Theory of Evolution There is diversity in living things even within a species We don't all look alike We don't all behave alike Those traits can be passed on from parent to offspring Darwin didn't know how. Mendel did = Genes There is a struggle to survive Many organism mass produce offspring and few make it. There is high infant mortality for humans as well in some places

Theory of Evolution Organisms that are best suited to their environment have a survival advantage Doesn't necessarily mean the strongest At times it might be good to be small and quiet (early mammals) Survival of the fittest Those with a survival advantage will produce more offspring and pass their traits on to those offspring, thus the population will begin to have those particular traits Natural selection Already known from "unnatural selection" breeding techniques Large boar with large sow = large piglet.

Fundamental Genetics In a classic experiment Mendel studied the inheritance of seed color. Dichotomous traits peas can be brown or white True breeding lines plants bred to produce only white or only brown peas

Bred white pea plants with a brown pea plants offspring had all brown peas Then he bred the offspring with one another 75% brown and 25% white

Implications we do not necessarily inherit the traits of our parents Traits can be passed on across generations Phenotype Organisms observable traits Genotype Genetic material that can be passed on You may have Brown hair and so might your spouse Brown hair phenotype But it is possible to have a red haired child Red hair Genotype

Mendelian theory 1) There are two kinds of inherited factors for each dichotomous trait For Seed color A brown seed factor controls brown A white seed factor controls white Now we call these factors genes

2) Each organism has two genes for each of its dichotomous traits Each pea plant has either Two brown seed genes Two white seed genes Or one of each These pairs of genes that control the same trait are called alleles Homozygous two identical genes for a trait Heterozygous two different genes for a trait

Dominant vs Recessive Genes 3) One of the two kinds of genes for each trait dominates the other in heterozygous organisms Brown seed is dominant over white seed if heterozygous it will have brown seeds The only way to have white seeds is to be homozygous for white seeds

4) Each organism randomly inherits one of it’s father’s two genes and one of it’s mother’s two genes.