Download ENVIRONMENTAL

ENVIRONMENTAL
ENGINEERING
Lect.2
Chemical Engineering department
Ecology and Ecosystem
DEFINITION
The word ‘Ecology’ was coined by a German biologist, Haans Reiter in 1865
and defined by another renowned biologist, Ernst Haeckel in 1870: “Scientific study
of the relationships of living organisms with each other and with their environment.”
The term is derived from the Greek roots ‘Oikos’ (meaning home) and ‘logos’
(meaning study or discourse). The living organisms and their physical environment
are closely related with each other so that any change in the environment has an
effect on the living organisms and vice versa.
The ecosystem is the functional unit in ecology as it consists of both the biotic
community (living organisms) and abiotic environment. The latter have close
interaction, essential for maintenance of life processes. The interaction is conducted
by energy flow (solar energy) in the system and cycling of materials (natural cycles).
From biological point of view, the ecosystem has the following constituents:
 inorganic substances (carbon, nitrogen, carbon dioxide, water etc.) involved
in natural cycles;
 Organic compounds (proteins, carbohydrates, humic substances etc.);
 air, water and substrate environment (i.e., biological base for growth)
including the climatic regimes and other physical factors;
 producers, autotrophic (i.e., self-sustaining organisms) green plants that can
manufacture food from simple inorganic substances;
 heterotrophic (i.e., depending on others for nourishment) organisms, mainly
animals which live on other organisms or particulate organic matter;
Sustainable Ecosystem
The developing countries face today the critical situation on economic and
environmental fronts. For economic growth they have to give priority to agricultural
and industrial bases but at the cost of environment. The resource base, once depleted,
sets in a chain of environmental degradation which finally weakens the economy.
Our population explosion remains the core issue. Our development policy should be
such that the ecosystem is sustainable i.e., it contains the element of renewability.
This requires sound management strategy which ensures the continuation of socioeconomic development in the long run. The important components of sustainable
development/ecosystem are:
• Population stabilisation
• Integrated land use planning
• Conservation of biodiversity
• Air and water pollution control
• Renewable energy resources
• Recycling of wastes and residues and
• Environmental education and awareness at all levels.
ASPECTS OF ECO-SYSTEM
The eco-system can be defined as any spatial or organizational unit including
living organisms and non-living substances interacting to produce an exchange of
materials between the living and non-living parts. The eco-system can be studied
from either structural or functional aspects.
1. Structural Aspect
The structural aspects of ecosystem include a description of the arrangement, types
and numbers of species and their life histories, along with a description of the
physical features of the environment.
2. Functional
The functional aspects of the ecosystem include the flow of energy and the cycling
of nutrients.
Habitat
The non-living part of the eco-system includes different kinds of habitats such as air,
water and land, and a variety of abiotic factors. Habitat can be defined as the natural
abode or locality of an animal, plant or person. It includes all features of the
environment in a given locality. For example, water is used as habitat by aquatic
organisms and it comprises three major categories-marine, brackish and freshwater
habitats. Each of these categories
May be subdivided into smaller unit, such a freshwater habitat may exist as a large
lake, a pond, a puddle, a river or a stream.
The land is used as a habitat for numerous terrestrial organisms. It includes many
major categories of landmasses, which are called biomes. Biomes are distinct large
areas of earth inclusive of flora and fauna, e.g. deserts, prairie, tropical forests, etc.
Soil is also used as a habitat by a variety of microbes, plants and animals.
Abiotic Factors
Among the main abiotic factors of the ecosystem are included the follwing:
(1) The climatic factors as solar radiation, temperature, wind, water currents,
(2) The physical factors as light, fire, pressure, geomagnetism,
(3) Chemical factors as acidity, salinity and the availability of inorganic nutrients
needed by plants.
Biotic or Biological Factors
The biological (biotic) factors of ecosystem include all the living organisms-plants,
animals, bacteria and viruses. Each kind of living organism found in an ecosystem
is given the name a species. A species includes individuals which have the following
features:
(1) They are genetically alike.
(2) They are capable of freely inter-breeding and producing fertile off springs.
Relationships
In an ecosystem, there exist various relationships between species. The relationship
may be as under:
(1) Effects
Two species may have any of the following kind of effects:
(i) They may have a negative effect upon one another (competition).
(ii) They may have a neutral effect (neutralism).
(iii) They may have beneficial effect (protoco-operation and mutualism).
(2) Other kinds of Relationship
The species may aggregate, or separate, or show a random relationship to one
another.
Population
A population is a group of inter-acting individuals, usually of the same
species, in a definable space. In this way we can speak of population of deer on an
island, and the population of fishes in a pond. A balance between two aspects
determines the size of a population of any given species:
(i) Its reproductive potential,
(ii) Its environmental resistance.
In this way population size is determined by the relative number of organisms added
to or removed from the group as under:
(i) Addition
Recruitment into the population is a function of birth rate and immigration rate.
ii) Removal
Loss from the population is a function of death rate and emigration.
Factors Regulating Population
Following factors does population regulation:
(i) Physical attributes of the environment (e.g. climate),
(ii) Food (quantity and quality),
(iii) Disease (host-parasite relationships).
(iv) Predation,
(v) Competition (inter-specific and intra-specific).
An ecosystem contains numerous populations of different species of plants, animals
and
Microbes; all of them interact with one another as a community and with the physical
environment as well. A community or biotic community, thus, consists of the
population of plants and animals living together in a particular place.
Division of Ecosystem
The ecosystem can be divided, from the energetic view point into three types of
organisms:
Producers, consumers, and reducers. These can be explained as under:
(1) Producer Photosynthetic algae, plants and bacteria are the producers of the
ecosystem; all other organisms depend upon them directly or indirectly for
food.
Commented [U1]:
(2) Consumers Consumers are herbivorous, carnivorous, and omnivorous
animals; they eat the organic matter produced by other organisms.
(3) Reducers Reducers are heterotrophic organisms like animals; they are fungi
and bacterial that decompose dead organic matter.
ENERGY PATH
The green plants absorb solar radiation and transform it into potential of food energy
through the process of photosynthesis.
The rest of the biological world other than chlorophyll bearing plants and
chemosynthetic bacteria derives its potential chemical energy from organic matters
produced either by plant photosynthesis or chemosynthesis. An animal takes in
chemical potential energy of food from the plant source, most of which is converted
into heat to enable a small part of the energy to be re-established as the chemical
potential energy of new protoplasm. During the transfer of energy from one
organism to another, a large portion (about 80 %) is degraded into heat at each step
of the transfer. The transfer and dispersal of energy is guided by the Stability
Principle which in turn follows from the Second Law of Thermodynamics.
According to the Stability Principle, any natural closed enclosed system with energy
flowing through it tends to change until a stable adjustment is developed through
self-regulating or homoeostasis mechanism. While matter in the natural cycles
(nitrogen cycle, oxygen cycle, phosphorus cycle etc.) moves in a cyclic path, energy
moves in a unidirectional way in the ecosystem and then passes to the biosphere.