a graph that shows the distribution of a variable used to “summarize” data visually on a graph

a single continuous variable broken into different intervals ~8-20 intervals

the number of individuals in that interval “amount”, “frequency” or “percentage”

Die Roll

Height (cm)

Height (cm)

Height (cm) Distribution Curve: a line drawn over the bars of a histogram to summarize patterns

Height (cm) Normal Distribution: a distribution that is symmetrical around the mean

Height (cm) Standard Deviation = 5 inches Standard Deviation = 2 inches

Height (inches) Standard Deviation: a measure of variance High Standard Deviation = High Variation Low Standard Deviation = Low Variation

RIGHT SKEWEDLEFT SKEWED

MEAN MEDIAN MODE

In a normal distribution, MEAN, MEDIAN, and MODE are centered in the middle

MEDIANMODE

MEAN MEDIANMODE

MEAN MEDIANMODE

In a skewed distribution, the MODE is at the peak the MEDIAN splits the area under the curve in half Area left of the median = Area right of the median the MEAN is in the direction of the skew The MEAN is most influenced by the skew.

Within a species, there is usually a great deal of variation among individuals.

Variation: is a measure of differences

INHERITED VARIATION results from the differences in DNA also known as “genetic variation” most inherited variation cannot be changed Examples: blood type, hair color, eye color, mid-digit hair, etc.

SOURCES OF GENETIC VARIATION Sexual Reproduction: genes mix when two parents create offspring Mutations: individual genes randomly mutate within an individual

ACQUIRED VARIATION results from differences in individual lifestyles does NOT affect your DNA does NOT get passed on to offspring Examples: muscle mass, obesity, hair dye, many skills

SOURCES OF ACQUIRED VARIATION the environment

North side, upper branches South side, upper branches North side, lower branches South side, lower branches The differences between apples are acquired during the growing season. Difference will not be inherited. Apples collected from different positions on the same tree.

Most differences in an individual are the result of inherited and acquired variations.

low variance high variance Cheetahs, Manatees Leopards, Cuttlefish Populations prefer to have high variation to increase their chance of survival Having high levels of variation allow more potential for evolution

 Clause Wedekind  1998  Bern University in Switzerland SWEATY SHIRT EXPERIMENT  49 men wore the same shirt for 2 days  44 women were asked to rank the shirts in order of smell preference  the scientists measured the MHC genes (genes related to smell) of each male and each female  the results found that women preferred shirt smells from males who had the most different MHC genes from their own  Women preferred males whose paired offspring would have the greatest genetic variation