The structure and functions are observable on a large scale. Therefore, many evolutionists study changes in animal structure and function. – Its examples are change in the shape of bill of a bird or change in the length of an animal’s neck However, all evolutionary changes take place due to changes in the base sequences in DNA and amino acids in proteins: Molecular evolutionists study DNA.and proteins for developing evolutionary relationships among organisms


Cytochrome c is a protein. It is present in the cellular respiratory pathways in all eukaryotic organisms. All closely related organisms have similar cytochrome c molecules. Little changes occurred in the cytochrome c during hundreds of millions of years. It suggests that mutations of the cytochrome c gene are always detrimental. The mutated organism died and rejected by the natural selection Cytochrome has changed little. Therefore, cytochrome c is conserved evolutionarily.

Not all proteins are conserved like cytochrome c. Variations in highly conserved proteins develop evolutionary relationships among distantly related organisms. isLlt, less conserved proteins are useful for looking at relationships among more closely related animals. Some proteins are conserved and others are not Therefore, a large numbers of proteins are compared between any two species.


Most the mutations are not selected. Sometimes, an extra copy of gene present. One copy may be modified. But the second copy synthesizes that essential protein. Therefore, the organism survives. Extra genetic material car arise by gene duplication. The accidental duplication of a gene on chromosome is called gene duplication.




Vertebrate hemoglobin and myoglobin are arisen from a common ancestral molecule. Hemoglobin carries oxygen in red blood cells. Myoglobin is an oxygern storage molecule in muscles. The ancestral molecule carried out both functions However, gene duplicated about 1 billion years ago. It is followed by mutation o one gene. Thus two polypeptides myoglobin and hemoglobin are formed. Further gene duplications occurred over the last 500 million years. Therefore, that hemoglobin of the most vertebrates have four polypeptides except primitive fishes.


A change in a portion of an organism while the basic form of the organisn is retained is called mosaic evolution.- Rates of evolution can vary both ii populations and in molecules and structures., A species is a mosaic of differen molecules and structures. These molcules and structures have evolved a different rates. Some molecules or structures are conserved in evolution. Othe molecules change more rapidly.

Example          –

All birds have highly conserved structures. They have structures like feathers bills, and a certain body form. Therefore, they are easily recognizable as bird However, particular parts of birds are less conservative. They have a higher rat’ of change. Wings have been modified for hovering, soaring, and swimminc Similarly, legs have been modified for wading, swimming, and perching. These are examples of mosaic evolution.

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