Identify and describe What is Variation?, The Role of Genes in Variation and The Role of the Environment in Variation in the context of evidence for evolution.
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GCSE Biology Revision
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GCSE Biology revision
Evidence for evolution
The development of understanding of genetics and evolution
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Explain the relationships between What is Variation?, The Role of Genes in Variation and The Role of the Environment in Variation and how they contribute to evidence for evolution.
Apply and analyse knowledge of What is Variation?, The Role of Genes in Variation and The Role of the Environment in Variation to interpret unfamiliar information about evidence for evolution.
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Key knowledge
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What is Variation?
- Variation refers to the differences in phenotypes observed between individuals within a population
- A phenotype describes the observable characteristics of an individual, resulting from the interaction of their genes and their environment
The Role of Genes in Variation
- Genes code for proteins, and the genome — all of an organism's genes combined — codes for the entire organism
- Apart from identical twins, every person has a unique genome, meaning slightly different combinations of proteins, which is why we all look different
- Most characteristics are influenced by many different genes working together, rather than just a single gene
The Role of the Environment in Variation
- Environmental factors such as diet, sleep, and sun exposure can influence how characteristics are expressed, even in individuals with identical genes
- For example, identical twins with the same genes for height may end up different heights if one has a poorer diet or less sleep
- Most traits are determined by the interaction of both genes and environmental factors, not one alone
Mutations and Genetic Variation
- A mutation is a change in the DNA code that may result in a different protein being produced
- Most mutations have no effect on the organism's phenotype, but occasionally they can cause slight changes to characteristics
- Very rarely, a mutation can be beneficial — for example, increasing resistance to disease or improving physical ability
Natural Selection and Survival of the Fittest
- Beneficial mutations make individuals more likely to survive, reproduce, and pass their advantageous genes on to the next generation
- Charles Darwin observed in the 1800s that the fittest individuals — those best suited to their environment — were more likely to survive, a concept he called survival of the fittest
- Darwin called this process natural selection, as the environment effectively 'selects' which traits are passed on most successfully
Darwin's Theory of Evolution
- Evolution describes how the inheritance of certain characteristics over multiple generations can lead to changes in a whole species or even the formation of a new species
- Darwin's theory implies that all current living species must have evolved from earlier, different species
- Evidence suggests that all living species can be traced back to simple life forms that first developed more than 3 billion years ago
Evidence for Evolution
- Darwin's theory took a long time to be accepted by the scientific community but has since been proven multiple times
- The development of antibiotic resistance in bacteria is a real-world example of evolution by natural selection happening in observable timescales
- Fossil records also provide supporting evidence for the theory of evolution
Speciation: The Formation of New Species
- Over time, if two populations within a species develop sufficiently different phenotypes, they may no longer be able to interbreed to produce fertile offspring
- When two populations can no longer interbreed to produce fertile offspring, a new species is said to have formed — a process known as speciation
Key Summary: Evolution by Natural Selection
- Evolution occurs through the natural selection of genetic changes (mutations) that produce phenotypes best suited to the environment
- Given enough time and environmental pressure, accumulated genetic differences between populations can lead to the emergence of entirely new species