Development and Evolution of Ecosystem
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The document outlines the evolution of ecosystems, highlighting the progression from prokaryotic life forms to complex ecological communities through processes like ecological succession. It describes how environmental modifications allow for species colonization and stabilizes ecosystems, with various causes and stages of succession. Additionally, it covers bioenergetics, food chains, and nutrient cycling, indicating that mature ecosystems are more efficient in nutrient retention compared to earlier stages.
Development and Evolution of Ecosystem
- 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.