Bug
u Native
of Mexico and Central
America.
u Believed
to have destroyed
huge crops of papaya in
Assam, West Bengal, and
Tamil Nadu.
Cotton Mealy Bug
Amazon Sailfin Catfish
Senna Spectabilis
u Ornamental tree from tropical and
central America
u Rapid growth and hardy stem
u Quickly taking over tropical
ecosystems around the world
Lantana camara
u Lantana is one of the
world's ten worst invasive
species and a species of
High Concern for India. It
competes with native plants
for space and resources,
and also alters the nutrient
cycle in the soil. This
invasion has resulted in the
scarcity of native forage
plants for wild herbivores.
