speciation Flashcards
adaptive radiation
the evolution of several different species of plant or animal from one ancestral species to occupy different ecological niches.
allopatric speciation
speciation occurring where organisms are initially capable of interbreeding but cannot because they are geographically isolated
analogous structures
structures that are superficially similar with the same job but have evolved in different ways and have no common ancestor leading to different bone makeup
biogeography
the study of the geographic distributions of organisms and ecosystems though geographical space and time
cline
gradual variation in the characteristics of a species or population over a geographical range
coevolution
occurs when two or more species reciprocally affect each other’s evolution. organisms change genetic composition in response to genetic change in another
convergent evolution
different species living in the same environmental niche look similar due to similar selection pressures with no shared common ancestor.
deme
population of organisms within which the exchange of genes is completely random. eg all mating combinations between individuals of opposite sexes have the same probility of occuring
divergent evolution
one species branches to form two or three. the accumulation of changes in the gene pooles of two or more populations leading to the formation of races, sub-species, species etc
evolution
the gradual process by which the present diversity of plants and animals arose from the earliest and more primitive organisms
endemic
only found naturally in a certain area
fossil records
document history, remains or imprints of organisms from earlier geographical periods presevered in sedimentary rock used to show evolution
founder effect
new population established by a very small number of individuals that have become reproductively isolated from a larger population
gene pool
the total number of genes of every individual in a population
gene flow
movement and exchange of genes or alleles from one population of species to another
genetic driift
the change in the frequency of existing alleles in a population due to random change alone and not natural selection.
random fluctuations in frequency of alleles due to change events
geographical isolation
physical barrier that physically prevents gene flow, separates organisms stopping them from exchanging genetic material with one another
geographical record
the fossils preserved in sediment rock layers used to trace the evolutionary history of a species
gradualism
slow changes between populations that occur as a result of different selection pressures
homologous structures
structures that have a similar evolutionary history but developed to suit different functions. common ancestor
hybrid
offspring of a mating where parents differ in characteristics like different varieties or species
hybridisation
offspring resulting frmo combining of qualities of two organisms of different breeds, varities or species through sexual reproduction
instant speciation
formation of new species through autopolyploidy or allopolyploidy cause chromosome numbers of new instant species do not match original species and they cannot interbreed
macroevolution
formation of completely new species
microevolution
acculutation of new characteristics in a species through mutation
mtDNA
dna located in the mitochondria inherited from the mother. used to trace maternal lineage far useful to study evolutionary relationships
mutation
permanent change in bases on the DNA, only way of creating new alleles
natural selection
process that brings new species by eliminating individuals that are less well adapted to their current environment from a population showing variation, allowing mainly individuals with advantageous adaptations to survive and reproduce
nondisjunction
the failure of homologous chromosomes or sister chromatids to separate during cell division resulting in cells with more than two copies of each chromosomes eg 3n instead of 2n
parallel evolution
development of related organisms along similar evolutionary paths due to strong selection pressures acting on all of them in the same way
polyploidy
when cells have more than 2n chromosomes, common in plants
population bottleneck
an event that drastically reduces the size of a population. event could be environmental disaster. decreases the gene pool of population as many alleles lost what is left is the surviving organisms
postzygotic isolating mechanisms
prevents formation of fertile offspring. includes hybrid inviability, sterility and breakdown
prezygotic isolating mechanisms
prevents fertilization of egs between species. spatial, temporal, mechanical, gametic, behavioural isolation
punctuated equilibrium
theory that states evolution occurs primarily through short bursts of instense speciation followed by lengthy periods of little change
reproductive isolation
barrier to breeding exists due to differnes in mating season or organs. mechanism that keeps species from mating with each other
ring species
2 apparently distinct species that are connected by a series of intermediate geographical and structural subspecies between which interbreeding can occur
sexual selection
a special case of ns, acts on an organisms ability to obtain or successfully copulate with a mate. often powerful enough to produce feature that are harmful to an individual’s survival. peacock etc
selection pressure
the extent to which organisms possessing a particular characteristic are either eliminated or favoured by environmental demands. environmental factors that favour certain phenotypes
speciation
development of one or more species from an existing species occuring sympatric or allopatric populations diverge so much from parents population that interbreeding cannot occur
species
catergory used in classification of organisms consists of a group of organisms that can usually breed together and produce fertile offspring
sub-species
group of individuals within a species that breed more freely among themselves that other members of the species and resemble e/o in more characteristics
sympatric speciation
speciation occuring when organisms living within the same area are theretically capable of interbreeding but cannot due to differences in behaviour
sympatry
describes groups of organisms that live in the same geographical area
temporal isolation
prezygotic reproductive barrier is temporal isolation. “isolated in time”, mechanism that prevents species from mating cause they breed at different times. differences can be time of day, season or even different year
vestigal organ
any part of an organism that has diminished in size due to evolution cause the function it serves has decreased in importance eg appendix in humans
vestigal structures
structure in an organism that has lost all or most of its original function in the course of evolution eg human appendix
y chromosomes
one of two sex chromosomes (allosomes) in mammals. y chromosome passed only from father to son and can be used to demonstrate relatedness
