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Ecology And Environment

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Ecology and environment PDF Notes, Important Questions and Formulas

Ecology and environment

Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.


  1. According to the IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but a more conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million.

  2. More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects. The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals.

  3. Although India has only 2.4 per cent of the world's land area, its share of the global species diversity is an impressive 8.1 per cent. That is what makes India one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India. How many Living species are actually there waiting to be discovered and named? If we accept May's global estimates. Only 22 per cent of the total species have been recorded so far.

Scientific study of human population is called demography. Population is defined as the total number of individual of a species present in a particular area at a given time. The population have specific character different from the character of individual.

1. Character of population:

A. Population density (Population size)
It is measured as total number of individual present in unit area or unit volume. The size of a population for any species is not a static parameter. It keeps changing in time depending on various factor including food availability, predation pressure and reduced weather. For human population density is officially counted in first four month of first year of each decade is called census.

  1. For human population density is calculated as number of person living in per square km area.
  2. The tiger census in our national park and tiger reserves is often based on pug marks and fecal pellets.

B. Birth rate / Biotic potential / Fertility / Natality:
Birth rate is defined as total number of birth in a population with respect to total number of individual of the population in a year. Birth rate is represented as per capita birth rate

 begin mathsize 12px style Per space Capita space birth space rate left parenthesis straight b )= fraction numerator Total space birth over denominator Initial space population end fraction end style

Eg. If in a pond there are 20 lotus plant last year and through reproduction 8 new plant are added, then the birth rate during the year is calculated as:


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<h1>Error 500</h1>



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Birth rate varies from region to region

  • Developed country has lower birth rate.
  • Developing or poor country have higher birth rate than developed country
  • Higher fertility in developing world is partially explained by large number of hand needed to perform work.
  • Population evolve different strategy to maximise their reproductive fitness. Some organism breed only once in their life time like Pacific salmon fish, Bamboo etc. and some produces small sized offspring like Oyester, Pelagic fishes etc. maximise their fitness by producing large number of offspring. Some organism breed many times in their life and produces a small number of large sized offspring (Birds, Mammals).

Death rate/ Mortality:
Death rate is defined as total number of death in a populations with respect to total number of individual of the population in a year.
Death rate is represented as per capita death rate

 begin mathsize 12px style text d= end text fraction numerator Total space number space of space death space over denominator Initial space Population end fraction end style

Eg.: If 4 individuals in a laboratory population of 40 fruit fly died during week. The death rate is calculated


 begin mathsize 12px style table attributes columnalign left end attributes row cell straight d equals fraction numerator Total space number space of space death space over denominator Initial space Population end fraction end cell row cell     = 4 over 40 end cell end table end style

D=d=0.1 individual per fruitfly per week

Growth rate:

Intrinsic growth rate(r) = b-d

begin mathsize 12px style text Growth rate= end text ΔN over Δt end style

begin mathsize 12px style text    Percent growth rate= end text fraction numerator left parenthesis ΔN over Δt right parenthesis over denominator straight N subscript degree end fraction cross times 100 end style 

Note: Natality, Mortality, Immigration and Emigration are the basic process responsible for fluctuation in population size under normal conditions, Natality and Mortality are the most important factors influencing population


Size than other two factor i.e., Immigration and Emigration.

Age and Sex Structures:
The age structure of a given population refers to the proportion of individuals of different age. This is important aspect because many functional aspect of individuals are related to age. (Like Reproduction)

Age structure of a population can be depicted in the form of a pyramid diagram. Diagram is particularly important in understanding future growth.

Population has 3 age groups.

  1.  Pre-Reproductive individuals
  2.  Reproductive individuals
  3.  Post-Reproductive individuals

Representation of age pyramids for human population

  • A higher number of pre-reproductive individuals, moderate number of reproductive individuals and fewer post reproductive individuals will form young population it shows rapid growth.
  • Fewer number of pre reproductive individuals as compared to reproductive ones will make population aged. It shows negative growth.
  • An equal number of pre reproductive and post reproductive individuals will constitute a mature population or stable population.
  • Developed countries have a steeper pyramid which represent nearly a stable population.

Population Growth Models / Curve
There are two type of growth curve

  1. Exponential growth (Geometric growth curve or J-shaped curve):
    Any species growing exponentially under unlimited resource conditions can reach enormous population densities in a short time. If in a population of size ‘N”. the birth rates are represented as b and death rates as d, then the increase in N during a unit time period t begin mathsize 12px style text ( end text dN over dt right parenthesis end style will be



Definition – Total living factor (biotic) and total non-living factor (abiotic) of the environment present in a particular area is called ecosystem.
A.G.Tansley – The term "ecosystem" first of all coined by A.G. Tansley.
According to Tansley – Ecosystem is symbol of structure and function of nature.
E.P. Odum – Father of ecosystem ecology.
According to E.P. Odum – Ecosystem is the smallest structural and functional unit of nature or environment.
Karl Mobius – Used term biocoenosis for ecosystem


A.  Natural Ecosystem – 

  1. Terrestrial Ecosystem – e.g. forest, grassland, tree, desert ecosystem
  2. Aquatic ecosystem – Aquatic ecosystem is again of two type:

(i)    Lentic ecosystem à stagnant fresh water, lake, pond, swamp.
(ii)  Lotic – Running fresh water ecosystem e.g. - river.

 B.  Artificial Ecosystem Man made e.g. cropland, Gardens etc. 

On the basis of size types of ecosystem

  1. Mega ecosystem – Ocean/Sea
  2. Macroecosystem – Forest
  3. Microecosystem – Pond
  4. Nanoecosystem – Drop of water

Every ecosystem is composed of two components - BIOTIC COMPONENT
It involve all livings (plant, animal and microbes) of ecosystem. Biotic component are mainly of two type.

1.   Producers –
All the autotrophs of ecosystem are called producers. They prepare their own food. The green plants are the main producers. In the process of photosynthesis, producers absorb solar energy and convert it into chemical energy so producers are also called transducers or converters.

Energy enters into the ecosystem through the producers. The solar energy is the only ultimate source of energy in ecosystem. This energy is available for the remaining living organisms.

  • In aquatic ecosystem: Floating plants called phytoplankton are the major autotrophs.

2.   Consumer –

All the heterotrophy of the ecosystem are known as consumers. They directly (herbivores) or indirectly (Carnivores) depend on the producers for food.

Types of consumer

  1. Macroconsumers
  2. Microconsumers

i.    Macro consumers (Photographs or holozoic) – They digest their food inside the body of organism i.e. first ingestion then digestion.

Macro consumers are of following type

  1. Primary consumer – Such living organisms which obtain food directly from producers or plants are known as primary consumers. e. g. herbivores of ecosystem, cow, grazing cattle, Rabbit. These are also known as secondary producers
  2. Secondary consumers or primary carnivores – Animals which feed upon primary consumers and obtain food. Those carnivores which kill and eat the herbivores. e.g. Dog, cat, snake
  3. Top Consumers – Those animals which kill other animals and eat them, but they are not killed & eaten by other animal in the nature. e.g. Lion, man, hawk, peacock

ii.  Micro Consumers/Decomposers or Saprotrophs /osmotrophs –

Those living organisms which decompose the dead body of producers and consumers are known as decomposers or reducers or transformers or osmotrophs.

Functional aspects of ecosystem:

  1. Energy flow
  2. Nutrient cycling
  3. Productivity
  4. Decomposition

Energy flow – The storage, expenditure, transformation of energy is based on two basic law of thermodynamics

First law of thermodynamics: - Energy is neither created nor destroyed but only transformed from one state to another state.

Second law of thermodynamics (the law of entropy) - The transfer of food energy from one to another organism leads to loss of energy as heat due to metabolic activity.

Introduction to pollution
"Any undesirable change in physical, chemical or biological characteristic of air, water and land which is harmful to the man directly or indirectly through his animals, plants, industrial units or raw materials is called pollution".

Pollutants: - "Any material or act on the part of man, or nature which leads to pollution is called pollutants."


Nondegradable Pollutants– Many of such pollutants are usually not degraded or degraded partially in environment. Such as aluminium pecks, Mercury compounds, Iron, Compounds of phenols, Glass, D.D.T. benzene, BHC pesticides, etc.

  1. Such type of substances should be banned by law,
  2. Use their alternative substances.

Biodegradable Pollutants– If much of domestic sewage papers, woods, garbage, livestock wastes, etc. are easily degraded completely by microorganisms, it becomes useful. But if these materials enter the environment in such large quantities, that they cannot be degraded completely then addition of these materials causes pollution in environment.

Other Type of Pollution

  1. Natural pollution – Caused by natural sources like, CH4 from paddy fields and cattle, marsh, forest fire.
  2. Anthropogenic pollution – Caused by human activities.
  1. Negative pollution – Loss of soil productivity. e.g., Overgrazing, Soil erosion. Removal or absence of desirable substances at right place which results in loss of soil productivity.
  2. Positive pollution – Presence or addition of undesirable substances at wrong place which results in reduction of soil fertility e.g. more use of bio-fertilizer, Land filling by wastes.

Main Sources of Pollution:

  1. Point source pollution – Where the effluent discharge occur at a specific site. e.g. factory outlet and Municipal sewage
  2. Line source pollution – It is passed along a narrow belt, Roads e.g. Rods, Railway tracks
  3. Diffuse source pollution – It is over a large area e.g. sprayed fertilizer or pesticides through run off
  4. Area source pollution – Industrial estate & mining area.

Different Kinds of Pollution AIR POLLUTION

The air pollution is caused due to addition of unwanted substances or gases. The atmospheric pollution is mainly caused by the activities of man and concentrated to the inhabited and the industrial complexes in cities.

There are two main categories of air pollutants

  1.   Gases
  2. Particulates

The study of interaction or inter-relationship of organisms with their environment is called ecology.
Organism and environment are always interdependent, inter related or mutually reactive.


It is based on organism level

  1. Autecology – Study of the relation of a species with its environment is known as autecology
  2. Synecology – Study of the relation of the group of different species with their environment

 begin mathsize 12px style rightwards arrow from table attributes columnalign left end attributes row cell Size    rightwards arrow    Increase end cell row cell complexity    rightwards arrow Increase end cell end table to table attributes columnalign left end attributes row cell Organism rightwards arrow Population left parenthesis species right parenthesis rightwards arrow community end cell row cell rightwards arrow Ecosystem rightwards arrow Biome rightwards arrow Biosphere end cell end table of end style

An organism is the smallest unit of ecological hierarchy and basic unit of ecological study.

  • It may be small, large, unicellular or multicellular.
  • Fixed life span and organized life cycle (birth to death)

A group of Individuals (members) of same species living at one place (specific geographical area) constitute a population.

Definition - Species is a basic unit of classification, defined as the group of living organisms similar in structure, function and behaviour and produced by similar parents, have common gene pool, can inter breed under natural conditions and reproductively isolated from other group of organism.

Groups of organisms of different species that live in common area, which are interrelated and interdependent. It is a natural aggregation of plants and animals in the same environment.

Biotic Community = Animal community + Plant community + Microbial community

Characteristics of a community –
Species Diversity
There are different types of population (species) found in community, this is called species diversity.
It depends on size of the area, type of area, type of soil, altitude and climate.

B. Dominance
The highest number of organism of a species present in community, is called as the dominant species.
Whole community is known by the name of that particular dominant species. E.g. Prosopis community at Aravali hills, Pinus community at Himalaya

The different growth form (trees, shrubs, under shrubs, herbs) determines the structure of a plant community. Stratification is based on mode of arrangement of various growth forms.



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