BIOL 250 REVIEW WEEK 13 LESSON 37 LEARNING OBJECTIVES 1 Learn how the evolution of life altered the earth and this altered evolution eukaryotes 2 Understand some of the key events in the evolution of 3 Know how the evolution of multicellular life could have occurred and how we can study this transition Major transitions in the history of life 1 Major transitions defined as Fundamental changes in how life is organized Replicators vs cells cells vs multicellular multicellular vs individuals individuals vs eusocial groups 2 Key innovations in evolution altered the earth in fundamental ways and influenced subsequent evolution Niche construction organism modifies its own environment in ways that change selection on it or other species MANY KEY INNOVATIONS IN EVOLUTION OCCUR DURING THE PERIOD WHEN MOST LIFE IS SIMPLE Earth forms Origin of life 4 0 4 5 Billions of years ago All life is unicellular 3 0 2 0 l n o i s o p x e n a i r b m a C r a u l l l e c i t l u m t s r i F m s i n a g r o 1 0 i i s n n m o h f o n o i t a d a R i 0 Today simple forms of multicellularity evolved much earlier e g chains of cells Key evolutionary innovations alter the earth s environment Why was the evolution of photosynthesis in cyanobacteria a key event in the history of life hint what is a waste product of photosynthesis Production of atmospheric O2 move from mildly reducing oxidizing atmosphere Hydrothermal vents volcanism produces chemicals used by early life e g hydrogen gas iron ions Cyanobacteria from 1 billion year old stromatolitic cherts oldest cyanobacteria 2 5 bya Modern stromatolites from Shark Bay Australia Formed by gradual deposition of cyanobacteria been found as far back as 3 5 bya Life Changes the Earth Great Oxygenation Event What does chart below suggest about the timing of the GOE and the origin of aerobic photosynthesis Aerobic photosynthesis arises almost 1 by before GOE perhaps because they were more rare or lots of methane rocks etc that are oxygen sinks and limit O2 level in atmosphere Fournier et al 2021 Proc Royal Soc B Chart of levels of O2 in the atmosphere over the earth s history Middle of Stage 4 evolution of photosynthetic eukaryotes Red line spike woody plants Cyanobacteria diversification and evolution of multicellularity Lecture Point Based on diagrams in the figure which do you think is more likely to explain origin of multicellarity in cyanobactera A Coming together B Staying together As they divide they stick together rather than coming together from living separately Dated divergences of cyanobactera based on 16S sequences with some multicellular forms shown Schirrmeister et al 2013 PNAS EUKARYOTIC CELLS EVOLVED SOMETIME AFTER OXYGEN INCREASED IN ATMOSPHERE Earth forms h t r a e f o n g i r O i Origin of life 4 0 4 5 Billions of years ago s l l e C c i t o y r a k u E t s r i F All life is unicellular 3 0 2 0 l n o i s o p x e n a i r b m a C r a u l l l e c i t l u m t s r i F m s i n a g r o 1 0 i i s n n m o h f o n o i t a d a R i 0 Today First clear eukaryotic fossils 1 2 bya Based on molecular clocks may be as far back as 2 2 bya Great Oxygenation Event LECTURE POINT DOMAIN EUBACTERIA DOMAIN ARCHAEA DOMAIN EUKARYOTA a i r e t c a b a i r e t c a b m u i r e t c a b o n a h t e M s u c c o c o n a h t e M s u c c o c o m r e h T s u b o g o e a h c r A s u c c o c o a H l l s u r y p o n a h t e M s u e t o r p o m r e h T m u i t c i d o r y P s u b o o f l u S l a i r e t c a b e v i t i s o p m a r G r u f l u s n e e r G a g o t o m r e h T a i r e t c a b o n a y C a i r e t c a b o v a F e p r u P l l s u m r e h T x e f i u q A 8 7 P p 7 2 P p 2 1 L S p 7 1 L S p J J s e t a l l l a m o s o n a p y r T s d o m e m e a b e o m a t n E e g a fl o n D a n e g u E S a d r a G i l i i l i l l e a g a n w o r B e a g a n e e r G e a g a d e R s m o t a D i l s e t a i l i C i s l a m n A s t n a P g n u F l i Using this phylogeny and lecture material which of the following is NOT true A Fungi and whales are more closely related to each other than either is to cyanobacteria B Giardia are the most basal group in the eukaryota C The archea are more closely related to eubacteria than eukaryota since they are all prokaryotes D The divergence between eubacteria and eukaryota is at least a billion years ago E The deep divergences in this rRNA tree are consistent with unicellular life over much of the earth s history Endosymbiosis for origin of mitochondria and chloroplast Why might chloroplasts and mitochondria have been important for the evolution of multicellular life Mitochondria produce larger amounts of energy allows cell specialization Chloroplast more energy led to land plants diversification of aquatic plants therefore evolution of herbivores Model for Endosymbiosis event of aerobic bacteria with Asgard archaeal cell This lab was first to culture these archaeal cells in a lab setting Some features thought to be fundamental to eukaryotic genes are showing up in the genomes of these archaeal cells Hiroyuki Imachi et al 2020 Nature Three Domains vs Two Domains of Life Note that fusion of two lineages kind of violates typical set up of a phylogenetic tree Which pattern two domain or three domain …