How do new species arise? -- Speciation -- • Species : group of organisms that can interbreed and produce fertile offspring • Speciation : the process by which genetically distinct species arise. Speciation: Formation of new species • As adaptations and differences accumulate, the organisms become so different that they cannot interbreed (reproduce) anymore
19
Embed
How do new species arise? -- Speciation -- Species: group of organisms that can interbreed and produce fertile offspring Speciation: the process by which.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
How do new species arise?-- Speciation --
• Species: group of organisms that can interbreed and produce fertile offspring
• Speciation: the process by which genetically distinct species arise.
Speciation: Formation of new species
• As adaptations and differences accumulate, the organisms become so different that they cannot interbreed (reproduce) anymore
A population is a group of individuals, of the same species, living in the same area, that interbreed (reproduce)
• The Unit of Evolution is a Population:
• Populations Have Genetic Variation (Variability)Individuals in a population are different. Small differences are determined by their genes (DNA sequences)
1. Geographic Isolation• A physical barrier separates (splits) the original
population
• As time passes, the environment may selects for different traits and the 2 populations become genetically different AND can’t reproduce
• Barriers: Rivers, mountains, bodies of water
Kaibab and Abert Squirrels- The Kaibab squirrel
(Sciurus aberti kaibabensis) became geographically isolated from the common ancestor about 10,000 years ago.
- Its closest relative is the Abert squirrel (Sciurus aberti aberti)
- They live in opposite sides of the Grand Canyon
Kaibab Abert
Example: Emus, ostriches, rheas, Cassowaries,
• Common ancestor lived in the continent of Gondwana (all southern continents together)
• When Gondwana broke up, the populations separated and changed over time. All these birds are closely related but live far apart.
Wrasses: Original population split up when the isthmus of Panama was formed
- 2 species now, one on each side of Central America
2. Temporal Isolation (Time of Reproduction)
• Groups of individuals reproduce at different times. The genes of the 2 groups do not mix.
• It is happening now with some of the migratory birds that decide not to migrate.
• The birds that do not migrate start mating before the migratory ones come back.
• Eventually they might become different enough that they may not recognize each other.
Robins usually migrate south to warmer climates. Some are not migrating. They reproduce before the migrating individuals return. Reproductive Isolation