species & speciation Flashcards
what does the criteria to define species include? (species concept)
morphological, biological, phylogenetic
what is the morphological species concept? and a limitation?
visible anatomical characteristics. species can very in size and colouration
what is the biological species concept? and a limitation?
reproductive isolation & genetic distinction. doesn’t apply to asexually reproducing species and can’t be used for extinct species
what is the phylogenetic species concept? and a limitation?
evolutionary history aka tree of life. not enough information and cant see which species are able to breed (gene pool)
what are ring species?
some plant/animal species have a ring shaped distribution that surrounds inhabitable territory. they may have variation depending on their area
what is clinal variation?
when species distributed over large, environmentally diverse area, some traits may exhibit a CLINE, a smooth patter of variation across a geographical gradient
what are the two types of isolating mechanism? and when do they occur?
prezygotic: prevents production of hybrid offspring before mating, postzygotic: prevents production after mating
what are the models of speciation?
allopatric & sympatric
when does allopatric speciation occur?
may take place when there’s separation
what is sympatric speciation?
reproductive isolation evolves between distinct supgroups (races) that arise within one population. this doesnt require separation
what is secondary contact?
contact after geographical isolation. provides test if genes have diverged enough for reproductive isolation. may resume interbreeding
what is reinforcement?
when prezygotic mechanisms reinforce postzygotic barriers
what is genetic divergence in relation to speciation?
allopatric. without geneflow, geographically separated populations accumulate genetic differences thru mutations, genetic drift, & natural selection
what is polyploidy in relation to speciation?
sympatric. generally results in instant speciation - may be reproductively isolated from parents. provides new genetic material for evolution
what is chromosome alterations in relation to speciation?
may foster postzygotic isolation from chromosomal differences (inversions, translocations, deletions, & duplications)
why is there no universal concept of of species that applies to all organisms?
we have different rules for different groups of organisms. species are defines with multiple lines of evidence (multiple species concept)
advantage and disadvantage to the species concept: phylogenetic
can be applied to all organism ONLY if data collected. data cant be taken from fossils but can from preserved remains, for example a mammoth frozen in permafrost/amber
advantage and disadvantage to the species concept: morphological
can compare traits with fossils. difficult to distinguish species that look similar. phenotypic variability is not consistent for different species. no info on how they evolved
advantage and disadvantage to the species concept: biological
geneflow within species, cohesive traits. explains how species evolves and is testable. doesnt work with asexually reproducing organisms and reproductive behaviour cant be determined for extinct species.
what are the prezyogtic isolating mechanisms?
ecological, behavioural, temporal, mechanical, gametic
what is the isolating mechanism: ecological?
occupy same region but live in different habitats
what is the isolating mechanism: behavioural?
signals not recognized by another
what is the isolating mechanism: temporal?
mate at diff times
what is the isolating mechanism: mechanical?
differences in structures prevent interbreeding
what is the isolating mechanism: gametic?
gametes not compatible, can not fertilize
what is the hybrid zone?
where individuals of previously separated populations interbreed. hybrids are often not adapted to areas outside of hyrbid zone.
what does reinforcement and isolation do in relation to hybrids?
reinforcement accelerated isolation after secondary contact. if postzygotic isolation occurs, hybrids tend to have lower fitness
what are traits involved in reproductive isolation?
anything that makes a difference in reproduction between individuals: structures, hormones, sperm recognition proteins, accessing recourses, behavioural differences
advantage and disadvantage to the species concept: ecological/environment
it explains the role of environment in speciation. but it is unable to explain existence of same species who live in different environments e.g. tadpoles and frogs
what are the post-zygotic isolating mechanisms?
hybrid inviability, hybrid sterility, hybrid breakdown
what is the isolating mechanism: hybrid inviability?
Would have 2 sets of distinct genes/developmental instructions that are too different to allow development.. But the offspring would die young
what is the isolating mechanism: hybrid sterility?
Can grow up but become unable to produce functional gametes.
what is the isolating mechanism: hybrid breakdown?
Can develop and also mate with other hybrids, and both parent species. However, second generation will have higher fatality, lower fertility. Long-term reproductive isolation rather than immediate.
Why is sympatric speciation more common in plants? Is polyploidy a possible mechanism of sympatric speciation for animals?
to undergo polyploidy, need to fertilize another gamete with twice the normal amount of genetic material. plants are able to self-fertilize and perpetuate this for multiple generations, whereas animals lack this ability.
Would it be considered speciation if the Northernmost bird population was unable to breed with the Southernmost bird population for clinal variation?
No. Because there is gene flow through intermediate populations, that would not be considered speciation, even if the two populations were unable to breed.
Two identical petri-dishes of Saccharomyces cerevisiae, also known as budding yeast, were grown in either Condition A or Condition B. After 100 generations (15 hours), yeast from both conditions were placed in the same petri dish and were grown together. If the two populations of yeast were unable to interbreed, did speciation occur?
Technically, speciation DID occur if you were looking at it through the biological species concept. However, in real life it would depend on the scientific governing body.
We’re very familiar with the case of larger organisms experiencing allopatric speciation over large time scales. But allopatric speciation can occur over short time scales as well.
