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KS4 Evolution, Speciation & Extinction
- Know that the differences in the characteristics of individuals in a population is called variation and may be due to differences in:
- the genes they have inherited (genetic causes)
- the conditions in which they have developed (environmental causes)
- a combination of genes and the environment.
- Know that mutations are continuous changes in the DNA code and that very rarely a mutation will lead to a new phenotype, but if the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.
- Students should be able to:
- state that there is usually extensive genetic variation within a population of a species
- recall that all variants arise from mutations and that: most have no effect on the phenotype; some influence phenotype; very few determine phenotype.
- Know that traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus.
- Know that Linnaeus classified living things into kingdom, phylum, class, order, family, genus and species.
- Know that organisms are named by the binomial system of genus and species.
- Be able to use information given to show understanding of the Linnaean system.
- Know that as evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed, new models of classification were proposed.
- Know that due to evidence available from chemical analysis there is now a ‘three-domain system’ developed by Carl Woese. In this system organisms are divided into:
- Archaea (primitive bacteria usually living in extreme environments)
- Bacteria (true bacteria)
- Eukaryota (which includes protists, fungi, plants and animals).
- Know that evolutionary trees are a method used by scientists to show how they believe organisms are related.
- Know that evolutionary trees use current classification data for living organisms and fossil data for extinct organisms.
- Be able to interpret evolutionary trees.
6.3.1 Theory of evolution
- Know that Charles Darwin, largely as a result of observations on a round the world expedition, backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils, proposed the theory of natural selection:
- Individual organisms within a particular species show a wide range of variation for a characteristic.
- Individuals with characteristics most suited to the environment are more likely to survive to breed successfully.
- The characteristics that have enabled these individuals to survive are then passed on to the next generation.
- Know that Darwin published his ideas in On the Origin of Species (1859) and that there was much controversy surrounding these revolutionary new ideas.
- Know that the theory of evolution by natural selection was only gradually accepted because:
- the theory challenged the idea that God made all the animals and plants that live on Earth
- there was insufficient evidence at the time the theory was published to convince many scientists
- the mechanism of inheritance and variation was not known until 50 years after the theory was published.
- Know that other theories, including that of Jean-Baptiste Lamarck, are based mainly on the idea that changes that occur in an organism during its lifetime can be inherited, and we now know that in the vast majority of cases this type of inheritance cannot occur.
6.3.2 Speciation New: knowledge of the pioneering work by Alfred Russel Wallace.
· Be able to describe the work of Darwin and Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on biology.
- Know that Alfred Russel Wallace independently proposed the theory of evolution by natural selection and that he published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year.
- Know that Wallace worked worldwide gathering evidence for evolutionary theory and that he is best known for his work on warning colouration in animals and his theory of speciation.
- Know that Alfred Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation.
- Know that new species arise as a result of:
- isolation of populations
- genetic variation between populations
- natural selection: operating differently on the two populations
- speciation: the populations become so different that successful interbreeding is no longer possible
6.3.4 Evidence for evolution
- Know that the theory of evolution by natural selection is now widely accepted.
- Know that evidence for Darwin’s theory is now available as it has been shown that characteristics are passed on to offspring in genes.
- Know that there is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria.
- Be able to 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 a new species.
- Know that the theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.
- Know that evolution occurs via natural selection:
- individual organisms within a particular species may show a wide range of phenotype variation because of differences in their genes
- individuals with characteristics most suited to the environment are more likely to survive to breed successfully
- the genes that have enabled these individuals to survive are then passed on to the next generation.
- Know that if two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species.
- Know that extinctions occur when there are no remaining individuals of a species alive.
· Know that extinctions may be caused by:
- changes to the environment over geological time
- new predators
- new diseases
- new, more successful, competitors
- a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids.
6.3.7 Resistant bacteria
- Know that bacteria can evolve rapidly because they reproduce at a fast rate.
- Know that mutations of bacterial pathogens produce new strains.
- Know that some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises. The resistant strain will then spread because people are not immune to it and there is no effective treatment.
- Know that MRSA is resistant to antibiotics.
- Know that to reduce the rate of development of antibiotic resistant strains:
- Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
- Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.
- The agricultural use of antibiotics should be restricted
- The development of new antibiotics is costly and slow and is unlikely to keep up with the emergence of new strains.
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