Evolution Theories
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1.-Conditions of the environment change and generate new needs in the individual which demand that they modify their behaviour
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Lamarckism or impersonation Species transform due of the environment induced modifications of the place where they live these transformations a transmitted to their descendants.
2.-The need creates the organism the organs most used develop more and the least used atrophy or can even disappear
3.-The acquired modifications are transmitted to their offspring and favor the origin of a new species
Darwinism or evolution by natural selection: species evolve slowly by the action of natural selection. 
1.-Between individuals of the same species there are differentiated characteristics or variations that are inherited
2.-The fight for survival the individuals generate as many descendants as possible.
3.-Survival of the most apt the individuals that have more beneficial variations survive and produce more descendants
4.-The natural selection acts over the species and has beneficial variations causing them to change continuously and to originate a new species
Neo-darwinsim or synthetic of evolution: the evolutionary processes are produced by the changes presents in the genetic composition of populations
1.-Mutations as a source of variability. these are inherited changes produced in the genetic material and give place to differentiation among individuals .
2.-Sexual reproduction increases variation because it generates new gene combinations thus different individuals
3.-Natural selection acts over certain individuals so that they have more possibilities of producing offspring
4.-The adaptation to an environment is produced in the course of time and leaves as result a population which is better prepared to survive in the enviromente
5.-The speciation is a mechanism of formation of a new species from populations already adapted to the environment it is the product of three factores
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Example: as a giraffe stretches its neck to browse higher in trees, the continuation of the habit over an extended period results in a gradual lengthening of the limbs and neck.
Example: treefrogs are sometimes eaten by sneak and frogs
Example: .