From geneticsto evolutionendless forms most beautiful Darwin (and Wallace) s Theory of Evolution "the single best idea anybody ever had (Daniel Dennet, Philosopher) a big idea, arguably the most powerful idea ever (Richard Dawkins, Philosopher) Its publication (The Origin if Species) changed the world Some reminders (from genetics) How do we express difference? Continuous/discontinuous variation Discontinuous variation Single gene traits Phenotype has distinct categories There are no in- betweens Blood types Genetic diseases How are we different? Continuous variation Due to contribution from multiple genes The variation in phenotype follows a normal-type distribution, with most individuals falling in the middle of the range Skin colour is another example of continuous variation What makes us different? Genetic variation Environmental effects on genotype Environmental effects on phenotype Sequoia sempervirens tree Meiosis and genetic variation Genes are changed by mutation The basis of genetics the fuel for evolution the destroyer and creator of life Thanks to mutation, were not all still in the primordial soup Gene mutation A change in a gene or a chromosome Caused by COPYING ERRORS OF DNA or external damage to DNA Mutations are the source of brand-new characteristics in the gene pool They are the final source of all genetic variation How mutation works What is the Theory of evolution? Evolution Synonyms: Charles Darwin used Descent with modification Survival of the fittest Theory of Natural selection Richard Dawkins Theory of Evolution Given sufficient time, the non random survival of hereditary entities (which will occasionally mis- copy) will generate complexity, diversity, beauty and an illusion of design so persuasive that it is almost impossible to distinguish from deliberate intelligent design Gene comparison slider Charles Darwin An introduction to Charles Darwin. The Mechanism of Evolution: Natural Selection How does natural selection work? 1.Too many offspring (over-production) 2.Genetic variation (sex and mutation) 3.Competition: the Struggle for survival 4.Differential survival and reproduction (survival of the genetically fittest) 5.Advantageous characteristics passed on to offspring 6.GRADUAL change over many generations Too many offspring Results in competition for available resources food, shelter, mates, water, sunlight Darwins Theory of Evolution by Natural Selection can be summarized with the simple acronym VISTA: Variation Inheritance Selection Time Adaptation) 21 Natural selection takes several forms Stabilising selection in a stable environment Directional selection in a gradually changing environment Disruptive selection in a fluctuating environment Natural selection does not always cause change Change will only occur when there is environmental change, or when a brand new advantageous mutation arises Most of the time, natural selection keeps populations stable over the generations: and is considered as stabilising selection Extreme variations are eliminated and the established phenotype is maintained Directional selection Results in evolution of a population Associated with gradually changing conditions The phenotype gradually shifts towards the better adapted variety 1. Peppered Moths in the UK Peppered moth simulation 2. Antibiotic resistance in bacteria Disruptive selection Favours two extremes of a trait at the expense of the intermediate form Associated with a fluctuating environment Gives balanced polymorphism (a balance of different types) Disruptive (diversifying) selection Heterozygous advantage in natural selection: Sickle Cell anaemia Natural selection can lead to speciation Natural selection can lead to extinction You need to be familiar with the evidence for evolution Evidence for Evolution 1. The GENOME 2. The Fossil Record 3. Geographical Distribution 4. Artificial Selection breeding of plants and domestic animals 5. Homologous Structures 6. Embryological development 7. Adaptive radiation Opponents to The Theory of Evolution: The Blind Watchmaker oh yeah, it's David Attenborough again... Evidence for Evolution 1: DNA By sequencing and databasing genes, we can see similarities and differences between species The closer the genome match, the closer their evolutionary history Human Chromosome 2 came from fusion of two great ape chromosomes Karl Miller on human evolution The time-tree of evolution Evidence for Evolution 2: The Fossil Record The Fossil Record Palaeontologists uncover fossilised remains in sedimentary rock deposits and use the information to create timelines Organic matter trapped in sand/ silt/fossils Compressed over time Dated by isotopic carbon (50,000 years), potassium 40 (1.28 Billion years), 238 Uranium Oldest fossils are at the bottom, youngest at the top Other methods for dating fossils Dating Methods Fossil Evidence for Evolution whale valley Whale evolution Evidence for evolution: Geographical Distribution Before humans arrived, Australia had > 100 types of marsupials, but no placental mammals HawaiI and New Zealand have unique biotic environments plants, insects, birds but no placental mammals HawaiI and New Zealand have unique biotic environments plants, insects, birds but no placental mammals Adaptive radiation The diversificaiton (speciation) of a group of organisms into different types specialised for different ecological niches Darwins finches. Evidence for Evolution 2: Homologous structures Homologous traits have similar embryological origins and development Indicative of common ancestry: what Darwin called Unity of Type Indicative of adaptive radiation Pentadactyl limb Human appendix Whale pelvic and thigh bone Homologous structures: Pentadactyl Limb Homologous structures: Whale Pelvic bone Homologous structures: Human appendix Evidence for evolution 3: Artificial Selection Evidence for evolution: Artificial selection An avid pigeon breeder, Darwin knew that breeders could change a species by choosing individuals with interesting traits that occurred at random and by allowing those individuals to breed. Over generations, those traits become more common and the population changes over time. Artificial Selection 53 In addition to traits intentionally chosen by breeders, Darwin noted this observation in The Origin of Species ... not a single domestic animal can be named which has not in some country developed drooping ears. Darwins Observations 54 Not only drooping ears, but also: piebald coloration, forehead star wavy hair rolled, shorter tails changes in reproductive cycles What could this mean? Traits Common In Domesticated Species 55 Dogs, the first domesticated animal species, were domesticated from gray wolves in Southwest Asia over 15,000 years ago. Canis lupusCanis lupus familiaris Wolves, Dogs, & Domestication 56 Morphologically, dogs and wolves share a number of traits because they are canids. Genetically, they are 99.8% similar in their mtDNA, which strongly indicated dogs were domesticated from wolves. Wolves and coyotes are only 96% similar. Wolves, Dogs, & Domestication 57 Evidence for evolution: Embryology Evidence for Evolution: Observable changes in response to environmental changes Development of new species is RAPID in species with a short reproductive cycle: bacteria, viruses, parasites, moths Evolution in response to environmental change 1.Peppered moths in Great Britain 2.Antibiotic resistance in tuberculosis 3.Sickle Cell anaemia