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Evolution
The World of Darwin
Genes and Phenotype
Genes and Phenotype
Every living organism is the outward, physical manifestation of internally coded, inheritable information.

Starting from a fertilized egg, a goldfish has all the genes necessary to construct an agile, water dwelling creature capable of swimming. The genes on it's chromosomal DNA molecules are repeatedly copied as the cells divide in the embryo and are transmitted over and over again.

In each new cell transcription and translation decodes the genes and produces proteins. These proteins then function as enzymes, muscle fibers, components in membranes, and so forth, all combining to create the outward physical manifestation that we recognize as a goldfish. This is it's phenotype.

On the other hand, an eagle has all the genes necessary to construct an aerodynamic, air-breathing, feather-covered carnivore that is at home in the high mountains and wildness areas. This is it's phenotype, and this too was the product of its genotype.

Adapted Both organisms are well adapted to their environments. With gills and a streamlined body, the fish moves easily though ponds and streams, whereas the eagle has the most efficient lungs of any creature and its feathered forelimbs are shaped into near perfect airfoils.

The bodies of the fish and the eagle, and hence their phenotypes, are exactly right for their place in the local ecology in almost every way.

They fit into the web of life with the correct specifications for obtaining energy, growing, reproducing and passing on the genes that enable them to do all this in the first place.

Genes in a fertilized egg express themselves as a phenotype that fits or is adapted for the environment in which the organism lives.

A good fit
If this phenotype is a suitable one and the adaptation good, then that organism will flourish, grow, and stand and excellent chance of passing on those genes to the next generation.

If the combination of genes produces a poorly adapted phenotype, then the chances of survival will be lower, and the likelihood for successful reproduction will be less. There is a strong connection between genotype-phenotype and the environment in which they must function.

In the march of time, it is the survivors who pass on their genes to the next generation. Success is measured by how many of your genes end up in the offspring surviving into the next generation and beyond.


BIOdotEDU
© 2001, Professor John Blamire