Evolution Flashcards
Evolution
The change in the genetic composition of a population during successive generations which may result in the development of new species
3 Modes of Evolution
Allopatric, sympatric, parapatric
Allopatric Evolution
Gene flow is disrupted as populations become physically separated through geographic isolation. Due to genetic drift or different selecting pressures on the two populations, the populations diverge and become new species
Sympatric Evolution
The evolution of two or more new species from a single population within the same place. Requires a reproductive barrier that isolates members of a population from the rest of the population in the same area
Parapatric Evolution
Could arise if members of a population expand into surrounding areas where conditions favor a set of alleles different from the main population. Gene flow would still continue in the bordering areas but over time the populations would diverge to become better adapted to different conditions in different areas. A hybrid zone would form where the populations meet, hybrids are often less fit than either populations and reinforce reproductive barriers: spatial distance, patchy, changed habitats
Divergent Evolution
Occurs when a population splits into two or more species. This may be due to competition, or when a new niche becomes available in an environment. Individuals that have variation due to mutations that are beneficial for the new environment have an advantage
Adaptive Radiation
The evolutionary process where organisms diversify rapidly from an ancestral species into several divergent species
Parallel Evolution
Independent evolution of similar traits in species that once shared a common ancestor meaning two or more species in the same environment develop similar adaptations or characteristics; closer ancestral relationship
Convergent Evolution
The independent development of similarities between species as a result of them having similar ecological roles and selection pressures; more distant ancestral relationship than parallel evolution
Coevolution
When two or more species reciprocally affect each other’s evolution. When two species are very reliant on each other, each species exerts a strong selective force on the other
Macroevolution
The variation of allele frequencies at or above the level of species, over geological time, resulting in the divergence of taxonomic groups from the ancestors
Speciation
The evolution of one or more new species from an ancestral species
Mechanisms of Isolation
Geographical: seas, mountains, distance or habitat
Temporal (Time): breed different times of the year or times of the day
Behavioural: courtship patterns
Morphological: different reproductive structures
Gene Frequency
There are different alleles for one gene and their frequency in a population depends on the environmental selection pressures. If a particular phenotype is advantageous than the frequency will increase and if it is selected against, it will decrease in a population
