Transcript Mr Men Variation and Inheritance

Variation and Inheritance
LO: To learn how
characteristics can vary.
with…
The Mr Men Match.
Variation
“Variation” is the name given to differences between individuals of the SAME species.
Variation is due to GENETIC or ENVIRONMENTAL causes. For example, consider
identical twins:
1) Ways in which Tom and James
are the same (caused by
genes):
2) Ways in which Tom and James
are different (caused by
environment):
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What’s that then?
Genes, Chromosomes and DNA
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Where is this information stored?
Section of a chromosome:
Genes for blood
group:
Genes for eye
colour
Genes for hair
colour
Different species have different numbers of chromosomes.
Humans have 46 (23 pairs) in every cell.
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Genes
Sexual Reproduction
The human egg and
sperm cell
(“GAMETES”) contain
23 chromosomes each.
When fertilisation happens the gametes
fuse together to make a single cell called a
ZYGOTE. The zygote has 46
chromosomes (23 pairs).
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So what causes variation?
Meet our Mr Men
And our Little Misses
Now lets meet their children!
What did we learn from this?
• Children inherit features from their parents
• If two parents have a certain characteristic then
their child may show it even more (e.g. Mr Small +
Little Miss Tiny = Mr Very Small!)
• Some things such as glasses, scars and muscles
we get from our environment, they are not
inherited.
Genetic information
• The instructions that make up a plant or
animal comes from their parents.
• ½ comes from the sperm and ½ from the
egg
• These instructions are found in the
nucleus of the cells.
• The instructions for each characteristic are
called GENES.
We saw that when Mr Small and Little Miss Tiny
produced a child it was even smaller.
What would happen if Mr Very Small had a child with
Little Miss Miniscule??
This is called selective breeding and can be used
to make larger animals and crops that produce
more fruit
Large fruited Dad
Large fruited Mum
Very large fruited child!
This is depending on the
strength of the genes...
• Some genes have more clout when it
comes to deciding a feature than others.
• “Stronger” genes are known as dominant
• “Weaker” genes are known as recessive.
• The gene for brown eye colour is
dominant. If one of your parents have
brown eyes it is very likely you will too!
• There’s still a small chance of blue eyes but the
probability is decreased.
Variation
• Level 4 – Recognise difference between
organisms of the same species
• Level 5 – Explain what may have caused
some examples of variation within a
species
• Level 6 – Suggest why variation might
increase an organisms chances of survival
• Level 7 – Explain, using variation, why
certain species have become extinct
Variation…your task
• You have been asked to produce a poster for Year 8 students to
teach them about ‘variation’.
• Use you LOs as your level ladder for this task and tick them off as
you go 
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Key words;
Variation
Gene
Inherit
Environmental
Survival
Extinction
Organism
Don’t forget to include the two types
of variation and examples of each!
Lets see what you’ve learned:
Farmer Hemming wants to breed cows that are
large and meaty so that he can sell them for
more.
1. What advice would you give him in order to
produce larger cows?
2. He can’t seem to breed cows with nose rings!
Why not?
3. How many chromosomes are in your cells?