Variation Flashcards
What influences a phenotype?
Genotype and environment
What are the features of discontinuous variation?
-Distinct categories
-No overlap between categories
-Monogenic
-unaffected by environment
What are the features of continuous variation?
-No distinct categories
-Overlap between categories
-Polygenic
-Affected by environment
What is genetic drift?
A change in the frequency of an allele due to chance variations. The gradual random shift in gene frequencies of a small population results in different genotype rations and speciation
What is the bottleneck effect?
Sharp reduction in population due to environmental changes
What is the founder effect?
Loss of genetic variation in a new population established by a small number of individuals from a larger population
What are the Hardy-Weinberg conditions?
-Large population
-Random mating
-No gene flow
-No mutation
-No natural selection
What are the factors that limit population growth?
-Breeding sites
-Availability of light, water, and food
-Pathogens
-Predation
-Competition
What are the assumptions of Darwin’s evolution?
-There is a struggle for survival and the fittest phenotypes win
-Survivors will reproduce, passing beneficial alleles on
How does speciation occur?
Result of an isolated population which originated from one species. eventually as allelic frequencies in each population fluctuate, 2 separate species emerge.
What is allopatric speciation?
-A physical barrier stops gene flow within a species
-genetic drift of both pools occur as allelic frequency changes due to different selectional pressures of each deme
What are some examples of sympatric speciation?
-reproductive isolation
-Pre and post zygotic isolating mechanisms
What are examples of pre zygotic isolation?
-Seasonal
-Behavioural
-Mechanical
-Gametic
What is seasonal isolation?
If breeding seasons of two groups don’t coincide
What is behavioural isolation?
Share same geographic location but have different behaviour i.e. courtship displays
What is mechanical isolation?
Morphological differences prevent hybridization i.e. incompatible genitalia
What is gametic isolation?
Pollen grain fails to pollenate or sperm fails to survive
What are examples of post zygotic isolation?
-Hybrid inviability
-Hybrid sterility
-Hybrid breakdown
