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,...

Isolating mechanisms can lead to the accumulation of different genetic information in populations, potentially leading to new species.Species and speciationspecies: a group of organisms withsimilar morphological, physiological, biochemical and behavioural featurescan interbreed to produce fertile offspringreproductively...

General theory of evolution: organisms have changed over time.Molecular comparison between species1. Comparing amino acid sequences of proteinsNumber of difference in the nucleotide sequences measure how closely related the species are.2. Comparing nucleotide sequences of mitochondrial DNAHuman mtDNA:inherited through...

Humans use selective breeding (artificial selection) to improve features in ornamental plants, crop plants, domesticated animals and livestock.- selective pressure: humans- individuals with desirable features are chosen to interbreed = selective breeding- some of these desirable alleles are passed onto offspring- offspring...

Populations of organisms have the potential to produce large numbers of offspring, yet their numbers remain fairly constant year after year.Natural selection occurs as populations have the capacity to produce many offsprings --> compete for resources --> individuals best adapted to survive breed and pass on their...

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.Discontinuous variation- qualitative differences- genetic basis:different alleles at a single gene locus have...

17.1 Variation17.2 Natural and artificial selection17.3 EvolutionCharles Darwin and Alfred Russel Wallace proposed a theory of natural selection to account for the evolution of species in 1858. A year later, Darwin published On the Origin of Species providing evidence for the way in which aspects of the environment act...