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B14 Variation and evolution revision - Coggle Diagram
B14 Variation and evolution revision
Genetic engineering
Genetic make-up changed of an organism
Genes transferred to organism in early stage of development - gives them a desired characteristics (resistance to disease)
Steps
Desired characteristics selected
Gene for desired characteristics is cut out of chromosome of an organisms using an enzyme
Gene inserted into an organism - a vector (carrier) such as plasmid or virus may be used to transfer the gene
Plants
New genes can be transferred to crop plants
Crops with changed genes are GM - genetically modified
GM crops may make own pesticide, be herbicide-resistant and usually have increased yields
Natural selection
All offspring have a wide range of variation due to differences in genes
All organisms in the population will compete for food, shelter from predators and mates
Organisms with characteristics most suited to environment will survive (survival of the fittest)
Organisms that can survive, breed successfully and pass on genes
Gene Mutation
When DNA is not accurately copied --> different sequence of amino acids --> different protein made --> variation in characteristic
Selective breeding
Farmers and breeders select animals with desired characteristics
Cows that produce most milk
High-yielding cows crossed with bulls of mild temperament
Seeds selected from plants with biggest grains for next crop
Used for
Disease resistance in food crops or garden plants
Animals that produce more meat or milk
Domestic dogs and farm animals with gentle nature
Large, unusually bright coloured or heavily scented flowers
Steps
Chose characterises
Chose parents that show the desired characteristics from a mixed population - bred together
Best offspring with desired characteristics chosen to product next generation
Process repeated over many generation until all offspring show characteristics
Limitations
Reduces number of alleles
Less variation
New disease or climate could destroy whole population
Inbreeding of related organisms - le to inherited defects
Variation
Caused by
differences in genes inherited
conditions they have developed in
combination of genetic and environmental causes
Genes are most important factor in controlling appearance of an individual
Environmental variation
plant affected by lack of light, nutrients or space
human development may be affected during pregnancy - if mother smoke or drinks alcohol, baby may have low birthweight
once animals are born - too little or too much food can alter characteristics (an athlete)