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ENVIRONMENT & ECOLOGY
ENVIRONMENT AND BASIC CONCEPTS
Handout
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Environment Concepts Scope of The Topic: I. Environment
II. Habitat III. Difference between Environment and Habitat IV.
Biosphere V. Ecosystem
VI. Components of Ecosystem-Biotic and Abiotic VII.
Classification of Ecosystems
VIII. Ecology a) Levels of Organization in Ecology b) Adaptation
c) Acclimatization d) Evolution e) Ecotone f) Characteristics of
Ecotone g) Ecological Niche
IX. Functions of Ecosystem X. Ecological Succession
a) Primary and Secondary Succession XI. Homeostasis
XII. Energy Flow through Food Chain-Trophic Levels XIII. Food
Chain
a) Types of Food Chain-Grazing and Detritus Food Chain b) Food
Web
XIV. Interspecific Interaction a) Amensalism b) Comensalism c)
Mutualism d) Parasitism e) Predation
XV. Ecosystem Services a) Supporting Services b) Provisioning
Services c) Regulating Services d) Cultural Services
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Environment
Environment is the Physical surrounding in which biotic (living)
and abiotic (nonliving) factors interact with each other. The
environment constitutes the physical factors (nutrients, water, air
etc.) and biological factors (organisms) along with the
interactions between them. These interactions affect an organism.
All organisms are dependent on the environment to carry out their
natural life processes (birth to death) and to meet their physical
requirements (food, energy, water,oxygen, shelter etc.). The
environment is not static. Both biotic and abiotic factors are
dynamic and keep changing continuously. Habitat Habitat is the
physical environment in which an organism lives. It corresponds to
the address of an organism. A single habitat may be common for
morethan one organism which has similar requirements.For example, a
single aquatic habitat maysupport a fish, frog, crab,
phytoplanktonand many other kinds of organisms. The various species
sharing a habitat thushave the same ‘address’. Forest, river etc,
are other examples of habitat. All habitats are part of the
environment but all the places in the environment are not habitats.
Difference between Habitat and Environment? A habitat always has
life in it, whereas theenvironment does not necessarily have lifein
it. There are certain places in the environment like the summit of
Mt. Everest or the Mariana Trench where the living conditions are
extreme and life cannot exist. Biosphere The biosphere is the
biological component of earth which includes all living organisms
on earth, together with the dead organic matter produced by them.
Biosphere is absent at extremes of the North and South poles, the
highest mountains and the deepest oceans, since existing hostile
conditions there do not support life. EcosystemAn ecosystem is the
functional unit of nature, where living organisms [producers,
consumers, and decomposers] interact among themselves and also with
the surrounding physical environment.
Ecosystem varies greatly in size from a small pond to a large
forest or a sea.
Forest, grassland and desert are some examples of terrestrial
ecosystems; pond, lake, wetland, river and estuary are some
examples of aquatic ecosystems. Crop fields and an aquarium may
also be considered as man-made ecosystems.
In the ecosystem, biotic and abiotic components are linked
together through nutrient cycles and energy flows.
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Components of an Ecosystem
Abiotic Components Abiotic components are the inorganic and
non-living things which act as major limiting factors. Limiting
factor Lot of factors determine the survival of an organism. One
single factor can limit the range of an organism. This single
factor is called as a limiting factor. For example, seeds don’t
germinate quickly in evergreen rain forests in spite of good rains
and vegetation as the surface soil is heavily leached (nutrients
washed away by running water). Here, poor soil is the limiting
factor. Biotic Components Primary producers - Autotrophs
(self-nourishing)
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Primary producers are basically green plants, certain bacteria
and algae that carry out photosynthesis. In terrestrial ecosystem,
grasses, plants and trees are the primary producers while in
aquatic ecosystem, microscopic algae [plankton] and aquatic plants
are the primary producers. Consumers — Heterotrophs or Phagotrophs
(other nourishing) Consumers are incapable of producing their own
food. They depend on plants, animals or both for food. Consumers
can be divided into two broad groups namely micro and macro
consumers. Macro consumers: Herbivores are primary consumers which
feed mainly on plants e.g. cow. Carnivores which feed on primary
consumers e.g. lion which can eat wolves, snakes etc. Omnivores are
organisms which consume both plants and animals e.g. man, bear,
etc. Micro consumers - Saprotrophs (decomposers).Also known as
Detrivores. They are bacteria and fungi which obtain energy and
nutrients from dead organic substances (detritus) of plant and
animals. The products of decomposition such as inorganic nutrients
which are released in the ecosystem are reused by producers and
thus recycled.
Take Home Point: Virus are not decomposers. Several species of
bacteria and fungi are decomposers. Decomposition is the process by
which organic substances are broken down into simpler matter.
Decomposition process is a part of the nutrient cycle and is
essential for recycling the finite matter in the environment.
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Classification of Ecosystems
Ecology
Ecology is the branch of study concerned with the relations of
organisms to one another (energy flow and nutrient cycling) and to
their physical surroundings (environment). Ecology encompasses
study of individual, organisms, population, community, ecosystem,
biome and biosphere which form the various levels of ecological
organization.
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What is the difference between ecology, environment, and
ecosystem?
Ecology- Etymology is oikos+ logy. Oikos means house or
dwelling.
Ecology is the study of relationships and interactions of living
organismswith other living organisms and its surrounding
environment.
Thus there are 3 things that we study in ecology-
1. Living organisms 2. Their relationship & interactions
with other organisms. E.gwhat kind of
relationship is there between the bacteria rhizobium and plant
roots, or Competition among herbivorous animals for foodetc.
3. Their interactions with surrounding environment. It means how
the organism responds to climate, soil, topography, water
availability, etc. Example: Animals in deserts have long ears to
increase heat loss and keep themselves cool while animals in cold
areas have small ears to prevent heat loss. The interactions with
other organisms and environment include Energy flow (Food
chains/Food web) and nutrient cycles.
Environment refers to the surroundings. It has 2 components
biotic and abiotic.
Biotic includes - surrounding plant & animal communities and
microorganisms. Abiotic factors includes- soil, sunlight,
topography, water, atmosphere, nutrients etc
Ecosystem is a functional unit of nature( Like how cell is the
functional unit of life). It includes environment (biotic+ abiotic)
and ecology(how living organisms interact with each other and with
the environment).
Ecosystem can be as big as our Earth or as small as a drop of
water(water + micro-organisms).
Thus Ecosystem= Ecology+ Environment
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Levels Of Organizations In Ecology Ecology not only deals with
the study of the relationship of individual organisms with their
environment, but also with the study of populations, communities,
ecosystems, biomes, and biosphere as a whole. Organism: is an
individual living being that has the ability to act or function
independently. It may be any organism. Species: Species are a group
of similar organisms consisting of similar genetic structure and
are capable of interbreeding. Population: Population is a large
number of organisms which belong to one species. Ex: populations of
tigers, lions, rhinos etc. Community: Populations of two or more
different species living together in an area is known as community,
Communities in most instances are named after the dominant plant
form (species). For example: A grassland community is dominated by
grasses, though it may contain herbs, shrubs, and trees, along with
associated insects and animals of different species. Ecosystem: An
ecosystem is a community of organisms interacting with each other
and with their environment.The interaction leads to flow of energy
and cycling of nutrients. Biome: Biome is a large naturally
occurring community of flora and fauna occupying a major habitat.
E.g. Rainforest biome or tundra biome.Plants and animals in a biome
have common characteristics due to similar climatic condition
throughout the biome. Biosphere: The biosphere is the biological
component of earth which includes the lithosphere, hydrosphere and
atmosphere. The biosphere includes all living organisms on earth,
together with the dead organic matter produced by them.
Future Connects: Read about the major types of Biomes in the
world and biomes in India and their characteristics in Biomes
Chapters
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Some Concepts of Ecology: Adaptation: Each organism is adapted
to its particular environment. An adaptation is thus, “the
appearance or behavior or structure or mode of life of an organism
that allows it to survive in a particular environment”. Adaptation
is any attribute of the organism that enables the organism to
survive and reproduce in its habitat. Ex: when trees grew higher,
the giraffes neck got longer; In the absence of an external source
of water, the kangaroo rat in North American deserts is capable of
meeting all its water requirements through its internal fat
oxidation. Some desert plants like Opuntia, have no leaves - they
are reduced to spines-and the photosynthetic function is taken over
by the flattened stems [less leaves = less area available for
transpiration]. Acclimatization We need to breathe faster when we
are on high mountains. After some days, our body adjusts to the
changed conditions on the high mountain. Such small changes that
take place in the body of a single organism over short periods, to
overcome small problems due to changes in the surroundings, are
called acclimatization. Evolution Evolution is the change which
gives rise to new species. It happens in order to make the organism
better suit to the present environment. Evolution leads to
speciation or formation of new species.
Ecotone An ecotone is a zone of junction or a transition area
between two biomes or ecosystems. It is where two communities from
two different ecosystems meet and integrate. For e.g. the mangrove
forests represent an ecotone between marine and terrestrial
ecosystem. Other examples are grassland (between forest and
desert), estuary (between fresh water and salt water) and marsh
land (between dry and wet). Characteristics of Ecotone It may be
narrow (between grassland and forest) or wide (between forest and
desert). As it is a zone of transition, it has conditions
intermediate to the adjacent ecosystems. A well-developed ecotone
contains some organisms which are entirely different from that of
the adjoining communities. Edge Effect – Edge Species
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Sometimes the number of species and the population density of
some of the species in the ecotoneis much greater than either
community. This is called edge effect. The organisms which occur
primarily or most abundantly in this zone are known as edge
species. In the terrestrial ecosystems edge effect is especially
applicable to birds. For example the density of birds is greater in
the mixed habitat of the ecotone between the forest and the desert.
Significance of Ecotones:Ecotones are considered areas of great
environmental importance. They provide habitat for a large number
of species, they often experience influx from animals looking to
nest or searching for food. They may also be considered a habitat
of greater bio-diversity. An Ecotone can act as a “buffer-zone”
protecting the neighbouring ecosystem from possible environmental
damage – i.e. a wetland (Riparian Buffer) area could absorb
pollutants preventing them from entering into a river or lake.
Ecological Niche Niche refers to the unique functional role and
position of a species in its habitat or ecosystem. In nature, many
species occupy the same habitat but they perform different
functions. Habitat of a species is like its ‘address’ (i.e. where
it lives) whereas niche can be thought of as its “profession” (i.e.
activities and responses specific to the species). A niche is
unique for a species while many species share the habitat. No two
species in a habitat can have the same niche. This is because of
the competition with one another. A species' niche includes all of
its interactions with the biotic and abiotic factors of its
environment [habitat niche - where it lives, food niche - what is
eats or decomposes & what species it competes with,
reproductive niche - how and when it reproduces]. Significance of
Ecological Niche:Niche plays an important role in conservation of
organisms. If we have to conserve species in its native habitat we
should have knowledge about the niche of the species and should
ensure that all requirements of its niche are fulfilled.
Functions Of Ecosystem The functions of an ecosystem
include:
• Ecological succession • Homeostasis • Energy flow through food
chain • Nutrient cycling (biogeochemical cycles)
Ecological Succession Communities are dynamic in nature and
change over a period of time. The process by which species of
plants and animals in an area are replaced or changed into another
over a period of time is known as ecological succession.
Future Connections: Read about Riparian Buffer from Water
Pollution and Wetlands chapters.
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Succession occurs when a series of communities replace one
another due to large scale destruction (natural or manmade). This
process continues with one community replacing another, until a
stable, mature community develops. Succession is a progressive
series of changes which leads to the establishment of a relatively
stable climax community. The first species to colonize an area is
called the pioneer community. The final stage of succession is
called the climax community. The stages leading to the climax
community are called successional stages or seres. Each
transitional (temporary) community that is formed and replaced
during succession is called a stage in succession or a seral
community. Succession has the following characteristics: increased
productivity, increased diversity of organisms with increased niche
development and a gradual increase in the complexity of food webs.
The terminal (final) stage of succession forms the community which
is called as climax community. A climax community is stable,
mature, more complex and long lasting. Primary Succession Primary
succession takes place an over a bare or unoccupied areas such as
rockss, newly formed deltas and sand dunes, emerging volcano
islands, lava flows as well as glacial moraines (muddy area exposed
by a retreating glacier) where no community has existed
previously.
SecondarySuccession Secondary succession occurs when plants
colonize an area in which the climax community has been
disturbed.Secondary succession is the sequential development of
biotic communities after the complete or partial destruction of the
existing community. In primary succession on a terrestrial site the
new site is first colonized by a few hardy pioneer species that are
often microbes, lichens and mosses. The pioneers over a few
generations alter the habitat conditions by their growth and
development. The new habitat conditions are suitable for the growth
of other organisms. Eventually the pioneer community gets replaced
by the other species. Unlike in the primary succession, the
secondary succession starts on a well-developed soil already formed
at the site. Thus secondary succession is relatively faster as
compared to primary succession which may often require hundreds of
years.
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Homeostasis Homeostasis is the maintenance of a stable
equilibrium, especially through physiological (through bodily part
functions. E.g. Cooling your body through sweating) processes.
Organisms try to maintain the constancy of its internal environment
(a process called homeostasis) despite varying external
environmental conditions that tend to upset its homeostasis.
Ecosystems are capable of maintaining their state of equilibrium.
They can regulate their own species structure and functional
processes. This capacity of ecosystem of self-regulation is known
as homeostasis. Energy Flow Through an Ecosystem – Trophic Levels
The flow of energy from producer to top consumers is called energy
flow which is unidirectional. To understand the energy flow through
the ecosystem we need to study about the trophic levels. Trophic
level is the representation of energy flow in an ecosystem. The
trophic level of an organism is the position it occupies in a food
chain. Trophic levels Autotrophs Green plants (producers)
Heterotrophs Herbivore (primary consumers) Heterotrophs Carnivores
(secondary consumers) Heterotrophs Carnivore (tertiary consumers)
Heterotrophs Top carnivores (Quarternary consumers) Energy flows
through the trophic levels from producers to subsequent trophic
levels is unidirectional. Food Chain Transfer of food energy from
green plants (producers) through a series of organisms with
repeated eating and being eaten link is called a food chain. E.g.
Grasses → Grasshopper → Frog → Snake → Hawk/Eagle. Each step in the
food chain is called trophic level. A food chain starts with
producers and ends with top carnivores.The trophic level of an
organism is the position it occupies in a food chain. Types of Food
Chains
Grazing food chain Detritus food chain
Grazing food chain The consumers which start the food chain,
utilizing the plant or plant part as their food, constitute the
grazing food chain. This food chain begins from green plants at the
base and the primary consumer is herbivore.For example, In
terrestrial ecosystem, grass is eaten by caterpillar, which is
eaten by lizard and lizard is eaten by snake.In Aquatic ecosystem
phytoplankton (primary producers) are eaten by zoo planktons which
are eaten by fishes and fishes are eaten by pelicans.
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Detritus food chain This type of food chain starts from dead
organic matter of decaying animals and plant bodies. Dead organic
matter or detritus feeding organisms are called detrivores or
decomposer. The detrivores are eaten by predators.The two food
chains are linked. The initial energy source for detritus food
chain is the waste materials and dead organic matter from the
grazing food chain. In an aquatic ecosystem, grazing food chain is
the major conduit for energy flow. As against this, in a
terrestrial ecosystem, a much larger fraction of energy flows
through the detritus food chain than through the grazing food
chain. Food Web Multiple interlinked food chains make a food web.
Food web represents all the possible paths of energy flow in an
ecosystem.If any of the intermediate food chain is removed, the
succeeding links of the chain will be affected largely.The food web
provides more than one alternative for food to most of the
organisms in an ecosystem and therefore increases their chance of
survival. Also food availability and preferences of food of the
organisms may shift seasonally e.g. we eat watermelon in summer and
peaches in the winter. Thus there are interconnected networks of
feeding relationships that take the form of food web.
Relationship Between the Species- Interspecific Interaction
Amensalism One species harms or restricts the other species without
itself being adversely affected or harmed by the presence of the
other species.
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Organisms that secrete antibiotics and the species that get
inhibited by the antibiotics are examples of amensalism. For
example the bread mould fungi Pencillium produce penicillin an
antibiotic substance which inhibits the growth of a variety of
bacteria. A large tree shades a small plant, retarding the growth
of the small plant. The small plant has no effect on the large
tree. Commensalism In this relationship one of the species benefits
while the other is neither harmed nor benefited. Some species
obtain the benefit of shelter or transport from another species.
For example sucker fish, remora often attaches to a shark by means
of its sucker which is present on the top side of its head. This
helps the remora get protection, a free ride as well as meal from
the left over of the shark’s meal. The shark does not however get
any benefit nor is it adversely affected by this association.
Another example of commensalisms is the relationship between trees
and epiphytic plants. Epiphytes live on the surface of other plants
like ferns, mosses and orchids and use the surface of trees for
support and for obtaining sunlight and moisture. The tree gets no
benefit from this relationship nor are they harmed.
Mutualism This is a close association between two species in
which both the species benefit. One example of a mutualistic
relationship is that of the oxpecker (a kind of bird) and the
rhinoceros or zebra. Oxpeckers land on rhinos or zebras and eat
ticks and other parasites that live on their skin. The oxpeckers
get food and these animals get free pest control. However, some
mutualisms are so intimate that the interacting species can no
longer live without each other as they depend totally on each other
to survive. Such close associations are called symbiosis (symbiosis
is intense mutualism – E.g. coral and zooxanthellae). An example of
such close mutualistic association is that of termite and their
intestinal flagellates. Termites can eat wood but have no enzymes
to digest it. However, their intestine contains certain flagellate
protists (protozoans) that have the necessary enzymes to digest the
cellulose of the wood eaten by termites and convert it into
sugar.
Parasitism In this type of interaction, one species is harmed
and the other benefits. Parasitism involves parasite usually a
small size organism living in or on another living species called
the host from which the parasite gets its nourishment and often
shelter. Many organisms like animal, bacteria and viruses are
parasites of plants and animals. Predation Predators like leopards,
tigers and cheetahs use speed, teeth and claws to hunt and kill
their prey.
Future Connections: Read about Coral Polyps and Coral Bleaching
in Water Pollution chapter.
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They keep prey populations under control. Without predators,
prey species could achieve very high population densities and cause
ecosystem instability. When certain exotic species are introduced
into a geographical area, they become invasive and start spreading
fast because the invaded land does not have its natural predators.
Ecosystem Services: These are the benefits people obtain from
ecosystems. These are the different goods and services people get
freely from the nature. There are four categories of Ecosystem
Services. They are:
1) Supporting Services: These include services such as: nutrient
recycling, primary production, soil formation, pollination etc.
These services make it possible for the ecosystems to provide other
services. So these form the basis for the other services. 2)
Provisioning Services: These services are:
• Food:Food crops, foods such as honey and fruits obtained from
the forests.
• Raw materials: Including timber, skins, fire wood, bio-mass,
fodder etc • Genetic Resources: Genetic resources are beneficial
genes present in the
organisms which give the organism beneficial characteristics
which are valuable to mankind. Ex: Food crops which are pest and
drought resistant, cattle which give good quality milk etc.
• Fresh Water and Air • Bio-genic Materials- Thseare materials
or minerals obtained from living
organisms example: Calcium Carbonate made by coral polyps. •
Medicinal Resources: Like medicinal plants. • Ornamental Resources:
including handicrafts, jewelry, decoration, furs,
aquarium fish etc. 3) Regulating Services:
• Carbon Sequestration and climate regulation. • Waste
decomposition • Purification of water and air. • Pest control
4) Cultural Services: • Use of nature in books, film, painting,
folklore, national symbols, advertising
etc. • Spiritual use, including use of nature for religious
purposes. • Recreational use, including eco-tourism, outdoor sports
etc. • Science and education, including use of nature for research,
scientific
discoveries, learning etc. • Therapeutic uses, including
Eco-therapy, animal-assisted therapy, etc.
Future Connections: Read about coral polyps in Water Pollution
Chapter.
Carbon Sequestration: It is the process of absorption of
atmospheric carbon di oxide and storing it in bodies such as water
bodies.
Future Connections:Read about Climate Change and Carbon
Sequestration in Climate Change Chapter.
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SPACE FOR ROUGH WORK
Trophic levels
