Terrestrial and aquatic ecosystems, structure and function of ecosystems, interactions

1. Environmental Studies
&
Disaster Management
Somanath Sarvade
Assistant Professor (Agroforestry)
College of Agriculture Balaghat
E-mail: somanath553@jnkvv.org
Jawaharlal Nehru Krishi Vishva Vidyalaya,
Jabalpur

2. Ecology is the scientific study of the interactions between
organisms and their environment.
• It is the science that seeks to describe and explain the
relationship between living organisms and their environment.
• Ecology is describing the
relationships between living
organisms and their environment.
• Ecology comes from the Greek
words Oîkos= House -λογία, -logia=
Study of Life
• Study of the “house/environment” in
which we live.

3. Ernst Haeckel, a German zoologist coined
the term Ecology in 1866.
Danish botanist, Eugenius Warming
elaborate the idea of Ecology.
Ramdeo Misra is known as the Father of
ecology in India.

4. For the study of ecology it is often convenient to divide the
environment into four broad categories.
1. Terrestrial environment - The terrestrial environment is based on land
and consists of biomes, such as grasslands, one of several kinds of forests,
savannas, or deserts.
2. Freshwater environment - The freshwater environment can be further
subdivided between standing-water habitats (lakes, reservoirs) and running-
water habitats (streams, rivers).
3. Oceanic marine environment - The oceanic marine environment is
characterized by saltwater and may be divided broadly into the shallow waters
of the continental shelf composing the neritic zone
4. Oceanic region - The deeper waters of the ocean that constitute the
oceanic region.

5. Two major subdivisions of modern ecology are
• Ecosystem ecology - which views ecosystems as large units,
and
• Population ecology - which attempts to explain ecosystem
behavior from the properties of individual units.

6. Levels of Organization
• Species (smallest)
• Populations
• Communities
• Ecosystems
• Biomes
• The Biosphere (largest)

7. ECOSYSTEM
• The term ecosystem was coined in 1935 by the Oxford ecologist A.G.
Tensely to encompass the interactions among biotic and abiotic
components of the environment at a given site.
• Ecosystem was defined in its presently accepted form by Eugene Odum,
“an unit that includes all the organisms, i.e., the community in a given area
interacting with the physical environment so that a flow of energy leads to
clearly defined trophic structure, biotic diversity and material cycles, i.e.,
exchange of materials between living and non-living, within the system”.

8. • However, the term ecosystem is most preferred, where eco refers the
environment, and system implies an interacting and interdependent
complex.
• The organisms of any community besides interacting among
themselves always have functional relationship with the environment.
• This structural and functional system of communities and environment
is called ecological system or ecosystem.
• It is the basic functional unit in ecology, since it includes both biotic
and abiotic environment, influencing each other for maintenance of
life.

9. • An ecosystem may, in its simplest form, be defined as a self-sustained
community of plants and animals existing in its own environment.
• An ecosystem may be as small as a drop of pond water (micro-
ecosystem) or as large as ocean.
• It can be of temporary nature, e.g., a fresh pool or a field of cultivated
crops, or permanent e.g., a forest or an ocean.
• A balanced aquarium may be thought of as
an artificially established self-sustained
ecosystem.

10. Characteristics of Ecosystem
According to Smith (1966), the ecosystem has the
following general characteristics:
• It is a major structural and functional unit of ecology.
• Its structure is related to its species diversity; the
more complex ecosystems have high species diversity
and vice versa.
• Its function is related to energy flow and material
cycling through and within the system.
• The relative amount of energy needed to maintain an
ecosystem depends on its structure.
• The more complex the structure, the lesser the energy
it needs to maintain itself.

11. • It matures by passing from fewer complexes to more complex states.
• Early stages of each succession have an excess of potential energy and a
relatively high energy flow per unit biomass. Later (mature) stages have less
energy accumulation and its flow through more diverse components.
• Both the environment and the energy fixation in any given ecosystem are
limited and cannot be exceeded without causing serious undesirable effects.
• Alternations in the environment represent selective pressures upon the
population to which it must adjust.
• Organisms which are unable to adjust to the changed environment must
necessarily vanish.

12. Kinds of Ecosystems
1. Natural ecosystems
These operate under natural conditions without any major interference by man.
On the basis of the type of habitat these may be further divided as:
a) Terrestrial
Forest, grassland, desert, etc.
b) Aquatic
Fresh water - which may be lotic (e.g., running water as spring, stream or
rivers) or lentic (e.g., standing water as lake, pond, pools, puddles, ditch,
swamp, etc.).
Marine - such deep bodies as ocean or shallow ones as seas or an estuary, etc.

13. Artificial (Man - engineered) ecosystems
These are maintained artificially by man whereby addition of energy and
planned manipulation, natural balance is disturbed regularly, e.g. cropland
ecosystem.
In addition to above types, some other types such as spacecraft and micro-
ecosystem have also been recognized.

16. Structure or components of an Ecosystem
• The term structure refers to the various
components.
• So the structure of an ecosystem explains
the relationship between the abiotic (non –
living) and the biotic (living) components.
An ecosystem has two major components
•Biotic (living) components
•Abiotic (non living) components

18. Biotic components
The living organisms (or) living members in an ecosystem
collectively form its community called biotic components (or)
biotic community.
Examples
• Plants (producers),
• Animals (consumers),
• Transformers
• Microorganisms (decomposers).

19. Members of components of an ecosystem (or)
Classification biotic components
The members of biotic components of an ecosystem are
grouped in to three based on how they get food.
• Producer (plants)
• Consumer (Animals)
• Transformers
• Decomposers (Micro-organisms)

20. 1.Procedures (Autotrophs)
Procedures synthesize their food themselves through
photosynthesis
Example : All green plants, trees.
Photosynthesis
The green pigments called chlorophyll, present in the leaves of
plants, converts CO2 and H2O in the presence of sunlight into
carbohydrates.
6CO2 + 12H2O ----> C6H12O6 + 6O2+6H2O
This process is called photosynthesis

22. Consumers (heterotrophs)
Examples
Plant eating species Insects, rabbit, goat, deer, cow, etc.,
Classification of consumers
Consumers are further classified as
(i) Primary consumers (Herbivores) (Plant eaters)
Primary consumers are also called herbivores, they directly depend on the
plants for their food. So they are called plant eaters.
Examples :
Insects, rat, goat, deer, cow, horse, etc.,

23. (ii) Secondary consumers (primary
carnivores) (meat eater)
Secondary consumers are primary carnivores,
they feed on primary consumers. They directly
depend on the herbivores for their food.
Example: Frog, cat, snakes, foxes, etc.,
Omnivores (Biophages ) - eat both
vegetables and flesh (cockroaches, fox,
humans).
(iii) Tertiary consumers (Secondary
carnivores) (Meat-eaters) Tertiary
consumers are secondary carnivores, they
feed on secondary consumers. They depend
on the primary carnivores for their food.
Examples: Tigers, lions, etc.,

24. TRANSFORMERS
• Transformers are certain types of bacteria.
• They attack on materials excreted by other living organisms (even
dead plants and animals).
• They transform the above into either organic or inorganic
substances.
• These substances are suitable for the nutrition of green plants.
• Transformers help in recycling the nutrients which came as waste
already.

25. DECOMPOSERS
• They are also called as micro-consumers.
• They depend on dead organic matter for their food.
• They are chiefly micro organisms like bacteria and fungi.
• They break the complex organic matter found in plant and animal bodies,
and release simple substances.
• These substances will be used by autotrophs once again.
• Some invertebrate animals like protozoa and earthworms use these dead
organic matter for their food.
• They are called as secondary decomposers.

26. • Scavengers consume the soft tissues of dead animals.
Examples of scavengers include vultures, raccoons, and
blowflies.
• Detritivores consume detritus-the dead leaves, animal feces,
and other organic debris that collects on the soil or at the
bottom of a body of water. On land, detritivores include
earthworms, millipedes, and dung beetles (see Figure 9.17). In
water, detritivores include ‘‘bottom feeders” such as sea
cucumbers and catfish.
• Saprotrophs are the final step in decomposition. They feed on
any remaining organic matter that is left after other
decomposers do their work. Saprotrophs include fungi and
single-celled protozoa. Fungi are the only organisms that can
decompose wood.

27. Abiotic components
Structurally abiotic components include –
• Climate regime: Precipitation, temperature, light, and other physical
factors.
• Inorganic substances: Elements such as C, N, H, O, P, S, etc., involved
in material cycles.
• Organic Compounds: Carbohydrates, proteins, lipids and humic
substances that link the abiotic components with the biotic components
(for details see any elementary book on ecology).

28. • The minerals and atmospheric gases keep on cycling.
• They enter into biotic systems and after the death and decay of organisms
return to the soil and atmosphere.
• This is known as biogeochemical cycle.
• This circulation of materials involves trapping of the solar energy by the
green plants which are ultimately lost by the organisms in several ways.
• The amount of abiotic materials present in an ecosystem is called standing
stage.

29. Functions
• The function of the ecosystem is to allow flow of energy and cycling of
materials which ensures stability of the system and continuity of life.
• These two ecological processes including interaction between the abiotic
environment and the communities.
• For the sake of convenience, the ecosystem dynamics may be analyzed in terms
of the following: (i) food chains, (ii) food pyramids, (iii) energy flow, (iv)
nutrient cycles, (v) development and evolution of ecosystem, and (vi)
homeostasis and stability of ecosystem.

30. There are four primary groups of ecosystem functions
(1) regulatory functions,
(2) habitat functions,
(3) production functions and
(4) information functions.

31. (1) Regulatory functions: this group of
functions relates to the capacity of natural
and semi-natural ecosystems to regulate
essential ecological processes and life
support systems through bio-geochemical
cycles and other biospheric processes.
• In addition to maintaining the ecosystem
(and biosphere health), these regulatory
functions provide many services that have
direct and indirect benefits to humans (i.e.,
clean air, water and soil, and biological
control services).

32. (2) Habitat functions: natural ecosystems
provide refuge and a reproduction habitat
to wild plants and animals and thereby
contribute to the (in situ) conservation of
biological and genetic diversity and the
evolutionary process.

33. (3) Production functions: Photosynthesis and
nutrient uptake by autotrophs converts energy,
carbon dioxide, water and nutrients into a wide
variety of carbohydrate structures which are
then used by secondary producers to create an
even larger variety of living biomass. This broad
diversity in carbohydrate structures provides
many ecosystem goods for human
consumption, ranging from food and raw
materials to energy resources and genetic
material.

34. (4) Information functions: Since most of
human evolution took place within the
context of an undomesticated habitat,
natural ecosystems contribute to the
maintenance of human health by providing
opportunities for reflection, spiritual
enrichment, cognitive development,
recreation and aesthetic experience.

35. Productivity in the Environment
The productivity of an ecosystem is the rate at which solar energy is
fixed by the vegetation of the ecosystem; it is further classified into
primary productivity, secondary productivity and net productivity.
• Primary productivity refers to the rate at which radiant energy is
stored by photosynthetic and chemosynthetic activity of
producers; it is further distinguished as gross primary productivity
(GPP) and net primary productivity (NPP).
• It is expressed in terms of weight (g/m2/yr) or energy (kcal/m2).
• Secondary productivity refers to the rates of energy storage at
consumer levels.

36. Interactions among living organisms are grouped into two major
groups viz.,
I. Positive interactions
Here the populations help one another, the interaction being either one way or
reciprocal. These include (i) Commensalism, (ii) Proto co-operation and (iii)
mutualism.
1. Commensalism
In this one species derives the benefits while the other is unaffected.
Eg. (i) Cellulolytic fungi produce a number of organic acids from cellulose
which serve as carbon sources for non-cellulolytic bacteria and fungi.
(ii) Growth factors are synthesized by certain microorganisms and their
excretion permits the proliferation of nutritionally complex soil inhabitants.

37. 2. Proto-cooperation
It is also called as non-obligatory mutualism. It is an association
of mutual benefit to the two species but without the co-operation
being obligatory for their existence or for their performance of
reactions.
Eg. N2 can be fixed by Azotobacter with cellulose as energy
source provided that a cellulose decomposer is present to convert
the cellulose to simple sugars or organic acids.

38. 3. Mutualism
Mutually beneficial interspecific interactions are more common among
organisms. Here both the species derive benefit. In such association
there occurs a close and often permanent and obligatory contact more
or less essential for survival of each.
Eg. (i) Pollination by animals. Bees, moths, butterflies etc. derive food
from hectar, or other plant product and in turn bring about pollination.
(ii) Symbiotic nitrogen fixation:
Legume - Rhizobium symbiosis. Bacteria obtain food from legume and
in turn fix gaseous nitrogen, making it available to plant.

39. II. Negative interactions
Member of one population may eat members of the other population,
compete for foods, excrete harmful wastes or otherwise interfere with the
other population. It includes (i) Competition, (ii) Predation, (iii) Parasitism
and (iv) antibiosis.
(i) Competition
It is a condition in which there is a suppression of one organism as the two
species struggle for limiting quantities of nutrients O2 space or other
requirements.
Eg. Competition between Fusarium oxysporum and Agrobacterium
radiobacter.

40. (ii) Predation
A predator is free living which catches and kills another species for
food. Most of the predatory organisms are animals but there are
some plants (carnivorous) also, especially fungi, which feed upon
other animals.
Eg. (i) Grazing and browsing by animals on plants.
(ii) Carnivorous plants such as Nepenthes, Darligtoria, Drosera
etc. consume insects and other small animals for food.
(iii) Protozoans feeding on bacteria.

41. (iii.) Parasitism
A parasite is the organism living on or in the body of another
organisms and deriving its food more or less permanently from its
tissues. A typical parasite lives in its host without killing it, whereas
the predator kills its upon which it feeds.
Eg. Species of Cuscuta (total stem parasite) grow on other plants on
which they depend for nourishment.
Parasitism may occur even with in the species. Hyper parasites which
are chiefly fungi growing parasitically on other parasites, (ie) Parasite
on a parasite.
Eg. Cicinnobolus cesatii is found as hyper parasite on a number of
powdery mildew fungi.

42. (iv) Antibiosis
The phenomenon of the production
of antibiotic is called as antibiosis.
Antibiotic is an organic substance
produced by one organism which in
low concentration inhibits the growth
of other organism.
Eg. Streptomycin - S. griseus,
Penicillin - P. notatum, Trichoderma
harzianum inhibits the growth of
Rhizoctonia sp.

44. Thank You