3.5 Evolutionary processes leading to speciation Flashcards
divergent evolution/ divergence
an evolutionary pattern where two related but isolated populations accumulate genetic differences and become more and more different due to each population being subjected to different selection pressures.
adaptive radiation
The rapid evolution of a large number of species from a common ancestor, to occupy a variety of different ecological niches (vacant niches)
convergent evolution
an evolutionary pattern in which 2 or more unrelated species (no common ancestor) evolve similar adaptations in response to similar niche requirements and similar selection pressures.
co-evolution
an evolutionary pattern that describes the reciprocal evolutionary effect that two interacting species can have on each other. Each species acts as a natural selective influence on the other
gradualism
A slow, constant rate of change within a species occurring over time which involves the transition of one species into another, in response to changes in selection pressures.
punctuated equilibrium
An evolutionary pattern characterised by long periods of little change (stasis), followed by a rapid burst of evolutionary change with the sudden appearance of new species
stasis
long periods of time with little to no evolutionary change
homologous structures
adaptations/structures that are similar in structure and origin, but are different in function
analogous structures
structures present in different unrelated species (no common ancestry) that have the SAME FUNCTION, due to similar selection pressures.
vestigial structures/ organs
structures that have been reduced and/or lost their function, but the remnant of the structure shared with the common ancestor/ closely related species is still present
selection pressure
Selection pressures are external factors which affect an organism’s ability to survive in an environment (the effects of natural selection on the population). Individuals with favourable phenotypes/ better suited to the environment will have a greater chance of survival and reproduction.
parallel evolution
a pattern of evolution where two or more related groups evolve along similar lines independently
mutation
A random, spontaneous, permanent change in the nitrogen base sequence, which gives rise to new alleles
common ancestor
An ancestor that two or more descendants have in common.
speciation
A process that involves the formation of new species as a result of populations becoming reproductively isolated; therefore no longer sharing a common gene pool.
anagenesis
formation of a new species where no splitting is occurring (the new species replaces the old species and so no members of the old species exist anymore)
phylogeny
the study of evolutionary relationships
phylogenetic tree
Diagrams that show the evolutionary relationships between different groups (taxa)
pentadactyl limb
A limb with five digits (e.g. hand), characteristic of tetrapod vertebrates (amphibians, reptiles, birds, and mammals). It evolved from the paired fins of primitive fish as an adaptation to locomotion on land and is not found in modern fish.
prezygotic isolating mechanism
mechanisms that act prior to fertilisation; includes structural/ behavioural/ geographical/ temporal/ ecological barriers
postzygotic isolating mechanism
mechanisms that act after fertilisation; includes hybrid inviability/ hybrid sterility/ hybrid breakdown
Geographic isolation
RIM caused by physical barriers, such as rivers, mountain ranges, and oceans separating populations.
Structural isolation
RIM caused by the evolution of differences in structure of the external sex organs (genitalia), so that the male is no longer able to successfully transfer sperm to the female.
Ecological isolation
RIM caused by differences in habitat/ niches within the same geographical area, so that populations have greatly reduced contact with each other.
Temporal isolation
RIM caused by species’ breeding behaviours occurring at different times.
Behavioural isolation
RIM where, within one geographical area, variations in the courtship displays/ behaviours (e.g. songs) of different individuals of the same species developed.
Gametic isolation
RIM caused by the evolution of incompatible gametes.
Hybrid inviability
When the embryo is inviable- i.e. doesn’t survive/ develop normally, therefore dies early in development.
Hybrid sterility
When the hybrid survives to reach maturity, but is infertile, and therefore can’t reproduce sexually
Hybrid breakdown
mechanism/ process which involves the hybrid surviving to reach maturity and being fertile, yet the next/ subsequent generations are infertile/ have reduced fertility.
polyploidy
A form of sympatric speciation that involves the formation of organisms with multiple sets of chromosomes in their somatic cells. Results in the formation of a new species without isolation from the parent species.
auto polyploidy
A from of polyploidy where the polyploid organism was produced by organisms of the same species.
allopatric speciation
The formation of new species from an ancestral species, due to geographical isolation (caused by geographical barriers).
sympatric speciation
The formation of new species from an ancestral species while both inhabit the same geographic area.
reproductive isolating mechanisms
factors that prevent interbreeding between groups of individuals which leads to speciation.
ring species
A special type of cline that forms a loop because the two ends of the cline overlap. The two ends of the cline are connected by a series of intermediate, interbreeding populations.
ring species
A special type of cline that forms a loop because the two ends of the cline overlap. The two ends of the cline are connected by a series of intermediate, interbreeding populations.
comparative anatomy
The comparison of body structure between different species, both from the fossil record and those living.
comparative anatomy
The comparison of body structure between different species, both from the fossil record and those living.
species
Organisms that can interbreed and produce viable (fertile) offspring.
species
Organisms that can interbreed and produce viable (fertile) offspring.
subspecies
populations of a species that are different to each other in one more characteristics, but can still breed with each other.
deme
Local interbreeding (with existing gene flow) populations that may be geographically separated.
