Variation and Evolution Flashcards
What is variation?
The differences between members of the same species
What can variations be a result of?
Genes
The environment
What is discontinuous variation?
Variations with a limited number of phenotypes and no intermediates
What is continuous variation?
Variation with a large range of phenotypes between two extremes
What are mutations?
Permanent changes in nucleotide sequences in DNA
How does evolution happen?
When a mutation proves to give a species a better survival advantage
How can the rate of mutations be increased?
Ionising radiation and some chemicals
What is gene therapy?
When a diseased allele is replaced by a normal allele of the same gene
Why isn’t gene therapy a permanent solution to cystic fibrosis?
As cells with the transplanted gene die, they are replaced with cells with the disease gene again
What is cystic fibrosis?
A disorder of the cell membranes which causes thick, sticky mucus to build up in the lungs and digestive system
What are the main principles of natural selection?
Individuals with the best chances of survival are the most likely to breed successfully (because they survive) and so the best characteristics are passed on through generations
When can resistance evolve?
When a small number of individuals survive a certain threat and survive to reproduce, passing their resistance (immunity) to the threat onto all their offspring.
