Specijacije

undergraduate thesis

• Title (english): Speciation
• Author: Jerko Štambuk
• Mentor: Mirjana Kalafatić (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2009, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Vrsta je skup jedinki koji se mogu međusobno razmnožavati. Specijacija je proces nastanka novih vrsta. Alopatrijska specijacija je vjerojatno najrasprostranjeniji oblik specijacije. Kod alopatrije je protok gena među populacijama spriječen fizičkom barijerom, omogućavajući gensku raznolikost prirodnom selekcijom i genetičkim driftom. Peripatrijska specijacija je teoretski oblik alopatrijske specijacije u kojoj genetički drift u malim perifernim populacijama potiče brzu evoluciju i reproduktivnu izolaciju. Simpatrijska specijacija je primjer nastanka vrsta pod utjecajem disruptivne selekcije i ona se pojavljuje ako rekombinacija ne alternira selekciji. Specijacija poliploidijom je česta kod biljaka. Kao primjer se navode alopoliploidne hibridne biljke koje su nastale križanjem među genetski različitim populacijama. Za uspostavu poliploidnih populacija vjerojatno je potrebna ekološka segregacija. Kod nekih biljaka neki genotipovi diploidnih hibrida su fertilni i reproduktivno izolirani od roditeljskih vrsta. Taj oblik specijacije nastao je rekombinacijom. Vrijeme potrebno za specijaciju poliploidijom i rekombinacijom je kraće nego u ostalih vrsta specijacije i traje oko 2-3 milijuna godina. U životinja brzinu specijacije povećavaju spolna selekcija, a u biljaka prijenos sjemena preko životinja. Specijacije su izvor raznolikosti organizama koji se spolno razmnožavaju i svako grananje u stablu života označava jedan specijacijski događaj.

Abstract (english)

Specie is group of organisms capable of interbreeding. Speciation is a process by which new species arise. Allopatric speciation is probably the most common mode of speciation. In allopatry, gene flow is reduced by physical barriers, allowing genetic diversity by natural isolation and genetic drift. Peripatric speciation is a teoretical mode of allopatric speciation in which genetic drift in a small periphernal population initates rapid evolution and reproductive isolation. Sympatric speciation is an example for arising species under the conditions of distruptive selection and may appear if recombination does not oppose selection. Speciation by polyploidy is common in plants. For example are taken alopolyploid hybrid plants arised by crossing between genetically divergent populations. For establishment of polyploid populations ecological segregation is probably required. In some plants genotype of diploid hybrids are fertile and reproductively isolated from ancestral species. That mode of speciation has arisen by recombination. Time required for speciation by poliploidy and recombination is shorter than in other modes of speciation and may require 2-3 million years. In animal world sexual selection enhances rates of speciation, and in plants that role belongs to animal pollination. Speciations are origins of diversity in sexually reproducing organisms and every branch in that great tree of life presents one speciation event.

• Keywords: specijacija
• Keywords (english): speciation
• Language: croatian
• URN:NBN: urn:nbn:hr:217:222221
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-03-21 11:14:32