Lesson 6 - Representing Variation

Question 1

How is variation studied?

Answer 1

• Scientists take measurements of different characteristics within a species.
• Collect measurements from large numbers of the population to ensure that reliable conclusions are formed.
• Represent the data graphically, this enables patterns to be seen.

Question 2

Different types of variation shown by data collected?

Answer 2

• Discontinuous variation
• Continuous variation

Question 3

Discontinuous variation?

Answer 3

Characteristic that can only result in certain values is said to show discontinuous variation.

Question 4

Continuous variation?

Answer 4

Two extremes with a full range of values in-between. There is a graduation in values from one extreme to the other of a characteristic (this is known as continuum)

Question 5

Examples of continuous variation?

Answer 5

• Height
• Weight
• Number of antigens on a cell
• Number of leaves on a tree

Question 6

Draw a graph for continuous variation?

Answer 6

https://uk.images.search.yahoo.com/search/images;_ylt=AwrkMu1FWpNnKAIArYwM34lQ;_ylu=Y29sbwNpcjIEcG9zAzEEdnRpZAMEc2VjA3BpdnM-?p=graph+for+continuous+variation&fr2=piv-web&type=E210GB384G0&fr=mcafee

Question 7

What traits show continuous variation?

Answer 7

Those regulated by multiple genes (polygenes) and influenced by the environment

Question 8

Discontinuous variation definition?

Answer 8

Distinct categories with no intermediate values.

Question 9

Examples of discontinuous data?

Answer 9

• Hair colour
• Animals sex
• Blood group
• Shape of bacteria
  
  • Spherical (cocci)
  • Rods (bacilli)
  • Spiral (spirilla)
  • Comma (vibrios)
  • Corkscrew shaped (spirochaetes)

Question 10

Distribution of discontinuous data?

Answer 10

Individuals tend to be distributed evenly between different categories.

Question 11

What factors are traits that show discontinuous data influenced by?

Answer 11

Regulated by a single gene and aren’t under environmental influence.

Question 12

Representation of discontinuous data?

Answer 12

• Bar chart
• Pie chart

Question 13

What single gene are blood groups controlled by?

Answer 13

ABO gene

Question 14

Data representation of continuous variation?

Answer 14

• Frequency table
• Plotted onto histogram
• Curve is drawn on graph to show trend.

Question 15

What is a normal distribution curve?

Answer 15

Bell shaped curve which usually represents the distribution of continuous data.

Question 16

Characteristics of a normal distribution curve?

Answer 16

• Mean, mode and median are the same
• Distribution has a characteristic ‘bell shape’ which is symmetrical about the mean.
• 50% of values are less than the mean and 50% are greater than the mean.
• Most values lie close to the mean value - the number of individuals at extreme are low.

Question 17

Standard deviation?

Answer 17

• Measure of how spread out the data is.
• The greater the standard deviation, the greater the spread of data.
• In variation, a characteristic with a high standard deviation has a large amount of variation.

Question 18

Usual findings of standard deviation:

Answer 18

• 68% of values are within 1 standard deviation of the mean
• 95% of values are within 2 standard deviations of the mean
• 99.7% of values are within 3 standard deviations of the mean.

Question 19

Equation for standard deviation?

Answer 19

https://uk.images.search.yahoo.com/search/images;_ylt=Awr.rE.QXZNn6wEAnWUM34lQ;_ylu=Y29sbwNpcjIEcG9zAzEEdnRpZAMEc2VjA3BpdnM-?p=standard+deviation+equation&fr2=piv-web&type=E210GB384G0&fr=mcafee

Question 20

Flagella length variation in salmonella?

Answer 20

Salmonella bacteria have a number of flagella to enable them to move. There is continuous variation within the length of the salmonella flagella.

Question 21

Student’s t test

Answer 21

Compare the means of data values from two populations.
- Data collected must be normally distributed and enough data should be collected to calculate a reliable mean. Different sample sizes may be used.

Question 22

Spearman’s rank correlation coefficient?

Answer 22

Used to consider the relationship between two sets of data.

If two sets of data are related they are said to be correlated.

Question 23

Spearmen’s rank correlation coefficient?
Types of data shown?

Answer 23

• No correlation (no relationship between the data)
• Positive correlation (as one set of data increases in value, the other set of data also increases in value)
• Negative correlation (as one set of data increases in value, the other set of data decreases in value)