This lesson introduces how biologists define species and how one ancestral species can split into two. It explains why reproductive isolation is central to speciation and how barriers to reproduction can act before or after fertilization.
For sexually reproducing organisms, the biological species concept defines a species as a group of actually or potentially interbreeding individuals. Members of one species can mate with one another and produce fertile offspring. Under this definition, two groups are considered different species when individuals from the groups cannot successfully interbreed to produce fertile offspring.
All flashcards
What is the biological species concept?
For sexually reproducing organisms, it defines a species as a group of actually or potentially interbreeding individuals that can produce fertile offspring.
What is a prezygotic barrier?
A reproductive barrier that acts before fertilization by preventing individuals from meeting, mating, or successfully fertilizing an egg.
What is a postzygotic barrier?
A reproductive barrier that acts after fertilization, such as hybrid offspring failing to develop, survive, or reproduce.
What is allopatric speciation?
The formation of new species after populations become geographically separated and evolve independently.
What is polyploidy?
The condition of having extra complete sets of chromosomes.
Quiz questions
What condition is central to allopatric speciation?Answer: Geographic separation reduces gene flow, allowing populations to evolve independently.
A river changes course and divides a population already living in the area. What type of separation is this?Answer: Vicariance, because a new barrier divides an existing population.
What pattern does adaptive radiation describe?Answer: One ancestral species diversifying into species adapted to different ecological niches.
Two groups occupy the same region, but differences in host preference lead them to mate mostly within their own groups. Which form of speciation could result?Answer: Sympatric speciation, because reproductive separation develops without geographic separation.
Why does the effectiveness of a geographic barrier depend on the organism?Answer: Different organisms vary in their ability to cross the barrier and maintain gene flow.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.