Home » E-Books » NCERT » Class 11 » Biology 11 » OTBA for Class 11th Biology Theme 1-2015

OTBA for Class 11th Biology Theme 1-2015

OTBA Biology for Class 11th Theme 1


Theme – Quantifying Evidences of Sensitivity

Shifting the focus from guilt and indignation generated because of deteriorating / degrading
environmental quality and gearing to quantity the evidences of successful restorative efforts, positively
influences the intensity of encouragement and motivation which gets reflected in the act of enactment.
Mother Nature is beautiful and bountiful. It has provided us with all possible means of sustenance
and a happy and fulfilled life. It has taken care of our need for food and fresh clean water, life
sustaining oxygen and beautiful companions in the form of birds, butterflies, flowers and trees.
Since ages man has lived in harmony with Mother Nature deriving benefits from its bounty and
being protected from all kinds of harm. Along with it, the huge biodiversity on the earth is
important for humans through ecosystem services and goods. Ecosystem services are – regulatory
such as air and water purification, provisioning (goods), such as fuel and food and cultural and
supporting such as pollination and nutrient cycling.
However, with the advent of the industrial revolution in about 1760 to sometime between 1820
and 1840, began an era when man broke the umbilical cord with Mother Nature and went on a path
of rampant plunder of nature’s beauty and bounty. Setting up of factories and mass production led
to degradation of certain natural resources,leaving our environment permanently/sustain ably

One example of this depletion was deforestation. When the trees were cleared, the wildlife in the forest also became uprooted.Scarcity of trees compounded the problem of carbon emissions. Forests help to emit oxygen and balance its percentage in the air, whereas factories emit poisonous emissions and eliminate the source of oxygen. The pollution that has resulted from factories involved not only in airborne emissions but in land and water pollution also and shifted the world from green house effect toglobal warming and climate change.

Capture  n

Non – sympathetic deforestation is being continued at an alarming rate since early 1950s. Almost
half of the original forest habitat has been cut down. The removal of trees without replenishing with
sufficient reforestation has resulted in serious damage to habitats, biodiversity and led to aridity. It
has unfavorable impacts on atmospheric carbon dioxide levels and has permanently destroyed the
habitats of thousands of plant and animal species.

n1  nn

In the rain forests and the Himalayas, for instance, many species that had yet to be discovered have
been destroyed forever due to bizarre destruction of their habitats, fragmentation of the habitats
and killing and poaching.
Mass extinctions have taken place on the earth earlier too and new species took the place of older
ones, for example, mammals took over reptiles or angiosperms replaced ferns. However, this time
unlike the mass extinction events of geographical history, current extinction challenge is one for
which a single species – ours- is almost wholly responsible and will also bear the maximum brunt.


Although, it is we the humans who are almost wholly responsible for the mass extinction episode, it
is our species only that is taking the maximum steps to alleviate the situation.
Thus a large number of restoration drives have taken place and are still on to restore the Earth’s
ecosystem to its old pristine form.
One of the best examples of ecosystem restoration can be seen in the form of Aravalli Biodiversity
Park. Once a dense forest, Bhatti-Asola area on Delhi-Haryana border was ravaged by mining.
Now the area is gradually trying to come back to life due to continuous and combined efforts along
with the coming back of peacocks, birds, reptiles, amphibians and other wild live stock, that were
on the verge of getting extinct from the area in the upshot of large-scale mining. Approximately
5,566 acres of land in the Aravalli range of Delhi-Haryana border has been cultivated. Breeding of
If there are 100,000,000 species on the planet and the extinction rate is just 0.01% per year,
at least 10,000 species go extinct ever year.

If the approximate number of species is 1.9 million, given the present rate of extinction, how
long would it be before we lose all the species in the world???
Insects like cockroaches are said to be able to survive even in a nuclear holocaust. Do you think that insects may one day replace mammals as the dominant species due to global warming and habitat loss!!!

reptiles has also increased along with which the area is becoming a habitat for some of the most
venomous snakes and lizards, avians and amphibians. A leopard was also reported to have been
spotted some time back.

13 old ponds have been converted into relatively bigger water bodies by increasing the area and
about 95 percent of the land has been covered with vegetation. This has happened because the
government declared the area as a wildlife sanctuary and steps were taken to rehabilitate it.

mm1  mm2

These water bodies in the area were once reduced to arid patches by
continual mining, now the water bodies are healthy again

                 mm3  mm4

    The swathes were once dense forests but were ravaged by quarrying, they are green once again

On the same lines, restoration of the coral reefs is also taken up at war footing by countries
including India that have a marine ecosystem and coral reefs. Coral reefs are extremely complex
marine ecosystems which provide habitat to numerous aquatic species. Coral reefs are considered
to be the most biologically diverse and productive ecosystems on the earth. They occupy
approximately 0.2% of the world’s ocean surfaces.


However, coral reefs around the world are declining due to human-caused changes in water quality
which increases water temperature, and adversely affect the nutrients, as well as from direct
physical damage from being hit by massive ships and boats, anchoring, destructive fishing
techniques, and other intensifying human stresses.
If water temperature stays higher than usual for many weeks, the zooxanthellae, on which corals
are dependent for food, leave their tissue. In absence of zooxanthellae, corals turn white because
zooxanthellae give corals their colour. White, unhealthy corals are called bleached which are weak
and less able to combat diseases.
Besides increase in temperature, ocean acidification affects other living beings too, for example, in
snails, clams, and urchins; the process of making of calcium carbonate shells by absorption of
calcium is being hindered.
The following set of pictures show a progressive increase in the level of atmospheric CO2 has
affected the acidity of the ocean and consequently the Coral Reefs:



Damage to coral reefs is causing severe declines in catches, stocks, sizes, and diversity of fish and
other marine animals, and it also causes erosion of beaches and coastal structures, and loss of
tourism revenues.
To address these issues, innovative techniques like underwater coral farming and reattachment of
broken coral pieces are being used. The emphasis is on preventive aspects as the restoration work
is both costly and time consuming.
The Ministry of Environment in India has established a National Coral Reef Research Centre at Port
Blair. It is a two-tier system at National and State level which is in operation for efficient coordination to implement the Scheme on Mangroves and Coral Reefs. The Ministry’s task is to provide financial assistance to the State Forest Departments of all identified coral reef areas for activities like monitoring, surveillance, education and awareness. Research and development activities are also being supported with emphasis on targeted research on coral biodiversity and its management, including various aspects of pollution in these areas.

(Source: Data from Ministry of Environment & Forest)

When prevention was found to be not enough, active redressal of the damaged coral reefs was
done. In U.S, special request was made to the trained scuba divers to work on the reefs. These
divers transplanted the pieces of coral by using cement or epoxy putty. The goal was to
restore/repair coral reefs to allow the natural inhabitants a chance to thrive. Scientists have found
that the corals, which are grown in the nurseries, are able to reproduce in their new homes. It
means genetic diversity can be achieved along the reefs by allowing for stronger and more resilient
ecosystems in our oceans. In August 2002, the 36-feet long boat Lagniappe II (a huge ship) ran aground on a shallow coral reef near Key West, Florida and injured approximately 376 square-feet of living corals coming under the sanctuary.

After assessment of damage to the reef by sanctuary staff, restoration biologists
discovered and used special cement that hardens under water to reattach approximately 473 corals
and their fragments that had been toppled or dislodged during the grounding. The sanctuary was
tracked for coral condition at the restoration site over an eight-year period, began in 2002. By 2009,
the reattached coral fragments were undistinguishable from the adjacent undamaged coral
colonies. Surprisingly after a year, the population of corals at the restoration site was higher than at
the reference site.


Similar to the coral reefs, are the Mangrove forests of India. Mangroves are salt-tolerant forest
ecosystems of tropical and subtropical intertidal regions and are abundant along the coasts of the
Indian subcontinent. Like terrestrial tropical forests, mangroves have been a significant part of the
Indian economy for thousands of years and are a reservoir of valuable natural resources.

They are multiple use ecosystems and play a role in mitigating the impact of natural disasters such
as cyclone, storm surges and tsunami in coastal zones. They provide livelihood to millions of fishers
and act as critical habitat for wildlife.
However, not all coastal areas are suitable for mangrove plantation as mangrove requires an
appropriate mix of saline and freshwater,and soft substrate like mudflats to be able to grow and

Thirty eight mangrove areas have been identified in India for intensive conservation and management. The Coastal Regulation Zone Notification, 2011, recognizes the mangrove areas as ecologically sensitive which implies that these areas are accorded protection of the highest order.

FSI(Forest Survey of India) has been assessing the mangrove cover using remote sensing since
1987. The recent assessment shows that the mangrove cover is 4,662.56 km 2 or 0.14% of total
geographical area.

The very dense mangrove comprises 1,403 km2 (30.10%) and moderately dense
mangrove 1,658.12 km2 (35.57%), with open mangroves 1,600.44 km2 (34.33%).
Compared with 2009 assessment, there has been a net increase of 23.34 km2 in India’s mangrove
cover, attributable to increased plantations, particularly in Gujarat, and regeneration of natural
mangrove areas.
(Source: Ministry of Environment & Forests Government of India, Brief Statement on Activities and Achievements 2013)


The indiscriminate use of the coastal wetlands causes loss of nutrients, soil erosion, and decreasing
fishery potential, which in turn has led to many ecological and economic problems along the coast.
For Example, the Mahim Creek, a coastal wetland in Mumbai, considered a heavily polluted area, is
under several developmental pressures including railroad lines, water pipes, bridges, industries
and slums. Water, heavily contaminated with toxic industrial waste, cannot support animal life.

Inorder to alleviate the situation for this heavily polluted area, the Mumbai Municipal Corporation and the World Wide Fund for Nature (Mumbai) jointly agreed to rehabilitate this area as a mangrove park for habitation by diverse bird fauna. Setting up of a mangrove nursery led to mangrove afforestation in the Mahim Nature Park (MNP) possible.

Today, the Mahim Creek supports a flourishing evergreen mangrove forest. This vegetation and the
surrounding areas are favourite roosting spots for aquatic and migratory birds that spend winter in
the Indian subcontinent. That is why the Mahim Nature Park has become a popular spot for
birdwatchers from mid October to February-March. Though the water of Mithi river is polluted, but
Mahim Nature Park and surrounding mangroves provide resting spots for thousands of birds.



The common house sparrow – Passer domesticus is one of the most ubiquitous birds in our
surroundings and is one of the most familiar winged companions of humans. It has, during the
course of evolution, evolved with us. It is the most familiar bird to us. Its chirping still awakes the
people in the villages. Since we share the same habitat, it becomes our moral responsibility to save
This bird was continuously on the decline over its large natural range, both in the rural and urban
habitats. The decline in the number of the house sparrow was a signal of continuous degradation of
the environment.


March 20 is being celebrated as World Sparrow Day. The purpose behind it is not only to organize
events on that day but to use it as a tool for spreading awareness among the masses about the need
of the hour to protect urban biodiversity. The celebration aims at bringing together the various
strata of individuals to work for the cause. It also aims at awakening scientific community and
government to take its notice and implement the idea of protection and reform policies for it.
Scientists observed it in 1990s and since then surveys are being conducted to know the cause of
decline in their number and advertisements, campaigns and outreach and awareness programmes
are being conducted to combat the situation. The celebrations are worldwide in form of activities to
protect it. Citizen Sparrow is an ongoing programme on the same lines, in India, to seek the
contribution of every individual in knowing the actual and timely status of every corner of the
country and a link is given where the information can be uploaded. This can be done at personal
and community level wherein school children can also participate in shouldering the responsibility
of being global citizen.
There are the observations and reports of expert ornithologists in journals such as Indian Birds and
also on the website of Common Bird Monitoring of India (CBMI), a Citizen Science Programme of
Nature Forever Society. Many organizations and individuals are part of the programme. The
programme was intended to collect data on common Indian birds. Though the monitoring exercise
was not as long-standing as that of CBMI, a survey done between April and July, 2012 by Citizen
Sparrow has been an intense exercise in monitoring the concerned species, with 10,666 records,
from 5655 participants across 8425 locations in India. This was a big initiative involving every
citizen possible; the oldest participant was 91, and the youngest, 7. The findings did indicate a fall in
the number of House Sparrows.
There are some more anecdotes which make us aware about the individual and communal steps
taken in this direction. Students from Women’s College, Patna, scattered millets for sparrows. In
2012, sparrow was declared as the state bird of Delhi and it was said that the idea behind it is to
protect it. The Nature Forever Society with the Burhani Foundation (India) started a campaign
named ‘SOS’ = Save Our Sparrow, in which they distributed 52,000 bird feeders around the world
on a non-profit basis. The Postal Department of India has also contributed in spreading awareness
as it released a stamp of the house sparrow on March 20, 2010.

Youth of Purunabandha village of Ganjam district got attracted towards the issue and they took up
conservation attempts as their hobby. The combined and dedicated efforts started showing the
results as the team started with 11 sparrows around them and reached to 50 within a year. This
team has inspired the youth of surrounding villages too to find causes of vanishing of other birds
including sparrows from the periphery and to root them out.
India has one more property along with many others – the big cats. Country has half of the world’s
tiger population. Recently tiger census report has been released on 28th March, 2011, according to
which there are 1,706 tigers in the country, ranging from 1,571 to 1,875. This report was released
by National Tiger Conservation Authority.


According to Tiger Census report 2008, there were 1411 tigers in all 17 tiger states of the country,
classified into 6 landscapes; Central Indian Landscape Complex, Eastern Ghats, North Eastern Hills,
Western Ghats, Shivalik – Gangetic plains and Sunderbans. It was threatening to know from various
sources of information that 923 tigers were killed from 1994 to 2010 and it was further sad to
know that this figure includes only reported cases which may be a fraction of real data. Many of the
tiger population, particularly those outside protected reserves, are fragmented and suffer from
intense poaching pressure, a dwindling prey base and plenty of over-used habitats.
In spite of all these problems, India holds better chances of tigers’ survival and conservation with
overall 17 tiger states and 7 states with tiger population more than 100.

There are many dedicated organizations in India working for it on a national level and trying to
increase political will to secure the future of tigers.
Strategy for tiger conservation by NTCA and WPA 1972 included the setting up of 66 national parks
and 421 wildlife sanctuaries. Later on the number was increased to 102 and 515 and further 44
conservation reserves and 4 community reserves were set up. A ban had put up on poaching and
tiger trade. These efforts resulted in increase in the tiger density. Training, support and better law
enforcement were the key points of protection measures. Loss of vital habitats due to urbanization,
building of dams has been observed seriously and reduced a lot.
From June, 2010 to July, 2011 the National Tiger Conservation Authority (NTCA) in collaboration
with the Wildlife Institute of India (WII) undertook a self-regulating Management Effectiveness
Evaluation (MEE) of all 39 tiger reserves in India. The category-wise outcome of MEE Process
summarized that out of all of them Jim Corbett, Bandhavgarh, Bandipur, Kanha, Mudumalai,
Nagarhole, Pench (Madhya Pradesh) and Dudhwa hold excellent records in tiger population
whereas, Annamalai, Bhadra, Kalakkad-Mundathurai, Dandeli-Anshi, Kaziranga, Parambikulam,
Mudumalai, Periyar, Bori-Satpura and Sundarbans hold very good, Buxa, Dampa, Satkosia (Odisha),
Udanti-Sitanadi, Manas, Pakke, Namdapha, Valmiki, Rajaji, Pench (Maharashtra)and Panna hold
good and Indravati, Nagarjunsagar-Srisailam, Kawal, Sariska, Nameri, Sanjay-Dubri, Sahyadari have
satisfactory results.
Conservationists rejoiced when the figures of number of tigers from 2011 census were released.
According to the second all-India tiger population estimation study, carried out in the designated 39
tiger reserves across the country, there found an increase of 295 tigers in India. Some exhaustive
studies indicate that better protected tiger source sites, especially tiger reserves, have maintained
viable tiger populations, however, the area occupied by tigers outside protected areas has
decreased considerably. This demonstrates the need for securing corridors for tigers to move
between source sites. The existing tiger reserves represent around one-third of India’s high density
forest area.


Government of India has enacted Biological Diversity Act, 2002 (BDA 2002) according to which
national, state and local level mechanisms have been provided for implementation of the Act. At
national level, National Biodiversity Authority (NBA) was established by Government of India on 1
October 2003.

The Government aims to promote capacity building and awareness raising activities, already
initiated in five Project States, namely Andhra Pradesh, Gujarat, Himachal Pradesh, Sikkim and West
Bengal which assist the States in notifying threatened species in their areas of jurisdiction. So far
the species which are on the verge of extinction have been notified in fifteen states and one UT
(A&N Islands). The activities facilitate projects related to digitations of biodiversity-related data,
design/implement the Indian Biodiversity Information System (IBIS), undertake/facilitate projects
related to biodiversity conservation such as, The Economics of Ecosystems and Biodiversity
(TEEB), etc.



The ecosystem is like a building in which we live, removing a few bricks or planks of wood from
some random places may not affect us immediately and it may seem to be of no consequence,
however, when we continue to remove bricks and planks of wood from all floors of the very
building in which we live and do not replace them, the consequence is anybody’s guess and just a
matter of time. This analogy can easily be applied to the ecosystem biodiversity. Extinction of a few
species may not have affected us grossly till now but as we continue to put various species of plants
and animals in the endangered list, it may affect us in ways that we have never even thought of. For
example, the use of pesticides can remove pollinators from the environment and the extinction of
pollinators would mean that we will have to look for some other (expensive) means of pollination,
and hence for variation in plant for better adaptability and sustenance which will further increase
the price of food and indirectly affect economy adversely.
From the above details it clearly emerges that our mother nature is facing an unprecedented threat.
However, it also emerges that we are taking measures to overcome this situation and to make the
earth a safe place for all creations.
As responsible global citizens, it is our duty to alleviate the situation while we still have the time.
We know that we are on the job but modern scenario demands to expedite it.

Sample Questions
1. Establish a correlation between hierarchy of animals followed in the text and the phyla
studied during regular course of study. As a responsible global citizen, critically analyze the
causes and consequences of efforts taken to conserve and restore priceless Biodiversity of the
Mother Planet. (5)
2. Justify your perception about the title of the text material “Quantifying evidences of
sensitivity”. Also justify the significance of this text material in context of modern scenario.
What insight do you get out of this text material to the world outside? (5)
Marking Scheme
1. From simple to complex organisation in organisms from lower to higher groups of
classification. (2)
Analysis of Causes & Consequences with global perspective. (3)
2. Perception about the title with Justification. (2)
Justification about the significance of text material in modern scenario (2)
Insight about the world outside (1).















I am a person who is positive about every aspect of life.I am a Computer Science lecturer in a school. I love to spend my free time in learning new things.Working for eVirtualGuru gives me a lot extra knowledge and immense joy.

Leave a Reply

Your email address will not be published. Required fields are marked *