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Transcript
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
ENVIRONMENTAL FACTORS
1 BIOTIC COMPONENT
The biotic components of environment are the living components of environment like
plants (producers of food), animals(consumers) including human beings and
microorganisms. Biotic components form an important part of any ecosystem.
PLANTS AS BIOTIC COMPONENTS OF ENVIRONMENT
The green plants are the producers of food for all living beings in an ecosystem. The
leaves and other green parts of the plant contain chlorophyll which help in synthesizing
food and releases oxygen through photosynthesis. The process of photosynthesis
needs sunlight and it manufactures food with the help of water absorbed from the soil
and harmful carbon dioxide from the atmosphere.
ANIMALS AS BIOTIC COMPONENTS OF ENVIRONMENT
They are known as the consumers of an ecosystem. They depend on plants for their
survival. Animals like earthworm and wood lice help in running of nutrient cycles by
providing food to decomposers. Certain animals like jackals, crows, vultures etc. act as
scavengers and consume the dead and decayed bodies of animals.
MICROORGANISMS AS BIOTIC COMPONENTS OF ENVIRONMENT
The microorganisms are also known as the decomposers of an ecosystem. The
microorganisms form a very large group of biotic components. They are found in all
types of habitats and climatic conditions. They are members of bacteria, viruses and
fungi group. Nitrogen fixing bacteria converts atmospheric nitrogen to a form in which it
can be used by living organisms. Some bacteria such as cyanobacteria engage in plantlike photosynthesis in producing food. A cyanobacteria, Spirulina is used as rich source
of protein and used as food in humans. Bacteria also play an important role in
production of human food like cheese, curd, etc. Microorganisms play vital role in
recycling of nutrients.
INTERLINKING BETWEEN BIOTIC COMPONENTS
Thus, all the three components of the biotic environment are closely interlinked to each
other. The plants are producers which provide food and oxygen. The animals are
consumers which fully depend on the plants for their survival. Microorganisms though a
separate components of the biotic environment but help in various ways in the
maintenance of the environment
2 ABIOTIC COMPONENT
Abiotic factors are the non-living factors in an ecosystem that affect the survival of
organisms in that ecosystem. They include:
water availability
sunlight
temperature range
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
substrate - rock type or sand
geographical terrain
oxygen availability
exposure
3 EDAPHIC FACTORS
These include
 Soil and substrate
 Soil profile
 Topography
 Minerals
 pH
 Fire
 Range of tolerance
SOIL
The word soil is derived from the Latin word solum meaning earthy material in which
plants grow. The science which deals with the study of soil is called Soil Science,
Pedology (pedos = earth) or edaphology (edaphos = soil). The process of formation of
soil is called pedogenesis. A soil complex is formed of 5 categories of components
namely mineral matter, organic matter or humus, soil water, soil air and living
organisms. The quality of soil is due to its fertility, texture, structure, organic contents
and air - water relationship.
SOIL PROFILE
The vertical layered structure of soil is called the soil profile. There are 4 main horizons
in a soil profile.
O - horizon is the organic layer composed of dead organic residues.
A - horizon is the top soil, the upper most layer which contains roots.
B - horizon is the sub soil.
C - horizon is the less weathered parent material.
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
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



Comparison of soil profile (a) temperate deciduous forests (b) tropical rain-forests
The organic matter in the soil is of 2 types.
1. Freshly dead and partially decomposed plant and animal material called litter or
detritus
2. Colloidal, amorphous and dark coloured humus.
Soil helps in
providing water and minerals to the land plants
It acts as a substratum for a variety of organisms like bacteria, fungi, many kinds of
animals and plants.
It is the site for decomposition of plants and animals.
It provides water, minerals and fossil fuels to man.
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
The type of soil (clayey, sand and loamy) and its water retention aeration and mineral
contents determine the nature of plants and animals. On the basis of these characters
of soil, the plants are divided into 5 ecological categories.
Halophytes - plants found on saline soil
Psammophytes - plants found on sandy soil
Lithophytes - plants found on rocky surface
Chasmophtyes - plants found in rock - crevices
Oxylophytes - Plants found on acid soils
The ground dwelling animals which may be cursorial (running) such as ostrich, rhea,
ungulates, wolves, cats, bears, hyaenas etc, saltatory (jumping) such as rodents,
rabbits, wallabies, kangaroos or graviportal (heavy) such as turtles armadillos,
elephants etc exhibit different kinds of adaptations for different kinds of soil. For E.g., if
the soil is firm and hard, the large animals inhabiting the ecosystem tend to have small
hooves or paws. If the soil is wet and spongy, they tend to have broad hooves or paws.
TOPOGRAPHY
Topography includes the physical features of the earth like altitude, slope, exposure,
mountain chains, valleys, plains, etc.
Marked variations in temperature at different altitudes result in the division of earths
vegetation into different zones such as equatorial, tropical rain forests, desert or
grasslands, deciduous forests, coniferous forests, tundra, ice and snow of poles.
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
Height above sea level forms the altitude. At high altitudes, the velocity of wind remains
high, temperature and air pressure decrease, humidity as well as intensity of light
increases. Due to these factors, vegetation at different altitudes is different showing
distinct zonation.
The directions of mountain chains or ranges and high mountains act as wind barriers
and affect the climate and rainfall and other factors which have a significant effect on
the growth of vegetation and the distribution of animals.
Slope is the characteristic feature of mountains. The steepness of a slope has a distinct
effect on the climate of the area, namely the incidence of solar radiations, rainfall, wind
velocity and the temperature of the region. Steepness of the slope decides the rapidity
with which water flows away from the surface and determines the characteristic of the
soil. A slope remains exposed to the sun and wind and this affects greatly the kind of
plants growing there.
MINERALS
Minerals are also called as biogenic materials and are essential for the proper growth of
organisms. So the type and distribution of plants and animals are determined by specific
distribution of minerals. Deficiency or absence or excess of minerals results in abnormal
growth or even death of organisms. To derive the required nutrients, organisms are
adapted differently.
Examples:
a) Plants found in nitrogen - deficient bog soil have either nitrogen fixing bacteria or
become insectivorous.
b) Snails occur in soils rich in calcium content to form their shell.
c) Halophytes and many marine animals have salt secreting glands.
d) Leguminous plants like pea, gram methi show symbiosis with nitrogen fixing bacteria
in their root nodules.
High concentration of minerals generally limits the distribution of animals.
Example: Dead sea is devoid of vegetation because of high salt content.
pH

pH is the relative acidity or alkalinity of medium. Every organism needs a specific pH
called optimum pH for its optimum growth. Some organisms prefer alkaline medium
(more than pH 7). For example prtozoans and molluscs, where as some organisms
prefer acidic (less than pH 7). For example euglena and other pyhtoflagellates flourish
in water having pH 2.8. Still other forms can survive in a wide range of pH. For example
tapeworm (pH range from 4 to 11).
FIRE
Fire has important effects on the environment. Fire removes plant cover, burns litter on
the soil surface and causes loss of nutrients. Due to forest fires a variety of animals
groups die.
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
RANGE OF TOLERANCE
Plants and animals show a range of tolerance to environmental factors. The factor,
which is present in least amount may become limiting. For example water availability
limits plant growth in deserts.
But, not only “too little” of something is a limiting factor, even “too much” may be the
limiting factor.
The response of an organism to a range or gradient of an environmental factor
The organisms are abundant in the central optimum range. In the zone of stress, only a
few organisms survive and in the zone of intolerance, organisms are absent.
If the organism has wide range of tolerance, it is usually distributed and if its tolerance
range is narrow it is restricted.
The gradual adjustment of an organism to slowly changing new environmental condition
is called as Acclimatisation.
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
BIOTIC FACTORS & TROPHIC LEVELS
• The term 'biotic factors" refers to all living organisms in an ecosystem.
• Depending on how the living organisms in an ecosystem obtain, store and utilize
release energy, they are
categorized into three main trophic levels,
(a) producers (b) consumers and (c) decomposers or detritivores.
Producers:
Life cannot exist without energy. The ultimate source of energy for the functioning of an
ecosystem is teh sun. They can starch by the process of photosynthesis utilizing radiant
energy, C02 water and minerals. The producers occupy the first trophic level in a food
chain. Certain bacteria such as sulphur bacteira obtain energy by breaking down
chemical substances. These are described as chemoautotrophs. The producers occupy
the first trophic level in an ecosystem are described as chemoautotrophs.The producers
occupy the first trophic level in an ecosystem. The plants and their products containing
stored energy form the source of energy for the animals, which directly feed on them,
(herbivores), the producers occupy the first tropic level in an ecosystem.
Consumers:
Animals feed on autotrophs or their products either directly or indirectly. They occupy
different trophic levels and accordingly ihey are divided into three types.
Primary consumers:
Feed on producers directly. These are also called herbivores. The primary consumers
constitute the second trophic level in an ecosystem. Ex: Protozoans, crustaceans,
molluscs etc. On land the primary consumers include animals such as cows, deer,
rabbits, grasshoppers, snails etc. In the aquatic environment the herbivores include
some protists, crustaceans, molluscs etc. The microscopic free-floating zooplankton
constitutes the primary consumers. The primary consumers from the second trophic
level in an ecosystem.
Secondary consumers:
• Feed on the primary consumers. They constitute the third trophic level. Ex.: Frogs,
dogs, foxes etc.Wolves of the terrestrial eco-system and fishes of the aquatic
ecosystem.
• Approximately 50 % of light energy that falls on the plants is absorbed. Of this 1% is
converted into chemical energy.
Tertiary consumers:
Feed on secondary consumers and also on primary consumers, these are also called
as 'Climax consumers'. Ex: Hawks, vultures, lions, tigers etc.
Decomposers:
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• When organisms die their bodies and the waste materials passed from the bodies of
living organisms form a source of energy and nutrients for other organisms.
• Decomposers are also called microconsumers, saprotrophs or osmotrophs etc. Eg:
Fungi and bacteria.
• Producers and consumers can not survive without decomposers, because
decomposers play an important
role in an ecosystem by breaking down complex molecules of dead organisms into
simple molecules. These are converted into nutrients which are available for the
producers to prepare food material.
• An Ecosystem has two functional aspects (a) Biogeochemical cycles and (b) Energy
flow.
• Recycling of the inorganic nutrients is brought about by the decomposers (Bacteria
and fungi) which breakdown the compiex molecules of deed organisms and waste
materials. The nutrients are utilized by producers to store energy. These activities form
the "Biogeochemical cycles".
Decomposion of organic matter includes 3 stages
i. Particulate detritus formation by saprophytes
ii. Conversion of detritus into humus by saprophytes and detrivores
iii. Slower mineralization of humus
Characaters of a biotic community
• The kinds of organisms present in biotic community are called - Species composition.
• A few species which are dominant in terms of number and biomass are referred to as Dominant species
• The species which greatly influence biotic community relative to their abundance in
biomass or number are
said to be - Keystone species
• Species like Mycorhizal sps absorb nutients from soil and organic residue and are
called Link species.
• Insects, as they are useful in pollination referred to as- Critical link species. The
transition zone between two
biotic communities is called - Ecotone
• Dominant species are - Pine trees in taiga and grass in grass lands
• Keystone species are - Fig trees in tropical forests (as they produce large number of
fruits )
• Ecosystem is seriously, influenced by - Removal of either keystone species (or)
dominant species Example of
ecotone is the zone between forest and grass land.
• The increase in the number of organisms and diversity of organisms in ecotone is
called Edge effect.
• The species in ecotone are called - Edge specie;
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
Interactions
• Lemna gibba dominates Spirodela polyrhiza and is called Competetive exclusion.
• When in a same medium Competitive exclusion is observed between aquatic aroids
called duckweed or Spirodela and Lemna (Acquatic aroids) Lemma gibba excludes Spiro dela polyrhiza
• Chemical inhibition of one species by another is called Allelopathy
• Different species interacting with one another and live together intimately and is called
– Symbiosis
• Association between two organisms which and metabolically dependent on each other
and both are benefited is called – Mutualism
• Association in which one gets benefitted and the other one is unaffected is called Commensalism
• Association in which one is living at the expense o the other is called - Parasitism
• In commensalism one is harmed and other is Uneffectuated
• Interaction in which one organism is killing the other for the food is called – Predation
• predation helps for the transfer of energy in a food chain. Population size of the prey is
limited by- predation.
• Important adaptations in animals to avoid predator are - camouflage, venomous
nature, spiniscence mimicry,
warning coloration etc.
• Two species resembling each other to escape from predators is called - Mimicry
• The type of protection in defenceless organism is to mimic.
• Mimicking other organism with defence is called - Batesian mimicry.
• The process in which the mimics share the same defence mechanism as model is Mullerian mimicry
ECOLOGICAL SUCESSION
• The process of occurance of gradual, orderly and predictable changes in the
composition of communities towards a climax type is called Ecological succession
• The succession which begins on an area which is not in habited by any biotic
community to establish a climax community is - Primary Succession
• The succession that begins in an area from which a community was removed to
establish a climax community is called Secondary Succession
• An inorgamic environment which get: predominated by autotrophs is called Autotrophic Succession
• Polluted areas with more decomposed matter get: dominated by heterotrophs is called
Heterotrophic Succession
• The first community that is established either in primary or secondary succession is
called Pioneer Community
• Climax community is established after the Stabilization of environment
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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• Climax community can not be replaced
• The ecological succession that starts on barren Rocks or in places where there is 10
extreme deficiency of water is said to be -Xerosere
• The ecological succession that starts in the habitat which is rich in water is called
Hydrosere
• The ecological succession in the habitat which i: moderate in water is called Mesosere
• In ecological succession finally - Climax stage, woodland stage is established
FOOD CHAINS
• The transfer of food-energy from plants to animals and then to other animals by
successive stages of feeding is called food chain.
• The cyclic interdependence of one trophic level over the others forms a food chain.
• In an ecosystem energy is transfered through a series of organisms, each feeding on
the preceding organisms and providing raw materials and energy for the next
organisms.
• Each stage of the food chain is known as trophic level.
• The first trophic level is occupied by the autotrophic organisms, so they are called
producers.
• The organisms of the second trophic level are called primary consumers or
herbivores. 20% - 30% of net primary production is consumed by the herbivores.
• The organisms of the third trophic level are called secondary consumers or primary
carnivores.
• The organisms of the fourth trophic level are called tertiary consumers or secondary
carnivores.
• The final carnivore of a food chain is not eaten by other animals, so it is known as
climax carnivore.
• The grazing food chains are linear and are usually with 4 to 5 trophic leves in the
chain.
• The grazing food chain starts from a green plant base, goes to grazing herbivores and
onto carnivores, (predator food chain and parasitic food chain).
• In predator food chain one animal captures and devours (eats) another animal.
• An animal that eats another animal is called a predator.
• The animal consumed by the predator is called prey.
• A predator that consumes members of its species is known as cannibalistic.
• An animal that eats dead animal is referred to as scavenger.
• The plants and animals of a grazing food chain are infected by parasites. The
parasites derive their energy from their hosts. Thus a parasitic food chain is formed
within a grazing food chain.
• The detritus food chain starts from dead organic matter and ends in inorganic
compounds.
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• The organic waste materials and the dead bodies of producers, consumers of a
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grazing food chain form detritus.
• The organisms which feed exclusively on the dead bodies of animals and plants and
organic waste materials are known as detrivores (algae, fungi, bacteria, insects worms,
nematodes, centipedes).
• Detritus ecosystem develops on organic debris, living producers may be absent,
sunlight is not directly essential.
• The cross-linking of many food chains in an ecosystem is called food web.
• Stability of the ecosystem is maintained by Food web.
• A direct linking between prey and predator without any branching is called Iota link
• A branching link in which a predator feeding on more than one type of organisms is
Lamda link
• A branching link in which one prey organism is predated by more than one predator is
Gamma Link
• The number, biomass and energy of organisms gradually decrease from producer
level to the consumer level. This can be represented in the form of a pyramid called
ecological pyramid
• Ecological pyramid is the graphic representation of the number, biomass and energy
of the successive trophic levels of an ecosystem.
• The concepts of ecological pyramid was first described by Charles Elton. Ecological
pyramids represent the trophic structure (feeding relationships) and trophic function
(efficiency of energy transfer through biotic components) of an ecosystem.
• Pyramid of numbers depicts the number of individual organisms at different trophic
levels of food chain.
• The total weight of living matter per unit area present in the ecosystem is called
biomass.
• Pyramid of biomass depicts the amount of biomass at different trophic levels of food
chain.
• Pyramid of energy depicts the amount of energy at different trophic levels of food
chain.
• Ecological pyramids are always upright, ie. the apex is pointed upwards.
• In some ecosystems the number and biomass of producers are less and those of
consumers are more. So the apex is directed dowards. This type of pyramid is called
inverted pyramid.
• Inverted pyramid of numbers is found in parasitic food chain. Inverted pyramid of
biomass is occur in pond and lake ecosystems.
• The pyramid of energy is always upright (never inverted).
Functional aspects of an ecosystem
• Energy that enters the ecosystem is- Light energy
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• Light energy is converted to chemical/potentia energy by the process Photosynthesis
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• Potential energy is converted to- Kinetic energy
• Biological systems get closed if there is no continuous entry of - Solar energy
• Regarding the energy flow, the earth is considered as an Open system
• Regarding the flow of elements in an ecosystem the earth is considered as Closed
system
• Cycling of elements occurs endlessly in an ecosystem between -Biotic & abiotic
factors
• The elements whose non-supply tend to limit biological activity are called nutrients
Biogeochemical Cycles:
• The pathway by which a chemical element or molecule moves through both biotic and
abiotic components of an ecosystem is called -Biogeochemical cycles
• All biogeochemical cycles are closed systems. The place where chemicals are held for
long period: of time at one place in biogeochemical cycle is called -Reservoir
• The place where chemicals are held for short periods are called Exchange pools
• Reservoirs & Exchange pools are generally Abiotic & Biotic factors respectively.
• The period of time a chemical is held in one place is called its Residence time is called
its -Residence time.
• Reservoir of gaseous cycles like Nitrogen, Carbon etc is –Atmosphere
• Reservoir of sedimentary cycles like sulphur, phosphorus etc are -Sedimentary rocks
Nitrogen cycle
• The very important element of proteins, DNA & RNA, Nucleic acids is - Nitrogen
• Nitrogen is fixed in the form of Nitrates
• Nitrogen is fixed in soil by Azatobacter Nitrogen is fixed in the roots of legumes by
Rhizobium
• In water cyanobacteria act as Nitrogen fixing bacteria
• Nitrogen is changed into ammonia by ammonifying bacteria Nitrosomonas (Nitrite
bacteria) present in the soil converts Aminonia into nitrite Nitrobactor (Nitrate bacteria)
converts Nitrites to nitrates Pseudomonas & Clostridium (denitrifying bacteria) convert
Nitrates into nitrogen.
Phosphorus Cycle
• Atmosphere does not play a role in the movement of phosphorus, because they are
present as solids On the earth
• Phosphate normally occurs in nature as part of a Phosphate ion
• Most of the phosphates are found in –Ocean
• Sediments or in rocks Phosphates are carried back to the oceans by weathering of
rocks and from soil as runoff Phosphorus occurs in nature as Orthophosphate (P04)3
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• Geological process which brings ocean sediment on to land are - Geological up
heavals
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Energy Flow
• The study of the laws of energy and its transformation is called- Energetics
• The standard international unit of energy is the joule
• Energy flow in an ecosystem is -Unidirectional
• The weight or quantity of organisms in an area at a given moment is called-Standing
crop
• The total amount of organic material produced by living organisms of a particular area
within a set period of time is called - Productivity
• The rate at which biomass is produced by organisms which convert inorganic
substrates into complex organic substrates is called -Primary productivity
• Organisms like bacteria convert chemical energy to biomass by —Chemosynthesis
• The total primary productivity is known as -Gross Primary productivity (GPP)
• Energy stoted in plant tissues is considered as Net Primary productivity
• Net primary production = Gross primary production- energy utilised for respiration-NPP
= GPP - R
• The rate at which consumers of an ecosystem convert the chemical energy of their
ingested food material into their own body substance (biomass) is called -Secondary
productivity
• The percentage of production of one trophic leve that is ingested by the next higher
trophic level is called Exploitation efficiency
• The percentage of energy ingested that is actuall) absorbed across the wall of gut is
called Assimilation efficiency
• Assimilation efficiency of herbivores is less than that of carnivores due to the presence
of relatively indigestible cellulose in their food material
Exploitation efficiency
food ingested / total food available for ingestion X 100
Assimilation efficiency
food digested / total food ingested x 100
• The total plant material ingested by herbivore - the materials lost as faces is called Gross secondary production (GSP)
• Energy stored in the tissues of consumers is - Ne secondary production (NSP)
• Percentage of energy lost in the transformation of absorbed solar energy to chemical
energy by producers is as high as 99%
• The efficiency of transfer of energy from one trophic level to the higher trophic level is 10%
• The rule that states that only 10% of net energy ii transferred to next higher trohic level
in an ecosystem is referred to as -10% rule (Lindermann's trophic efficiency rule)
LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA
• Percentage of net primary production that i^ converted to net secondary production in
herbivore: is called - Trophic efficiency of herbivores.
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