PCB4674 Evolution Scott Steppan Lecture 1 Introduction Core concepts 1 Evolution is the central unifying concept in biology 2 Definition Decent with modification Pattern History all species evolved from a common ancestor Process change within species There are three really BIG questions in science 1 The origin of the universe how that produced the incredible astronomical diversity of today 2 The origin of life how that produced the incredible biological diversity of today Bulk of science covers this topic This class deals with this question 3 The origin of human consciousness and society how that produced the incredible cultural diversity and complexity of today Bulk of social science covers this topic Evolution is the central unifying concept in biology and it is one of the most influential and controversial scientific concepts in modern society The Big Picture Concepts to learn from this course 1 Appreciate the extreme diversity of life and gain a general idea of their relationships 2 Tree thinking the ability to read and write phylogenetic trees to describe evolutionary relationship and understand what the trees indicate about the evolution of species and traits 3 Population thinking understand how processes like natural selection acting on individuals produce the changes in populations that yield the diversity in 1 Populations and species evolve individuals do not 4 What species are and how new species evolve speciation Secondary Concepts and Skills 5 As indicated above evolution refers to both process and pattern Process Population thinking Pattern Tree thinking 6 Understand the scientific nature of evolutionary biology that in total and in its parts it is subject to the scientific method of observation hypothesis testing natural experiments and repeat 7 Estimate the phylogenetic history of species from raw data 8 Understand the role of chance and probability in evolution 9 Calculate the amount of evolutionary change adaptation under several different situations 10 Understand how past evolutionary history shapes the future Lecture 2 Evidence for and Testing of Evolution Concepts 1 Evidence is observations that can disprove one or more hypotheses 2 The standard theory of evolution single origination is just one of many possible models 3 Species share virtually every feature with other species especially fundamental features of organization homology 4 Repeated concordance among data sets are powerful tests of evolution 5 Imperfect design one of clearest evidences Some personal favorites and how they demonstrate the scientific method What is evidence How do we test a theory model hypothesis Models of the history of life There are many possible models for the history of life Ranging from single origins panspermia standard evolutionary theory to billions or trillions of originations spontaneous generation Each makes some predictions about pattern that can be tested Evidence Not from perfect function 1 Homology structural similarity in parts shared among species The basis for all comparative biology Homologies are evidence of common ancestry because of a process of common inheritance What does evolutionary theory predict Groups of species sharing a homologous trait will share more homologous traits in common than expected by chance or alternatively homologies will not yield incompatible groups A Homologies are not random among species but grouped or nested EX tetrapod limbs identical parts in same numbers and positions with respect to other parts Orchids 3 sepals 3 petals middle petal modified male and females parts fused inferior ovary B Functionally unimportant parts are consistently shared with related species Vestigial organs Processed pseudogenes non functional copies of genes Genetic code Thus we see species are built using the same parts as related species whether they are optimal or not and more fundamental aspects are shared more broadly 2 Fossil record one source of evidence for the historical sequences of events A Stratigraphic sequence of fossil species is nearly the same throughout the world B Features transform through time e g cetaceans Special example Transformation of jaw articulation from non mammal to mammals 1 Non mammal forms had jaw joint articulation between the articular and the quadrate 2 Some Cynodonts early mammal ancestors relatives exhibit a transitional double jaw articulation between articular and quadrate AND between dentary condyloid process and squamosal 3 Modern mammals have only the dentary squamosal articulation The articular and quadrate are now the malleus and incus and are involved in hearing 4 Supported not only paleontologically but also embryologically same sequence in geologic time as in development Correspondence to phylogenetic sequence based on living species Absolute and relative dates radionucleotide dating corroborates stratigraphy What does evolution predict and what are alternatives Biogeography A Species sharing structural homologies tend to live near each other Many Hawai ian groups fruitflies spiders silverswords Darwin s finches and giant tortoises on Galapagos Malagasy rats B Functionally similar species often do not live near each other relationship is more important Fish eating rats live near relatives not unrelated fish eating rats Phylogenetic concordance A Independent data sets yield the same hypothesis of relationships I use this to test evolution almost every day Example the flightless ratite birds and the flying tinamous Selection and response observed Soapberry bugs and see Selection lectures Speciation observed A New species have been observed to evolve in a short time Three spine stickleback fish Pacific northwest lakes 10 000 years Reintroduced salmon 50 years Fruit flies in the lab 6 months B Fossil transition sequences e g Yellowstone diatoms oceanic foraminfera We can only see a small slice of the speciation process because we have only been looking closely for the last 50 100 years Poor design selection can only optimize a feature that it has to work with with occasional new features often selection works with suboptimal features Many cases of poor design may be due to constraints aspects of the genetic or developmental program or manner of construction that preclude certain traits from evolving Giraffe neck circulation stapedial artery in mammals passes through middle of stapes in inner ear Summary the proof is in the trash best evidence is found in the functionally unimportant details Lecture 3 Tree