BIOL 1P92 Winter 2025 Evolution Lecture Notes PDF

WELCOME TO BIOL 1P92! Winter 2025 Dr. Szuroczki c0-ordinates Week 1 – 3 Email: [email protected] Please email me any questions you may have regarding the lecture content from weeks 1-3! Week 1 -3 (my content) on midterm, not on final exam Other important people If you miss a re...

WELCOME TO BIOL 1P92! Winter 2025 Dr. Szuroczki c0-ordinates Week 1 – 3 Email: [email protected] Please email me any questions you may have regarding the lecture content from weeks 1-3! Week 1 -3 (my content) on midterm, not on final exam Other important people If you miss a report, test, or an exam; please email the BIOL 1P92 Course Coordinator Katie Hunter as soon as possible ([email protected]) If you are missing lab grades on BS, contact Dr. Martin ([email protected]) Course Marking Scheme Evaluation Grade Weight Date Component Midterm Test 30% February 24th Monday after reading week (covers week 1- 6) Final Exam 35% TBA (April 9-24) Laboratory 35% Throughout, see assignments BS or syllabus Topic Schedule Chapter Topics 22 An Introduction to Evolution 23 Population Genetics (Microevolution) 26.1 – 26.2 History of Life on Earth Dr. 24 Origin of Species (Macroevolution) Szurocz 25.1 – 25.3 Taxonomy & Phylogenetics 27 - 29 Biodiversity (Bacteria, Archaea, ki Protists, Fungi) in an Evolutionary Dr. Context Hunter 31 Evolution of Land Plants & Dr. Charophycean Algae 33 Animal Diversity & Choanoflagellates Glasgo 34, 35.1 The Invertebrates & Vertebrates w 41, 47. 4 Animal Bodies & Homeostasis 42.1-42.4 Neuroscience INTRODUCTIO N TO E VO LU T I O N Dr. Szuroczki Chapter 22 Key Concepts 1. Overview of Evolution 2. Evidence of Evolutionary Change 3. The Molecular Processes that Underlie Evolution Introduction Evolution: Heritable change in one or more characteristics of a population or species from one generation to the next Microevolution: Viewed on a small scale = Changes in a single gene or allele frequencies in a population over time Macroevolution: Viewed on a larger scale Formation of new species or groups of related species Introduction Species: Group of related organisms that share a distinctive form Population: All members of the same species that live in the same area at the same time and have the opportunity to interbreed  “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzahnsky 11 Where did we come from? For thousands of years, the answers came from religion and philosophy In 1600s, a scientific revolution began, creating the basis of empirical thought Relies on observation to form an idea or hypothesis, rather than trying to understand life from a non-physical or spiritual point of view This shift encouraged scholars to look for the basic rationale behind a given process of phenomenon Scientists who set the stage Mid- to late-1600s, John Ray was the first to carry out a thorough study of the natural world Developed an early classification system based on anatomy and physiology Established the modern species concept Extended by Carl Linnaeus who developed the binomial system of nomenclature Homo sapiens This systematic classification helped scholars perceive similarities and differences among organisms Scientists who set the stage In late 1700s, a small number of European scientists suggested life forms are not fixed George Buffon: Living things change through time Jean-Baptiste Lamarck hypothesized that species change over many generations by adapting to new environments From fossils, realized that some animals had remained the same while others had changed Believed living things evolved in a continuously upward direction toward “human perfection” Inheritance of acquired characteristics Idea proposed by Lamarck In response to environmental change, organisms alter their behaviour, which modifies traits Modifications are inherited by offspring E.g. If a giraffe frequently stretches its neck to reach leaves, it will elongate, and its offspring will inherit the longer neck Scientists who set the stage Erasmus Darwin was an early advocate of evolutionary change and suggested life on Earth could have descended from a common ancestor Made many observations based on selective breeding practices (“Artificial cultivation”) Influence from other fields of study Uniformitarianism hypothesis from geology: Slow geological processes lead to substantial change Earth is much older than 6,000 years In contrast to catastrophism, which fit with religious teachings: earth is 6,000 years old and only catastrophic events have changed its geological structure Thomas Malthus, an economist, published an important essay on population growth in 1798 Not all members of a population will survive and reproduce Charles Darwin British naturalist born in 1809 Played a central role in developing the theory that existing species have evolved from pre-existing species Darwin’s ideas were most influenced by his own experiences and observations Voyage on HMS Beagle from 1831 – 1836 Galapagos finches Darwin and the Voyage of the Beagle Galapagos Island Finches Charles Darwin Darwin formulated his theory of evolution by mid-1840s Species evolve from pre-existing species through the process of natural selection In 1858, Alfred Wallace sent Darwin an unpublished manuscript proposing many of the same ideas Papers by Darwin and Wallace both published, but were not well recognized On the Origin of Species was published in 1859 One of the most important contributions to our understanding of biology Darwin’s Theory of Evolution “The theory of descent with modification through variation and natural selection” Evolution occurs from generation to generation due to two interacting factors: 1. Variation in traits that occur among individuals and are heritable from parents to offspring Genetic basis was not yet known 2. Natural selection: Individuals with traits that make them better suited to the environment flourish and reproduce, while others are less likely to survive and reproduce Favourable traits become more prevalent in a population over time Source of genetic variation are Geneticrandom mutations variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population Can be caused by mutation (which can create entirely new alleles in a population) Random mating, random fertilization, and recombination between homologous chromosomes during meiosis Advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population Spirit Bears: recessive mutation in the melanocortin 1 receptor gene Evolutionary adaptation by natural selection The Elephant’s Trunk: Lamarck vs. Darwin Types of Evidence 1. Beak Depth on Daphne Major Medium ground finches on Daphne Major have been studied for over 40 years as a model of natural selection Beak depth is a heritable trait Measured yearly in parents and offspring Provides evidence of natural selection in action 1. Beak Depth on Daphne Major A severe drought in 1977 resulted in fewer smaller seeds on the island Finches had to eat large dry seeds (harder to crush) Offspring in 1978 had larger average beak size than 1976 2. Selective breeding Programs and procedures designed to modify traits in domesticated species = artificial selection Differs from natural selection in how the parents are chosen Desirable phenotypes chosen by breeders Made possible by genetic variation  Example: Darwin’s pigeons Drawings of rock pigeon varieties Examples of rock pigeons studied in published in Darwin’s “Variation in 2017 to learn about the genetic Animals and Plants under changes that lead to feathered feet Domestication" in 1868 Example: Wild mustard 3. Biogeography Study of the geographic distribution of extinct and living species Isolated continents and island groups have evolved their own distinct plant and animal communities Endemic – naturally found only in a particular location Island fox Only found on Channel Islands Evolved from mainland gray fox During last ice age, foxes crossed to island then were cut off from the mainland Example: Australia First mammals arose ~200 mya when Australia was still connected, but placental mammals arose after Australia separated Australia has no native large terrestrial placental mammals Bats, mice & rats arrived ~15 – 5 mya Other species introduced by humans, beginning with dingos ~5000 years ago Australia has >100 species of marsupials, most not found anywhere else 4. Convergent evolution Two species from different lineages have independently evolved similar characteristics because they occupy similar environments These similar characteristics = analogous structures, or convergent traits Not similar due to shared evolutionary history 5. Fossil Record Fossils are compared according to their age, from oldest to youngest Successive evolutionary change becomes apparent Transitional form: Fossils that provide a link between an ancestral form and its descendants Fishapod (Tiktaalik roseae) Transitional form between fishes and tetrapods Had broad skull, flexible neck, eyes on top of head, primitive wrist, and five finger-like bones Could peek above water and look for prey Example: Evolution of whales Order cetacea includes whales, dolphins, and porpoises Closest living relatives are hippos Over 50 million years evolved from terrestrial tetrapods to aquatic animals lacking hind limbs 6. Homology Fundamental similarity due to descent from a common ancestor Homology may be: 1. Anatomical 2. Developmental 3. Molecular Anatomical homology Modern vertebrates have same set of bones in forelimbs Have undergone evolutionary changes to perform different functions in different species Homologous structures are similar because they are derived from a common ancestor Evolution also produces vestigial structures Have no current function but resemble structures of presumed ancestors Examples of vestigial structures Developmental homology Species that differ as adults often bear striking similarities during early embryonic development Human embryos have gill ridges and long bony tails Molecular homology Similarities at the molecular level that indicate that living species evolved from a common ancestor All living species use DNA to store information (snapshot of evolution at the molecular level) Certain biochemical pathways are found in all or nearly all species Many genes are found in a diverse array of species Sequences of closely related species tend to be more similar to each other than to distantly related species Homologous genes Two or more genes derived from the same ancestral gene Homologous genes in different species = orthologs Two sequences may be similar, but not identical, due to the independent accumulation of different random mutations Gene families Two or more homologous genes within a single species = paralogs Produced by gene duplication events Gene family = two or more paralogs within the genome of a single organism Globin genes: Allows for specialized function, expression at different times or in different tissues Paralogs vs Orthologs Horizontal gene transfer Vertical evolution: New species arise from pre-existing species by accumulation of genetic changes In horizontal gene transfer, an organism incorporates genetic material from another organism, without being its offspring Same or different species Widespread among bacteria Evolution at the genome level Can involve changes in chromosome structure and number Can affect the ability of two organisms to breed with one another Important in establishment of new species Summary Video