Lecture 3 Microbial Ecology.pptxkjhkjhkjhjhkhklhhkl

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1. Lecture 3 Ecological Communities: Colonization, Succession, Diversity, and Structure By Dr.Khawaja Shakeel Ahmed

2. What is an Ecological Community? A community is a group of different species (plants, animals, microbes, etc.) that live in the same area and interact with each other. Example: A forest with trees, birds, insects, fungi, and mammals. Focuses on how species coexist and interact .

3. Colonization ✅ Definition: Colonization is the process by which new species arrive and establish themselves in an area where they were not previously found. 🌀 How it Happens: Dispersal : Seeds, spores, animals move from one place to another (e.g., wind, water, animals). Environmental Suitability : New area must have the right conditions (light, water, food). Competition : New species must compete with existing species for resources. 📌 Examples: After a volcanic eruption, lava fields are colonized by mosses and lichens. Birds establishing nests on a newly formed island.

4. Succession ✅ Definition: Succession is the natural, gradual process of change in the types of species in a community over time. Type Description Example Primary Succession Starts in areas with no previous life (no soil) Lava flows, glacier retreats Secondary Succession Occurs in areas where a community existed but was disturbed After a fire, flood, or farming

5. Stages of Succession: Pioneer Species : First to colonize (e.g., lichens, mosses). Can survive harsh conditions. Intermediate Species : Grasses, shrubs begin to grow. Soil improves. Climax Community : Stable, mature ecosystem. High biodiversity. E.g., Old-growth forest.

6. Community Structure ✅ Definition: Community structure refers to how many and what kinds of species are present in a community and how they interact . 🧩 Components of Structure: Species Composition : Which species are present. Species Abundance : How many individuals of each species. Trophic Structure : Who eats whom (food chain/web). Spatial Structure : How species are arranged in space (e.g., layers in a forest). 🌲 Example – Forest Structure: Canopy – Tall trees Understory – Shrubs, small trees Herb Layer – Grasses, herbs Forest Floor – Fungi, decomposers

7. Biodiversity (Diversity in Communities) ✅ Definition: Biodiversity is the variety of life in a community, including: Species Richness : Number of different species. Species Evenness : How evenly individuals are distributed among species. 🌐 Why is Diversity Important? Increases stability and resilience . More niches (roles) filled. Better resource use . Greater productivity . 📉 Threats to Biodiversity: Habitat destruction Pollution Climate change Invasive species

8. Interactions in Communities 🔄 Types of Species Interactions: Interaction Type Effect on Species A Effect on Species B Example Competition – – Trees competing for light Predation + – Lion eats zebra Mutualism + + Bees and flowers Commensalism + Barnacles on whales Parasitism + – Tick on a dog

9. Factors Affecting Community Development Abiotic Factors : Climate, soil, water, temperature. Biotic Factors : Predation, competition, mutualism. Disturbances : Fires, storms, human activity.

10. Summary Table Concept Definition Key Point Colonization Arrival of new species Leads to community formation Succession Gradual change in species Primary & secondary types Structure Organization of species Includes composition, abundance, spatial & trophic Diversity Variety of life Richness + evenness

11. Real-World Example: Abandoned Farm to Forest Abandoned farmland (bare soil) Weeds and grasses grow first (pioneer) Shrubs and small trees develop (intermediate) Mature forest forms (climax) Animals return as habitat improves

12. Conclusion Ecological communities are dynamic , not static. They develop over time through colonization and succession . Their structure and diversity determine how stable and productive they are. Understanding communities helps in conservation and ecosystem management .

13. Thank You