Ecology And Environment, All Concepts and Important MCQs

This section is about Ecology and environment. In this section, you will read about various important concepts like Ecology, levels of ecological organization, ecological succession, ecological pyramids etc. A the end of this section, you will also get to solve some important MCQs on the topic to check and enhance your level of preparation for competitive exams.

What Is Ecology?

The word ecology is derived from the Greek words “Oikos” meaning Home/habitation, and “logos” means to study. So ecology is the study of the habitation of organisms.

This term was coined by Ernest Haeckel in 1869, and it deals with scientific study of the interactions between organisms and their organic and inorganic environment.

Even though this term was coined by Ernest Haeckel, but It is the German geographer and explorer Alexander Von Humboldt, who is considered as the father of ecology. Ramdeo Misra is considered as the father of Indian Ecology.

Ecology explains the following:

  1. Life processes and adaptations.
  2. Distribution and abundance of organisms.
  3. Transfer of matter and energy between living communities.
  4. Development of ecosystems etc.

If ecology is studied with main focus on animals, it is called animal ecology, and if it is studied with main focus on plants, then it is called plant ecology. If both are studied with equal focus, it is called bio ecology

Synecology is the study of communities taken together and the study of species is called autoecology.

Levels of Ecological Organisation | Ecological hierarchy

Hierarchical organization of different groups of organisms and their physical environment is called ecological hierarchical.there are mainly six levels of organizations and they are as follows:

  1. Individual/organism: it is the smallest and basic unit of ecological hierarchy . An organism may be unicellular or multicellular in nature.
  2. Population: When a group of individuals of same species live in a given area, they constitute a population. It is a group of interacting and freely inter breeding organisms. The growth of population is influenced by its interactions with its environment.
  3. Biological Community: An assemblage of populations is known as community. These populations interact and affect each other’s distribution and abundance. Alternately, community can be defined as the set of populations of different kinds of organisms living together and sharing the same habitat.
  4. Ecosystem: The smallest unit that can sustain life in isolation from all except atmospheric surroundings is called an ecosystem. It comprises of a group of organisms and abiotic components which exchange matter and energy with each other.
  5. Biome: These are the large scale areas of similar vegetation and climate. It is a regional unit with characteristic vegetation zones, fauna and flora.
  6. Biosphere: It is the biologically inhabited part of earth, where atmosphere, hydrosphere and lithosphere interact with each other to support life.


A zone of junction between two or more diverse ecosystems is known as ecotone. For e.g.,The mangrove forests acts as an ecotone between marine and terrestrial ecosystems.

Features of ecotone

The features of an ecotone are as under:

  1. An ecotone may be very narrow or very wide. It has the conditions that represent a mix of the two adjacent ecosystems. Hence, it is a zone of tension.
  2. It is linear as it shows the increase in species composition of one incoming community and a simultaneous decrease in species of other outgoing adjoining community.
  3. It may contain some organisms that are entirely different from the adjoining communities.
  4. It has an edge effect. Edge effect means that density of species in this zone is much greater than either of the adjoining communities.

Ecological Niche

A description of all the biological, physical and chemical factors that a species needs to survive, stay healthy and reproduce, is known as Ecological Niche.

It defines the functional role an organism plays in a community. It is like the “profession” of an organism.

No two species have exact identical ecological niches. This is because if two species occupy the same niche, they will compete with one another untill one is displaced. Niche plays an important role in the conservation of organisms.

Ecological Succession

Communities are dynamic in nature and change with time. The communities living in a specific area get replaced or changed into another with the passage of time, and this process is called ecological succession.

In ecological succession, both biotic as well as abiotic factors play their part.

Ecological Succession is of two types. They are:

1. Primary Ecological Succession

When a community of populations occupies a totally bare or unoccupied area, it is called primary succession.

It is the succession, in which a community does not replace any other community, rather it is the first community to occupy any area. For example, when a community occupies a bare rock, or newly formed deltas, it as a process is called primary succession. Such a community is called pioneer community and the species of organisms in such community are known as pioneer species.

The pioneer community gets replaced by another community after some time, which itself will get replaced by another community and the process continues untill the most stable community arrives. Such a stable community is called Climax Community.

Primary succession is a relatively slow process, as the substrate lacks all kinds of nutrients that are required to support life. In addition, it is not seen so commonly, as there are hardly few places on earth that are not already occupied by communities of organisms.

2. Secondary Ecological Succession

Secondary succession is the most common succession that occurs in areas, which were earlier, inhabited but had been subsequently destroyed or removed. This succession is fast, as the substrate has the required nutrients as well as seeds and other dormant stages of life.

The stages of succession from pioneer community to the climax community are called Seral Stages.

Examples Of Ecological Succession

1. Succession On A Bare Rock | Xerarch

When ecological succession occurs on a bare rock or any other terrestrial area with almost zero moisture and nutrients, it is called Xerarch.

The species that invade the area first are Lichens and Mosses. They cause weathering of rocks and form a mat over them. This mat then supports germination of seeds and growth of small plants and shrubs.

These small plants and shrubs slowly decay and in this way the substrate gets enriched with nutrients.

With the course of time, a climax community arrives and it is comprised of tall trees.

2. Succession In Aquatic Environment | Hydrarch

When ecologial succession occurs in an aquatic environment, it is called hydrarch.

The process starts with the arrival of the drifters (phytoplanktons and zooplanktons) in a water body.

They are followed by submerged aquatic plants having their roots in the mud below. these plants decompose and lead to siltation and enrichment of water with nutrients. Eventually the rooted plants with aerial leaves colonise the pond.

Finally, the pond starts getting shallower and gradually turns into a terrestrial habitat.

Ecological Pyramids

Ecological Pyramids are a graphical representation of trophic structures on parametres like number of organisms, dry weight (that is biomass), and rate of energy flow. This concept was put forward by Elton in 1927.

Pyramid Of Individuals

Pyramid of individuals is a graphic representation of number of individual organisms in various trophic levels. Generally, the number of individual organisms decreases with increasing trophic levels, but in smaller ecosystems, the number of individual organisms decreases with increasing trophic levels.

It does not take into account the size of the organisms, rather it just takes number of organisms into account.

It can either be inverted or upright.

Pyramid Of Biomass

Pyramid of Biomass is a graphic representation of total Biomass of organisms in various trophic levels. Instead of numbers, it takes into account the total weight of the individuals at each level.

Biomass is the total dry weight of all individuals at a given time.

It can either be inverted or upright. Generally, it is upright as biomass decreases with increasing trophic levels, but in case of aquatic ecosystems, the bio mass increases with increasing trophic level. So, in case of aquatic ecosystems, it is generally inverted.

Pyramid Of Energy

Pyramid of Energy is a graphic representation of total Energy in various trophic levels. It is always upright. It can never be inverted, as energy transfer is unidirectional and there is a loss of 10% of energy from one trophic level to another.

Now That You Have revised the topic, It is time to solve these Best MCQs On Ecology and Environment.

Best Quiz On Ecology

Which among the following is not correct about ecology?

  1. Ecology is the study of the interactions between biotic and abiotic aspects of the environment.
  2. Ecology is a discipline that is independent from natural selection and evolutionary history.
  3. Ecologists may study population and communities of organisms.
  4. Ecology spans increasingly comprehensive levels of organisation, from individuals to ecosystem.

Ecology is a discipline that is independent from natural selection and evolutionary history.

Who is the father of Ecology?

  1. Alexander Von Humboldt
  2. Ernest Haeckel
  3. Ramdeo Misra
  4. Robert Hooke

Alexander Von Humboldt.

Ecological footprint is a method of gauging the: (KAS 2021)

  1. Biodiversity of a region
  2. Human dependence on natural resources
  3.  Volume of human migration
  4. Amount of carbon dioxide emitted

Human dependence on natural resources

Who is considered as the father of Indian Ecology?

  1. Ramdeo Misra
  2. Dr Salim Ali
  3. Raman Sukumar
  4. Jadav Payeng

Ramdeo Misra

Ecological Succession is typified by;

  1. Forest naturally changing into a grassland with time.
  2. Grassland changing naturally into a forest with time.
  3. Bare ground remaining bare after clearance of vegetation.
  4. Animals growing in size with time.

Grassland changing naturally into a forest with time.

The five levels of organisation in the environment, from first to fifth level are:

  1. organisms, population, biosphere, ecosystem, community
  2. organisms, population, ecosystem, community, biosphere
  3. organisms, population, ecosystem, biosphere, community
  4. organism, population, community, ecosystem, biosphere

organism, population, community, ecosystem, biosphere

Which among the following is true?

  1. Succession starts from complex to simple living organisms.
  2. the succession that occurs on denuded forest land is an example of primary succession.
  3. The succession that occurs on a bare rock is called xerarch.
  4. secondary succession is less common than the primary succession.

The succession that occurs on a bare rock is called xerarch.

Which of the following ecological pyramids can never be inverted?

  1. Pyramid of biomass
  2. Pyramid of individuals
  3. pyramid of energy
  4. none

pyramid of energy

Who gave the concept of ecological pyramids?

  1. Ernest Haeckel
  2. Alexandar Von Humboldt
  3. Elton
  4. Ramdeo Misra


Match the following: (KAS 2021)

(1) Auteecology(a) Study of life form and environment of post ages
(2) Synecology(b) Study of individual species in relation to its environment
(3) Palaeo ecology(c) Study of plant communities in relation to environment
(4) Genecology(d) Study of ecology in relation to genetics
  1. 1-b, 2-c, 3-a, 4-d
  2. 1-c, 2-b, 3-a, 4-d
  3. 1-d, 2-c, 3-a, 4-b
  4. 1-b, 2-a, 3-c, 4-d

1-b, 2-c, 3-a, 4-d . Remember Auto means Self single, Syn means together and Palaeo means ancient

Which one is not the characteristic of primary ecological succession?

  1. It occurs on such areas which were hitherto inhabited.
  2. It is very commonly found.
  3. It is a very slow process.
  4. none

It is very commonly found.

Who coined the term “Ecology”?

  1. Ernest Haeckel
  2. Alexander Von Humboldt
  3. Elton
  4. Sir Rthur Tansley

Ernest Haeckel

The ecological succession that occurs in terrestrial area with low moisture and nutrients is called:

  1. Hydrarch
  2. Xerach
  3. Orarch
  4. Euarch


In an ecosystem, energy flow is:

  1. Unidirectional
  2. Bidirectional
  3. Ambidirectional
  4. Multidirectional


Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of; (UPSC)

  1. algae and bacteria
  2. algae and fungi
  3. bacteria and fungi
  4. fungi and mosses

algae and fungi

With reference to food chains in ecosystems, consider the following statements: (UPSC)

  1. A food chain illustrates the order in which a chain of organisms feed upon each other.
  2. Food chains are found within the populations of a species.
  3. A food chain illustrates the numbers of each organism which are eaten by others.

Which of the statements given above is / are correct?

  1. 1 only
  2. 1 and 2 only
  3. 1, 2 and 3
  4. None

1 only

Which one of the following terms describes not only the physical space occupied by an organism, but also its functional role in the community of organisms? (UPSC)

  1. Ecotone
  2. Ecological niche
  3. Habitat
  4. Home range

Ecological niche

With reference to the food chains in ecosystems, which of the following kinds of organism is / are known as decomposer organism/organisms? (UPSC)

  1. Virus
  2. Fungi
  3. Bacteria

Select the correct answer using the codes given below.

  1. 1 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3    

2 and 3 only

  1. Chipko Movement
  2. Narmada Bachao Andolan
  3. Rio+20 conference
  4. Conference of parties 21

Chipko Movement

Homeostasis means: (KAS 2022)

  1. A tendency of an ecosystem to resist change and to remain in a state of equilibrium.
  2. A property of an ecosystem to withstand all kinds of environmental changes.
  3. A characteristic of an ecosystem to convert into changes of pollution
  4. An ecosystem never respond to environmental change.

A tendency of an ecosystem to resist change and to remain in a state of equilibrium

Consider the following statements regarding biome;

  1. Two biomes can never be alike.
  2. A biome is not an ecosystem.
  3. Boundaries between two biomes are always sharply defined.

Which among the following option/s is/are correct?

  1. 1 and 3 only
  2. 2 and 3 only
  3. only 2
  4. 1 and 2 only

1 and 2 only

In an ecosystem, zooplankton is an example of:

  1. Producers
  2. Autotrophs
  3. Plant community
  4. Hetereotrophs


Which of the ecological pyramids is always upright?

  1. Pyramid of energy
  2. pyramid of biomass
  3. pyramid of individuals
  4. none of the above

Pyramid of energy

Environment Protection Act was passed in:

  1. 1982
  2. 1986
  3. 1992
  4. 1996


The largest ecosystem of earth is:

  1. Biosphere
  2. Lithosphere
  3. Hydrosphere
  4. Biome


Which of the following is formed from the association of Algae and Fungi?

  1. Epiphyte
  2. Mycorrhiza
  3. Mosses
  4. Lichens


An example of abiotic component of environments is:

  1. Vegetation
  2. Animals
  3. Air
  4. All of the above


Also Check: Our environment complete notes.

Also check: Green House Effect MCQs

These were some best MCQs on Ecology and Environment. We are sure that these Best MCQs on Ecology and Environment will be very useful for you and hope that you will share them with your friends and other aspirants.

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