1. Ecosystems: Concept & Structure
Ecology (BIO C322)
Ecosystems: Concept & Structure

2. The Ecological Hierarchy Ecosphere Biome Ecosystem Community
Population
Organism
Organ system
organ
tissue
cell

3. Ecosystem: Living Beings Interacting with Abiotic Factors

4. Ecosystem Biotic community interacting with the physical environment.
Cycling of materials.
First complete unit in ecological hierarchy.
Unity of organisms & environment.
Boundaries natural or arbitrary.

5. Open systems  Importance of input & output environments.
Sun the ultimate source of energy.
Other sources?
Three basic ecosystem components:
Community;
Energy flow (non-cyclic); utilized + heat;
Nutrient flow (cyclic).

7. Ecosystem’s Dependence on Environment
Size of system: Larger, less dependence.
Metabolic rate: Higher, more dependence.
Autotrophic-heterotrophic balance: Greater imbalance, more dependence.
Stage of development: Younger, more dep.
e.g. Himalayas vs Bangalore

8. Trophic Structure of Ecosystem
Autotrophic stratum: Green belt  Fixation of light energy.
Heterotrophic/phagotrophic stratum: Brown belt  Accumulation & decomposition of organic matter (by saprotrophs/microconsumers).
Products of decomposition: Particulate OM, Dissolved OM, Volatile OM.

9. What makes the Earth’s ecosystems habitable?

10. Comparative Atmospheres of Mars, Earth and Venus:
High O2 (21%) & low CO2 (0.03%) levels on Earth;
High CO2 (95%) & low O2 levels (Traces) on Mars & Venus.

12. Practice Concept
The atmosphere of Earth did not just develop by a chance interaction of physical forces into a life-sustaining and self-regulating condition, and then life evolved to adapt to this condition. Rather, organisms from the very beginning played a major role in the development and control of a geochemical environment favourable to themselves…It is the microorganism web of life operating in the brown belt as an intricate control system that functions to maintain a pulsing, homeorhetic balance.

13. Gaia Hypothesis Goddess Earth in ancient Greece.
Proposed by James Lovelock.
Organisms not only adapt themselves, but also change the environment to suit their biological needs.

14. A Ring-shaped Coral Reef called Atoll in Pacific Ocean:
Formed by CaCO3 Secretion by corals (Sea Animals);
Support a Great Variety of Animal and Plant Life.

15. Restoration Ecology
Humans modify their env beyond restoration to suit immediate needs  Global climate change.
Restoration ecology: Recovery of ecosystems damaged by pollution or invasion of exotic species.
Restoration by natural processes time-taking.
Prevention vs cure.

16. Examples of Restoration Ecology
Restoration of nitrogen-poor soil: Application of artificial/organic fertilizers (short-term) or introduction of N-fixing plants (long-term).
Acacia tree plantation on coal mine waste areas in India.

17. Revegetation: Encouraging immigration of seed carriers, especially birds.

18. Phytoremediation: Accumulation of metals (Zn, Ni, Pb, Cu) in harvestable biomass  Incineration  Recovery of metals in ash.
Brassica juncea (Indian mustard) used for Pb removal.

19. Agroecosystems Differ from natural ecosystems: Costs:
Solar energy supported by labour, fertilizers, pesticides, irrigation water;
Plants/animals artificially selected.
Costs:
Soil erosion;
Pollution (fertilizers, pesticides);
Reduced biodiversity;
Increased vulnerability to weather changes, pests.

20. Types of Agriculture
Pastoralism: People herding cattle in arid/semi-arid regions of low rain (grasslands of Africa), high altitudes; living on animal products (milk/meat).
Shifting agriculture (slash-and-burn): Forests cut, debris burned  Cultivation of crops for some years till nutrients used up  Move on, forest regrowth (Tropical regions/Asia).
Flood irrigation: Along rivers, fertile deltas; most productive.

21. Pre-industrial: Provide food for limited population, self-sufficient, use of labour.

22. Industrial: Mechanized, use of fertilizers & pesticides  pollution, soil erosion, habitat loss.
Low Input Sustainable Agriculture (LISA): Sustaining crop yields (profits), while reducing inputs of fertilizers, pesticides, fossil fuels.

23. Indian Perspective

24. Creation of homogenous crop varieties (reduced diversity).
These perform well only if supplied with large amounts of water, fertilizers, pesticides.
Such practices followed for cereal crops (wheat, rice); legumes ignored.
Result: Scarcity of pulses  Price rise  Protein deprivation for poor.

25. Diversity Matters
Thousands of years of Indian agricultural practices  Tremendous genetic diversity.
Much of India’s crop diversity preserved in agricultural research stations in India & seed banks owned by foreign commercial companies.

26. - A few years ago, rice crop in SE Asia infected by brown leaf hopper insect.
- Solution: Gene (insect-resistance) in rice variety from Pattambi (Kerala) in a collection at Int. Rice Research Institute in Philippines.
- The gene incorporated into high yielding variety by classical breeding techniques.
MNCs see commercial potential  Biotechnological production & sale of new varieties incorporating imp. genes.

27. Gradients Zonation of physical factors.
e.g. Temperature gradient from poles to Tropics.
e.g. Thermal stratification in temperate lakes.
Generally, environmental conditions & adapted organisms change gradually along a gradient.

28. Vegetation based Gradients or Zonation
On Land (With Respect to Altitude)

29. Ecotone or Edge Habitat or Interface zone:
Transition Zone between Ecosystems.
e.g. Sea beaches, mangrove forests, coral reefs
(land-sea ecotones).

30. Ecotone characterized by Increased Biodiversity (Edge Effect)
Unique Species Inhabiting Edge Habitats:
Edge Species.
Human activities Edge sharpening  Poor diversity (Uncut vs clear forest).

31. Biodiversity:
Species Richness (No. of Species in ecosystem);
Relative Abundance or apportionment
(No. of Individuals in each species.

32. Two Ecosystems may have same Richness, but
differ in Relative Abundance of Constituent Species

33. Biodiversity of India
One of the top 12 countries in terms of biodiversity.
Great productivity; year-round occurrence of conditions favourable to life; lower level of impact of ice ages in past.
High species turnover near sea & mountains.
Endemic species found in isolated regions like Andaman, Nicobar, Lakshadweep islands.
15,000 species of flowering plants; 317 species of mammals; 969 species of birds; 389 species of reptiles.

34. Himalayas & Western Ghats
very rich in biodiversity

35. The Making of Salim Ali (1896-1987)

36. Dr. Ali regarded one of the greatest biologists of 20th century India.
Shot birds as a child.
Meticulous observation & recording of lives of birds  Biodiversity conservation.
His magnum opus, the ten volume Handbook of the Birds of India & Pakistan.
Autobiography: The Fall of a Sparrow (1985).

37. Birds at Sariska National Park, Rajasthan

38. Practice Concept (Dr. Madhav Gadgil, IISc, Bangalore)
In India, efforts at protecting diversity have focused exclusively on large nature reserves & sanctuaries. Little thought or effort has gone into the conservation of biodiversity outside the nature reserve system.
An alternative system of biodiversity conservation, covering all of rural India, might provide a solution. Locality-specific knowledge of biodiversity elements possessed by “ecosystem people”, i.e. local & tribal populations, can be tapped to feed into a wider process of biodiversity conservation.
In turn, these people can be rewarded for protecting biodiversity by provision of funds or educational and health facilities in their locality.

39. SRISHTI Organization founded by Dr. Anil Kumar Gupta, IIM, Ahmedabad.
Organized biodiversity contests in different states.
Discovery of exceptional individuals who know hundreds of local species.
Due credit given to winners.

40. Shannon’s Diversity Index (H): Used to Calculate Biodiversity
H value varies from Zero to 4.6
E value varies from Zero to 1