3 31 Evolution

Key Points:
1. Evolution : A change in the form of organisms.
                     A change in the frequency of alleles.
2. Natural selection is the mechanism of evolution, and was proposed by Charles Darwin.
3. A chemical called Methecilline can kill Staphlococcus Aureus. The ones that can be killed are known as the succeptable. A random mutation to the genotype of Staphlococcus Aureus may cause it to be able to methecilline, and this kind of staphlococcus aureus is known as the resistant form.
4. There are now forms of the bacteria, when antibiotics are applied to the population (change in environment) then the susceptable form lowers in numbers, and the resistant ones gain numbers.
5. There are two features to be noticed: 1. Random mutation 2. Non random selection
This is known as natural selection

3.30 Mutation

Key points:
1. In the diagram there is a molecule called DNA.
2. Certain events can result in a change in this sequence, such as UV radiation.
3. Having a mutation in the gene can result in the production of a completely different type of protein.
4. Different alleles exist because of mutation, which changes the base sequence of the gene.

3.29 Species Variation

Key points:
1. Variation can be described as the differences in the phenotype of individuals. How things appear.
2. It is possible to count or measure these differences and show them in a graph form. The appearance is because of their genotype, which can be modified by the environment. Variation is a variation of all these factors.
3. Variation in population = Variation in genotype + Variation in the environment.
4. Blood groups are an example of where the environment has no effect whatsoever on the variation in population.
5. The height of individuals can be affected by both the environment AND the genotype.
6. A third possibility is that the variation in the population is entirely due to environmental variation, so genes have no role in the differences, an example of this would be language.

3.21a Genetic Probabilities

3.20b Pedigree 2

3.20a Pedigree diagrams

3.18C Codominance

As seen in the photo above, the homozygous pairs both have either BB or WW, and are either blue or white. The heterozygous plant's phenotype is orange, and seeing as BB and WW reproduced, they each contributed only one allelle, therefore making the heterozygous plant's genotype BW.