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It's all in the name! Reverse osmosis actually is the reverse of osmosis where water molecules will move against its concentration gradient .


Osmosis is the movement of water molecules across a semi permeable membrane from where they are in higher concentration to an area where they are in lower concentration.


Osmosis is a natural process where diffusion of solvent takes place across a semi permeable membrane. This means that no energy expenditure is required to move the water across the membrane from its higher concentration to its lower concentration.

Water molecules move on their own.

Reverse osmosis is a process that is used to take water molecules from an area where they are in low concentration to an area where they are in high concentration . It is the exact opposite of osmosis.

Reverse osmosis is usually used in water purification . More specifically in desalination of sea water to make it drinkable.


As you can see in the image above, pressure is applied to water where solutes are present in higher concentration, so that it moves through the partially permeable membrane on the opposite side.

This leaves the salt and other small contaminant particles behind and we get clean water.


mRNA carries a written message from DNA . Ribosomes are able to read the message and accordingly proteins are made.



DNA is a huge book where recipes of proteins are written. Each written recipe is called a gene. Each cell of the body stores a complete recipe book in the form of genomic DNA though all recipes are not always required to be cooked.

Our body is made up of different types of cells. Hepatic cells form liver, Osteocytes form bones, Macrophages fight the germs, and so on.

Cells of different tissues require to produce different proteins. For example keratin protein is generated only in skin/nail/hair. Protein components of mucin and chondrin are produced respectively in goblet cells and chondroblasts. All this means that specific cells produce specific proteins.

Thus each cell requires to copy few specific recipes from the DNA stored within it. This is done by Transcription of genes on DNA to generate corresponding RNAs which are called messenger RNA. It is like copying a particular recipe on a page from a huge cook book. Thus a messenger RNA carries a particular information from genomic DNA.

Readable codes for protein synthesis are carried by messenger RNAs from genomic DNA to cellular pool, where ribosomes are able to read the message.

Small subunit of ribosome attaches to messenger RNA, large subunit then joins and protein synthesis begins. The sequence of amino acids in protein is dictated by the sequence of codons on mRNA.


Organisms which are from different evolutionary lines, often show similar adaptive tendencies to occupy similar habitats. Such a phenomenon is called convergent evolution.


Convergent evolution allows unrelated organisms to live in a habitat in similar manner. For example, ducks and frogs both show webbed feet, as they both spend time in aquatic habitat. It is also true for development of flippers in penguin, a bird and dolphin, a mammal.


There are examples from fossil evidence as well, like reptilian organism pterodactyl, which developed wings to fly like bird and bat, a mammal.


Convergent evolution leads to appearance of analogous organs , which means there could be morphological similarity in structure but the underlying infrastructures differ.

  • For example thorns and spines in plants may develop from axial buds, but in cacti, thorns are modified leaves.
  • Likewise wing of bat is a patagium, i.e. folds of skin supported by highly elongated fingers while in birds fingers are vestigial and wing is feathery. Then there are insects with wings but those are without any bony support: insect wings are actually made of polysaccharide chitin.



Smallest taxonomic group containing organisms of different species is GENUS .


In hierarchical classification there are several categories: each category may include different taxa. Genus is the lowest category that includes different species.



For example Genus Panthera. It is the genus under which there are different specie of big cats.

  • Panthera tigris is scientific name of tiger.
  • Panthera leo is scientific name of lion.
  • Panthera pardus is scientific name of leopard.
  • Panthera onca is scientific name of jaguar.


Nephrons are convoluted tubular structures of kidney . These are associated with urine formation, hence nephrons are functional units of nephron.


Nephron has four parts:-

  1. Bowman's capsule
  2. Proximal convoluted tubule (PCT)
  3. Henle's loop
  4. Distal convoluted tubule (DCT)

To know more about structure and histology read this.

Bowman's capsule encloses a capillary tuft, named glomerulus which is supplied by Afferent arteriole while drained by a narrower Efferent arteriole. This increases blood pressure within glomerulus and it helps in filtering excretory materials from blood.

Glomerular filtrate accumulates in Bowman's capsule.

Water and necessary materials from filtrate are reabsorbed by PCT, and Henle's loop.

Some ions, etc are secreted in the filtrate by the wall of DCT.

So three physiological phenomena together produce urine. Some water gets reabsorbed by collecting ducts of kidney as well. Urea is the primary excretory material present in urine.




Archea means Ancient, as in archeology. The word arises from Greek word for beginning.


The name of archea bacteria reflects the belief that these bacteria are perhaps the oldest form of life on earth.

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