Variation and Evolution

• variation is the differences in the characteristics of individuals in a population
• the cause of variation is genetics and environments
• genetic variation is the variation in genotypes of organisms of the same species due to the different alleles they have
• phenotype is the physical appearance or observable characteristic of an organism
• environmental variation is caused by environmental factors that affect an individual's phenotype
• mutations are changes in DNA sequence which can be caused by errors during replication or exposure to radiation or chemicals
• natural selection is the process whereby some members of a population survive better than others because of their inherited traits
• a mutant gene is one with a change in its base pairing sequence
• genetic variation in a species is created by spontaneous mutations and sexual reproduction
• the first 22 pairs of chromosomes determine our characteristics such as eye colour and height
• three types of gene mutation insertion, deletion and substitution
• deletions remove bases from the DNA sequence
• insertions add extra bases into the DNA sequence
• substitutions replace one base with another
• gene mutation affect an organisms phenotype by

  1. neutral mutation does not change the sequence of amino acids. protein structure and function same. no affect on phenotype
  2. mutation may cause a minor change in an organisms phenotype e.g change in eye colour