B5.2 Natural selection and evolution
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B5.2 Natural selection and evolution
B5.2a state that there is usually extensive genetic variation within a population of a species
B5.2b describe the impact of developments in biology on classification systems to include natural and artificial classification systems and the use of molecular phylogenetics based on DNA sequencing
B5.2c explain how evolution occurs through the natural selection of variants that have given rise to phenotypes best suited to their environment to include the concept of mutation
B5.2d describe evolution as a change in the inherited characteristics of a population over time, through a process of natural selection, which may result in the formation of new species
B5.2e describe the evidence for evolution to include fossils and antibiotic resistance in bacteria
This subtopic is best started by looking at the variation in the class. The realisation that there is not a standard human being difference in hair colour/tongue rolling/ear lobe structure/hairline/hitcher thumb/coriander taste etc. are good starts.
The horse is a suitable model for evolution this given it has a complete fossil record. Learners need to spend time appreciating the step wise nature of the development of a species and the way in which successive changes cause divergence between species.
Common misconceptions or difficulties learners may have
Some learners confuse find it difficult to say whether variation is the result of environmental or genetic causes or both.
Some learners will require significant guidance here. Learners often hold the misconception that a single mutation will always result in a large scale change in the make-up of a species (extra fingers, limbs etc) and that evolution of a species takes place on a short timescale rather than over millennia and as a result of a catalogue of slight mutations, each conferring a slight advantage. This may be reviewed during the study of selective breeding (topic 6.2c). Learners can see that it takes many generations to get a desirable trait even if the breeding programme is being controlled.
A Lamarkian view is often held by some learners, for example that the loss of a limb can result in the absence of that limb in the offspring. Learners sometimes confuse the term ‘fittest’ with respect to evolution and instead take this to mean physical fitness (e.g. speed).
Conceptual links to other areas of the specification – useful ways to approach this topic to set learners up for topics later in the course
6.1b 6.1c 6.2c
Learners can consider how species may evolve in the future given challenges from both the environment and human activity (6.1b).
Discussion of the impact of biodiversity on the process of evolution (6.1c) would further develop learners’ understanding of both aspects of the course.
How selective breeding can lead to a change in phenotype (6.2c).
Approaches to teaching the content
Learners can relate this subtopic back to prior learning on how animals and plants are adapted to their environment. By the end of this subtopic they should be able to explain how those adaptations have arisen. Learners need to consider how species they are familiar with have arisen and how they are similar yet distinct from other species.
Learners are introduced to a scenario where their parents were mutated by UV radiation resulting in mutation of their DNA.
They are exposed to different environmental challenges to demonstrate natural selection.
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