a graph that shows the distribution of a variable used to “summarize” data visually on a graph
TRANSCRIPT
HISTOGRAM• a graph that shows
the distribution of a variable
• used to “summarize” data visually on a graph
X-AXIS
• a single continuous variable broken into different intervals
• ~8-20 intervals
Y-AXIS
• the number of individuals in that interval
• “amount”, “frequency” or “percentage”
Die Roll
1 2 3 4 5 6
Height (cm)
130 140 150 160 170 180 190 200
Height (cm)
130 140 150 160 170 180 190 200
Height (cm)
130 140 150 160 170 180 190 200
Distribution Curve: a line drawn over the bars of a histogram to summarize patterns
Height (cm)
130 140 150 160 170 180 190 200
Normal Distribution: a distribution that is symmetrical around the mean
Height (cm)
130 140 150 160 170 180 190 200
Standard Deviation = 5 inchesStandard Deviation = 2 inches
Height (inches)
130 140 150 160 170 180 190 200
Standard Deviation: a measure of variance High Standard Deviation = High Variation
Low Standard Deviation = Low Variation
RIGHT SKEWED LEFT SKEWED
MEANMEDIAN
MODE
In a normal distribution,MEAN, MEDIAN, and MODE are centered in the middle
MEDIANMODE
MEANMEDIANMODE
MEAN MEDIAN MODE
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 variationallow 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