Types of Variation Understanding of variation is
Description: Types of Variation Understanding of variation is an important skill in classifying organisms and understanding their heritage What are the differences? In pairs study the differences that you can see between your hands and write a list of
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slide1. Types of Variation Understanding of variation is an important skill in classifying organisms and understanding their heritage<br>
slide2. What are the differences? In pairs – study the differences that you can see between your hands and write a list of them<br>
slide3. LEARNING OBJECTIVES To demonstrate knowledge of interspecific and intraspecific variation
To recall genetic and environmental causes of variation<br>
slide4. Differences between individuals Differences in organisms are known as variation
This variation is brought about by two different factors;
Genes
Environment
Even identical twins – who are clones of one another – have differences – how?<br>
slide5. Variation within a species – intraspecific variation Make a list of characteristics that can vary in humans
Now make a list of characteristics that can vary in sea-horses
It is far more difficult because we do not study them or relate to them in the way we relate to other humans
However sea-horses can tell one another apart as easily as we can<br>
slide6. Variation between species – interspecific variation This tends to be so obvious that Linnaeus was able to base a whole taxonomic system on it
E.g. a mouse has four legs and a tail, but so does a dog and you still see stark differences between them<br>
slide7. Genetic causes of variation Each gene can have many variations, even within one species
These different forms are known as alleles
E.g. human blood has 3 alleles – A, B and O
These can make 4 different blood types
The alleles each individual has are dependent on those inherited from its parents<br>
slide8. Genetic causes of variation These alleles are also open to change at anytime due to mutations
Mutations can be point mutations – where there is an addition, deletion or substitution to one or more base pair
What effect will this have on the organism?
They can also be chromosomal mutations where whole or parts of chromosomes are added or deleted
These have a far more obvious effect, more often than not they are even fatal<br>
slide9. Genetic causes of variation Mutations are a regular occurrence during cell division, estimated at once every 8 divisions
However as most of them happen in somatic (body) cells little effect is usually felt
If the mutation occurs during meiosis however the gamete and therefore every cell of the new individual is affected and the mutation is passed through generations<br>
slide10. Genetic causes of variation Sexual reproduction results in variation
This is because the gametes only pass on 50% of each parents genes
Meiosis also leads to the mixing up of the parental chromosomes through independent assortment and crossing over
Each gamete an individual makes is completely unique<br>
slide11. Genetic causes of variation Even siblings of the same gender must be, at least, subtly different due to chance combinations of gametes
This chance combination is known as random fertilisation as each combination must hold some difference no matter how slight
Species that reproduce sexually have greater variation than those who reproduce asexually where only mutation will have an effect<br>
slide12. Environmental causes of variation What colour was my hair when I started working here?
Environmental changes can be a choice or they can be thrust upon the individual
Make a list of environmental factors that can affect the physical or morphological characteristics of an organism – explain their effects<br>
slide13. A combination of the two! Most variation results from a combination of both the organisms genetics and their environment
Skin colour
Weight
Academic intelligence -
What about height?
This is known as “nature versus nuture”<br>
slide14. Back to our twins Make a list of characteristics that will be identical in the twins and another that might be different
What has caused each?
Now take a look at the twin study information on pg 250 and answer the 3 questions<br>
slide2. What are the differences? In pairs – study the differences that you can see between your hands and write a list of them<br>
slide3. LEARNING OBJECTIVES To demonstrate knowledge of interspecific and intraspecific variation
To recall genetic and environmental causes of variation<br>
slide4. Differences between individuals Differences in organisms are known as variation
This variation is brought about by two different factors;
Genes
Environment
Even identical twins – who are clones of one another – have differences – how?<br>
slide5. Variation within a species – intraspecific variation Make a list of characteristics that can vary in humans
Now make a list of characteristics that can vary in sea-horses
It is far more difficult because we do not study them or relate to them in the way we relate to other humans
However sea-horses can tell one another apart as easily as we can<br>
slide6. Variation between species – interspecific variation This tends to be so obvious that Linnaeus was able to base a whole taxonomic system on it
E.g. a mouse has four legs and a tail, but so does a dog and you still see stark differences between them<br>
slide7. Genetic causes of variation Each gene can have many variations, even within one species
These different forms are known as alleles
E.g. human blood has 3 alleles – A, B and O
These can make 4 different blood types
The alleles each individual has are dependent on those inherited from its parents<br>
slide8. Genetic causes of variation These alleles are also open to change at anytime due to mutations
Mutations can be point mutations – where there is an addition, deletion or substitution to one or more base pair
What effect will this have on the organism?
They can also be chromosomal mutations where whole or parts of chromosomes are added or deleted
These have a far more obvious effect, more often than not they are even fatal<br>
slide9. Genetic causes of variation Mutations are a regular occurrence during cell division, estimated at once every 8 divisions
However as most of them happen in somatic (body) cells little effect is usually felt
If the mutation occurs during meiosis however the gamete and therefore every cell of the new individual is affected and the mutation is passed through generations<br>
slide10. Genetic causes of variation Sexual reproduction results in variation
This is because the gametes only pass on 50% of each parents genes
Meiosis also leads to the mixing up of the parental chromosomes through independent assortment and crossing over
Each gamete an individual makes is completely unique<br>
slide11. Genetic causes of variation Even siblings of the same gender must be, at least, subtly different due to chance combinations of gametes
This chance combination is known as random fertilisation as each combination must hold some difference no matter how slight
Species that reproduce sexually have greater variation than those who reproduce asexually where only mutation will have an effect<br>
slide12. Environmental causes of variation What colour was my hair when I started working here?
Environmental changes can be a choice or they can be thrust upon the individual
Make a list of environmental factors that can affect the physical or morphological characteristics of an organism – explain their effects<br>
slide13. A combination of the two! Most variation results from a combination of both the organisms genetics and their environment
Skin colour
Weight
Academic intelligence -
What about height?
This is known as “nature versus nuture”<br>
slide14. Back to our twins Make a list of characteristics that will be identical in the twins and another that might be different
What has caused each?
Now take a look at the twin study information on pg 250 and answer the 3 questions<br>