Bio 111.Developmental Genetics: Ecological Developmental Biology

Dr. Scott Gilbert    Martin 302   8049     email

"Evolution is the control of development by ecology"

-Leigh van Valen , 1976

 

It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the conditions of life and from use and disuse: a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms.”   -Charles Darwin, 1859

      The tangled bank arises through interactions between organisms. And as Darwin noted, most organisms do not survive to adulthood. So the tangled bank originates from the interactions between juvenile forms and between those juveniles and the adult forms that constitute the environment within which they are developing. Ecological developmental biology (“Eco-devo” to some of its practitioners) is one of the newest sciences in existence. It seeks to place development into its ecological context. Most animals do not develop in laboratories. A frog tadpole developing in an aquarium looks different from a tadpole growing in the wild. This is because the tadpole growing in the wild has modified its development, integrating signals from predators and competitors. Moreover, such a tadpole in the wild may be much more susceptible to herbicides than a tadpole in the laboratory.

     This seminar will look at development in the natural world. It will concentrate on a fundamentally important concept: phenotypic plasticity. Here, the genetics of the organism do not produce a predictable phenotype. Rather, the genome provides the organism with a repertoire of possible phenotypes, and the organism has evolved ways that allow environmental signals to cause it to develop in a manner that favorably biases survival in that particular habitat.  The seminar will also look at teratogenesis, the mechanisms through which  environmental compounds can disrupt development and cause congenital anomalies. Last, we will look at how modern evolutionary theory is using developmental plasticity to forge a new type of evolutionary synthesis between genetics, development, and ecology.

Student responsibilities:

Depending on how many students are in this seminar, your responsibilities will vary. In any manner, it will be a full 2-credit seminar, and I expect that you will be preparing material every other week. I will be taking part as a participant as well as an observer. (The seminar will be graded; but not the students, individually. Welcome to the real world of science.) The first two weeks will be lecture and field trips. This is so that we can cover the background material and bring everyone to the same place. Starting the third week, the seminar will meet for discussions on Tuesday and for laboratories on Thursdays.

   The main student responsibilities will be to (1) to read all the assigned material before coming to the seminar discussions, (2) to prepare assignments a week ahead of time so that everyone has time to reads them; (3) to prepare a thoughtful analysis of your topic and present it by Powerpoint, bringing into the discussion new material; (4) to politely criticize the material being presented; and (5) to think about the material, and (6) to write and hand out the following week a detailed summary of the topic.

            Laboratories:

The first exercises will have you be part of an ongoing research project involving the generation of the turtle shell. Later, I am hoping that we can plan some experiment on the local fauna as winter approaches. In most weeks, the laboratory will start on Thursdays. Sometimes, this means that people have to come in on Fridays to finish the experiments. 

            Final exam:

            I am in favor of group finals. You will be reading the book by Mary Jane West-Eberhard, Developmental Plasticity and Evolution. (Oxford University Press, 2003.) You will also have read a book by John Odling-Smee and company. Both propound new theories of evolution, based on phenotypic plasticity. (You will have portions of the first book assigned during the seminar so that you won’t have to read the entire book at the end.) The final exam will be for you to write a paper integrating these perspectives into the work you did during the semester, updating these theses, or coming up with your own proposal for the origin and propagation of new variation. Nothing less!

TENTATIVE SYLLABUS

A. Introduction to Ecological Developmental Biology (Week 1; Sept. 5,7)

            1. Tuesday: Scott lectures. Eco-Devo: Biology meets the real world

                        1. Gilbert textbook: Ch22

                                    2. Waddington, C.H. 1953. “The evolution of adaptations”

      3. West-Eberhard, M. J. 2005. “Phenotypic accommodation”

                                    4. West-Eberhard, Chapters 1, 2.

            2. Thursday: Scott lectures: Introduction to developmental genetics

                        1. Gilbert textbook: Ch. 1, 2, 3

                        2. West-Eberhard, Ch5

B. Developmental genetics and signal transduction (Week 2; Sept. 12,14)

            1. Tuesday: Scott lectures. Differential gene expression

                        1. Gilbert Chapter 4, 5 (Big chapters!)

            2. Thursday: Scott lectures on signal transduction

                        2. Gilbert Chapter 6

C. Phenotypic plasticity: Normative

            1. Temperature-dependent polyphenisms (Week 3; Sept. 19)

                        Background: West-Eberhard, Chapter 3.

                        a. the butterfly Bicyclus

                        b. Sex determination schemes (turtles, crocodiles)

            2.  Nutrition-dependent  (Weeks 4, 5; Sept 26, Oct. 3)

                        Background: West-Eberhard, Ch. 4 (wk 4)

                                                Gluckman and Hanson, The Fetal Matrix (wk 5)

                        a. Dung beetles; ant caste determination

                        b. Vertebrates—Barker hypothesis, PARs, and methylation

            3. Predator- and stress-induced polyphenism (Week 6; Oct. 10)

                        Background: West-Eberhard, Ch. 6

                        a. Daphnia and other invertebrates (incl. transgenerational effects)

                        b. Frog tadpoles and other vertebrates

FALL BREAK

            4. Symbiotic relationships (Week 7,8; Oct. 24, Halloween)

                        Background: West-Eberhard, Ch 7, 8 (This finishes part I)

                        a. Euprymnea/Vibrio; Wolbachia

                        b. Mammals/bacteria

DR. ANA SOTO TALK “Estrogens in plastics reunite development and carcinogenesis” Science Center 101 at 2:00 PM, November 3. (Senior Seminar)

D. Teratogenesis: Abnormal development

             1. Natural teratogenesis (Week 9; Nov. 7)

                              Background: Gilbert, Ch 21.

                        a. ethanol

                        b. retinoic acid

                        c. cyclopamine/jervine

            2. Endocrine disruptors (Weeks 10,11; Nov. 14, Nov. 21)

                        a. DES, herbicides, pesticides, transgenerational effects (Week 10)

                        b. PCBs, BPA   (Week 11)

E. The Grand Synthesis of Ecology, Evolution, Genetics, and Development

                        Weeks 12, 13, Finals. November 28 through December 21.

For the next two weeks, you should finish reading the West-

Eberhard volume and read John Odling-Smee et al. Niche Construction: A Neglected Process in Evolution. Both these books propose evolutionary theories based on developmental plasticity. We will meet Tuesdays and Thursdays to discuss these books. Your final exam will be to get together to write (as a group) an updating or integration of these volumes, or your own theory for the generation of evolutionary novelty.

Since most of this seminar will be conducted using new literature, the three books (Gilbert; West-Eberhard; Odling-Smee et al)  will be on reserve.