organism and population

• Ecology

  Study of interaction between living and non-living
• Levels of organisation in ecology

  • Basic unit of ecology
  • Organism
  • Population
  • Community
  • Ecosystem
  • Biosphere
• Organism

  Basic unit of ecology, understood in terms of its behaviour, physiology and distribution
• Population

  Group of individuals belonging to the same species, capable of interbreeding
• Community

  Interbreeding population of different species living in an area
• Ecosystem

  Living component interacts with non-living, recognised by the presence of vegetation
• Biosphere

  Entire living system of Earth, including terrestrial and marine components
• The term 'Ecology' was used by 'relter'
• R. Mishra is the Father of Ecology in India
• 4 Major Biomes in India

  • Desert
  • Deciduous Forest
  • Tropical Rainforest
  • Sea coast
• Habitat

  The place where an organism lives, where it can tolerate the conditions and utilise the resources
• Niche

  The range of conditions and resources that an organism can utilise
• Major abiotic factors

  • Temperature
  • Light
  • Water
  • Soil
• Temperature


  Most ecologically relevant, directly controls enzymatic activities
• As temperature increases

  Enzymatic activity increases
• As temperature decreases


  Enzymatic activity decreases
• Stenothermal organisms

  Organisms with a narrow range of temperature tolerance
• Eurythermal organisms

  Organisms that can tolerate a wide range of temperatures
• Thermophiles

  Organisms that can survive in extreme temperatures
• Water

  Second most ecologically relevant factor, life originated in water, covers 71% of Earth's surface
• Stenohaline organisms

  Organisms that cannot tolerate a wide range of salinity
• Euryhaline organisms

  Organisms that can tolerate a wide range of salinity
• Light


  Photosynthetically Active Radiation (PAR) between 400-700nm, important for photosynthesis and photoperiodism
• Soil

  Edaphic factor, formed by weathering of rocks, with varying water holding capacity and grain size
• Regulators

  Organisms that maintain a constant internal environment even as the external environment changes
• Conformers


  Organisms that cannot maintain a constant internal environment, their internal environment changes with the external environment
• Partial regulators

  Organisms that can partially regulate their internal environment
• 99% of organisms on Earth are conformers
• Adaptations in desert plants (Xerophytes)

  • Thick cuticle
  • Sunken stomata
  • CAM photosynthesis
  • Spines instead of leaves
• Allen's rule - Polar bears have shorter limbs and ears to minimize heat loss
• Altitude sickness is caused by low partial pressure of oxygen at high altitudes
• Archaebacteria can survive extreme conditions like high temperature and salinity
• Desert lizards move into shade to avoid heat, and bask in the sun when cold this is behavioral adaptation
• Population

  Group of interbreeding organisms occupying a dedicated geographical area
• Birth rate

  Number of births per 1000 individuals in a given time
• Death rate


  Number of deaths per 1000 individuals in a given time
• Sex ratio

  Number of females per 1000 males
• Population age structure

  • Pre-reproductive
  • Reproductive
  • Post-reproductive
• Population density

  Number of organisms occupying a given area
• Biomass

  Total mass of organisms in a given area