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Variation, genetic engineering, cloning, fossils and speciation (Genetic…
Variation, genetic engineering, cloning, fossils and speciation
Variation
Organisms of the same species look different as there is variation within a species - 2 types - genetic and environmental
Genetic variation
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Some characteristics are determined only by genes - eg. eye colour, blood group and inherited disorders eg. cystic fibrosis
Environmental variation
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Eg. a plant grown in lots of sunlight would be healthy and green, while a plant grown in the dark would be tall and spindly, and have yellow leaves
Most characteristics are due to a mixture of genetic and environmental factors eg. weight, athletic prowess etc.
Mutation cause variation
If the environment changes, and the new phenotype makes an individual more suited to the new environment, it can become common throughout the species relatively quickly by natural selection
Genetic engineering
Idea is transferring a gene responsible for a desirable characteristic from one organisms genome to another, so that it also has that desired characteristic
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Vector usually a virus or bacterial plasmid depending on the type of organism the gene is inserted into
When vector is introduced to the target organism, the useful gene is inserted into its cells
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Controversial
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Worries about long term side effects of genetic engineering - changing an organisms genes might accidentally create unplanned problems which could be passed onto future generations
GM crops
Advantages
- Can increase yield
- Can be engineered to provide nutrients that people aren't getting - 'golden rice'
Disadvantages
- Will affect number of wild flowers that live in and around the crops - therefore also affect insects and reduces farmland biodiversity
- Concern that we don't fully understand the effects of them on human health - could develop allergies to food that has been genetically modified
- Transplanted genes may get out into natural environment - eg. herbicide resistance may be picked up by weeds - creating a new 'superweed'
Fossils
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Formed in 3 main ways
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Casts and impressions - fossils formed when an organism buried in soft material like clay - clay hardens and organisms decays, leaving a cast of itself eg. animals burrow or plant roots
Preservation - where no decay happens eg. in amber or tar pits no oxygen or moisture so decay microbes don't survive, glaciers its too cold for the microbes to survive and peat bogs are too acidic for decay microbes
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Early lifeforms were soft bodied, which tends to decay completely so fossil record is incomplete
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Cloning
Tissue culture - where few plant cells put in growth medium with hormones and they grow into new plants - clones. Made very quickly in little space and can be grown all year. Uses include preserving rate plants and plant nurseries to produce lots of stock quickly
Cuttings - gardeners can take cuttings from good parent plants, and then plant them to produce genetically identical copies - produced quickly and cheaply
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Adult cell cloning
Take an unfertilised egg cell and remove its nucleus - the nucleus is them removed from an adult body cell and is inserted into the egg cell
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When embryo is a ball of cells it's implanted into the womb of an adult female and grows into a copy of the original adult body cell as it has the same genetic information - used to create Dolly the Sheep
Issues with cloning
Cloning gives a reduced gene pool - fewer different alleles makes the population vulnerable to a disease
Could lead to greater understanding of the development of the embryo, and of ageing and age-related disorders
Possible cloned animal not as healthy as previous one - Dolly had arthritis which tends to occur in older sheep
Some worry humans might be cloned in the future - any success would have followed many unsuccessful attempts eg. children born with severe disabilities
Speciation
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Speciation occurs when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
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Alfred Wallace
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Observations made by Wallace as he travelled the world provided lots of evidence to support theory of evolution by natural selection
Eg. He released warming colours are used by some species to deter predators from eating them - example of a beneficial characteristic
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