Plants reproduce sexually. Therefore, pollen, which contains sperm fuses with an ova to produce a fertilized egg plus food or endosperm. Since there are two parents, two haploid sets of chromosomes are given to the offspring. Due to the law of independent assortment, combinations of genes in the sperm and eggs will vary and no two sperm and eggs will be identical. Therefore, in every fertilization, a unique individual will be produced. Another reason why seedlings will differ could be due to mutations. If a gene is mutated, it can produce a phenotype with traits different from the parents. Another reason seedlings may differ is due to the environment. In multifactorial traits, the environment plays a role in gene expression. Temperature, nutrients, amount of light can all play a role in how a particular gene is expressed in a phenotype.