Variation
LO: state the causes of continuous and
discontinuous variation
-define a mutation and the factors which can
cause mutations
TASK: These are all genetically identical twins. However, they
don’t look exactly alike? Discuss with your partner possible
reasons for this.
Organisms can be genetically
identical (clones) but still show
variation due to environmental
differences between them
Eg. One of these twins had an
increased supply of blood in the
uterus so it was born larger.
Some characteristics are purely genetic
while others are environmental or a
combination of both
Genetic, environmental or a
combination of both?
Normal hair colour
Eye colour
Weight
Good at maths
Foot size
Height
Hand size
Skin colour
Ability to sing
Nose shape
Mouth shape
Tongue rolling
Cut on hand
Missing tooth
Blood type
Personality
Freckles
Language you talk
Your name
Your sex
Inherited diseases
Ability to draw
Length of hair
Colour of birds
feathers
TASK: Measuring variation
•
•
Measure height in cm using tape measure
Eye colour: (blue, green, hazel, brown, grey,
black)
• Natural hair colour: (blonde, brown, red,
black)
• Can you roll your tongue? (yes/no)
1. Record your results in a table
Discontinuous Variation
• Are distinct, separate peaks/bars
•
•
•
•
Distinct phenotypes eg. Blood type A,B, AB, O
Tends to have no overlap between categories
Are controlled by a small number of genes
Are largely unaffected by the environment
What did we find?
• Height shows a
continuous variation –
there is a range of
values with most people
roughly in the middle
• Eye colour, hair colour
etc show a
discontinuous variation
– there are distinct
groups but some are
more common
Eye colour in 9K
8
7
6
5
4
Frequency
3
2
1
0
blue
green
hazel
brown
grey
black
Continuous Variation
• Is a continuous range of values so get a smooth bell
curve (normal distribution)
•
•
•
•
Are no distinct categories to place individuals e.g height
Tends to have overlap between categories
Are controlled by a large number of genes
Are significantly affected by the environment
Mark scheme
Genotype + environment = phenotype
Summary
1. Sudden random changes in genes that are passed from one
generation to the next are
A mutations B hybrids. C antibodies. D daughter cells.
2. Mutations can become adaptations if
A. they are harmful to the organism.
B. they make the organism less able to survive in the
environment.
C. they help an organism to survive and reproduce in the
environment.
D. are neither harmful nor beneficial to the organism.
Investigating variation
Name
Height
(cm)
Hand span
(cm)
Is there a
relationship
between your
height and hand
span?
Homework
1. Create a title page for this module
2. Make a family tree of your parents, yourself
and any brothers / sisters. List the
differences between you which you have
inherited and those which are due to the
environment