Water - properties and functions, Biology

Assignment Help:

WATER

Occurence

  1. Water is the most abundant substance, covering 70% of earth's surface.
  2. It constitutes 60-90% of living cells.

             5-6% in tooth enamal, 60 - 70% in human adults, 90-92% in brain cells, 90 - 95% in human embryo, 99% in Jelly                   Fish.

  1. 95% of the total water occurs in the free state.
  2. Only 5% is found in bound state.

PROPERTIES

  1. Water freezes at 0oC and boils at 100oC. It remains liquid in between the two temperatures.
  2. Water is colourless and transparent.
  3. Pure water does not have any odour or taste.
  4. All the essential mineral elements dissolve in water. Water is a medium for their availability to organisms.
  5. Water is a very poor conductor of electricity in the pure state. However, it is good conductor of electricity in the presence of ionised chemicals.
  6. Pure water is neutral with a pH of 7.
  7. Water is a small polar molecule having positive and negative charges.
  8. Water has a high dielectric constant which enables the oppositely charged ions of electrolytes to remain suspended in water.
  9. Surface Tension is very high.
  10. Water has the maximum specific heat.  Water has the maximum density at 4oC.

FUNCTIONS OF WATER

  1. Water is a major component of cells and body fluids.
  2. Water is a habitat of numerous animals, plants and other organisms.
  3. Water has the maximum solvent action for both electrolytes and nonelectrolyte polar substances.
  4. Water is also dispersion medium for hydrophilic or reversible colloids.
  5. Water is transport medium in both plants (xylem, phloem) and animals (blood and and lymph).
  6. Excretory products are eliminated mainly in solution form. It helps in homoeostasis.
  7. Water maintains the turgid state of cells and soft organs.
  8. In photosynthesis, water molecules undergo photolysis, evolve O , provide H+ ions and electrons for reduction of CO to organic state.
  9. Water present in tissue fluid, coelomic fluid, pericardial fluid, cerebrospinal fluid, etc. keeps the tissues moist for their optimum functioning. It is also a lubricant of joints.
  10. Seeds and spores require water for their germination.
  11. Cornea is protected from microbe infection and dust by lachrymal fluid. Mucus protects the nasal tract from the same. In both water is the main ingredient for flushing of teh particles.
  12. Heat spreads in water quite repidly due to high thermal conductivity. It distributes heat uniformly and prevents sudden changes in temperature.
  13. Shortage of water on land has been a major selection pressure in evolution of xerophytes, desert animals, seed plants, etc.

Related Discussions:- Water - properties and functions

Coelenterata, mode of digestion in coelenterata

mode of digestion in coelenterata

Endosperm - pollen biology, Endosperm - Pollen Biology The examination...

Endosperm - Pollen Biology The examination of live material of j. montana reveals that the division of the primary endosperm nucleus is transverse, followed by the laying down

Transition of the vertebrates, Q Which is the chordate class considered an ...

Q Which is the chordate class considered an evidence of the transition of the vertebrates from the aquatic to the dry land environment? The amphibians are totally aquatic in th

What is chromosomes, What is Chromosomes ? The terminology used to desc...

What is Chromosomes ? The terminology used to describe DNA replication may sometimes be confusing. Originally, the term "chromosome" referred to the structures seen through the

Which is the type of nitrogen waste birds produce, Which is the type of nit...

Which is the type of nitrogen waste birds produce? Why does this feature, besides being an adaptation to the terrestrial environment, also mean an adaptation to flight? Birds a

Archaeological records of human campsites, Archaeological Records of Human ...

Archaeological Records of Human Campsites Archaeological records of human campsites indicate that early humans started out as small bands of hunters who supplemented kills wit

Define need of vitamin e and k during pregnancy period, Define need of vita...

Define need of vitamin E and K during pregnancy period? Vitamin E needs are believed to increase during pregnancy but deficiency in humans rarely occurs. Vitamin E in the infan

Explain offspring of heterozygous for autosomal trait mates, If a male who ...

If a male who is heterozygous for an autosomal trait mates with a female who is also heterozygous for that trait, what percent of their offspring are probable to be heterozygous fo

What happens to pepsin when it passes into the duodenum, Q. Since pepsin is...

Q. Since pepsin is a gastric enzyme does it have a basic or an acid optimum pH? What happens to pepsin when it passes into the duodenum? Pepsin acts contained by the stomach so

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd