Evolution

Evolution

1. Stage for Darwin

   • Plato - imperfect copies
   • Aristotle - teleology: purpose/event. Great chain of being
   • Galileo + Newton - efficient cause, mechanisms
   • Hutton + Lyell - Geology, slow process --> dramatic change, age of earth
   • Cuvier - fossils/strata characteristics catastroplism
   • Lamarck - Transformism, inherit used organs. Environment --> Evolve complex
   • Malthus - rate of human increase --> starvation
   • Linnaeus - naming system, hierarchy

2. Variation

   • Macroevolution
     • patterns in species/speciation
     • diversity of species
       • 25%, 350000 beetles
       • Challenged Special creation
       • 120 animals in Bible
         • Not science, no classfication
     • biogeography
       • particular kinds of organisms in particular areas. geographical distribution of species.
       • related species on close islands/mainland
       • Flora on Tristan was African + South American
       • Distribution of species - continental drift. Mechanism unaware
     • fossils
       • evidence; decent w/ moddification
         • unlike Cuvier who believed catastrophism
       • Missing transitional fossils
       • supported by molecular archive
         • reconstruct evolutionary relationships w/ DNA +genome
     • homologous
       • Common ancestry
       • May have different functions, appearance
     • adaptation + vestigal
       • organisms influenced by environment
       • unrelated organism, similar niche. Convergence
         • Basilsaurus - no hind limbs, early whale
         • Tylosaurus - marine lizard
         • Stem reptiles
           • Mammal like
             • primitive mammal
               • bat
           • Bird like
             • Primitive bird
               • gull
           • Adaptive aerial convergence
             • pterodactyl
       • Imperfect adaptation
         • Pelvis + femur in whale
     • Mass extinction
       • 65mil yrs dominant dinosaurs --> Mammals
         • adaptive radiation. Niches left by dinosaurs filled by birds and mammals
       • Impact w/ earth - disaster, 'rain for fire'
         • storms, tsunamis, cold and darkness, greenhouse warming, acid rain and global fire
       • 5 extinctions; appearance of new/dominant forms
       • Crater underwater, iridium found; in meteorites
   • microevolution
     • Artificial selection
       • Domestic dogs - Middle Eastern gray wolf. Inbreeding
       • HIV - evolve rapidly. Drug resistant
         • drug resistant strain - 100% of population in a few weeks
     • Maintain variation
       • Mutation
         • Source of genetic novelty. Random - no benefit to cell Most are silent
         • In gamete -> new allele
           • Some can result in genetic disorder
         • Rare but substantial
       • Sexual reproduction + recombination
         • most important -> genetic variability
       • Diploidy /refuge
         • Diploidy preserve variation
           • Shelters rare allele, recessive refuge. persist over generations
       • Outbreeding
         • unrelated promote variability
       • heterozygote
         • some recessive alleles selected
           • hetero sickle cell anemia - protect from malaria
     • Affecting variation
       • Genetic drift
         • Loss of variation
           • Bottleneck
             • Abundant + diverse pop -> reduced
               • only retain some alleles. by chance
           • Founder's effect
             • allele change after population translocated
           • generational
             • Evident in small populations
             • Chance in reproductive success
       • Gene flow
         • increase/maintain variation
           • individuals move between populations. alleles move in/out of gene pool
             • successful reproduction
       • Inbreeding
         • Matter of degree -common in humans Incest - 1st order cousins
         • Lose variation, increased homozygous
           • eg. 7x risk for cystic fibrosis 1st cousins
     • African Cheeteh
       • Pleistocene extinction; 75% large mammals Africa
         • Environmental change, disease or humans?
       • Inbreeding due to bottleneck
         • defect sperm, breeding difficulties
         • loss of variation, v low genetic compared to other mammals
         • low diversity in MHC genes for immune + self recognition
           • Could not recognise other cheetahs from self. Successful autograft and allograft.

3. Genetic basis

   • mechanism for inheritance
     • Problems with blending
       • Also thought inheritance by blood
       • Cant transform population 'favorable' trait
       • Reappearance of traits
       • Traits not blended out
     • Mendel
       • Traits determined by 'units/particles'From each parent
       • Recessive - may appear in later generations
       • 1900 used Mendel against Darwin. Mutation only changing force.
         • Explaining new species and complex forms
         • 'Sport' mutation recessive. Albino - homozygous.
     • Darwin hypothesis
       • Darwin had no mechanism for heredity
       • Inheritable : mutation, atavistic traits
         • Atavistic traits: silenced but not lost, e.g. dolphin hind limbs
       • Not inheritable: abnormal develop
   • Synthetic Theory
     • Variation in population (mutation/recomb)
       • Not by needs of organism/ acquired adaptations.
     • Evolution influenced by natural selection, genetic drift, gene flow.
       • Characterized by changes in gene frequency.
     • Adaptive variation - change phenotype accumulates.
     • Geographically isolated - reproductively isolated - speciation.
     • Genetic differences (guide by NS) -> groups above species (genus,family)
   • Hardy-Weinburg
     • No: mutation, gene flow, natural selection, genetic drift. Panmictic, random mating.
     • P^2 + 2pq + q^2=1

4. Natural Selection

   • Environment + Heritability. Genotypes differ is fitness. Fitness - rate of genotype increase relative
   • Categories
     • Stability
       • Extreme phenotypes eliminated
         • eg swiss darling brood size
     • Disruptive
       • extreme phenotypes selected
     • Directional
       • one extreme favoured
         • eg. corn oil
   • Sexual selection
     • female preference may put males at risk/ disadvantage
       • peacock, widowbird
   • Adaptation
     • microevolutionary
       • clines
         • gradual variation. geographic dstribution
           • eg. yarrow plant in ranges and plateau
       • ecotype
         • same species/ different phenotype+habitat
           • eg killer whales different prey
     • macroevolutionary
       • coevolution
         • selective force, between species
           • mimicry, mullerian +batesian
       • convergent evolution
         • adaptive radiation after mass extinction, leading to convergent evolution
         • unrelated species resemblance
           • adapting to common enivronment
           • placental & marsupials. analogous structures
       • divergent evolution
         • related population dissimliar
           • homologous structures

5. Origin of species + classifications

   • Modes of speciation
     • BY biological species concept. Species - population that can interbreed with ach other
     • Allopatric
       • geographically isolated
       • dispersal - chance movement
       • vicariance - geographic disruption
     • Sympatric
       • without isolation
       • polyploidy - increase genome number
         • hybridisation
         • Autopolyploidy - self fertilisation
         • Allopolyploidy - hybrid 2 parents
           • meiotic / mitotic error can produce viable fertile offspring
       • sexual selection
       • disruptive selection - genetic discontinuties
   • Patterns of speciation
     • leads to macroevolution
     • Anagenesis (phyletic)
       • gradual change - single lineage. Tuatara
     • Cladogenesis
       • branching populations. alternate paths diversity
     • Adaptive radiation
       • rapid formation of many species from 1 ancestral group
       • can lead to convergence, similar niche + trait
     • extinction
       • fossil show steady extinction, bursts of mass extinction
       • disappearance of species
     • punctuated equilibrium
       • challenged darwin's gradual
       • rapid speciation, displace existing, persist w/o change, sudden extinction
   • Reproductive mechanisms
     • Prezygotic
       • may breakdown if in captivity
       • spatial
       • ecological
       • temporal
       • behavioural
       • morphological
     • Postzygotic
       • zygotic mortality
       • hybrid sterility
         • hybrid cannot reproduce
       • hybrid breakdown
         • hybrid offsprings cannot reproduce
   • Phylogeny
     • evolutionary relationships among organisms.
   • Grades, Clades
     • Classifications - similarities in characters should to hoomlogous
     • Grades - groups that evolved new adaptive features
       •  Traditional taxonomy relied on morphological similarities based on grades
     • Clades / Cladistic/ Cladogram
       • focus on shared derived characteristics, ignoring ancestral
       • Focus on shared derived characteristics, ignoring ancestral
         • Monophyletic
           • e.g. anapsid. skull openings
             • diapsid, 2 holes
               • birds, crocs, lizards
             • synapsid, 1 hole
               • mammals
             • turtles
         • Polyphyletic
         • Paraphyletic
   • Characteristics
     • Ancestral
       • inherited with little or no change
     • derived
       • recent change, share with closely related species
   • WHALES
     • artiodactyls have ankle bones, whales do not
       • artiodactyls - cows, camels, deer, hippos
       • So whales related to mesonychids?
         • like hyenas with hooves, meat eating
         • WRONG! Whales are related to hippos. Similar to mesonychid by convergence
           • fossils of transitional whale with ankle bone
           • New grade in Order - Cetartiodactyla
             • suborder - cetacea

6. Darwin's basis

   • Hypothetico-deductive method observation -> speculate pattern -> further observation.
   • Like organisms reproduce. Stability
   • population Initial > survive/reproduce
   • Chance variation, some inheritable
     • Modern species from ancestral forms
     • challenged essentialism
   • inheritable favoured variation, more common. Natural selection
     • mechanism for evolution - natural selection
     • nullify teleology/metaphysics
   • natural selection --> changes differentiate groups
   • Galapago islands
     • on HMS Beagle
     • Observation. Beak: large - large seed, small - small seed
     • Average size increased with drought
     • Relaxed back to just above pre-drought

7. Descent of Humans

   • Primates
     • Prosimians
       • grabby tail, eg. lorises, lemurs
     • anthropoids
       • hominoids, all apes
         • hominids
           • greater apes
           • hominins
             • humans
             • 5 species
               • Austalopithecus afarensis,  A. africanus,  A. robustus,  A. boisei   Homo habilis
               • 'recent' humans
                 • erectus
                   • 1.6 mil to 300,000 yrs. tall, stone tools, heavy skulls
                 • neanderthals
                   • 300000 - 35000 yrs. fire, caves, clothing, hunt
                 • sapiens
                   • 'replaced' neanderthals, symbols, tools/weapons
                   • Archaic to modern
                     • Eve: origin Africa 150,000yrs rapidly spreading, replacing
                       • cladogenesis
                       • mitochondrial DNA - common maternal ancestor
                         • African expansion
                     • Multi-regional: slow 700,000 yrs gene flow
                   • non-African bred with neanderthals?
                 • Flores man, Indonesia. 12,000yrs
               • walked upright 3.6-1.4 mil yrs ago
       • New + Old world monkeys
   • Models; archaic to modern