Natural selection Flashcards
What is genetic diversity?
number of different alleles of genes in a species or population
What is genetic diversity within a population increased by?
- Mutations in the DNA forming new alleles
- Gene flow
What is gene mutation?
change in sequence of base pairs in DNA molecule that may result in an altered polypeptide
Why don’t some mutations result in an altered polypeptide?
the genetic code is degenerate
What is deletion?
When a nucleotide is randomly deleted from the sequence
What does deletion cause?
changes the amino acid that would of been coded for, also changes the groups of the next three bases in the sequence
What is substitution?
When a DNA base is randomly substitute with a different base
What cause does substitution have?
Changes the amino acid but does not have a knock on effect on other amino acids
What are mutagenic agents?
Mutagenic agents are environmental factors that increase the mutation rate of cells
What are examples of mutagenic agents?
- high energy radiation
- ionising radiation
- toxic chemicals
What is non-disjunction?
chromosomes fail to separate during meiosis
What happens if abnormal gametes take part in fertilisation?
a chromosome mutation occurs as the diploid cell will have the incorrect number of chromosomes
What is a chromosome mutation?
A change in the number of chromosomes
What is the purpose of meiosis?
produces daughter cells that are genetically different to each other.
Why are the daughter cells genetically different?
- independent assortment
- crossing over
Explain crossing over?
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that its alleles are exchanged
Explain genetic variation?
exists within population due to a combination of different alleles, under certain environmental conditions organisms with certain alleles will have a greater chance of survival
What happens with organisms with alleles that have better chance of survival?
They reproduce and produce organisms and pass down the advantageous allele to future generations
What are the two different types of natural selection?
- stabilising
- directional
What is stabilising selection?
keeps allele frequency constant over time, this means things stay the same unless there is a change in environment
What is directional selection?
produces a gradual change in allele frequencies over time, this usually happens when there is a change in environment and leads to an increase in beneficial alleles
What are anatomical adaptations?
Structural and physical feature change
What are physiological adaptations?
Biological processes within the organism
What are behavioural adaptations?
The way an organism behaves
