How do characteristics within a species vary? variability is important for survivability some variations are based on genetics –heritable traits (e.g. hair colour) some variations are based on behaviors –non heritable traits (e.g. good at soccer) some variations in individuals result from interactions with the environment (e.g. a plant placed in window with lots of light will be green and bushy, a plant placed away from light will look pale and spindly)

Discrete Variation EITHER/OR –differences in characteristics that have a defined form – e.g. a cat has either blue eyes or brown eyes Continuous Variation –differences in characteristics that have a range of forms (not one or the other) –e.g. height of people

Check it out! clasp your hands –which thumb is on top (L or R) –try it a few more times…does the result change –class stats. –is this a discrete variation or a continuous one? check out your ear lobes compared to your neighbors –are they attached? or not? –is this a discrete variation or a continuous one? can you roll your tongue? –is this a discrete variation or a continuous one?

How are traits transmitted from parents to offspring? heritable trait – a characteristics you get from your parents –e.g. hair colour, dimples, ear lobes, eye colour its in the genes … & its called inheritance

How does it work? A dominant trait is one that will always be visible if it is present. –e.g. brown hair is a dominant trait in humans so if a gene for brown hair is present you will have brown hair A recessive trait will always be hidden unless no dominant trait is present –e.g. blond hair is a recessive trait in humans and will only be seen if these are the only genes present

How do you get your traits? For each trait (e.g. hair colour) offspring will have two forms of the same genes (one from each parent) called alleles. Both can be a dominant trait, both can be a recessive trait, or one can be dominant and one can be recessive. we use a PUNNETT SQUARE to predict possible trait outcomes based on the alleles

Punnett Square

purebred –only dominant or recessive traits present hybrid –dominant and recessive traits are present –the dominant trait shows up

What if you get a mix? incomplete dominance – when the outcome is a blend of the dominant and recessive trait

Write your own story draw a Punnett square for eye colour using your parents –what trait did you? –what trait did your sibling(s) get? –are you purebreds or hybrids? pick a partner – draw a Punnett square for eye colour imagining that you were to be parents –what eye colour traits might your children have –what are the chances of a particular outcome? try this exercise with hair colour or another trait you are interested in

Who’s Related in Muggsville?