Biol 103: Introductory Biology I Lecture 14 PDF

Lecture 14 Biol 103: Introductory Biology I Introduction Evolution I – The Theory Dr. Michael D. Preston Assistant Professor, Ecosystem Science and Management Email: [email protected] Office hours – 12:20-1:00 pm Mon/Wed/Fri 7-238 or by appointment...

Lecture 14 Biol 103: Introductory Biology I Introduction Evolution I – The Theory Dr. Michael D. Preston Assistant Professor, Ecosystem Science and Management Email: [email protected] Office hours – 12:20-1:00 pm Mon/Wed/Fri 7-238 or by appointment Outline the developments that led to the theory of evolution Learning Explain how natural selection causes Objectives evolution of organisms Describe examples of evolution Readings Chapter 16 – Evolution the Development of a Theory  Seeds of the Theory “Nothing in biology makes sense except in the light of evolution” (famous quotation by Russian-born evolutionary biologist Theodosius Dobzhansky) So, what is evolution? The slow change of species overtime. So, what is evolution? The slow change of species overtime. So, what is evolution? The slow change of species overtime.  Evolution by Natural Selection Antibiotic Resistance Antibiotic resistance in bacteria is a consequence of evolution by natural selection [Insert Fig. on p. 393] Natural selection and drug resistance 9 Natural selection and drug resistance 10 Natural selection and drug resistance 11 Selection for desired traits: Artificial Selection Teosinte to corn (maize) Selection for desired traits: Artificial Selection Fitness Organisms with heritable traits that allow them to outcompete others for limited resources, or avoid predation/disease, will increase their rates of survival and reproduction and leave more offspring. Fitness = Reproductive Success Organisms with heritable traits that allow them to outcompete others for limited resources, or avoid predation/disease, will increase their rates of survival and reproduction and leave more offspring. Natural Selection among variants in the Wild The individual does not evolve over their lifetime, but a population could. An individual mammoth did not get hairy Yukon 2022; 30,000 years old An individual mammoth did not get hairy Slow changes to the population over eons Populations Change over Time [Insert Fig. 16.11 on p. 399] Populations Change over Time [Insert Fig. 16.11 on p. 399] Populations Change over Time [Insert Fig. 16.11 on p. 399] Defining Evolution Biological evolution is change in the frequency of individuals bearing particular characteristics (or alleles) within populations over time Individuals possess traits that are favourable in a given environment, and so survive and reproduce. Evolutionary change is measured in generations rather than years Natural Selection Selection pressure applied in the natural environment (i.e., not human) Examples: - Limited food, habitat, - Predation, competition, disease, - Anything that effects the ability of an organism to survive and reproduce  Evidence for Evolution by Natural Selection Evidence Early evidence for natural selection came from observations of island populations. Each island can be seen as an isolated habitat with conditions that are sometimes very distinctly different and so exert different selective pressures. Galápagos Islands Descent with Modification The Galápagos Islands are a prime example for collecting such observations. Four mockingbird species (genus Nesomimus) are all descended from a common ancestor but have adapted to different environments. Descent with Modification The view that all organisms are related through descent from an ancestor that lived in the remote past  Adaptions Species on different islands experience different environments (e.g., food resources), leading to natural selection, which favours different traits from island to island. Adaptation—the inherited aspects of an individual that make it better suited to a particular environment than other individuals It’s predicted that species become better adapted to specific environments over time. Fitness – revisited Fitness—an individual’s reproductive success One organism has higher fitness than another if it leaves more surviving offspring. Three aspects of fitness important to understanding how evolution works: 1. Fitness is a relative concept. 2. A trait is only adaptive if it increases fitness. 3. The traits that increase fitness may change. The source of variation is random mutation Variation in DNA sequences gives rise to individuals within a population exhibiting different inherited traits. The DNA sequence of any individual may be different because of mutations. Mutations are random, heritable changes in the DNA sequence. May come from errors in DNA replication, or physical, chemical, or biological agents Natural Selection is NOT random Mutations do not try to supply an organism with what it needs. They do not happen because they are useful. Natural selection is not random. Acts on these random changes Nothing random about predation, disease resistance, etc.  Peppered Moth (Biston betularia) Example, change in environment causes a change in natural selection. The selection pressure was predators. Monarch Butterfly and Milkweed Milkweed sap – contains a cardiac glycoside (Cardenolides) that blocks Na-K ATPase in sodium potassium pumps (impairs nerve signals) Monarch Butterfly – single base-pair substitution causes a missense mutation – subs Asparagine for Hisidine in the polypeptide, rendering the butterfly immune to Cardenolides. Bark Scorpion and Grasshopper Mouse Bark Scorpion venom – activates Nav.17 voltage-gated Na channels in pain receptors (causing severe pain response) Grasshopper Mouse – related Nav.18 protein activated, which causes an analgesic (pain-reliever) effect to Nav.17 activation. Experimental Evolution Experimental Evolution Relative fitness = Growth rate of evolved population/Growth rate of ancestral population Transitional forms in fossil record  A little background The Scale of Nature The Greek philosopher Aristotle created a ladderlike classification of nature (Scala Naturae). Led to Natural theology stated that – Organisms had been specially created by God. – Species could never change or become extinct. – New species could never arise. Development of Evolutionary Theory Carolus Linnaeus Jean Baptiste de Lamarck Theory of Evolution in 1809 Radical for suggesting species change over time Suggested mechanism: Inheritance of acquired characteristics Simple organisms evolve into complex ones Acquired Characteristics are NOT inherited If true Arnold Schwarzenegger's children would be more muscular than other people who did not weight train. Image: Fenton Biology 4th edition Acquired Characteristics are NOT inherited Lamarck believed that as wading birds stretched their legs to keep their bodies dry while feeding, successive generations would have progressively longer legs.  Darwin’s Voyage In 1831, Charles Darwin (22) embarked on a voyage around the world on the naval surveying ship HMS Beagle. The primary purpose of the expedition was to map the coast of South America. History of Evolutionary Theory Darwin and Wallace: Evolution by Natural Selection Charles Darwin Alfred Russel Wallace  Ideas that Influenced both Darwin and Wallace Geology Cuvier - Progressive change in fossil assemblages over time, punctuated by abrupt change of fossil organisms within successive layers of rock. Hutton’s observation that gradual geologic processes acting over long periods of time can create massive changes in landscapes Lyell’s arguments that geologic processes that have acted throughout earth’s history occur at the same rates as we see them today Fossils Fossils found on mountain tops of sea creatures Fossils of strange unseen species Fossils of similar species, why did one go extinct. Against prevailing ideology of the day Glyptodonts and armadillos Biogeography – species and their distributions - Why did some species have large distributions and others small? - Why were some from Africa and Asia so different and other similar? - Why where non-flying mammals not found on islands? Biogeography Presence of similar species/groups across widely dispersed geographic areas, but lack of similarity between some groups in closely-associated areas Slight morphological differences between related species among isolated populations Morphologic similarities between unrelated species occupying very different areas Convergent evolution of Analogous traits in distantly related groups arise when groups independently converge on similar morphology to adapt to similar environmental pressures Morphology Radius Similarity in underlying Ulna morphological structure between very different organisms (e.g. Homologous structures, whose anatomical resemblances represent variations on a structural theme present in a common ancestor) Presence of body parts that appeared to have reduced in size to the point of being “useless” vestigial structures (e.g. reduced toes on pigs/deer; hind limb spokes on pythons) Lamarck and Biological Evolution Lamarck had four important ideas that were used by Darwin and Wallace: 1. All species change through time 2. Changes are passed from one generation to the next 3. Organisms change in response to their environments 4. Specific mechanisms caused evolutionary change Limitations on Population Growth Thomas Malthus (1798) – populations have the potential to grow exponentially, but this can outpace resources they rely upon (food supply). 19th Century London Slum Observations, hypotheses, and Prediction Aside: Ernst Mayr: Summarized Darwin’s On the Origin of Species into five observations and three inferences Four Characteristics of Darwin’s Theory 1. The origins of biological diversity can be explained by purely physical processes 2. Evolutionary change occurs in groups of organisms (population), rather than in individuals 3. Evolution is a multistage process occurring over generations 4. Evolution occurs because some organisms function better than others in a particular environment Principle of Natural Selection Pesticide resistance in Agricultural pests Selection against Selection favours Proportion of Population Low High Pesticide Resistance Ability Proportion of Population Low High Pesticide Resistance Ability Misconceptions Misconceptions Misconceptions Misconceptions Misconceptions