Variation and Inheritance LO: To learn how characteristics can vary. with…

The Mr Men Match.

Variation Ways in which Tom and James are the same (caused by genes): “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: Ways in which Tom and James are the same (caused by genes): Ways in which Tom and James are different (caused by environment): 06/04/2017

What’s that then?

Genes, Chromosomes and DNA 06/04/2017

Where is this information stored? Section of a chromosome: Genes for eye colour Genes for blood group: Genes for hair colour Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell. 06/04/2017

Genes Human cells have 46 chromosomes other organisms have different numbers of chromosomes.

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). 06/04/2017

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 Mum Large fruited Dad Very large fruited child! At this point give out picture of the giant bull.

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  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. 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?