B13a Variation and evolution Flashcards
Give a definition of variation
Differences in the characteristics of individuals in a population
What are the causes of variation?
Mutations
Genes they have inherited
Environment
Combination of genes and the environment
What is a mutation?
A change in the DNA
When do mutations occur?
Continuously
What effect can mutations have on variation within a population?
Most have no effect on the phenotype
Some influence the phenotype
Very few determine the phenotype
Give a definition of evolution
A change in the inherited characteristics of a population over time through the process of natural selection.
Could result in the formation of a new species
Give a definition of a species
Individuals can interbreed and produce fertile offspring
What is genetic variation?
Variations in the genotypes of organisms of the same species
due to the presence of different alleles
Creates differences in phenotypes
What creates genetic variation in a species?
Mutation
Sexual reproduction
Outline the theory of natural selection
Wide range of variation in a population
Individuals with characteristics most suited to the environment more likely to survive and breed
beneficial characteristics are passed on to the next generation
How is a new species formed?
Two populations of one species become different in phenotype
No longer interbreed to produce fertile offspring
What is selective breeding?
Humans choose parents with desired characteristics
Breed together
Offspring with desired characteristics bred together
Continue over many generations until all offspring show desired characteristics
How long ago did simple life develop on Earth?
More than 3 billion years ago
Give four examples of selective breeding
Disease resistance in food crops
Animals which produce more meat or milk
Domestic dogs with a gentle nature
Large or unusual flowers
Selective breeding can lead to ‘inbreeding’.
What does this mean?
Closely related animals or plants are bred together
Why might inbreeding be a problem?
Some breeds are prone to disease or inherited defects
What are the main advantages of selective breeding?
Creates organisms with desirable features:
Crops produce a higher yield
Cows produce a greater volume of milk
Animals produce more meat
Hens lay more eggs
Plants produce larger fruit
Domesticated animals
Outline the disadvantages of selective breeding
Reduction in the variety of alleles present in the population - harmful if sudden environmental change occurs
Inbreeding results in genetic disorders
Development of physical problems eg breathing problems in bull dogs
Disease can wipe out a crop
What is genetic engineering?
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
Give 3 examples of genetic engineering
Plant crops - increased resistant to disease
Plant crops - increase size of fruit
Bacteria cells - produce useful substances eg human insulin
Outline the process of genetic engineering
Gene from human is cut out of the chromosome
Transferred to cells of other organisms
Benefits of genetic engineering
Increased crop yield for a growing population
Useful in medicine eg making insulin to treat diabetics
GM crops produce higher concentrations of minerals and vitamins eg golden rice
Disadvantages of genetic engineering
Long term effects of eating GM crops unknown
Negative environmental impacts eg reduction in biodiversity,
Impact on food chains, contamination of non-GM crops
Late onset health problems in GM animals
GM seeds are expensive. LEDCs may be unable to afford them
Give 3 example of a genetically modified crop
Crops that are resistant to insect attack
Crops that are resistant to herbicides
Crops with increased yield
