1. Evolution

2. Starter
What do you remember about evolution from GCSE?

3. Learning Objectives Success criteria
Understanding the mechanisms evolution and examining the evidence
Success criteria
Learners should be able to demonstrate and apply their knowledge and understanding of:
the evidence for the theory of evolution by natural selection
To include the contribution of Darwin and Wallace in formulating the theory of evolution by natural selection AND fossil, DNA (only genomic DNA at AS level) and molecular evidence.

4. What is evolution?
Evolution is the cumulative change in the heritable characteristics of a population.
Cumulative change – small changes upon small changes over many generations
Heritable characteristics – gene-controlled factors
Population – not an individual

5. Developing the theory of evolution
Using p286 write a brief summary of the history of the development of the theory of evolution. Include :
Contributions from Darwin and Wallace
Observations and conclusions
10 mins

6. Evidence for evolution
Palaeontology
Comparative anatomy
Comparative biochemistry

7. Palaeontology
Fossil record: A fossil is the ancient preserved remains of an organism. The fossil can be dated from the age of the rock formation.
Sequences of fossil can show the gradual change of an organism over geological time.
Continuous fossil records are rare as:
many organisms are soft-bodied and decompose quickly
Conditions for fossilisation are not always present
Many fossils have been destroyed or remain undiscovered

8. Palaeontology Evidence provided by the fossil record:
Gradual change - Simplest organisms are found in older rocks
Sequence matches ecological links - Plants fossils appear before animal fossils
Closely related organisms have a common ancestor -studying similar anatomy of fossils
Fossils allow relationships between living and extinct organisms to be investigated

9. Comparative anatomy
Homologous structures: All of life is connected through evolutionary history and consequently those organisms more closely connected might reasonably be expected to share common structures or homologous.
Group of organisms closely related share a common form or derived trait which has been inherited from the common ancestor.
Homologous structures provide evidence for divergent evolution

10. Homologous structures
A classic example of homologous structures is the pentadactyl limb of the vertebrate.
a) Humerus
b) Radius
c) Ulna
In each example the bones are modified and adapted to the locomotion of the animal.
In homologous structures it is normal to find that parts of the structure will be modified, enlarged or reduced (vestigial).

11. Comparative biochemistry
Certain molecules are found throughout the living world
Two closely related species will have separated only relatively recently will have very similar biological molecules
Similarity in biological molecules
Cytochrome c – a protein used in respiration
Ribosomal RNA

12. Comparative biochemistry
Neutral variations in the molecular structure of a molecule do not affect its function and therefore are not affected by natural selection. They occur at a fairly regular rate (different for different molecules).
By comparing the molecular sequence scientists can estimate the point at which 2 species separated.
Species that are closely related have more similar DNA and proteins

13. Plenary - exam question June 2011 q.3