Download discrete-and-continuous

National 5 Biology
Key Area 5:
Variation and Inheritance
National 4 Biology
Key Area 4
Genetic Information
By the end of the lesson you
will be able to …..
• Name the two types of variation that
exist amongst members of a species.
• Give examples of traits that
demonstrate the two types of variation.
Differences between
members
of the same species is called
Spot
the difference!
‘variation’.
How thegenes
pupils
below
from each
other?
Combining
from
two different
parents contributes
to variation
within a species ~ sexual reproduction!
Gender
Hair
colour
Hair
type/
texture
Eye
colour
Eye
shape
Nose
shape
Skin
colour
Face
shape
Skin
type
Ear
shape
Height
Leg
length
It’s not just humans….
Any organism (animals and plants) produced by
sexual reproduction will display variation….
Variation within a species
• Our genes determine our features, e.g.
our height.
• Combining genes (during sexual
reproduction) from two parents
contributes to variation within a
species.
Why is variation important?
Variation is important because it allows
organisms to adapt and survive.
Discrete Variation
• E.g. 4 Blood groups: A, B, AB and O
Discrete Variation
• E.g. Fingerprint Type
Discrete Variation
• E.g. earlobe
attachment
Discrete Variation
• A characteristic shows discrete variation
if it can be used to divide the species into
two or more distinct groups
• These traits are controlled by single gene
inheritance
• E.g. Tongue rolling
Discrete Variation
• Statistics on
discontinuous
variation are
presented using BAR
GRAPH
• Bars DO NOT touch
each other or the Yaxis
• Labels on both X and
Y-axis
Continuous Variation
• E.g. Weight
Continuous Variation
• E.g. Birth weight
Rumaisa Rahman weighed
8.6 oz – same as a can of
coke
In 2005, 17lb Ademilton dos Santos
was born.
In 1879, Anna Bates in Canada gave
birth to a 23.12lb baby (died 11 hours
after birth)
Continuous Variation
• E.g. Skin colour
Continuous Variation
• A characteristic shows continuous variation if
members of the species vary in a smooth continuous
manner over a range of values – there are NO
DISTINCT GROUPS
• These traits are controlled by many genes polygenic inheritance
• E.g. height
Continuous Variation
• Statistics on
continuous
variation are
shown on a
HISTOGRAM
• The range of
values are
divided into
small groups
• Bars should
touch each other
Can you now ….
• Name the two types
of variation that
exist amongst
members of a
species.
• Give examples of
traits that
demonstrate the two
types of variation.