Ecology and Environment

Habitat

Meaning: A habitat is the natural environment or the specific place where a species lives, grows, and reproduces. Think of it as an organism's "address."

Key Points:

• Determined by abiotic factors (temperature, light, water) and biotic factors (food, predators).
• Scale varies from as large as an ocean to as small as a rotting log.

Examples:

• A pond for a lotus plant.
• A tropical rainforest for an orangutan.

Real-Life Use: Urban Planning. Architects use "urban ecology" to create green corridors so pollinators can survive in concrete cities.

Population Interactions

When two different species coexist, they interact in various ways:

• Mutualism (+/+): Both species benefit.
  • Example: Lichens (Algae provides food; Fungi provides shelter).
  • Real-Life Use: Bio-fertilizers using Rhizobium bacteria to increase soil nitrogen.
• Competition (-/-): Both struggle for limited resources.
  • Example: Weeds competing with wheat crops for nutrients.
  • Real-Life Use: Business Economics (companies competing for market share).
• Predation (+/-): One eats the other.
  • Example: A lion hunting a zebra.
  • Real-Life Use: Biological Pest Control (releasing ladybugs to eat aphids).
• Parasitism (+/-): One lives on/in a host and harms it.
  • Example: Tapeworms in the human gut.
  • Real-Life Use: Medicine (developing anti-parasitic drugs for Malaria).

Population Attributes

• Natality: The birth rate.
• Mortality: The death rate.
• Age Pyramids:
  • Expanding: Triangular shape (lots of young).
  • Stable: Bell shape (balanced).
  • Declining: Urn shape (more old than young).

Population Growth Models

1. Exponential Growth: Occurs when resources are unlimited (J-shaped curve).

2. Logistic Growth: Occurs when resources are limited; population reaches "Carrying Capacity" (K) (S-shaped curve).

Numerical Illustration

Question: A population of 100 bacteria has a growth rate (r) of 0.1 per hour. If resources are unlimited, what will be the rate of increase (dN/dt)?

Components of an Ecosystem

• Abiotic: Non-living (Air, Water, Soil, Sunlight).
• Biotic: Living (Producers $\rightarrow$ Consumers $\rightarrow$ Decomposers).

Productivity and Energy Flow

• Primary Productivity: Biomass produced by plants via photosynthesis.
• 10% Law: Only 10% of energy is transferred to the next trophic level; 90% is lost as heat.

Ecological Pyramids

• Pyramid of Number: Counts individuals at each level.
• Pyramid of Biomass: Total organic matter.
• Pyramid of Energy: Always upright (energy always decreases).

Nutrient Cycling & Succession

• Carbon Cycle: Atmosphere $\rightarrow$ Plants $\rightarrow$ Animals $\rightarrow$ Atmosphere.
• Phosphorus Cycle: Sedimentary cycle (Rocks $\rightarrow$ Soil $\rightarrow$ Plants $\rightarrow$ Animals).
• Primary Succession: Starts on bare rock (Slow).
• Secondary Succession: Starts in destroyed areas, e.g., post-fire (Fast).

Levels of Biodiversity

• Genetic Diversity: Variation within a species (e.g., 50,000 rice varieties in India).
• Species Diversity: Variety of species in a region (e.g., Western Ghats).
• Ecological Diversity: Variety of ecosystems (e.g., Deserts, Mangroves).

Conservation Comparison

• Pollution:
  • Air: CFCs, SO₂ causing acid rain.
  • Water: Eutrophication (Algae blooms $\rightarrow$ Oxygen depletion).
  • Soil: Pesticides and plastics.
• Greenhouse Effect: CO₂ and CH₄ trapping heat $\rightarrow$ Global Warming.
• Ozone Depletion: CFCs destroying the O₃ layer in the stratosphere.
• Deforestation: Habitat loss and increased CO₂.

Modern Tools: GIS (Mapping habitats) and Remote Sensing (Tracking ice caps/forests via satellite).

1. Which interaction is represented by (+/+)?
   Ans: c) Mutualism
2. The 10% law of energy transfer was given by:
   Ans: b) Lindeman
3. Which of the following is an example of Ex-situ conservation?
   Ans: c) Seed Bank
4. An urn-shaped age pyramid indicates:
   Ans: c) Declining population
5. The process of nutrient enrichment of a water body leading to oxygen depletion is:
   Ans: b) Eutrophication
6. Which pyramid is always upright?
   Ans: c) Pyramid of Energy
7. CFCs are primarily responsible for:
   Ans: b) Ozone depletion
8. Primary succession occurs on:
   Ans: c) Bare rock
9. Which of these is a sedimentary cycle?
   Ans: c) Phosphorus cycle
10. Rhizobium in root nodules of legumes is an example of:
    Ans: b) Mutualism

1. Q: Distinguish between Exponential and Logistic growth.
   Ans: Exponential growth occurs under ideal conditions (J-shaped curve). Logistic growth occurs when resources are limited, reaching a carrying capacity (S-shaped curve).
2. Q: What is the difference between In-situ and Ex-situ conservation?
   Ans: In-situ protects species in their natural habitat (National Parks). Ex-situ protects them in artificial environments (Zoos, Gene banks).
3. Q: Explain the "10% Law" of energy flow.
   Ans: Only 10% of energy at one trophic level is transferred to the next; 90% is lost as heat during metabolism.
4. Q: How does deforestation contribute to the Greenhouse Effect?
   Ans: Forests absorb CO₂. Cutting them stops this absorption and releases stored carbon, increasing heat-trapping gases.
5. Q: What is Ecological Succession? Name its types.
   Ans: The gradual change in species composition. Types: Primary (on bare land) and Secondary (after community destruction).
6. Q: Define Eutrophication and its impact on aquatic life.
   Ans: Nutrient enrichment causing algae blooms. This blocks sunlight and depletes oxygen, killing fish.
7. Q: What are the three levels of biodiversity?
   Ans: 1. Genetic Diversity, 2. Species Diversity, 3. Ecological Diversity.
8. Q: Explain the role of decomposers in an ecosystem.
   Ans: They break down dead organic matter into inorganic nutrients, returning them to the soil for producers.
9. Q: What is the difference between Predation and Parasitism?
   Ans: Predators usually kill prey immediately for food. Parasites feed off a host over a long period without killing it immediately.
10. Q: Describe the Phosphorus Cycle.
    Ans: Rocks $\rightarrow$ Soil $\rightarrow$ Plants $\rightarrow$ Animals $\rightarrow$ Decomposers $\rightarrow$ Soil.

• Population Interactions (The Sign Method):
  • Mutualism: Win-Win (+/+)
  • Competition: Lose-Lose (-/-)
  • Predation/Parasitism: Win-Lose (+/-)
• Biodiversity Levels: Use acronym "G-S-E" $\rightarrow$ Genetic $\rightarrow$ Species $\rightarrow$ Ecosystem.
• Nutrient Cycles: "C-N-O" are Gaseous; "P" (Phosphorus) is Petrified (Sedimentary).