Organisms and Populations

Population and ecological adaptations

  1. A favourable internal environment maintained by the organism, whatever may be the external condition is called homeostasis.
  2. Living organisms maintain homeostasis by its responses against abiotic factors.
  3. Regulators are organisms that are able to maintain a constant body temperature despite changes in the external environment. Eg: Birds, mammals.
  4. Certain organisms like plants and animals, where body temperature and osmotic concentration changes according to ambient conditions of water are formed as conformers.
  5. Partial regulators have the ability to regulate body functions to a limited extent. Beyond that limit they become conformers.
  6. Migrators jump to other locations temporarily from the unfavourable environment to more favourable area and they return when unfavourable conditions are over.
  7. The organisms under unfavourable conditions stop their work for certain time called as suspensors.
  8. Hibernation – winter sleep. Eg: Polar bear
    Aestiration – Summer sleep. Eg: Snails/Fish
  9. Hydrophytes – Plants requiring plenty of water
  10. Mesophytes – Plants requiring moderate water.
  11. Xerophytes – Plants requiring extreme dry conditions in desert, hilly region etc.
  12. Hydrophytes show different types of modification.
    (i) Submerged : Hydrilla, Vallisneria
    (ii) Free floating : Water hyacinth, Pistia, Salvinia
    (iii) Fixed floating : Nymphae, Trapa, Marsilea
    (iv) Amphibious : Ranunculus, Saggitaria
    (v) Hygrophytes : Fern grasses
  13. Xerophytes have deep not system with a thick cuticle, sunken stomata. Eg: Acacia, Prosopis, Zizyphers
  14. Halophytes grow in saline soils Eg: Avicennia, Rhizophora
  15. Epiphytes are present on the higher plant bodies to receive minerals and moisture from decaying bark. Eg: Vanda, Orichids
  16. Animals also possess short term (skin tanning, increased heart beat) and long term adaptations (development of beek, claw).
  17. Camouflage is the ability of an organism to blend with its environment Eg: Arantia rectifolia (grasshopper); Mantis religiosa (Praying mantis)
  18. Mimicry is the resemblance of one species with another in order to obtain benefits against predation. Butterflies show Mullerian mimicry.
  19. Allens rule – Animals (Endothermal) in colder areas possess thick fur, small extremities (feet, tail, ears etc) and subcutaneous fat compared to their relatives in warmer regions to minimise heat loss.
  20. Desert rat/kangaroo possess a thick coat to prevent/minimise evaporation and they seldom drink water. Loss of water is minimised by producing nearly solid urine and faeces.
  21. Desert lizard keep their body temperature fairly constant by behavioural means.

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