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B13 - Variation and evolution - Coggle Diagram
B13 - Variation and evolution
Variation
Variation may be due to differences in the genes inherited (genetic causes), the conditions in which organisms develop (environmental causes), or a combination of both genes and the environment.
Variation is the differences in the characteristics of individuals in a population.
Evolution by natural selection
If 2 populations of a species become so different that they can no longer interbreed to form fertile offspring, they have formed 2 new species.
Mutations occur continuously. Very, rarely, a mutation leads to a new phenotype. If the new phenotype is suited to an environmental change it can lead to a relatively rapid change in the species.
The theory of evolution by natural selection says that all species of living things have evolved from simple life forms that first developed 3 bln years ago.
Selective breeding
Problems can occur, including defects with some animals due to lack of variation.
Limitations - reduces number of alleles, less variation, new disease or climate change could destroy whole population & inbreeding has lead to inherited defects.
Desired characteristics include; disease resistance, increased food production in animals and plants, domestic dogs with a gentile nature and heavily scented flowers.
Selective breeding is a process where humans breed plants and animals for desired characteristics.
Genetic engineering
Crops that had their genes modified are known as genetically modified (GM) crops.
GM crops often have improved resistance to insect attack or herbicides and enterally produce a higher yield.
Genes can be transferred to the cells of animals and plants at an early stage of their development so they develop desired characteristics.
Process
Human cell with insulin gene in its DNA
Insulin gene cut out by enzyme
Insulin gene inserted into plasmid by another enzyme
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Bacterium with a ring of DNA called a plasmid.
Plasmid taken out of bacterium and split open by an enzyme.
Plasmid with insulin gene in it taken up by bacterium
Bacterium multiples many times
Insulin gene is switched on and the insulin is harvested.
Ethics of genetic technologies
There are benefits and risks
Benefits - People can correct genes - Medical drugs have been produced - GM crops resistant to herbicides or insects - Gm crops can grow in dry, hot or cold - improve growth rate of animals/plants.
Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders.
Risks - Farmer have to buy new GM seeds every year because infertile so expensive - accidentally introducing genes in to wild flower populations - insects could be infected - insect could become resistant - human health.