Lecture 2: How We Study Evolution (BIOB51 - Evolutionary Biology - Winter 2025) PDF

Lecture 2 How We Study Evolution E&Z, Chapter ON1 BIOB51 – Evolutionary Biology - Lecture 02 “I wish to acknowledge this land on which the University of Toronto operates. For thousands of years, it has been the traditional land of the Huron-Wendat, the Seneca, a...

Lecture 2 How We Study Evolution E&Z, Chapter ON1 BIOB51 – Evolutionary Biology - Lecture 02 “I wish to acknowledge this land on which the University of Toronto operates. For thousands of years, it has been the traditional land of the Huron-Wendat, the Seneca, and the Mississaugas of the Credit. Today, this meeting place is still the home to many Indigenous people from across Turtle Island and we are grateful to have the opportunity to work on this land.” BIOB51 – Evolutionary Biology - Lecture 02 I encourage you to participate during lectures via iClicker free with your purchase of the textbook & Achieve “BIOB51 – Evolutionary Biology – Winter 2025” https://join.iclicker.com/SSKG Join using the devices you already bring to class: computer, tablet, smart phone © MJ Fitzpatrick (2025) UTSC BIOB51 – Evolutionary Biology - Lecture 02 Which statement best describes your current view of evolution? A. A well-supported scientific theory. B. A topic with some scientific controversy. C. A concept I am unsure about. D. A concept that conflicts with my beliefs. © MJ Fitzpatrick (2025) UTSC BIOB51 – Evolutionary Biology - Lecture 02 Think about your high school education: Compared to other areas of biology (e.g. genetics, cells, photosynthesis, mitosis) A. I felt more prepared to study evolution than I did with other areas of biology B. I felt equally prepared to study evolution as I did with other areas of biology C. I felt less prepared to study evolution than I did with other areas of biology D. I felt under prepared to study evolution compared to other areas of biology © MJ Fitzpatrick (2025) UTSC BIOB51 – Evolutionary Biology - Lecture 02 Think about your high school education: Compared to other areas of biology (e.g. genetics, cells, photosynthesis, mitosis) A. I felt more prepared to study evolution than I did with other areas of biology B. I felt equally prepared to study evolution as I did with other areas of biology C. I felt less prepared to study evolution than I did with other areas of biology D. I felt under prepared to study evolution compared to other areas of biology © MJ Fitzpatrick (2025) UTSC BIOB51 – Evolutionary Biology - Lecture 02 Challenges with teaching & understanding evolution Despite incredibly convincing, ever-mounting evidence, it is the one area of biology that people somehow feel they can question Evolution is one of the most challenging biological concepts to grasp and teach: Mechanisms challenging to describe (e.g., modes of speciation) Issue with scale & concept of time Difficulty demonstrating & observing “evolution” in a teaching lab © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 “Evolution is just a theory, it’s not a fact” Scientific theory is different from our everyday use of ‘theory’ In Science: theory is not a guess or a hunch theory is a well-established, well-supported, well-documented explanation for our observations and is supported by facts ‘Theory becomes Law’ No hierarchy, but if there was then Theory > Law © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Theories & Laws Law of gravity – if you drop something it will fall to the ground This is a description, it does not explain why Theories explain why: Newton’s Theory of Gravity, Einstein’s Theory of Relativity Laws describe, Theories explain Gravity is real, it is true, it can be observed, it can be tested … this is also the case with evolution! © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Speciation © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Scale & the concept of time Millions of years ago 40 (MYA) 30 20 10 Lemurs Humans & chimpanzees shared common ancestor 5-7 mya Tarsiers New World That is a long time! Monkeys Old World Monkeys What does 1 million years look like? 1000 years? 100? 20? Gibbons 1 million = 20 yrs x 50,000 5 million – 20 yrs x 250,000 Orangutans Gorillas But in evolutionary terms 5-7my is often considered recent Chimpanzees 5-7myof divergence and our genomes are still 99% identical Humans © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Demonstrating Evolution © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 “It has been approximately 3.5 billion years since primeval life first originated on this planet. That is not an unimaginable number in itself, if you're thinking of simple, discrete units like dollars or grains of sand. But 3.5 billion years of biological history is different. All those years have really passed, moment by moment, one by one. They encompass an actual, already lived reality, encompassing all the lives of all the organisms that have come and gone in that time. That expanse of time defines the realm of biological possibility in which life in its extraordinary diversity has evolved.” Verlyn Klinkenborg, NY Times (2005) “Grasping the Depth of Time as a First Step in Understanding Evolution” © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 So how do we study evolution? And how do we teach it? © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Let’s consider two case studies Whales – mammals gone to sea Viruses – deadly escape artists © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Blue whale Largest animal to exist on earth … ever! 100,000 kg = 1000 people 30m long © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Virus (pictured: SARS-Cov-2) 50-140 nm diameter, 1000x smaller than width of a hair 26 protein coding genes (we have 20,000) © 2025, M.J. Fitzpatrick, UTSC Image: We Are Covert, Copyrighted free use, via Wikimedia Commons BIOB51 – Evolutionary Biology - Lecture 02 A tale of two extremes … with a common origin whales & viruses both products of evolution every organism that has ever existed on Earth By understanding evolution, we can understand: why the natural world is the way it is similarities & differences among and between species geographical distribution of species incredible adaptations (& weaknesses) of living thing © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 By studying evolution we can find new ways to fight the viruses and bacteria that make us sick understand how insects become resistant to pesticides understand ramifications of human impact on the planet e.g. invasive species, pollution, climate change learn how today’s extinctions compare with the past … to help make predictions and devise strategies to combat the current wave of extinction © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 How do we know that whales are mammals? Whales share numerous synapomorphies with mammals mammary glands three middle ear bones hair (in developing embryos) note: similarities with fish arose through convergent evolution © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Pakicetus (50mya) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Prehistoric cetaceans share traits with modern relatives Bottlenose dolphin Pakicetus 50mya Dorudon 40mya © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 talus = astragalus © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Plantigrade Digitigrade Unguligrade (e.g. human) (e.g. cat/dog) (e.g. cow, pig, horse) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Transitional fossils reveal links to land mammals Astralagus (ankle bone) shape astragalus connects cetaceans to artiodactyls (even-toed ungulates) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Sequence of fossils documents transition from land to water © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Further documenting the transition from land to water Isotopic analysis of fossil teeth Fossil analysis of hindlimb loss Embryonic analysis linked to gene expression © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Isotopic analysis of fossilized teeth extant (living) Terrestrial animals drink freshwater, marine extinct (fossil) animals drink saltwater marine cetaceans freshwater dolphins 18O/16O ratio higher in saltwater Georgiacetus Indian protocetids also, higher in the teeth of marine Remingtonocetus animals Attockicetus Abulocetids Pakicetids © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Fossils document pelvic & hindlimb loss © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Changes in gene expression led to hindlimb loss Hindlimbs begin to form but fail to fully develop Developing dolphin embryo © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 More whale evolution – teeth or baleen? © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Why baleen? © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Ancestors of modern whales had teeth.. and small patches of baleen! baleen completely replaced teeth in Mysticetes genes for building teeth have been disabled! © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Key Concepts I Whales & fish have evolved similar body forms (independently) Fossils representing the transition from land to water provide information on the details of this transition Independent lines of inquiry enrich our understanding of the mechanisms of evolution © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Let’s consider two case studies Whales – mammals gone to sea Viruses – deadly escape artists © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 SARS-CoV-2 © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Life cycle of SARS-CoV-2 replication of genetic material results in mutations © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Strains with beneficial mutations increase in frequency via natural selection No longer recognized by immune system Higher reproduction Dominates population in subsequent generations © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Origin of human SARS-Cov-2 © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Waves of variants © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Natural selection leads to diversity (Influenza) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Viral reassortment H7N9 influenza genome is derived from 4 different bird strains © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Pandemics - past & present Major flu pandemics: 1918: Spanish flu, > 50 million dead 1957-58: Asian flu, 1.5 million dead 1968-69: Hong Kong flu, 1 million dead 2009: Swine Fly, 280,000 died 2020: COVID-19, how many? 7.01 million deaths worldwide (April 2024) (was 1.8 million in December 2020!) (image: The Lancet) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 Key Concepts II Natural selection favours SARS-Cov-2 and influenza variants that evade the immune system Reassortment can result in strains that are both deadly and highly infectious With diligent monitoring, scientists can can identify newly evolved strains as they appear Evolution is a tapestry of complex phenomena that operate in both the short term (e.g., viruses) and long term (e.g., whales) © 2025, M.J. Fitzpatrick, UTSC BIOB51 – Evolutionary Biology - Lecture 02 So how do we study evolution? Multiple lines of evidence (e.g., fossil, DNA, experimental) Deep & extensive case studies Across a range of time scales inferring evolution across millions of years (e.g., whales)macroevolution observing allele frequencies change across generations (e.g., viruses) microevolution BOTH ARE EVOLUTION © 2025, M.J. Fitzpatrick, UTSC