LIFE SCIENCES 2012 Evolution Studies

Theories of the process of Evolution LamarckWallace / Darwin Law of use & disuse Law of inheritance of modified characteristics Natural Selection

Mechanisms of Evolution  Seldom ever only one mechanism involved  Most of the time a combination of mechanisms  Compare driving in a car, it is not simply going to its destination, many things must happen on the way: Petrol in the tank Spark plugs A driver Key in the ignition Map or idea where to go Generally 4 wheels with tyres

 If only one of these elements is missing the outcome will not be the same.  If one of these elements is different, diesel instead of petrol, the outcome will also be different.  In the same way the mechanisms and how they interact will determine the outcome of evolution.  An outcome is not necessarily beneficial, but we never see that creature because it will usually die.  Organisms with beneficial outcomes, have the ability to survive, but the environment still has to match their adaptations / characteristics.

 REMEMBER: the creature cannot CHOOSE to develop a needed characteristic, it is either born with it or not.  If the characteristic is not a ‘NORMAL’ one, then the organisms has undergone a mutation.

Gene Flow  During migration of individuals from one group to another, with interbreeding there is a mix of genes in the gene pool.

Genetic Drift  Small group of individuals leaves their population, starts a new population in geographically isolated area, they undergo changes because of their limited gene pool.  It does not necessarily need anyone to leave, the drift can occur because of outside factors never before experiences.  Simply, the genetic combinations get ‘FORCED’ in a specific phenotypic direction.

Types of Genetic Drift 1. Bottlenecks = when a specie or population is suddenly thinned out, the few that remain can only have kids that look like them, or their limited genetic variety. (seen in once large populations)

2. Founder Effects = with the start of a new colony by a few members of the original population, the offspring will show concentrated genes that existed with their parents in the beginning. (seen in small groups)

Adaptive Radiation  Evolution of ecological AND phenotypic diversity in fast multiplying population which results in new specie development.

Speciation  The final result of all the mechanisms, those things that were pushing and pulling what the organisms look like.  When a population is isolated by geographic barriers such as islands, the isolated organisms of that population can’t interbreed with their previous fellows, and will thus become different.  If they become so different that they cannot interbreed anymore, they have formed a new specie.

ALLOPATRIC SPECIATION – geographic isolation

SYMPATRIC SPECIATION – due to natural preferences or influences