Evidence for Evolution

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  • Created on: 18-03-13 21:37
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EVOLUTION ­ a change in allele frequency.
The complete range of alleles present in a population is the gene pool.
New alleles are usually created through gene mutation (changes in the base sequences of DNA that occur during DNA replication.)
The allele frequency is how often the allele occurs in a population. The frequency of an allele in a population changes over time ­ this is
evolution.
EVOLUTION OCCURS BY NATURAL SELECTION
1. Individuals within a population show variation in their phenotypes (due to different alleles).
2. Predation, disease and competition create a struggle for survival.
3. Individuals with better adaptations (beneficial alleles) are more likely to survive, reproduce and pass on their advantageous adaptations to
their offspring.
4. This means that a greater proportion of the next generation inherit the beneficial allele ­ so the frequency of the beneficial allele
increases from generation to generation.
EVIDENCE FOR EVOLUTION
Molecular Evidence: Molecular biology has provided a detailed source of evidence for
evolution, revealing information about the evolutionary history of organisms. Proteins and nucleic acid contain a record of genetic changes
over time. The study of DNA (genomics) and proteins (proteomics) are revealing these genetic changes.
DNA & Proteomic Evidence:
Evolution is caused by gradual changes in the base sequence of organism's DNA.
Comparing the DNA and amino acids in different species can show how closely related species are in evolutionary terms, this can be
done by DNA hybridisation or DNA profiling. The more similar the sequence, the more closely related the species.
Assessing the speed of mutation in DNA has shown that species have evolved over vast periods of time, as Darwin thought.
The SCIENTIFIC COMMUNITY validates evidence about evolution:

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Any new evidence must be carefully studied before it can be accepted. The scientific process has three hey aspects which try to ensure reliability and
viability:
SCIENTIFIC JOURNALS These are academic magazines where scientists publish their articles describing their
work ­ sharing ideas, theories, experiments, evidence and conclusions. The journals also allow other scientists to repeat the experiments ­ if the same
results are replicated then it improves the reliability of the evidence.…read more

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