Specijacije

Štambuk, Jerko (2009) Specijacije. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

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.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Kalafatić, Mirjana
Date: 2009
Number of Pages: 9
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 18 Dec 2014 12:13
Last Modified: 18 Dec 2014 12:13
URI: http://digre.pmf.unizg.hr/id/eprint/3547

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