Variation And Evolution Flashcards
Definition of variation
The differences between organisms of the same species
How is variation generated?
- crossing over
- random distribution of chromatids
- mixing of two different parental genotypes k
Discontinuous variation
No intermediate types and characteristics are discrete
Definition of monogenic
Controlled by single genes
Definition of continuous variation
Values show a gradation from one extreme to another within a range
Selection pressure
An environmental factor that can alter the frequency of alleles in a population, when it is limiting
Gene pool
All the alleles present in a population at a given time
Allele frequency
An alleles proportion of the whole gene pool
Genetic drift
Chance variations in allele frequencies in a population
Founder effect
The loss of genetic variation in a new population established by a very small number of individuals from a larger population
3 types of natural selection
- stabilising selection
- directional selection
- disruptive selection
Types of pre zygotic isolation
- geographical isolation
- behavioural isolation
- morphological isolation
- gametic isolation
- seasonal isolation
Types of post zygotic isolation
Hybrid inviability
Hybrid sterility
Geographical isolation
- allopatric
- population split by a group physical barrier into separate demes
Behavioural isolation
- sympatric
- mating rituals and courtship displays that are recognised by other member of the species
