Organisms and Populations
Population and ecological adaptations
- A favourable internal environment maintained by the organism, whatever may be the external condition is called homeostasis.
- Living organisms maintain homeostasis by its responses against abiotic factors.
- Regulators are organisms that are able to maintain a constant body temperature despite changes in the external environment. Eg: Birds, mammals.
- Certain organisms like plants and animals, where body temperature and osmotic concentration changes according to ambient conditions of water are formed as conformers.
- Partial regulators have the ability to regulate body functions to a limited extent. Beyond that limit they become conformers.
- Migrators jump to other locations temporarily from the unfavourable environment to more favourable area and they return when unfavourable conditions are over.
- The organisms under unfavourable conditions stop their work for certain time called as suspensors.
- Hibernation – winter sleep. Eg: Polar bear
Aestiration – Summer sleep. Eg: Snails/Fish
- Hydrophytes – Plants requiring plenty of water
- Mesophytes – Plants requiring moderate water.
- Xerophytes – Plants requiring extreme dry conditions in desert, hilly region etc.
- 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
- Xerophytes have deep not system with a thick cuticle, sunken stomata. Eg: Acacia, Prosopis, Zizyphers
- Halophytes grow in saline soils Eg: Avicennia, Rhizophora
- Epiphytes are present on the higher plant bodies to receive minerals and moisture from decaying bark. Eg: Vanda, Orichids
- Animals also possess short term (skin tanning, increased heart beat) and long term adaptations (development of beek, claw).
- Camouflage is the ability of an organism to blend with its environment Eg: Arantia rectifolia (grasshopper); Mantis religiosa (Praying mantis)
- Mimicry is the resemblance of one species with another in order to obtain benefits against predation. Butterflies show Mullerian mimicry.
- 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.
- 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.
- Desert lizard keep their body temperature fairly constant by behavioural means.
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