New Topic

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New Topic

• BD4
• Variation and Inheritance

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• Cell structure and functions
• Plant and animal cells
• Cell division
• Variation

Inheritance Evolution Natural selection Selective
Breeding
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Why do we look like we do?
All living things vary in the way they look or
behave.
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Look around the class
How are we all similar?

• We have 2 arms, 2 legs, 2 eyes etc
• We belong to the same species

How are we different?

• Some are male, some are female
• Some are taller, heavier
• Some have different coloured eye

Living things that belong to the same species
are all slightly different.This is called
variation
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Dont forget the plants!
Look at these rose bushes they are different
too. How are they different?
They have different colours, different height and
some have more flowers than others.
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Differences
The differences between organisms are known as
VARIATION.
The differences between two trees are only small
because they have similar GENES.
There are wide differences between a tree and a
panda because there is a big difference in their
genes.
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The small differences between organisms of the
same SPECIES are caused by two factors INHERITED
CHARACTERISTICS small differences in the genes
or chromosomes within a species. ENVIRONMENTAL
CHARACTERISTICS differences brought about due
to environmental conditions. Things we learn to
do.
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Inherited Characteristics
Humans get half of their genetic information from
their mother and half from their father. We gain
INHERITED CHARACTERISTICS from our parents.
Can you roll your tongue??
It is an inherited characteristic. What sort of
characteristics are inherited
Eye colour
Hair colour
Height
Genetic diseases
Blood group
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Genes
As well as controlling the cell, the NUCLEUS also
contains GENETIC INFORMATION.
Nucleus
The nucleus of human cells (not sperm and ovum)
contains 23 PAIRS OF CHROMOSOMES, making a total
of 46 chromosomes in every nucleus.
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These chromosomes contain GENES (again in pairs).
Each gene controls a characteristic hair colour,
eye colour etc. There are thousands of different
genes, so the combination of genes is endless
the chance of 2 people having the same genes is
virtually impossible. Identical twins are the
exception
SPERM and OVUM cells contain 23 chromosomes.
When they FUSE during FERTILISATION, they make a
total of 46 chromosomes.
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Environmental Characteristics
Our eye colour and blood group are inherited
characteristics. We get these genes from our
parents.
Other characteristics depend upon our
environment. These are called ENVIRONMENTAL
CHARACTERISTICS.
Your weight and eventual height depend, in part,
on your diet (as well as your genes). Weight and
height are environmental characteristics.
Task Imagine that there are two twin brothers.
One brother was brought up on a well-balanced
diet and one was brought up on a diet of junk
food. What possible differences could there be in
their appearance?
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Watch the video Gene genie to find out more
about his topic
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Causes of Variation
Genetic Inheritance
Environment

• Some characteristics are are passed down from
  parents

• Caused by the way you lead your life
• You are not born with them but you acquire or
  learn these features

For example rolling your tongue, eye colour,
hair colour
For example Body build, skin colour
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WHAT ABOUT AN OLYMPIC ATHLETE?
She needs speed, agility and strength. Are these
just inherited?
No. They are improved by training, diet and the
right lifestyle
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• Variation in animals
• We vary because of random way genes are inherited
• Environment can affect most of our
  characteristics
• Usually combination of inheritance and
  environment
• Inherited only eye colour, natural hair colour,
  blood group, inherited diseases

• Variation in plants
• Affected by small changes in the environment eg
  sunlight, moisture level, type of soil
• Plant growing in sunlight will grow much father
  than one in the shade
• Compare to dog living in England and moved to
  Africa!

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How can we prove the differences are due to the
environment?

• Produce clones of plants by taking cuttings.
• Cuttings are genetically identical to each other
• Grow them in different conditions
• Any differences will be due to environment
• If dont produce clones
• Replant them in different pace sand see if they
  grew more alike
• Place 2 plants of same species in same condition
  to see if environment caused differences again.
• Or look at identical twins brought up in
  different
• environments

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Which of these characteristics are inherited and
which are affected by the environment?
skill at languages body weight
E
E
Neat writing shape nose scars
E
E
Blood group freckles eye colour
E
E
Hair length an accent
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Types of Variation

• Differences between plants and
• animals show two types of variation
• continuous
• discontinuous

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Types of Variation
Discontinuous
Continuous

• 2 extremes
• No intermediates
• Usually due to genes
• Environment has no influence
• For example eye colour,
• blood groups,coloured flowers

• Range of of examples
• Usually environment responsible but can be
  genetic.
• For example, height

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Survey

• Investigate 5 people
• Which characteristics are inherited?
• Which characteristics are caused by the
  environment?
• Display your data in bar charts and pie charts
• Or
• Do investigation Roberts page 399

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Work to do

• Read Roberts pages 398 and 399 and/or worksheet
  11.4
• Answer assignments 1-5 on page 399
• Or
• Staged assessments workbook page 1
• Q. 1-4 and page 2 Q 8
• 0r
• Higher workbook pages 82/83
• Questions 1-9
• Or
• Foundation workbook pages 92-93