Unit 4 Topic 2 - Evolution Flashcards
Define natural selection
The process in which organisms with the most favourable phenotype/physical characteristic have an increased chance of survival and fecundity
Define an allele
Varying forms of a gene
What is the difference between a genotype and a phenotype
Genotype - Allele make up for a particular characteristic
Phenotype - Physical representation of a Genotype
What are selection pressures
External factors that affect an organism’s ability to survive
What is the difference between positive and negative selection
Positive selection promotes the spread of beneficial alleles whereas negative selection hinders the spread of harmful alleles.
note that negative doesn’t mean “bad” in this situation
Define Microevolution
Small variation in allele frequencies within a population
Define Gene flow
The movement of genetic material between populations
Define Genetic drift
random fluctuations of alleles in a population over time.
This effect is greater in small populations
What are the four patterns of diversification?
Divergent, convergent, parallel, coevolution
Define divergent evolution
The differentiation of distinctly different species from a common ancestor.
Define convergent evolution
The evolution of similar features in unrelated populations.
What does analogous refer to?
Features with similar functions that have evolved from different ancestral structures.
What is parallel evolution?
When related species evolve similar features independently
What is coevolution
Species that interact, often exert selection pressures on each other that encourage evolution.
(e.g. Prey-Predator relationships)
Define a bottleneck event and it’s effects on a population
Occurs when a population’s size is significantly reduced
Typically results in a change in the distribution of alleles and/or the complete loss of alleles. thus creates a higher chance of extinction
Define the founder effect
The founder effect is when a new population is established from an existing larger population.
Typically results in reduced genetic diversity and different allele frequencies.
What is Macroevolution?
The variation in allele frequency over generations that result in a divergence of taxonomic groups
What factor does macroevolution rely on in order to occur
Isolation
Name and define the 4 main prezygotic mechanisms of isolation
Geographical - Individuals are separated by geographic features.
Temporal - Individuals breed or are active during different seasons of the year (i.e. hibernation) or times of the day (I.e. Nocturnal animals).
Behavioural - Individuals have different courtship/mating patterns
Morphological - Individuals have different reproductive structures. Mating is physically impossible
Define the 2 forms of postzygotic isolation
Hybrid Inviability - the offspring of two different species is not viable. Offspring generally won’t survive gestation or infancy
Hybrid Sterility - Hybrid offspring are infertile.
What are the 3 modes of speciation (with definitions)
Allopatric - a geographic barrier divides a population
Parapatric - occurs when populations maintain a limited area of contact but there is significant variation between both populations habitats
Sympatric - Populations have contact however temporal or behavioral mechanisms reduce gene flow.
What is the difference between modes of speciation and isolation mechanisms
What are the three types of selection?
Stabilizing - intermediate phenotypes are prefered over extreme phenotypes (occurs due to negative selection removing deleterious phenotypes)
Directional - one extreme phenotype is favoured (occurs due to positive selection increasing favourable phenotypes)
Disruptive - both extremes of a phenotype are prefered.
What is comparative genomics
the comparison of genetic features to determine evolutionary relatedness
What is the difference between a somatic and germline mutation
A somatic mutation occurs within body cells and cannot be inherited.
A germline mutation occurs in the gametes and may be inherited
Explain the difference between a point mutation and a frameshift mutation
A point mutation involves a change in a single base in a DNA sequence (incorrect base) thus it only affects a single codon. whereas a frameshift mutation involved the insertion or deletion of a base in a sequence and affect every following codon.
What does non-disjunction result in?
aneuploidy (abnormal number of chromosomes in a daughter cell)
