One billion years later there were prokaryotic life forms which is considered to be the ancestors of all living organisms.

1. Development and
Evolution of Ecosystem
Prepared by:
Cari Edward C. Beñalet – MST. Bio

2. History…

4. • One billion years later there were prokaryotic life forms
which is considered to be the ancestors of all living
organisms.

5. Common characteristics of a living
species:
1. All life is cellular in nature.
2. Are made up of 50 – 90% water (source of protons, H, O,
and is a good solvent of biomolecule).
3. Major elements are C, H , O, N, P, S
4. There is a set of molecules (sugars, amino acids,
nucleotides, phospholipids, vitamins and coenzymes)
universally found in all living organism.
5. Presence of a universally type off membrane structure.

7. Miler – Urey Experiments
• Showed that “inorganic processes under the primitive earth
conditions could form organic molecule”.
• Using variations of their techniques, most major building
blocks of life have been produced. .

8. • The first organisms presumably consumed these molecules.
• The first forms of photosynthesis were probably non-
oxygenic using inorganic molecules as a source of electrons
to reduce carbon dioxide.

9. • Formation of closed, membrane vesicles was an early event
in cellular evolution where lipid molecule spontaneously
form membrane vesicles or liposomes.

10. DEVELOPMENT OF ECOSYTEM (OR) ECOLOGICAL
SUCCESSION
When stripped of its original vegetation by fire, flood, or glaciation, an area
of bare ground does not remain devoid of plants and animals. Beginning with
plants, area is rapidly colonized by a variety of both plant and animal species
that subsequently modify one or more environmental factors in the
ecosystem. This modification of the environment may in turn allow additional
species to become established.

11. • The development of the community by the action of vegetation
on the environment leading to the establishment of new
species is termed succession or development.

12. Causes of Succession:
1. Initial or Initiating causes - These are climatic as well as biotic in nature .
All these causes produce the bare areas or destroy the existing populations in
an area.
2. Ecesis or Continuing causes - These are processes as migration,
aggregation, competition, reaction, etc., which cause successive waves of popula
tions as a result of changes, chiefly in the edaphic (soil) features of the area
3. Stabilizing causes - These include factors such as climate of the area which
result in the stabilization of the community.

13. POSSIBLE SUCCESSION
• Aquatic ecosystem

14. Community Evolution
• Like the responses of communities to changing abiotic
conditions, community
evolution involves progressive changes in climax communities
. Because the
evolution is exceedingly slow, it cannot be observed in operatio
n, and few instances from the fossil record are sufficiently
complete to show the process inaction.

15. • By some 300 million years ago, reptiles had evolved that could feed
effectively on terrestrial invertebrates. An entirely land-based community was
theoretically possible in which all herbivore niches were assumed by
invertebrates and some of the carnivore niches vertebrates. However, the
palaeoccological evidences suggest that most contemporary carnivorous
vertebrates were unable as yet to realize an entirely terrestrial carnivore
niche, so that 'he great majority of the energy flow through the community
continued to pass through the aquatic route. The typical food chain to the
highest terrestrial vertebrate carnivore was plant aquatic invertebrate→ →
aquatic invertebrate-feeding vertebrate semi-aquatic predator→ →
terrestrial predator.

17. • “The principles of ecological succession bears importantly
on the relationships between man and nature”
- Eugene P. Odum

18. • In a word, this strategy of succession as a short-term
process is basically the same as the strategy of long-term
evolutionary development of the biosphere --namely,
increased control of, or homeostasis with, the physical
environment in the sense of achieving maximum protection
from its disconcertion.

19. Ecological succession may be defined in terms of the
following three parameters (Odum, 1963).
1. It is an orderly process of community development that is reasonably
directional and, therefore, predictable.
2. It results from modification of the physical environment by the
community; that is, succession is community controlled even though the
physical environment determines the pattern, the rate of change, and
often sets limits as to how far development can go.
3. It culminates in a stabilized ecosystem in which maximum biomass (or
high information content) and symbiotic function between organisms are
maintained per unit of avalaible energy flow

21. Bioenergetics of Ecosystem Development
• In the early stages of ecological succession, or in young
nature, so to speak, the rate of primary production or total
(gross) photosynthesis (P) exceeds the rate of community
respiration (R).

22. Food Chains and Food Webs
• As the ecosystem develops, subtle changes in the network
pattern of food chains may be expected. The manner in
which organisms are linked together through food tends to
be relatively simple and linear in the very early stages of
succession, as a consequence of low diversity.
Furthermore, heterotrophic utilization of net production
occurs predominantly by way of grazing food chains --that
is, plant-herbivore-carnivore sequences.

24. Nutrient Cycling
• An important trend in successional development is the
closing or tightening of the biogeochemical cycling of major
nutrients, such as nitrogen, phosphorus, and calcium.
Mature systems, as compared to developing ones, have a
greater capacity to entrap and hold nutrients for cycling
within the system.