Variation & Evolution Flashcards
What is discontinuous variation?
When there is clear distinct categories (such as blood group or tongue rolling)
What is continuous variation?
When there is no clear distinct categories (such as eye colour or leaf length)
What are some selection pressures?
› Availability of nesting sites
› Day length affecting reproductive behaviour
› Overcrowding allowing disease to spread
› Predation
› Human impact
What is meant by the gene pool?
The total of all of the alleles for all of the genes in a population
What is meant by genetic drift and the Founder effect?
› Genetic drift is the chance variation in allele frequency in a population
› The Founder effect happens when this is seen in a small population therefore causing large changes
What are the three types of natural selection?
› Directional selection (when phenotypes give a selective advantage or disadvantage)
› Stabilising selection (when extreme phenotypes are selected against in an unchanging environment)
› Disruptive selection (favouring individuals at the phenotypic extremes)
What is the Hardy-Weinberg principle?
The frequencies of dominant and recessive alleles and genotypes will remain constant in generations, as long as certain conditions are true
What are the conditions that enable the Hardy-Weinberg principle to work?
› Large population › No selection › Random mating › No mutations › Population is isolated
What are some isolating mechanisms?
› Geographical isolation (a physical barrier such as a river or mountain range)
› Seasonal isolation
› Behavioural isolation (mating routines failing in a sub-species)
› Morphological isolation
What is meant by evolution?
The process by which new species are formed from pre-existing ones over a period of time
Explain natural selection
› In any population there is variation
› Large numbers of offspring can be produced
› Competition takes place between offspring
› Individuals that survive and reproduce will pass on favourable characteristics to their offspring
