This lesson introduces the biological definition of a species and explains why reproduction and inherited genetic variation matter to the formation of new species.
A biological species is a group of organisms that can interbreed in nature and produce viable, fertile offspring. Viable offspring survive and develop; fertile offspring can reproduce themselves. Under this definition, two populations are distinct species when they cannot successfully produce fertile offspring together in nature.
All flashcards
What is a biological species?
A group of organisms that can interbreed in nature and produce viable, fertile offspring.
What does viable mean when describing offspring?
The offspring can survive and develop.
What is a hybrid?
An offspring produced by a cross between individuals of two different species; it may be viable but infertile.
What is a gene pool?
The collection of all gene variants, or alleles, present in a population or species.
Why must a change be heritable to contribute to evolution?
A heritable change can pass from parents to offspring, allowing its frequency to change across generations.
Quiz questions
What reproductive criterion defines a biological species?Answer: Its members can mate and produce offspring that survive and reproduce.
A population includes individuals with very different coat colors and body sizes, yet they interbreed in nature and produce offspring that survive and reproduce. Under the biological species concept, why can they still belong to one species?Answer: Their reproductive compatibility matters more than their differences in appearance.
What is a hybrid?Answer: Offspring produced by a cross between individuals of two different species.
A genetic change occurs only in an ordinary body cell of a sexually reproducing animal. Why is it unlikely to affect the next generation?Answer: It is unlikely to be present in a sperm or egg cell that contributes genetic information to offspring.
Two populations can mate, but their hybrid offspring cannot reproduce. What does this suggest about the populations?Answer: They are reproductively distinct because their offspring are infertile.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.