COR 401 Lecture #11 Mechanisms of Inheritance February 17, 2009

German biologist/artist Ernst Haeckel ( ),

Moore: If the hypothesis of evolution is true, only those variations that are inherited will be important

Even Aristotle knew about sex – But how is sex related to Wallace and Darwin?: Mechanism of Inheritance

Aristotle’s “Historia Animalium” ~350 BC

Aristotle’s Query: What is it exactly that parents transmit to their offspring?

Aristotle’s Male Semen/ Female Blood Coagulum Theory

A Cheesy Analogy Male Semen (bearing “movement”) Sets the Female Semen (bearing “substance”) Milk + Rennet = Cheese

Aristotle knew there was something up with the egg Oviparous Viviparous

Aristotle’s Embryology

Chick Embryology Time Lapse Video

48 vs 72 hr Chick Embryos “Blood is formed out of something that is not blood”

Aristotle’s Theory of Epigenesis Moore: Parents transmit not structures to their offspring but “information” (p 424)

Pangenesis: Every part of the adult body contributes some specific material to the semen which then configures the offspring If so: How are they packaged to allow for multiple kids? Why not produce 2 every time? ? ?

Aristotle: Modern Man in a Toga?

Fast Forward: 17 th -18 th C & Preformation Hartsoeker’s Humunculus (1694) Malphigi’s 2-Day Chick Embryo 1692 How could structures appear in the course of development from structureless material?

12 th C Virgin and Child Turkey

Epigenesis vs Preformation But if Preformist Theory is true: How can offspring be intermediate? Why this? And not this? If both sperm and egg preformed, why not 2 every time? ?

Epigenesis vs Preformation But if Preformist Theory is true: How to explain regeneration? How to conceptualize Infinite regress? If all from Eve, what about Human Variability

What about Dawkins’ Recipe and Blueprint Analogy ?

Which of the Following Statements Best Describes the Analogy: 1.A blueprint is like a scaled down version of an adult, whereas a recipe if obeyed in the right order will result in an adult. 2. The blueprint corresponds one-to-one with the finished product whereas there is no one-to-one correspondence between recipe and final product. 3. A blueprint implies set purpose and design, whereas a recipe can deviate from the end product depending on the materials and tools available in the kitchen. 4. Of the two, the comparison between epigenesis and recipe is more valid given the strong implication of the importance of process – it’s all about information driving form/structure

Discovery of cells Robert Hooke’s Compound Microscope

Discovery of cells Van Leeuwenhoek’s Simple Microscope

Blending Inheritance: Offspring are an average of parents Mom Dad But then where do Darwin’s adaptations come from?

Gregor Mendel Traits are controlled by heritable “factors” that we now call genes

Summary Aristotle performed the groundwork in suggesting that it is information, not structure that is inherited Aristotle’s epigenesis was challenged by Pangenesis and Preformist Thinkers Microscopes, put Preformist thought to rest Darwin struggled with Blending Inheritance as a mechanism by which adaptation would prevail in the struggle for existence. But it was Mendel who allowed us to understand the gene and its mode of inheritance.