Ecosystem – Composition, Structure, Function & Productivity YouTube Lecture Handouts for ICMR NET 2021

Dr. Manishika Jain- Join online Paper 1 intensive course. Includes tests and expected questions.

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Ecosystem - Biotic & Abiotic (Components), 3 Types & 2 Functions

Ecosystem

  • Self-regulated & self-sustaining
  • Structural and Functional unit of nature includes living beings and environment
  • Interact and exchange material
  • Open System – input of energy and matter
  • Result in productivity

Types of Ecosystem

Homeostasis/Biological Equilibrium

Functional balance which is not static and fluctuates within limits

Controls

  • Carrying Capacity
  • Recycling Waste
  • Self-Regulation
  • Feedback System

📝 Components of Ecosystem

👌 Biotic – food contains energy for body building, growth and functions

  • Producers (Autotrophs)
  • Consumers (Heterotrophs)
  • Decomposers (Reducers)

Abiotic – non-living factors

  • Temperature
  • Light
  • Wind
  • Humidity – epiphytes that grow
  • Precipitation
  • Water – xerophytes & hydrophytes
  • Background – Chameleon (change color) ; praying mantis & frog are green
  • Gases
  • Soil – water retention, aeration & minerals
  • pH – acidic (Euglena & flagellates) or basic (calcareous shells)
  • Relief – north & south faces of hill
  • Mineral Elements

Structure

  • Species Composition – identify and enumerate plants and animals
  • Stratification – vertical layers
  • Trophic Levels
  • 👌 Standing Crop – living biomass in unit area (dry weight is preferred as is independent of moisture differences)
  • 👌 Standing State – inorganic nutrients in ecosystem (non-living)

📝 Ecosystem Functions

  • Productivity
  • Decomposition
  • Energy Flow
  • Nutrient Cycling
Pond Ecosystem

Productivity

Rate of synthesis of energy containing biomass by any trophic level per unit area in unit time

Measured as

Measured as

👌 Primary Productivity – energy accumulation in green plants per unit area over time

Secondary Productivity – Rate of re-synthesis of material by consumers

Respiration loss is 20 % for autotrophs, 30 % for herbivores and 60 % for carnivores

Maximum productivity – tropical rainforest

Minimum productivity – desert or Arctic regions

Order of productivity:

Tropical Rainforest > Tropical Deciduous > Temperate Deciduous > Temperate Coniferous > Savannah > Temperate Grassland > Scrub

Factors Affecting Productivity

  • Solar radiation - maximum in tropics and so photosynthesis and NPP highest in tropics
  • Temperature – temperate forest have lesser productivity due to cold climate
  • Moisture
  • Nutrients
  • Photosynthetic Efficiency

Decomposition

Detritus

  • Above Ground – litter (plant driven) , dried plants
  • Below Ground – dead roots, underground dead animals

👌 Process

  • Fragmentation of Detritus (earthworm as farmer՚s friends)
  • Catabolism
  • Leaching – soluble substances are subject to leaching

👌 Products formed

  • Humus by humification – humus is dark colored organically rich in lignin and cellulose
  • Inorganic nutrients by mineralization – both non mineral () & mineral () from organic matter

Factors Affecting Decomposition

  • Temperature
  • Moisture – excess moisture impedes decomposition due to anaerobiosis
  • pH – alkaline soils are rich in detrivores and acidic nature decreases detrivores
  • Composition – chitin and lignin are slow to decompose
  • Aerobiosis – aerobic conditions are required

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