Sources of Variation

PHENOTYPHIC VARIATION

Due to variations in genetic constitution or to effect of environment

GENOTYPHIC VARIATION

Result of meiosis, chance fertilisations mutations

Gametes produced by meiosis are different

Chance fertilisation of egg cells by sperm cells = fusion of many types of sperm & egg cells can produce many different types of offspring.

Mutations = sudden, random changes in genetic code

Crossing over during Prophase 1

Random arrangement of chromosomes during Meta phase !

Lethal (most mutations) = mutated organism dies & harmful characteristics not passed to next generation

Few mutations are advantageous - they wipe out other alleles controlling same characteristic within population = FIXED MUTATIONS

Many mutations are neutral (have no effect on structure & functioning of organism)

SOURCES OF VARIATION