Organism and population

• Diversity is not only a characteristic of living organisms but also of content in biology textbooks
• Biology is presented as

  • Botany
  • Zoology
  • Microbiology
  • Classical
  • Modern
• Modern biology

  Molecular aspects of biology
• We have many threads which weave the different areas of biological information into a unifying principle
• Ecology

  A holistic perspective to biology
• Biological understanding


  Knowing how organisms, while remaining an individual, interact with other organisms and physical habitats as a group and hence behave like organised wholes, i.e., population, community, ecosystem or even as the whole biosphere
• Ecology explains all this
• This unit describes as well as takes a critical view of anthropogenic environmental degradation and the socio-political issues it has raised
• Chapters

  • 13. Organisms and Populations
  • 14. Ecosystem
  • 15. Biodiversity and Conservation
  • 16. Environmental Issues
• Ramdeo Misra


  Revered as the Father of Ecology in India
• Ramdeo Misra was born

  26 August 1908
• Ramdeo Misra obtained Ph.D in Ecology (1937) under Prof. W. H. Pearsall, FRS, from Leeds University in UK
• Ramdeo Misra established teaching and research in ecology at the Department of Botany of the Banaras Hindu University, Varanasi
• Ramdeo Misra's research laid the foundations for understanding of tropical communities and their succession, environmental responses of plant populations and productivity and nutrient cycling in tropical forest and grassland ecosystems
• Misra formulated the first postgraduate course in ecology in India
• Over 50 scholars obtained Ph. D degree under Misra's supervision and moved on to other universities and research institutes to initiate ecology teaching and research across the country
• Misra was honoured with the Fellowships of the Indian National Science Academy and World Academy of Arts and Science, and the prestigious Sanjay Gandhi Award in Environment and Ecology
• Due to Misra's efforts, the Government of India established the National Committee for Environmental Planning and Coordination (1972) which, in later years, paved the way for the establishment of the Ministry of Environment and Forests (1984)
• Our living world is fascinatingly diverse and amazingly complex
• We can try to understand the complexity of the living world by investigating processes at various levels of biological organisation–macromolecules, cells, tissues, organs, individual organisms, population, communities and ecosystems and biomes
• At any level of biological organisation we can ask two types of questions - 'How' questions seek the mechanism behind the process while 'Why' questions seek the significance of the process
• Ecology is a subject which studies the interactions among organisms and between the organism and its physical (abiotic) environment
• Ecology is basically concerned with four levels of biological organisation – organisms, populations, communities and biomes
• Ecology at the organismic level is essentially physiological ecology which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction
• Variations in temperature and precipitation account for the formation of major biomes such as desert, rain forest and tundra
• Regional and local variations within each biome lead to the formation of a wide variety of habitats
• Life exists not just in a few favourable habitats but even in extreme and harsh habitats
• Key elements that lead to variation in physical and chemical conditions of different habitats

  • Temperature
  • Water
  • Light
  • Soil
• The habitat includes both abiotic (physico-chemical) and biotic components with which the organism interacts constantly
• Eurythermal organisms


  Can tolerate and thrive in a wide range of temperatures
• Stenothermal organisms


  Restricted to a narrow range of temperatures
• There is a growing concern about the gradually increasing average global temperatures
• For aquatic organisms the quality (chemical composition, pH) of water becomes important
• Euryhaline organisms


  Tolerant of a wide range of salinities
• Stenohaline organisms


  Restricted to a narrow range of salinities
• Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems they would face
• Many plants are dependent on sunlight to meet their photoperiodic requirement for flowering
• Many animals use the diurnal and seasonal variations in light intensity and duration (photoperiod) as cues for timing their foraging, reproductive and migratory activities
• Deep (>500m) in the oceans, the environment is perpetually dark and its inhabitants are not aware of the existence of a celestial source of energy called Sun
• The spectral quality of solar radiation is also important for life