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Contents. Variation. What is variation?. Causes of variation. Classifying variation. Investigating variation. Variation quiz. Variation between species. Variety is the spice of life!. Variation is the differences between different living things.
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Contents Variation What is variation? Causes of variation Classifying variation Investigating variation Variation quiz
Variation between species Variety is the spice of life! Variation is the differences between different living things. How many differences between living things can you name? What causes the differences between species?
Variation between species Species are different because their genes are different. Genes are the biological code for different characteristics. Humans have human genes. Bananas have banana genes. Gerbils have (yes, you’ve guessed it) gerbil genes!
Variation within species The current population of planet Earth is more than 6 thousand million people! No two people are exactly the same. How is this possible?
Variation within species Members of the same species also show variation. These differences are called characteristics. How many human characteristics can you think of that show variation? What causes each person’s unique characteristics?
Contents Variation What is variation? Causes of variation Classifying variation Investigating variation Variation quiz
Spot the family likeness Members of the same family often look similar. Mum Dad son daughter Which parent do these children look more like? If the son grows up to have children who might they look like?
Inherited characteristics Why do members of the same family look similar? Mum Dad son daughter Humans, like all living things, inherit characteristics from their parents. How are characteristics passed on?
Inherited characteristics This new-born baby’s characteristics are passed in the genes it has inherited from its parents. Like all babies, this little boy carries a unique set of genes, half from his mother and half from his father.
Causes of variation People are different because they inherit different characteristics from their parents. But areyour characteristics only affected by your genes? What else will influence the characteristics of this baby as he grows up?
Causes of variation When he gets older, this baby might support a different football team (like Fulham) or not even like football. Your upbringing and the environment in which you live also affect how you turn out as an adult!
Causes of variation • Your unique characteristics are caused by: • the unique set of genes you have • inherited from your parents • the environment in which you have • developed Differences in some characteristics are due to a combination of bothinherited and environmentalfactors. Name three examples of this type of characteristic.
Variation in plants Plants inherit characteristics through their genes just like humans and other animals. What characteristics have these plants inherited? Are plants also affected by their environment?
What causes variation in plants? Plants are affected by four key environmental factors. Can you name them? With a little more moisture, light or warmth the size of a plant can double. (Imagine if that happened to us!) Plants are affected by their environment in a big way! water sunlight temperature nutrients in soil
Contents Variation What is variation? Causes of variation Classifyingvariation Investigating variation Variation quiz
How to classify variation Characteristics can be classified in different ways. How would you categorise variation in eye colour? Could you categorise variation in height in the same way? Variation in eye colour can be easily categorised in distinct groups. You either have a certain eye colour or you don’t. Height variation doesn’t fall into separate groups it covers a range of values. Your height changes as you grow.
How to classify variation Characteristics can be classified into two types: continuous variation discontinuous variation A feature that can be measured and given a value from a range of values shows continuous variation. A feature that cannot be measured but is one of a fewdistinct options shows discontinuous variation. Which type of variation are eye colour and height?
Continuous variation What is continuous variation? This type of feature varies over a continuous range of values. Examples of continuous variation include mass, height, skin colour, intelligence and leaf area. Bar chart to show the range of masses in a rugby team 6 5 4 3 number of rugby players 2 1 Continuous variation is due to the combined effects of genes and the environment. 0 1 70 80 90 100 110 120 130 weight (kg) Does this mean the value of such a feature is fixed or can it change?
Discontinuous variation • What is discontinuous variation? • This type of feature can only • be one of a few distinct options. • Either you have this type of characteristic or you don’t. • Examples of discontinuous • variation include blood group, • natural eye colour and inherited diseases. Bar chart to show the frequency of blood groups in a rugby team 6 5 4 3 number of rugby players 2 1 0 O A B AB blood group Discontinuous variation the result of genes only. Does this mean the value of such a feature is fixed?
Contents Variation What is variation? Causes of variation Classifying variation Investigatingvariation Variation quiz
Curious about variation How do we know about inherited variation and how it works? Meet Gregor Mendel, the first person to trace patterns of characteristics and predict how they were passed on. Gregor Mendel 1822 - 1884 Surprisingly Mendel was not a scientist but a monk who lived in Czechoslovakia (now called the Czech Republic).
Mendel’s experiments Mendel was inspired by walking in the monastery garden. He became curious about variation in plants and how characteristics were passed on to new generations. Another surprising fact about Mendel is that for his ground-breaking work on variation he carried experiments out on the humble garden pea!
Mendel’s experiments Mendel chose to experiment on pea plants for two reasons: 1. They could be easily grown in large numbers. 2. Their reproduction could be controlled. Over a period of seven years he experimented on more than 28,000 pea plants! Why was the pea plant a good choice for his experiments?
Mendel’s experiments Mendel studied several pea characteristics including: • pea shape (smooth or wrinkly) • pea colour (yellow or green) • pod shape (inflated or constricted) • pod colour (yellow or green) • stem length (tall or short) All these characteristics showed discontinuous variation. Why did this make them easier to study? Mendel also investigated one characteristic at a time. Why was this important for his experiments to be successful?
Mendel’s results Mendel’s investigations into seed shape (smooth or wrinkly) produced the following results: x cross-pollination parents: first generation: x self-pollination 100% second generation: 25% 75% dominant recessive
Mendel’s conclusions Mendel published his work in 1866 and made several conclusions about inheritance: • Certain traits can be dominant or recessive. Recessive traitsmay not show but can still be passed on. • Certain traits can be inherited in predictable patterns. • Inherited traits are passed on as bits of information called “factors”. What are these “factors” now called? Mendel did not know it but he had predicted the existence of genes more than 40 years before genes were discovered!
Father of Genetics Mendel’s work on the humble pea laid the foundations for modern genetics. Unfortunately, Mendel published his research in an obscure journal and the importance of his work was not recognised during his life. Scientists rediscovered Mendel’s work in 1900, sixteen years after he died! Today, Mendel is famously known as the “Father of Genetics”. Why is he given this grand title?
Contents Variation What is variation? Causes of variation Classifying variation Investigating variation Variation quiz
