#143 Summary of Selection and Evolution

1 Genetic variation within a population is the raw material on which natural selection can act. 

2 Meiosis, random mating and the random fusion of gametes produce genetic variation within populations of sexually reproducing organisms. Variation is also caused by the interaction of the environment with genetic factors, but such environmentally induced variation is not passed on to an organism’s off spring. The only source of new alleles is mutation. 

#142 Species and speciation

Isolating mechanisms can lead to the accumulation of different genetic information in populations, potentially leading to new species.

#141 Evolution and Extinction

General theory of evolution: organisms have changed over time.

#140 Artificial selection

Humans use selective breeding (artificial selection) to improve features in ornamental plants, crop plants, domesticated animals and livestock.

#139 Natural selection

Populations of organisms have the potential to produce large numbers of offspring, yet their numbers remain fairly constant year after year.

#138 Genetic variation

The variation that exists within a species is categorised as continuous and discontinuous. The environment has considerable influence on the expression of features that show continuous (or quantitative) variation.

#137 Selection and Evolution Syllabus 2016 - 2018

17.1 Variation
17.2 Natural and artificial selection
17.3 Evolution