Question 1:
Which one of the following is included in biosphere?
- only plants
- all living and non-living organisms
- only animals
- all living organism
Answer:
(d). all living organism
Question 2:
Tropical grasslands are also known as:
- the prairies
- the savannas
- the steppes
- none of the above
Answer:
(b). the savannas
Question 3:
Oxygen combines with iron found in the rocks to form:
- iron carbonate
- iron nitrites
- iron oxides
- iron sulphate
Answer:
(c). iron oxides
Question 4:
During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form:
- proteins
- amino acids
- carbohydrates
- vitamins
Answer:
(c). carbohydrates
Question 5:
What do you understand by the term Ecology?
Answer:
Ecology is a combination of two Greek words (Oikos) and (Logy) meaning house and science. Ecology is the study of earth as home of plants, humans, animals and bacteria. These are interdependent. German zoologist Ernst Haeckel was the first to use this term in 1869. He is known as the father of ecology. The study of interactions between life forms (Biotic) and (Abiotic) is the science of ecology.
Question 6:
What is an ecological system? Identify the major types of ecosystems.
Answer:
Structure and function. The structure of
an ecosystem involves a description of the available
plant and animal species present. It also describes
its history, populations and distribution. From a
structural point of view all ecosystems consist of
abiotic and biotic factors. Abiotic factors include
rainfall, temperature, sunlight, atmospheric humidity,
soil conditions, inorganic substances (carbon dioxide,
water, nitrogen, calcium, phosphorus, potassium etc.)
and organic substances (proteins, carbohydrates,
lipids and amino acids). Biotic factors include the
producers, primary consumers, secondary consumers,
tertiary consumers and the decomposers. The
producers include all green plants, which manufacture
their own food through photosynthesis. The primary
consumers include the herbivorous animals like deer,
goats, mice and all plant-eating animals. The
carnivores include all the flesh-eating animals like
snakes, tigers and lions. Certain carnivores that feed
also on carnivores are known as top carnivores like
hawk and mongoose. Decomposers are those that feed
on the dead organisms (for example scanvengers like
vulture, crow) and further breaking down of the dead
matter by other decomposing agents like bacteria and
various micro-organisms.
The producers are consumed by the primary
consumers ; whereas, the primary consumers are in
turn being eaten by the secondary consumers. Further,
the secondary consumers are consumed by the tertiary
consumers. The decomposers feed on the dead at each
and every level. They change them into various
substances such as nutrients, organic and inorganic
salts essential for soil fertility. Organisms of an
ecosystem are linked together through a food chain.
Question 7:
What do you mean by a food chain? Give an example of a grazing food chain identifying the various levels.
Answer:
Food Chain : The transfer of energy from
one organism to another in the ecosystem is
known as food chain. For example, the green plants
use solar energy for their growth.
These plants provide energy in the form of food for
the consumers. Thus, the food chain is really an energy
flow system. For example, in a grassland, herbivores
such as the deer, feed on the grasses. At the next stage,
carnivores such as the lion, feed on the deer. The food
chain, thus, involves the flow of energy in the form of
food from lower to higher levels.
Example. In a grazing food chain, energy is passed
from one level to another. When a herbivore feeds on
plants only a fraction of the energy is absorbed by
the body, the rest of the energy is lost as waste on
released by the animal during its movement. Likewise
when a carnivore feeds on its prey only a portion of
the energy from the prey is stored in its tissues. As
such organisms along a food chain pass on much less
energy than what they receive, as much of the energy
is lost at every level. The pyramid shaped food chain
shows many trees and shrubs providing food and energy
to giraffes. There are few giraffes than trees and shrubs
and even fewer lions than giraffes. In other words, a
large mass of living things at the base is required to
support a few at the top. This interdependence of the
populations within a food chain helps to maintain the
balance of plant and animal populations.
Ecological Pyramid :
Each group of organisms occupies a feeding level
called a trophic level. The different trophic levels may
be represented in the form of a pyramid called
ecological pyramid.
Man is at the top of the ecological pyramid. The
pyramid has a large base. It represents primary
producers. From base to the top, the numbers go on
decreasing at each level. All green plants and other
producers occupy the first trophic level. Herbivores
which feed on plants occupy the second trophic level.
Carnivores that eat herbivores are at the third trophic
level. At each level, the flow of energy is reduced ;
because only a fraction of energy is transferred from
lower to higher level.
Question 8:
What do you understand by Food Web? Give example.
Answer:
Food Web. The simple food chain does not
exist in any ecosystem. Many simple food chains
intermingle with one another to form a food web. For
example, each organism may eat a variety of food
derived from another organisms and in turn may be
eaten by number of organisms at a higher level of the
food chain. The primary producers use the energy of
the sun and provide it to consumers at higher level.
But energy is lost during each upward step in the
food chain. The relations between different organisms
in a food chain are represented by a pyramid of
numbers.
Examples. For example, a plant-eating beetle
feeding on a paddy stalk is eaten by a frog, which is
in turn eaten by a snake, which is then consumed by
a hawk. This sequence of eating and being eaten with
the resultant transfer of energy from one level to
another level is known as food chain. Transfer of
energy that occurs during the process of a food chain
from one level to another is known as flow of energy.
However, food chains are not isolated from one
another. For example, a mouse feeding on grain may
be eaten by different secondary consumers
(carnivores) and these carnivores may be eaten by
other different tertiary consumers (top carnivores).
In such situations even each of the carnivores may
consume more than one type of prey. As a result, the
food chains interlock with one another. This interconnecting
network of species is known as food web.
Generally two types of food chains are recognized.
1. Grazing food chain and 2. Detritus food chain. In a
grazing food chain the first level starts with plants
as producers and ends with carnivores as consumers
as the last level, with the herbivores being at the
intermediate level. There is a loss of energy at each
level which may be through respiration, excretion or
decomposition. The levels involved in a food chain
range between three to five and energy is lost at each
level. A detritus food chain involves the decomposition
or breaking down of organic wastes and dead matter
derived from the grazing food chain.
Question 9:
What is a Biome?
Answer:
A biome is a plant and animal community that covers a large geographical area. Therefore, a biome is a total assemblage of plant and animal species. There are five major Biomes—forests, deserts, grassland, aquatic and altitudinal.
Question 10:
What are biogeochemical cycles? Explain how Nitrogen is fixed in the atmosphere.
Answer:
BIOGEOCHEMICAL CYCLES
Sun is the basic source of energy on which all life
depends. This energy initiates life processes in the
biosphere through photosynthesis, the main source of
food and energy for the green plants. During
photosynthesis carbon dioxide is converted to organic
compounds and oxygen. Out of the total solar
insolation that reaches the earth surface only a very
small fraction (0.1 per cent) is fixed in photosynthesis.
More than half is used for plant respiration and the
remaining is temporarily stored or is shifted to other
portions of the plant.
Life on earth consists of a great variety of living
organisms. These living organisms exist in a diversity
of associations. The processes and interactions
involved within the biosphere are complex in nature.
Living organisms survive in multiplicity and diversity.
Such survival involves the presence of systemic flows
such as flows of energy, water and nutrients. These
flows show variations in different parts of the world,
in different seasons of the year and under varying
local circumstances. Studies have shown that for the
last one billion years, the atmosphere and hydrosphere
have been composed of approximately the same
balance of chemical components. This balance of the
chemical elements is maintained by a cyclic passage
through the tissues of plants and animals. The cycle
starts by absorbing the chemical elements by the
organism and returned back to the air, water and
soil through decomposition. These cycles are largely
energized by solar insolation. These cyclic movements
of chemical elements of the biosphere between the
organism and the environment are referred to as biogeochemical
cycles. ‘Bio’ refers to living organisms and
‘geo’ to rocks, soil, air and water of the earth.
There are two types of bio-geochemical cycles, the
gaseous and the sedimentary cycle. In the gaseous cycle
the main reservoir of nutrients is the atmosphere and
the ocean. In sedimentary cycle the main reservoir is
the soil and the sedimentary rocks and other rocks of
the earth’s crust.
The nitrogen cycle
Nitrogen is a major constituent of the atmosphere
comprising of about seventy-nine per cent of the
atmospheric gases. It is also an essential constituent
of different organic compounds such as amino acids,
nucleic acids, proteins, vitamins and pigments. Only
few types of organisms like certain species of soil
bacteria and blue green algae are capable of utilizing
it directly in its gaseous form. Generally nitrogen is
usable only after it is fixed. Ninety per cent of fixed
nitrogen is biological. The principal source of free
nitrogen is action of soil micro-organisms and
associated plant roots on atmospheric nitrogen found
in pore spaces of the soil. Nitrogen can also be fixed
in the atmosphere by lightning and cosmic radiation.
In the oceans some marine animals can fix it. After
atmospheric nitrogen has been fixed into an
available form green plants can assimilate it.
Herbivorous animals feeding on plants in turn
consume some of it. Dead plants and animals,
excretion of nitrogenous wastes are converted into
nitrites by the attachment of bacteria present in
the soil. Some bacteria can even convert nitrites
into nitrates that can be used again by the green
plants. There are still other types of bacteria
capable of converting nitrates into free nitrogen, a
process known as denitrification.
Question 11:
What is an Ecological Balance? Discuss the important measures needed to prevent ecological imbalance?
Answer:
Ecological balance
Ecological balance is a state of dynamic
equilibrium within a community of organisms in a
habitat or ecosystem. It can happen when the
diversity of the living organisms remains relatively
stable. Gradual changes do take place but that
happen only through natural succession. It can also
be explained as a stable balance in the number of
each species in an ecosystem. This occurs through
competition and cooperation between the different
organisms where population remains stable. This
balance is brought about by the fact that certain
species compete with one another determined by
the environment in which they grow. This balance
is also attained by the fact that some species depend
on others for their food and sustenance.
Example. Such accounts are encountered in vast
grasslands where the herbivorous animals (deers,
zebra, buffaloes) are found in plenty. On the other
hand the carnivorous animals (tigers, lions, coyotes)
that are not usually in large numbers hunt and feed
on the carnivores, thereby controlling their
population. In the plants any disturbance in the
native forests such as clearing the forest for shifting
cultivation usually brings about a change in the
species distribution. This change is due to
competition where the secondary forest species such
as grasses, bamboos or pines overtake the native
species changing the original forest structure. This
is called succession.
Causes of Ecological Imbalance.
(1) Ecological balance may be disturbed due to
the introduction of new species, natural hazards or
man-made causes.
(2) Man’s interference has affected the balance
of plant communities leading to disturbances in the
ecosystems. Such disturbances bring about
numerous secondary successions.
(3) Human pressure on the earth’s resources has
put a heavy toll on the ecosystem. This has
destroyed its originality and had caused adverse
effects to the general environment.
(4) Ecological imbalances have brought many
natural calamities like floods, landslides, diseases,
erratic climatic occurrences and such other hazards.
There is a very close relationship between plant
and animal communities within particular habitats.
Diversity of life in a particular area can be employed
as an indicator of habitat factors. Proper knowledge
and understanding of such factors provide a strong
base for protecting and conserving ecosystems.