READ: Macro Evolution

Lesson Summary

• Microevolution results from evolutionary changes that are small and do not lead to the creation of a new species.
• Macroevolution refers to large evolutionary changes that result in new species.
• Macroevolution may happen when many microevolution steps lead to the creation of a new species.
• Macroevolution may happen as a result of a major environmental change, such as volcanic eruptions, earthquakes or an asteroid hitting Earth, which changes the environment so much that natural selection leads to large changes in the traits of a species
• The creation of a new species is called speciation.
• Natural selection causes beneficial heritable traits to become more common in a population, and unfavorable heritable traits become less common.
• Artificial selection is when humans select which plants or animals to breed to pass specific traits on to the next generation.
• Allopatric speciation occurs when groups from the same species are geographically isolated physically for long periods.
• Sympatric speciation occurs when groups from the same species stop interbreeding, because of something other than physical separation, such as behavior.
• Allopatric speciation and sympatric speciation are both forms of reproductive isolation.
• The rate of evolution is a measurement of the speed of evolution. Genetically speaking, evolution is how much an organism’s genotype changes over a set period of time.
• Not all organisms evolve at the same rate.
• Evolutionary trees are used to represent the relationships between different species and their common ancestors.