Hierarchy of Life Module 1 Steeves and Farr

Hierarchy of Life Module 1 Steeves and Farr, UA, EEB Michod Lab

Hierarchy of Life • Life can be organized into various levels, from molecules through social organisms • Life evolves from less complex (molecules) into more complex organisms (social beings) • However, simple, single- celled prokaryotic organisms still exist today • Who is more fit?

Hierarchy of Life • Evolution not only occurs among individuals within populations but also through the integration of groups of individuals into higher-level individuals • These changes are known as Evolutionary Transitions in Individuality

Hierarchy of Life • Organization of the Hierarchy of Life • • • Genes gene networks Prokaryotic cells Eukaryotic cells Multicellular life Sexually reproducing individuals • Societies and social organisms

Evolutionary transitions in individuality • Unicellular to multicellular • Facilitated by opportunities for cooperation among cells • Problems with cheating • Cheating must be regulated

Evolutionary transitions in individuality • Multicellular organisms have “regulators” evolved within the organisms (germ line, programed cell death, determinant growth, immune system, etc. ) • Diseases such as cancer can be understood as a loss of this regulation against cheating cells.

Cooperation and Conflict • This lesson is focused on the evolution of complexity • Evolutionary transitions in individuality (ETI). . from unicellular to multicellular life. • Through cooperation and conflict we will see how unicellular life has evolved into multicellular life. • Just as in our personal lives, we are social organisms and are familiar with cooperation and conflict in our own lives.

Unicellular to multicellular • You have experienced how groups gain new function through cooperation (lab partners, sports teams, etc…) • Can these systems be reduced and still complete the same job just as well? • Within these groups…conflict also arises. . . and is regulated.

Unicellular to multicellular • This unit models the evolutionary transitions in individuality and explains WHY life has evolved from singlecelled to multicellular organisms. • The green alga Volvox and its relatives will serve as our model organisms.

Volvox and its relatives • Simple groups of cells evolve into complex organisms • Green algae…Volvox and its relatives are perfect examples of this evolution transition from uni to multicellularity Michod, R. E. (2007) Proc. Natl. Acad. Sci. USA 104, 8613 -8618

Volvox and its relatives A: Chlamydomonas B: Gonium C: Eudorina D: Pleodorina E: Volvox carteri F: Volvox aureus Michod, R. E. (2007) Proc. Natl. Acad. Sci. USA 104, 8613 -8618