Ecological succession and Ecological pyramids. ENVIRONMENTAL STUDIES

1. Ecological Succession & Ecological Pyramids
Ecological Succession
•Introduction
•Definition
•Types
•StagesProcess of succession
Ecological Pyramids
•Introduction
•Definition
•Types

2. Ecological Succession
Introduction:
Every place in the world did not evolve suddenly, it took a long
time and process to look like as it is today.
Ecological succession is the process of change in
the species structure of an ecological community over time.
The time scale can be decades (for example, after a wildfire),
or even millions of years after a mass extinction.
In 19th century, the French naturalist Adolphe D. Malle was the
first to make use of the word succession concerning the
vegetation development after forest clear-cutting.
Definition:
• Ecological Succession is the gradual process by which
ecosystems change and develop over time.
• In a place, the changes and development of biotic and abiotic
components is called as Ecological Succession.

3. Types:
Ecological Succession can be categorized as,
According to the formation on different types of areas
1. Hydrach or Hydrosere
2. Mesarch
3. Xerach or Xerosere: Starting in dry area or areas
without adequate moisture. Xerach has following
types,-
• Lithosere:
• Psammosere:
• Halosere:
According to the causes of occurrence
1. Primary Succession
2. Secondary Succession

4. According to the formation on different types of areas
1. Hydrach or Hydrosere: Starting in watery areas like
pond, swamp etc.
2. Mesarch or Mesosere: Starting in areas with
adequate moisture.
3. Xerach or Xerosere: Starting in dry area or areas
without adequate moisture. Xerach has following
types,-
• Lithosere: Starting in a bare rock.
• Psammosere: Starting on sand.
• Halosere: Starting on saline soil.

6. Hydrosere

7. Mesarch or Mesosere Succession

8. Lithosere Succession

9. Psammosere Succession

10. Halosere Succession

11. According to the causes of occurrence
1. Primary Succession: occurs in essentially lifeless
areas—regions in which the soil is incapable of
sustaining life as a result of such factors as lava flows,
rocks left from a retreating glacier etc.
2. Secondary Succession: occurs in areas where
a community that previously existed has been
removed; it is typified by smaller-scale disturbances
that do not eliminate all life and nutrients from
the environment.

12. Primary succession begins in barren areas, such as on bare rock exposed
by a retreating glacier. The first inhabitants are lichens or plants—those
that can survive in such an environment. Over hundreds of years these
“pioneer species” convert the rock into soil that can support simple
plants such as grasses. These grasses further modify the soil, which is
then colonized by other types of plants. Each successive stage modifies
the habitat by altering the amount of shade and the composition of the
soil. The final stage of succession is a climax community, which is a very
stable stage that can endure for hundreds of years.

13. Secondary succession follows a major disturbance, such as a fire or a
flood. The stages of secondary succession are similar to those of primary
succession; however, primary succession always begins on a barren
surface, whereas secondary succession begins in environments that
already possess soil. In addition, through a process called old-field
succession, farmland that has been abandoned may undergo secondary
succession.

14. StagesProcess of succession
Ecological Succession has five stages, they are-
Nudation: It is the development of a bare area without any life form.
The bare area may be caused due to landslides, volcanic eruption
etc. (topographic factor), or due to drought, glaciers, frost etc.
(Climatic factor), or due to overgrazing, disease outbreak,
agricultural/ industrial activities (biotic factors).
Invasion: It is the successful establishment of one or more species on
a bare area through dispersal or migration. Dispersal of the seeds,
spores etc. is brought about by wind, water, insects or birds. Then
the seeds germinate and grow on the land.

15. StagesProcess of succession
Competition and coaction: As the number of individuals grows there
is competition, both inter-specific (between different species) and
intra-specific (within the same species), for space, water and
nutrition. They influence each other in a number of ways, known
as coaction.
Reaction: The living organisms grow, use water and nutrients from
the substratum, and in turn, they have a strong influence on the
environment which is modified to a large extent and this is known
as reaction.
Stabilization: The succession ultimately reaches to a climax or point
of highest development. (more or less stable community) called
climax which is in equilibrium with the environment.

16. Ecological Pyramids
Introduction: Every food chain or ecosystem shows
different characteristics such as number of organisms,
weight (biomass) and energy level. Every trophic level
differs from each other in relation with numbers,
biomass and energy.
The concept of Ecological Pyramid was developed
by Charles Elton in 1927.
Trophic Level: Trophic level is the position of an organism
in a food chain or ecosystem.
Trophic levels can be represented by numbers, starting at
level 1 with plants. Further trophic levels are numbered
subsequently according to how far the organism is
along the food chain.
Cont...

17. Level 1: Plants and algae
make their own food and
are called producers.
Level 2: Herbivores eat
plants and are called
primary consumers.
Level 3: Carnivores that
eat herbivores are called
secondary consumers.
Level 4: Carnivores that
eat other carnivores are
called tertiary consumers.
Apex predators by
definition have no
predators and are at the
top of their food web.

18. Ecological Pyramid- Definition
An ecological pyramid is a graphical representation designed
to show the number, biomass and energy at each trophic
level in a given ecosystem.
An Ecological Pyramids are graphic pictures of food chain in
relation with the number, biomass and energy level of
organisms.
The base of every Ecological Pyramids consists of producers
and apex of every Ecological Pyramids consists top
carnivores.
Ecological Pyramids may be up right or inverted or semi
upright depending on increasing or decreasing of numbers,
biomass and energy level.
There are three types of Ecological Pyramids,
• Pyramids of Numbers
• Pyramids of Biomass
• Pyramids of Energy

19. Pyramids of Numbers
• It shows the relationship
between the producers,
herbivores and carnivores
in terms of their
numbers.
• This indicates the number
of organisms at every
trophic level
Pyramids of Number are
graphic pictures those
represent total number
of organisms at various
trophic level in a food
chain.

20. Pyramids of Numbers (Examples)
Forest Ecosystem
Pyramid of numbers of a tree (Parasitic food chain)
Grassland Ecosystem
Pond Ecosystem

21. Pyramids of Biomass
The amount of living
material in an organism is
called biomass.
Pyramid of biomass shows
quantitative relationship
existing at various trophic
levels.
Pyramids of Biomass are
graphic pictures those
represent total biomass
at each trophic level in a
food chain.

22. Pyramids of Biomass (Examples)
Forest Ecosystem
Pyramid of biomass of a tree (Parasitic food chain)
Pond Ecosystem
Grassland Ecosystem

23. Pyramids of Energy
Pyramids of energy show
the amount of total
energy trapped by the
organism at each
trophic level.
Energy pyramid is always
upright in all
ecosystems.
Pyramids of Energy are
graphic pictures those
represent the energy
level of organisms at
each successive trophic
level.