Heritable changes are those which change in the germ line, leading to eggs and sperm and can therefore be passed on through the generations. Evolution is the change in populations brought about by changes in heritable genetic information.
At the simplest level, the process of meiosis includes a stage where homologous chromosomes from each parent recombine - which is they exchange alleles, this produces gametes that are genetically different from their parents and so every generation individuals contain different combinations of alleles. Beneficial combinations will be 'seen' by natural selection, the individuals carrying them will survive to reproduce and the alleles will be passed on to the next generation. Change in the genetic structure each generation is basic evolution.
Then you can add various levels of complexity to this - mutation (often seen as negative) may change the DNA sequence, producing new alleles - which if beneficial will be subject to selection and will spread in the population over several generations. One example is the HbS allele, which affects one of the globin genes in blood - people who have one 'normal' HbA allele and an HbS allele have a hugely increased chance of surviving malaria and reaching reproductive age than those who have two normal HbA alleles and so the HbS allele rises in the population and the population evolves better resistance to malaria. The downside of this is that some individuals inherit two HbS alleles and have sickle cell anaemia - but to the population overall there is a benefit.
Another very common type of mutation is gene duplication and this indeed is one of the most important as it adds new genes to the genome. At first the new copy will be the same as the original from which it is copied, but over time it may change structure and function, while the original copy maintains that function. There are hundreds of examples, in humans the rhesus D gene is a duplication of another blood antigen gene.
At a much grander scale, during the divergence of the lineage which led to vertebrates, the whole genome was duplicated twice, vastly increasing the amount of genetic material on which evolution could act and allowing for the diversification of gene function. A really good example is again the globin genes. From one gene, we got two and a divergence into oxygen transporting molecules and oxygen storage molecules. The second round brought about improved efficiency with the evolution of modern haemoglobins, which allowed the development of fast swimming fishes in the first instance and later on tetrapods, which developed lungs and are able to take up a lot of oxygen from the environment.
There are lots more mechanisms by which genes have changed in the germ lines of different lineages and which lead to evolutionary change, but that's enough for now!
Natural selection gives creatures with favourable characteristics a greater chance of survival and reproduction. If those characteristics are heritable then they will be present in a (slightly) higher proportion in the next generation. This leads to adaptation, but so far not to evolution.
Next; if there is a mutation that gives an advantage and is heritable then this new gene has a higher chance of being passed on and eventually becoming fixed in the population and evolution has occured.
Then you have to realise that a beneficial mutation does not always add information to the genome. For example lactose tolerance in humans is a mutation that loses control of lactase production. It is beneficial since it allows to digest milk but it loses genetic information.
To get microbes to man evolution you need beneficial mutations to add all the difference between the genetic information for humans (~30,000 genes) and that for microbes (~hundreds of genes). The world hasn't been around long enough for this to happen.
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Heritable changes are those which change in the germ line, leading to eggs and sperm and can therefore be passed on through the generations. Evolution is the change in populations brought about by changes in heritable genetic information.
At the simplest level, the process of meiosis includes a stage where homologous chromosomes from each parent recombine - which is they exchange alleles, this produces gametes that are genetically different from their parents and so every generation individuals contain different combinations of alleles. Beneficial combinations will be 'seen' by natural selection, the individuals carrying them will survive to reproduce and the alleles will be passed on to the next generation. Change in the genetic structure each generation is basic evolution.
Then you can add various levels of complexity to this - mutation (often seen as negative) may change the DNA sequence, producing new alleles - which if beneficial will be subject to selection and will spread in the population over several generations. One example is the HbS allele, which affects one of the globin genes in blood - people who have one 'normal' HbA allele and an HbS allele have a hugely increased chance of surviving malaria and reaching reproductive age than those who have two normal HbA alleles and so the HbS allele rises in the population and the population evolves better resistance to malaria. The downside of this is that some individuals inherit two HbS alleles and have sickle cell anaemia - but to the population overall there is a benefit.
Another very common type of mutation is gene duplication and this indeed is one of the most important as it adds new genes to the genome. At first the new copy will be the same as the original from which it is copied, but over time it may change structure and function, while the original copy maintains that function. There are hundreds of examples, in humans the rhesus D gene is a duplication of another blood antigen gene.
At a much grander scale, during the divergence of the lineage which led to vertebrates, the whole genome was duplicated twice, vastly increasing the amount of genetic material on which evolution could act and allowing for the diversification of gene function. A really good example is again the globin genes. From one gene, we got two and a divergence into oxygen transporting molecules and oxygen storage molecules. The second round brought about improved efficiency with the evolution of modern haemoglobins, which allowed the development of fast swimming fishes in the first instance and later on tetrapods, which developed lungs and are able to take up a lot of oxygen from the environment.
There are lots more mechanisms by which genes have changed in the germ lines of different lineages and which lead to evolutionary change, but that's enough for now!
Natural selection gives creatures with favourable characteristics a greater chance of survival and reproduction. If those characteristics are heritable then they will be present in a (slightly) higher proportion in the next generation. This leads to adaptation, but so far not to evolution.
Next; if there is a mutation that gives an advantage and is heritable then this new gene has a higher chance of being passed on and eventually becoming fixed in the population and evolution has occured.
Then you have to realise that a beneficial mutation does not always add information to the genome. For example lactose tolerance in humans is a mutation that loses control of lactase production. It is beneficial since it allows to digest milk but it loses genetic information.
To get microbes to man evolution you need beneficial mutations to add all the difference between the genetic information for humans (~30,000 genes) and that for microbes (~hundreds of genes). The world hasn't been around long enough for this to happen.