speciation Flashcards
(28 cards)
Define natural selection
Natural selection is the process whereby organisms that are better suited towards the environment tend to survive and produce offspring
the overall effect of natural selection
those with a genotype or phenotype (dependent on the question) which suits their environments biological niche will be more likely to survive and pass on those advantageous genes into the gene pool
what is stabilising natural selection
natural selection for those individuals with a combination of both phenotypic extremities meaning those with one extremity and less likely to survive
What is directional natural selection
natural selection for one extreme phenotype at the expense of another
What is disruptive natural selection
natural selection against the average, natural selection for both extremities, over time this leads to a bimodal distribution of phenotypes
What is a deme
Local populations/sub-groups where phenotypic variations reflect the local environmental factors. there is limited gene flow between the two groups
What is a cline
the geographical gradient in the phenotype of individuals of the same species. Often occurs in relation to changing latitude or altitude
what is allopatric speciation
a group the becomes geographically isolated
what is sympatric speciation
Gene flow is altered/stopped by something other than geographical, for example temporal
Define reproductive isolating mechanisms
any factor that prevents two organisms from different species from mating and producing fertile offspring
what is geographical reproductive isolation
two groups are geographically issolated and therefore gene flow is limited (this is allopathic speciation)
what is Temporal reproductive isolation
The timing of activity or reproduction does not overlap eg diurnal vs nocturnal
what is ecological reproductive isolation
Closely related species (could produce fertile offspring) occupy different niches within the same environment eg sparrow and ground sparrow occupy a forest
what is ethological reproductive isolation
courting/ mating rituals that are species specific eg a fantail not recognizing a peacock dance
What is structural reproductive isolation
structural variations between species preventing reproduction
eg incompatible sex organs
What is convergent evolution
Species with similar niches develop similar adaptations despite having different ancestors due to having similar selection pressures.
define analogous organs
Organs that have the same basic structure and function but evolved independently from different ancestral organs in unrelated species, eg flippers on a dolphin vs shark
Define ecological equivalents
Species with different origins develop similar adaptations because they occupy similar niches in different geographical areas
What is divergent evolution/ when does it occur
when two or more related groups develop different adaptations over time because they occupy differently niches
What is adaptive radiation?
a type of divergent evolution when a number of different species develop from a common ancestor
What is homologous organs/ evolution
Found in related species that evolved from a common ancestral organ. They have different functions but similar structures, for example, tibias in dolphins’ flippers and humans’ legs
Parallel evolution
Similar features evolve in species with a common ancestor. This is because they’re subjected to similar selection pressures (for example, woolly mammoths and elephants.) they evolve parallel because of similar selection pressure.
What is co-evolution
the reciprocal evolutionary effect that two species can have on each other when they react. Each species provides a natural influence on each other and evolves together, for example, flowering plants have co-evolved with other pollinating partners
What is aneuploidy
1 too many or 1 two lesschromosomes (n+1, see above) and after an aneuploidy cell fertilisatises a normal gamete.
