evolution Flashcards
mutation
a random change to genetic material
- spontaneous and the only source of new alleles
evolution
the changes in organisms over generations as a result of genomic variations
why is a variation important?
allows organisms to become better adapted to their environment
adaptations
inherited characteristics that make organisms well suited to survival in their environment or niche
advantage
- better chance of surviving to reproduce
passes on their alleles to their offspring and advantage to the next generation
disadvantage
- they wont pass their DNA to next generation as lacking beneficial sequences of DNA
- frequency of sequences of DNA which confer a deleterious will reduce in population
natural selection
the non random increase in frequency of DNA sequences that increase survival
ALSO
the non random decrease of frequency of deletrious sequences
changes in phenotype frequency result in…
stabilisting, disruptive and directional selection
deleterious sequences
frequency of DNA sequences increases in population bc they are selected for
- can be lethal when caused by mutations and offsprings wont survive and not pass on these deletreious genes to their offspring
phenotype frequency
the number of indivisuals in a population that have a specific obsevable trait
- change as a result of selection overtime
selection pressures
external agents which affect and organisms ability to survive in a given environment
stabilising selection
when an average phenotype is selected for and extremes of the phenotype range are selected agaisnt
- gives an advantage to indivisuals that possess the average phenotype
- maintains the mean value in a population and the best adapted genotypes
directional selection
when one extreme of the phenotype is selcted for
- favours alleles at one phenogenetic extreme in response to change in environment pressure
- causes progressive change towards a characteristic over generations
disruptive selection
when 2 or more phenotypes are selected for
- favours 2 extreme forms of a characteristic
- occurs when 2 different habitats/types of resource become available
- population gets split into 2 distinct groups (sub-populations) each with its own mean value
inheritance
the passage of genetic information from parent to offspring
vertical gene transfer
when genes are transferred from parent to offspring as a result of sexual or asexual reproduction
sexual - offspring genetically different / different genomes > will display combo of maternal and paternal phenotype
asexual - no gametes produced, produces hundreds of offspring over short time, offspring is genetically identical to parent eg identical genomes
horizontal gene transfer
where genes are transferred between individuals in the same generation
