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Variation - Coggle Diagram
Variation
Genetic engineering
Genetic engineering is also called genetic modification or GM. It involves modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic.
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Selective breeding
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Selective breeding takes place over many generations. These are the main steps for both plants and animals involve:
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Repeat the process continuously over many generations, until all offspring show the desired characteristics.
Causes of variation
Individuals in a population are usually similar to each other, but not identical. Some of the variation within a species is genetic, some is environmental - the conditions in which they have developed and some is a combination of both
Children generally look a little like their mother and their father, but are not identical to either. They inherit their features from each parent's DNA.
Every sperm and egg cell contains half of the genetic information needed for an individual. Each sex cell is known as haploid, which has half the normal number of chromosomes. When the chromosomes fuse during fertilisation, a new cell is formed, which is known as a zygote. It has all the genetic information needed for an individual, which is known as diploid and has the full number of chromosomes.
Examples of genetic variation in humans include blood group, skin colour and natural eye colour.
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Fossils
A fossil is the preserved remains of a dead organism from millions of years ago. Fossils are found in rocks and can be formed from:
hard body parts, such as bones and shells, which do not decay easily or are replaced by minerals as they decay
parts of organisms that have not decayed because one or more of the conditions needed for decay are absent. For example, dead animals and plants can be preserved in amber, peat bogs, tar pits, or in ice
preserved traces of organisms, such as footprints, burrows and rootlet traces - these become covered by layers of sediment, which eventually become rock
Cystic fibrosis
Cystic fibrosis is an inherited disorder of cell membranes that mainly affects the lungs and digestive system. They can become clogged with lots of thick, sticky mucus as too much is produced. Over many years, the lungs become increasingly damaged and may eventually stop working properly. A number of treatments are available to help reduce the problems caused by the condition, but unfortunately average life expectancy is reduced for people who have it.
It is caused by a faulty recessive allele on chromosome 7. To be born with cystic fibrosis, a child has to inherit two copies of this faulty gene - one from each of their parents. Their parents will not usually have the condition themselves, because they will only carry one faulty gene and one that works normally.
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Antibiotic resistance
Bacteria can evolve quickly because they reproduce at a fast rate. Mutations of bacteria produce new strains. Some bacteria might become resistant to certain antibiotics, such as penicillin, and cannot be destroyed by the antibiotic. The evolution of the bacteria is an example of natural selection.
Evolutionary trees
Evolutionary trees are used to represent the relationships between organisms. Branches show places where specification has occurred, and a new species has evolved.