BIOL 1010 Lecture Notes - Lecture 14: Species Problem, Hybrid Speciation, Dna Barcoding
Origin of Species
November 18, 2014
What is a species? This is difficult to make a universal definition.
Morphological Species Concept:
• Based on morphological similarities
• Historically, most commonly used concept
• Hard to know how much difference is enough to distinguish between two separate
species
Molecular sequence similarities are now compared using methods such as DNA barcoding.
Biological Species Concept:
• Inter-fertility – populations that interbreed to produce fertile offspring
• Reproductive Isolation – do not normally successfully interbreed in nature with
other species
This concept is not always applicable but is usually the most useful *not based on similarity
Speciation
Reproductive barriers – inhibit gene flow between populations, allowing evolutionary
divergence EXAMPLES ON PAGES 524-525
• Prezygotic Barriers – act before fertilization
o Habitat isolation
o Temporal Isolation
o Behavioral Isolation
o Mechanical Isolation
o Gametic Isolation
• Postzygotic Barriers – act after fertilization
o Hybrid inviability
o Hybrid infertility
▪ Ex. Mules are organisms, which are created through the mating of a
horse and donkey. These animals are robust but infertile as it
contains incompatible chromosome organizations.
o Hybrid breakdown
Evolution of Reproductive Barriers
Many arise accidentally as a result of evolution in isolation. May evolve through natural
selection to reduce inter-species mating that lowers reproductive success.
Allopatric Speciation – geographic barrier blocks gene flow between populations
1. geographic barrier separates populations
2. an evolutionary change occurs on one or both sides of barrier
Geographic Barriers include:
• mountain ranges
• rivers
• open water (islands)
• lake formation
• land bridges
• ex. The Grand Canyon separates two populations of squirrel
• ex. Isthmus of Panama isolates many populations of marine animals
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
This is difficult to make a universal definition. Morphological species concept: based on morphological similarities, historically, most commonly used concept, hard to know how much difference is enough to distinguish between two separate species other species. Molecular sequence similarities are now compared using methods such as dna barcoding. This concept is not always applicable but is usually the most useful *not based on similarity. Inter-fertility populations that interbreed to produce fertile offspring: reproductive isolation do not normally successfully interbreed in nature with. Mules are organisms, which are created through the mating of a horse and donkey. These animals are robust but infertile as it contains incompatible chromosome organizations: hybrid breakdown. Many arise (cid:498)accidentally(cid:499) as a result of evolution in isolation. Allopatric speciation geographic barrier blocks gene flow between populations selection to reduce inter-species mating that lowers reproductive success: geographic barrier separates populations, an evolutionary change occurs on one or both sides of barrier.
