Lecture #1: Introduction to Ecology

30 10 2009

Logical Quetions:

It is quite logical and necessary to ask the fundamental question… “What is ecology?” before starting to learn ecology… We can go on to ask 4 more sub-questions… such as –

  1. How do we define ecology?
  2. What do ecologists do?
  3. What are ecologists interested in?
  4. Where did ecology emerge from in the first place?

Please note that sub-questions #1 and #4 are related as ‘how ecology as a discipline has originated’ will determine ‘how it is being defined’…

Some background information:

Ecology (originally in German: Oekologie) can lay claim to be the oldest science.

First defined by Ernest Haeckel (1866) as – “the comprehensive science of the relationship of the organism to the environment.”

It was Burdon-Sanderson (1893) who discussed various sub-disciplines of science defined ecology as – “the science which concerns itself with the external relations of plants and animals to each other and to the past and present conditions of their existence.”

Ricklefs (1973) defined ecology to be – “the study of the natural environment, particularly the interrelationships between organism and their surroundings”.

However, the disturbing fact is that all the previously said definitions seem vague since they tend not to address neither the physiological nor the morphological aspects of plants/animals…

This made Andrewartha (1961) to add a new term into the definition – “INTERACTIONS”!!!

And, obviously… (as it is expected) – zoologists, botanists and other sectoral specialists deviated to form definitions for ecology as per the scope and needs of their respective disciplines…

The COMPREHENSIVE definition of/for ecology:

And, as per Townsend et al., (2000) the comprehensive definition of ecology should essentially focus on aspects that explain:

  1. Where the organisms are found?
  2. How many occur there?
  3. Why???

Thus, Townsend et al., (2000) define ecology as: “the scientific study of the distribution and abundance of organisms and the interactions that determine distribution and abundance.”

Moreover, it is to be noted that… There is applied and pure science – as such, the question is: “where does ecology fall into”?

Is it an applied science or a pure science?

Applied = problem solving, management perspective (highly practical and not so ‘bookish’ i.e. academically inclined)

Pure = quantifying, determining, truth seeking (tends to be sometimes of very less practical value)

There can be no definite answer to this… But we know un understand that ecology being concerned (or focusing entirely) on the natural environment, needs to take in facts:

  1. That the environment is complex,
  2. And, canNOT be understood in a singular (linear) perspective…
  3. There, are many unanswered questions re: environment
  4. Yet the need to understand and comprehend is IMPORTANT for our survival

As such, focused questions are necessary from the ecologists if they are trying to understand  and explain ecological phenomena.

Explaining about systems/phenomena/entities in a scientific manner:

Explanations can be proximate or ultimate.

Where, proximate explanations focus on ‘what is going on here and now’. And, ultimate explanations focus on providing discussions on what has happened, what is happening, and, what is bound to happen – using evidence that has been accumulated historically etc.

Furthermore, when trying to explain what is to happen – ecologists predict what will happen in the future…

All this is necessary for managing the environment in an optimal sustainable manner (i.e. to see whether control without exploitation is achieved).

How is it DONE in ecology?

When posed with the question: ‘how ecology is practiced’? We need to focus on –

  1. How understanding is achieved?
  2. How this understanding can help us predict, manage, and control the environment?

The fundamental points that need to be understood about doing (or practising) ecology (as a profession) are, that:

  1. Ecological phenomena occur at a variety of scales (time and spatial).
  2. Ecological evidence comes from a variety of different sources.
  3. Ecology relies on true scientific evidence and application of quantitative methods (essentially statistics).

What is essentially addressed by the discipline of ecology?

The discipline of ecology addresses environmental relationships (i.e. between organisms and the physical environment from those of individual organisms to factors influencing the entire biosphere).

These broad range of subjects can be organized and facilitated by arranging them as levels in a hierarchy of ecological organization…

As per biological components there are (traditionally) four levels in the ecological hierarchy of organization:  i.e. individuals –> populations –> communities –> ecosystems!

Moreover, with the present trends in visualizing the Earth as a singular living entity – one can add biosphere as the fifth and the highest biological (entit-al) level.


That, as per the most comprehensive definition – ecology focuses on the investigation of the interactions between the biotic and abiotic components of the world/Earth. As such, we should consider the non-living physical and chemical components of the Earth also as part and parcel of the hierarchy of ecological organization.

For example

|<————- Earth System Level ——————>|

Biosphere –> Region –> Landscape –> Ecosystem –> Community –> Interactions –> Population –> Individuals

Note that the study of “(interactions, populations and individuals)” = intra-community level investigations!!!

Some Definitions:

  • Environment:  this means everything in the surroundings of an organism that could possibly influence it.
  • Habitat:  a habitat is where an organism lives i.e. where it obtains its food and shelter, and where it reproduces.
  • Population:  the (total) number of individuals of a particular species in a defined habitat (or given area).
  • Community: a community is made up of all the plants and animals living in a habitat.
  • Ecosystem: the community of organisms in a habitat, plus the non-living part of the environment (air, water, soil, light etc.) make up an ecosystem.

Individuals of the same species = POPULATION,

POPULATION + Populations of other species = COMMUNITY,

COMMUNITY + non-living part of the environment = ECOSYSTEM!

For example, a population of carp forms part of the animal community  living in a habitat  called a lake. The communities in this habitat, together with their watery environment , make up a self-supporting ecosystem. Or, to put it in other words, an ecosystem can be regarded as a self-supporting community plus the physical features of its environment. The Earth’s surface containing living organisms (i.e. the biosphere) can be considered as one singular and vast ecosystem or a collection of many inter-twining ecosystems…

NATURAL and ARTIFICIAL ecosystems:

Natural ecosystems – [Many examples of these have already been discussed. They may be ponds, rivers, lakes, woods, grasslands, forests, peat bogs, or dune systems to name just a few. These are self-supporting (and self-regulating), needing only sunlight, air, water and mineral nutrients to survive. They usually contain a wide range of interdependent plants and animals and need no inputs from humans.]

Artificial ecosystems – [Ecologically these are not very exiting but are essential to the human survival for they constitute of the farms, gardens, plant nurseries, agro-forestry plots, parks and/or domestic gardens. For example, on arable lands plants of a single species are introduced and grown in dense stands specifically for their food or other commercial value to humans. In these systems, the manager attempts to abolish food chains and food webs that could be present in the natural environment – so as to conserve energy, and for making control easy. Unless carefully managed, these could do long-term harm to their own and other environments.]

The SCOPE of ecology:

Ecology is usually considered as a branch of biology, the general science that studies living organisms. Organisms can be studied at many different levels, from proteins and nucleic acids (in biochemistry and molecular biology), to cells (in cellular biology), to individuals (in botany, zoology, and other similar disciplines), and finally at the level of populations, communities, and ecosystems, to the biosphere as a whole; these latter strata are the primary subjects of ecological inquiry.

Ecology is a multidisciplinary science. Because of its focus on the higher levels of the organization of life on earth and on the interrelations between organisms and their environment, ecology draws on many other branches of science, especially geology and geography, meteorology, pedology, genetics, chemistry, and physics.

Thus, ecology is considered by some to be a holistic science, one that over-arches older disciplines such as biology which in this view become sub-disciplines contributing to ecological knowledge.

In support of viewing ecology as a subject in its own right as opposed to a sub-discipline of biology, Robert Ulanowicz stated that “The emerging picture of ecosystem behavior does not resemble the worldview imparted by an extrapolation of conceptual trends established in other sciences”. Agriculture, fisheries, forestry, medicine, and urban development are among human activities that would fall within Krebs’ (1972: 4) explanation of his definition of ecology: “where organisms are found, how many occur there, and why(?)”.

Ecological knowledge such as the quantification of biodiversity and population dynamics has provided a scientific basis for expressing the aims of environmentalism and evaluating its goals and policies. Additionally, a holistic view of nature is stressed (as necessary) in both ecology and environmentalism.

Deep Ecology and Ecosophy:

Deep ecology is a recent branch of ecological philosophy (ecosophy) that considers humankind an integral part of its environment. Deep ecology places greater value on non-human species, ecosystems and processes in nature than established environmental and green movements.

Deep ecology has led to a new system of environmental ethics. The core principle of deep ecology as originally developed is Arne Næss’s doctrine of biospheric egalitarianism — the claim that, like humanity, the living environment as a whole has the same right to live and flourish.

Deep ecology describes itself as “deep” because it persists in asking deeper questions concerning “why” and “how” and thus is concerned with the fundamental philosophical questions about the impacts of human life as one part of the ecosphere, rather than with a narrow view of ecology as a branch of biological science, and aims to avoid merely utilitarian environmentalism, which it argues is concerned with resource management of the environment for human purposes.


  1. The well-being and flourishing of human and nonhuman life on Earth have value in themselves (synonyms: intrinsic value, inherent value). These values are independent of the usefulness of the nonhuman world for human purposes.
  2. Richness and diversity of life forms contribute to the realization of these values and are also values in themselves.
  3. Humans have no right to reduce this richness and diversity except to satisfy vital human needs.
  4. The flourishing of human life and cultures is compatible with a substantial decrease of the human population. The flourishing of nonhuman life requires such a decrease.
  5. Present human interference with the nonhuman world is excessive, and the situation is rapidly worsening.
  6. Policies must therefore be changed. These policies affect basic economic, technological, and ideological structures. The resulting state of affairs will be deeply different from the present.
  7. The ideological change is mainly that of appreciating life quality (dwelling in situations of inherent value) rather than adhering to an increasingly higher standard of living. There will be a profound awareness of the difference between big and great.
  8. Those who subscribe to the foregoing points have an obligation directly or indirectly to try to implement the necessary changes.


  1. Please list the topics/sections that have been taken-up for discussion in Lecture #1..
  2. Write a mini-report discussing the various sub-disciplines that will come under ecology. Your report should also include diagrams, definitions, flowcharts etc. and should also be accompanied by a ‘reference list’. Plagiarism will not be tolerated! [This will be a mock-tutorial excercise, and is given to you as a means of polishing up your writing skills. This will be taken up for discussion on the 10th/11th of November 2009].


  1. What communities might be present in a woodland?
  2. Answer both parts comprehensively: a). What is the habitat of an earthworm?  and, b). What makes up the environment of an earthworm?
  3. Name some of the producers, consumers, and, decomposers that might be present in a grassland ecosystem?
  4. Plants make their food by photosynthesis, so in what ways can they be said to ‘compete for food’?

Disciplines in Ecology:

Ecology is a broad discipline comprising many sub-disciplines. A common, broad classification, moving from lowest to highest complexity, where complexity is defined as the number of entities and processes in the system under study, is:

  • Palaeoecology deals with organisms and their environment in the geological past.
  • Ecophysiology examines how the physiological functions of organisms influence the way they interact with the environment, both biotic and abiotic.
  • Behavioral ecology examines the roles of behavior in enabling an animal to adapt to its environment.
    Population ecology studies the dynamics of populations of a single species.
  • Community ecology (or synecology) focuses on the interactions between species within an ecological community.
  • Ecosystem ecology studies the flows of energy and matter through the biotic and abiotic components of ecosystems.
  • Pollution ecology deals with the movement of pollutants in the environment, environmental deterioration, and the maintenance of its cleanliness and ambient quality.
  • Systems ecology is an interdisciplinary field focusing on the study, development, and organization of ecological systems from a holistic perspective.
  • Landscape ecology examines processes and relationship across multiple ecosystems or very large geographic areas.
  • Evolutionary ecology studies ecology in a way that explicitly considers the evolutionary histories of species and their interactions.
  • Political ecology connects politics and economy to problems of environmental control and ecological change.
  • Resource ecology deals with renewable and non-renewable resources and their judicious management.
  • Conservation ecology deals with the application of ecological principles to the proper management of resources leading to the sustainable management of the environment/biosphere.

Please note that, another recent classification by Dash (1993) characterizes that ecology can be broadly categorized into two spheres, namely organism-based studies and Habitat based studies





2 responses

30 10 2009

Hi mano
You work is really appreciated one. It is good to introduce the online learning system..
Actually, you will be informed in near future regarding the online learning system.. under the LMS which is to be practiced in vavuniya campus by our dept . phy sci. Really, we need your help in this task.
Regarding the topics you have disscussed in this site.. Is over all very useful and you have explained very complex idea in a simple way as such reader to understand.. Keep it up..

31 10 2009

Hi Krish,

Many thanks. Looking forward for the LMS to be launched in the faculty… that would be very useful, as it will provide with more facilities to upload, diagrams and animations – to make the lecture notes very student-friendly. One again many thanks – and, thank you very much for agreeing to be my mentor for the CTHE program.

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