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B14 Variation + Evolution - Coggle Diagram
B14 Variation + Evolution
Variation
Variation is the differences in the characteristics of individuals in a population.
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 the genes and environment.
Evolution by Natural Selection
The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed over 3 billion years ago.
Mutations occur continuously. Very rarely a mutation leads to a new phenotype. If the new phenotype is suited an an environmental change it can lead to a relatively rapid change in the species.
If two populations of species become so different they can no longer interbreed to form fertile offspring, they have formed two new species.
Selective Breeding
Selective breeding is a process where humans breed plants and animals for desired characteristics.
Desired characteristics include: disease resistance, increased food production in animals and plants, domestic dogs with a gentle nature, and heavily scented flowers.
Problems can occur with selective breeding including defects in some animals due to the lack of variation.
Genetic Engineering
Genes can be transferred to the cells of animals and plants at an early stage of their development so they develop desired characteristics. This is genetic engineering.
In genetic engineering, genes from the chromosomes of humans and other organisms can be 'cut out' using enzymes an transferred to the cells of bacteria and other organisms using a vector, which is usually a bacterial plasmid or virus.
Crops that have had their genes modified are known as genetically modified (GM) crops. GM crops often improved resistance to insect attack or herbicides and generally produce a higher yield.
Cloning + Adult Cell Cloning
A modern technique for cloning plants is tissue culture using small groups of cells taken from part of a plant to grow identical new plants. It is important for preserving rare plant species in nurseries as well as for commercial use.
Taking cuttings is an older and simpler method of producing many identical new plants from a parent plant. It is widely used by gardeners.
Transporting cloned embryos involves splitting apart cells from an developing animal embryo before they become specialised and then transplanting the identical embryos into host mothers.
In adult cell cloning, the nucleus is removed from an unfertilised egg cell. The nucleus from an adult body cell, such as a skin cell, is inserted into the empty egg cell. A small electric shock stimulates the egg cell to divide to form an embryo. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
The cells of the embryo contain the same genetic information as the adult skin cells.
Ethics
Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders.
There are benefits and risks associated with genetic engineering in agriculture and medicine.
Some people have ethical objections to genetic engineering.