Natural Selection: Evolution of the Theory PDF

Natural selection: Development of the theory BIOL 108 Andrea Botero Evolution “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzhansky -1973 Is the unifying theory in biology that explains the diversity and complexity of life Evolutiona...

Natural selection: Development of the theory BIOL 108 Andrea Botero Evolution “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzhansky -1973 Is the unifying theory in biology that explains the diversity and complexity of life Evolutionary scientist aim to develop broad principles and document common patterns of evolution to produce general principles that apply to diverse organisms and diverse kinds of characteristics Pre-evolutionary thought: Aristotle Scala naturae: Ladder-like classification of nature Each organism on earth occupies a specific step Living things could be assigned a hierarchical position on this metaphorical ladder that would represent their degree of perfection Hodos 2009 R. Lull 1512 Pre-evolutionary thought: Theological Creationism: Aristotle & Biblical account of creation Organisms created by God Species can’t change or become extinct New species could not arise Pre-evolutionary thought: Natural theology 18th Century: Natural theology Carolus Linnaeus (1758) Attempted to classify all living organisms Similar organisms are grouped together and organized into broader, more inclusive categories Pre-evolutionary thought: Natural theology Developed basic system of naming and classifying organisms Practical way for naturalists to keep track of discoveries Developed binomial nomenclature Species have Latin two-part names Genus + species Unique name for every species Pre-evolutionary thought: Natural theology Common name: Corn, maize, maiz Scientific name: Zea mays Zea: genus (plural: genera) A group of species that share similar characteristics mays: specific epithet (= species name) Genus + species= Unique name for each species Pre-evolutionary though: George-Louis Leclerc Buffon 1760’s George-Louis Leclerc Buffon published Natural history of animals Similarities in limb bones of different animals but used differently Comparative anatomy Why useless structures exist? Species change over time Vestigial structures might have functioned in ancestral organisms Pre-evolutionary though: Thomas Malthus 1798 An essay on the principle of population Imbalance between population growth and available food Influence on Darwin’s theory Pre-evolutionary thought: Catastrophism George Cuvier SPECIES DO NOT CHANGE OVER TIME Idea of extinction was troublesome although fossils proved different! Extinction through ‘catastrophes’ Catastrophe →Local extinction →Fossils in stratum→ New species move into area Pre-evolutionary thought: Uniformitarianism Charles Lyell Based on James Hutton ideas Earth is in constant change by natural events such as earthquakes, volcanos, erosion… Earth slowly transformed by imperceptible small changes that over time can produce vast changes. Catastrophes are rare James Hutton Charles Lyell First theory of evolution: Lamarckism 18th century Jean Baptiste Spontaneous generation Lamarck (1809) First evolutionary theory: Perfecting principle Different organisms originated separately by spontaneous generation Microscopic organisms replaced by spontaneous generation in Scala naturae Simple organisms evolved into more complex, moving up the Scala Nature First theory of evolution: Lamarckism Two-part mechanism by which gradual change of species might take place: Use and disuse How??? “natural tendency toward perfection” Lamarckian inheritance After acquired, traits can be inherited Why is Lamarck important? First theory of evolution: Lamarckism Organisms can’t evolve fundamental physiological changes during lifetime, and physical changes acquired are not passed to offspring Why is Lamarck important? He identified one of the major features of evolution: Species Offspring change over time Darwin’s theory of evolution 1831 5-year voyage in surveying ship HMS Beagle He based his theory on 3 major areas: Geology and fossil record Geographic distribution of species Comparative morphology of species Darwin’s theory of evolution: Geology and fossil records Darwin collected many fossils and some If both created at the same time, and both were found resembled living species in South America why didn’t glyptodons live alongside armadillos? Darwin’s theory of evolution: Biogeography Species different in different locations Too many species!!!, where do they fit in the San Cristobal Mockingbird scale of nature? Species in oceanic islands were more similar to species in the nearest continent Galápagos Mockingbird Floreana Mockingbird Española Mockingbird Darwin’s theory of evolution: Biogeography Species different in different locations Their morphology is dependent on resources available Darwin’s theory of evolution: Comparative morphology HOMOLOGY Similarities in structures= Organisms are related Group of organisms look similar because they are descendants of a common ancestor that possessed those features Homology: Similarity present in a group of organisms that share ancestry Darwin’s theory of evolution: Mechanism of evolution Gradual changes (Fossil record and comparative morphology) Species seem to match their environment: Competence for resources (Malthus) and only the most fit survives There is variation in populations and many variations seem to be inherited NATURAL SELECTION Only the fittest survive Darwin’s theory of evolution Most organisms produce more than one or two offsprings Individuals within Populations do not a population increase in size compete for indefinitely limited resources Food and resources are Population’s limited for most characteristics will populations change over generations as advantageous, heritable characteristics become more common Individuals within Hereditary characteristics populations exhibit may allow some variability individuals to survive longer and Many variations reproduce more than others appear to be inherited Fenton, et al. 2022 Theory of natural selection: Darwin and Wallace Darwin: all organisms are related by a common ancestor but have changed over time Alfred Russell Wallace had arrived at similar conclusion 1858 Wallace writes to Darwin about his idea Darwin put together The origin and published in 1859 Darwin’s evolutionary theory Components: 1) Evolution: Characteristics of organisms change over time 2) Common descent: Species diverged from common ancestor 3) Gradualism: evolution through small steps 4) Population change: Evolution occurs by changes in proportions of variants of a population 5) Natural selection: only the fittest survive Modern Evolutionary theory Darwin and Wallace theory didn’t understand traits inheritance Gregor Mendel publishes his work around same time but accepted until 1900 Thomas Hunt Morgan: Genes are carried in chromosomes Link Darwin and Mendel Modern Evolutionary theory Population genetics: Study of genetic variation in populations Modern synthesis: Unified theory of evolution Adaptative evolution is caused by natural selection on particulate genetic variation Mutation and natural selection together cause adaptative evolution Acknowledge of multiple causes for evolution, not only natural selection Evolutionary theory: Historical synopsis Evolution: Change in species over time; central to biology. 1. Pre-Darwinian Views: Scala naturae, creationism, and natural theology (taxonomy) 2. Early Thinkers: Buffon’s comparative anatomy; Malthus’ population principles (competence for limited resources) 3. Cuvier and Catastrophism: Extinction events without species change 4. Uniformitarianism: Lyell’s gradual geological changes shaping the earth 5. Lamarck’s Theory: Early ideas of species transformation and inheritance. Traits that are used a lot will get “stronger” and traits less used will “disappear”, acquired traits can be inherited to offspring 6. Darwin’s Voyage: Observations leading to the theory of natural selection. Darwin and Wallace: Independent conclusions on evolution and common ancestry. 7. Modern Synthesis: Integration of Mendelian genetics with Darwinian evolution. 8. Evolution Today: Recognizes multiple mechanisms beyond natural selection. Summary videos https://www.youtube.com/watch?v=x73bsC7WIsE https://www.youtube.com/watch?v=mZt1Gn0R22Q