Darwin's Postulates

Nicolas Olivares

Variation among individuals within species

Variation can be known as different individual within different species. We are surrounded by different organisms which are known to be as different species. Species as well are known to be different from each other making no individuals be identical. Something that can get to happen is asexual reproduction which produces identical offspring called clones and identical twins which are seen in sexual reproduction. Even though they are known as clones and identical twins they can also be different from one another depending on the environmental conditions they live in. Moreover, variations can be seen du to environmental or genetic factors. Environmental factors can be referred to food, temperature, etc.
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Some of the variation is heritable

So what does it mean for a trait to be heritable? Well as you know people tend to have similar aspects and character traits to their parents. For example, we can see how tall people most usually have tall parents, but other families tend to have shorter heights than others. Still, this does not define the whole concept of heritable traits, sometimes you can be passed some genes which are not necessary from you parents but another person in your tree line for example your grandmother or grandfather. Phenotypic variation must be heritable but there is also certain metabolic traits which are based on individual variation but no heritability. An important finding in the evolution of genetics is the discovery of substantial genetic variation which are called canalized characters. Genetic differences can be revealed if the organism is put in a stressful environment.

Overproduction of young is the rule

Most of the species start receiving the best offsprings which will help them survive at least to the reproductive age with certain selection pressures like predation and limited food supply or resources. A perfect example could be the rabbits in the activity we made, some had certain genes which helped them survive for a longer period of time than others such as the big teeth or the skin color to camouflage. The rabbits past the best offsprings to the next generations facilitating the way they live.

Non-random survival and reproduction

Those organisms or species which have more favorable traits will have higher possibilities of surviving and reproducing when naturally selected. In order for a specie to have greater chances of surviving different types of environments he need to inherit traits which match the environment they are in, this could be passed on by genes of their parents. The offspring that survive are known as the ones that have the greatest fitness therefore the best traits. A trait that helps the organisms survive because of its fitness is known as an adaptation. Since the offsprings that survives the longest are the fittest they keep on passing this same genes which are known as next fit allele generation.


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Griffiths, A. J. (2000, May 02). Heritability of variation. Retrieved April 07, 2016, from http://www.ncbi.nlm.nih.gov/books/NBK21911/

Hawks, J. (2011, November 13). What does it mean for a trait to be heritable? Retrieved April 07, 2016, from http://johnhawks.net/node/27924/

Smith, A. (2007, April 19). Introduction to Ecological Genetics. Retrieved April 07, 2016, from http://ib.berkeley.edu/courses/ib162/Week1.htm