{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter 26 Speciation - Chapter 26 Speciation How are new...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 26: Speciation How are new species formed? Genetic isolation Genetic divergence 1 How are species defined? * (pp. 527–530) Species are often thought of as evolutionary units Individuals within a species are evolving together Individuals of di ff erent species evolve independently (Fig. 26.1) Useful conceptually, but not practical There is no universal, practical definition of species Life is complex 1.1 Biological species Biological species are defined by reproductive isolation Di ff erent biological species either: Don’t breed in nature Breed but fail to produce o ff spring Produce inviable o ff spring – o ff spring do not develop to adult- hood Produce sterile o ff spring – o ff spring that cannot themselves re- produce 1
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Mechanisms of isolation Mechanisms of isolation are often divided into two classes: – Prezygotic isolation refers to any mechanism that prevents suc- cessful mating – Postzygotic isolation refers to any mechanism that prevents o ff - spring from producing o ff spring of their own “Zygote” means a cell formed by the fusion of a sperm and an egg Mechanism examples Pre- or post-? Di ff erent malaria parasites breed inside di ff erent hosts Di ff erent species of doves can nest together, but eggs fail to hatch or chicks fail to grow The o ff spring of horses and donkeys grow up to be healthy, infertile adults Sea urchin eggs cannot be penetrated by sperm from other species Species of pine trees release and receive pollen and di ff erent times of year Disadvantages of the biological species concept 2
Image of page 2
1.2 Morphological species
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern