6.2 Variation and Evolution Flashcards
What is variation ?
Differences in the characteristics of individuals in a population is called variation.
What are the causes of variation within a species?
• Genetics
• Environment
• A mixture of both of the above
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 ?
• Spontaneous mutations
• Sexual reproduction
What is a mutation ?
A random change to the base sequence in DNA which results in genetic variants.
They occur continuously.
State the three types of gene mutation
• Insertion
• Deletion
• Substitution
How may a gene mutation affect an organisms phenotype ?
• Mutation may cause a minor change in an organism’s phenotype e.g. change in eye colour.
• Mutation may completely change the sequence of amino acids. This may result in a non-functional protein. Severe changes to phenotype.
What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?
There will be a rapid change in the species
What is evolution ?
• A gradual change in the inherited traits within a population over time.
• Occurs due to natural selection which may result in the formation of a new species.
What is natural selection
Natural selection. Sometimes referred to as ‘survival of the fittest’. is a process where organisms that are better adapted to an environment will survive and reproduce
How do two populations become different species ?
When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring.
What is selective breeding ?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes.
Outline the main steps involved in selective breeding
- Identify a desired characteristic e.g. disease resistance.
- Select parent organisms that show the desired traits and breed them together.
- Select offspring with the desired traits and breed them together.
- Process repeated until all offspring have the desired traits.
Give examples of characteristics selected for in selective breeding.
• Disease resistance in crops
• Higher milk or meat production in animals
• Gentle nature in domestic dogs
• Large flowers
What is the main advantage of selective breeding ?
Creates organisms with desirable features:
• Crops produce a higher yield of grain
• Cows produce a greater supply of milk
• Plants produce larger fruit
• Domesticated animals
Other than in agriculture, where else is selective breeding useful?
• In medical research
• In sports e.g. horse racing
Outline the disadvantages of selective breeding ? (4)
• Reduction in the gene pool (which becomes especially harmful if sudden environmental change occurs).
• Inbreeding results in genetic disorders.
• Development of other physical problems e.g. respiratory problems in bulldogs.
• Potential to unknowingly select harmful recessive alleles.
What is genetic engineering ?
• The modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
• Enables the formation of an organism with beneficial characteristics.
Give an example of uses for genetically modified plants
• Disease resistance
• Produce larger fruits
