EVOLUTION 7.1 Steps Leading Up to Charles Darwin’s Theory
Enormous diversity of life- each species has own set of characteristics Theory – Theory – set of statements that have been tested repeatedly and are supported by evidence – evidence – theories can be used to make predictions CHARLES DARWIN – DARWIN – developed theory to explain diversity of life on Earth and how all organism are related to each other and to their environment, he sought to explain evolution Evolution – Evolution – idea that all species are descendents of ancient species that were different from modern day species
Changing Ideas about Natural World
James Hutton one of scientist who did not think the world was young o rock formation are continually formed o theory of uniformitarianism of uniformitarianism – – earth was formed entirely by slow moving o processes, such as erosion and sedimentation Charles Lyell o Wrote about uniformitarianism in Principles of Geology Georges Cuvier Compared mammoth and elephant bones o Classified mammoth as extinct o Basically discovered possibility of ancient creatures o Jean-Baptiste Lammark Proposed species evolve, and changed over time o Use it or lose it idea o Evolution due to adaption o Species were adapted to environment o i.e. Giraffes long necks to reach high trees o thought due to need to long necks, they stretched and acquired them o acquiring characteristic is not possible because that changes DNA o DNA plays a role in trait inheritance
Darwin’s Observation
Travelled worldwide – worldwide – studying geology, plants, animals Patterns of Diversity – Diversity – Darwin Discovered three 1
Species vary Globally Distantly related species living in similar habitat in different parts of the o world and acted similar Some unique species not found elsewhere o Plants and animals in area can differ from each other, more closely related o to plants and animals in own area Species Vary Locally Related animal species that occupy different habitats within local o environment varied o Each species adapt to environment and available avail able food Species Vary over Time From study of fossils o o Ancient species ancestors of modern day o Yet can look unlike to each other Wondered if this caused extinction o Geological Change Darwin read Lyell’s book o Saw block of land move upward die to quake o Reasoned Earthquakes lift marine fossils from sea floor o
Darwin Develops his Theory
Darwin convinced Earth was ancient Thomas Malthus – Malthus – problems to human cause by overpopulation, if we grow faster that the rate we get our supplies are produced lead to war, disease and famine Darwin recognized this - all species overpopulated and struggle The more individuals than the environment can support leads to struggle for existence Helped him create mechanism of evolutionary change
7.2 Darwin’s Theory
Theory of Evolution = idea that all organisms have common ancient ancestor that is diff. from modern day species Evolution = changes is species over time Observations that needed explanations Why do so many different animals have the same structure; the arm of a o whale = arm of human? 2
Why is the sequence of DNA very similar in some groups of organisms but not others? Why do embryos of animals look very similar at an early stage? o History of Evolution Charles Darwin made theory of evolution by natural selection o Wrote book called “the origin of species” o Called it descent with modifications o Explains how organisms changed over time (adapted ( adapted)) o Example of finches – finches – many finches with different looks, all have adapted to eating different types of food, but came from one ancestral species Natural Selection – Selection – favorable variation that is inherited by individuals are more suited for the environment and in turn survive, and reproduce, their offspring are also favorable = adaption o Adaption = feature favored by environment 1. Variation exist among individuals in a species (difference between individuals due to genetic makeup)(heritable) makeup) (heritable) 2. Individual will compete for resources (food, mate and space) 3. Competition would lead to the death of some individuals while other will survive 4. Individuals that have advantageous variation are more likely to survive and reproduce FITTEST, REPRODUCTION o VARAIATION, COMPETITION, SURVIVAL OF FITTEST, ENVIRONMENT; Ecological niche = sum of total of a species s pecies use of o biotic and abiotic factors in its environment Evidence for evolution o FOSSILS Show # of extinct animals Bones Similarities between extinct animals and animals that are alive today The earth’s layers show a time scale of species and when they appeared on earth (and when they died out) o Carbon dating Each element has isotope Isotope 14, and 12 in carbon 14 decay at constant If we know the rate we can determine amount of carbon 14 that has been released by fossil o
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Recreation of what organisms look like Homologues structures – structures –similar similar part with different functions Vestigial organs – organs – these are organs and parts that seem to have no function Analogous features features – – structure different but serve same purpose ex: bird wings, and bee wings Geographical Distribution Same species but are different due to different adaption Different species are the alike due to habitats that have adapted them to be similar Biochemistry and DNA Proteins, enzymes, hormones and chemical processes that occur in the body More closely similar more close DNA Embryological Development Embryos of different species develop in almost identical ways Direct observation of species change Bacteria resistance to antibodies Wolves bred over many generations to become dogs (artificial selection) selection) and bred again to create a variety of breeds Same genus and species only bred different in dogs
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8.1 Microevolution
Microevolution is the change in genes ALWAYS HAPPENING – HAPPENING – if not Hardy Weinberg Equilibrium – Equilibrium – no change in genetic pool, no evolution will occur Equilibrium will happen if o 1. Random Mating – Mating – not selective, no common allele, random alleles, crossbreeding 2. Large population – population – more likely to be equalized 3. No Mutations – Mutations – no changes in allele 4. No Natural Selection – Selection – no favourism of trait (adaption) 5. NO migration – migration – no new genes introduced, or leaving If conditions not met that the allele frequencies change – therefore there o will be microevolution
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How do changes in genes happen? 1. Natural Selection – Selection – affects the allele frequency b/c the environment puts selective pressure on a particular trait (adaption). The favoured trait became more frequent in population (b/c more of them surviving than others, then they reproduce passing on their traits) RESULT: stabilizing selection, directional selection and disruptive selection -> all are illustrations illus trations of which allele will become more frequent in the population
Ie: Pesticide and antibiotic resistance – resistance – more likely to survive, Restiance is an adaption that is passed on 2. Sexual Selection – Selection – when the male or female organisms of a particular species puts pressure on the opposite sex (b/c it favours a particular trait) This means that organisms w/ the favoured trait will more likely find a mate and reproduce Ie: Widow Birds – Birds – specific trait favored long tails - reproduce more 3. Artificial Selection – Selection – Human chose the desired trait and breed only those individuals with the desired traits therefore changing the allele frequencies (NOT RANDOM, SELECTIVE BREEDING) Ie: Breeding dogs, farmers will choose cows that have high yield in milk 4. Genetic Drift – Drift – the change in the gene pool of a population DUE DU E TO CHANCE. All pop. Are affected by genetic drift BUT smaller population have greater impact WHY? a) Bottle-Neck Effect – Effect – a change in the allele frequency due to a disaster (I.e. Flood, fire etc.) HOW? - original population has variation - DISASTER by chance, then only some individuals survive - Surviving group make up new population - Depending on what alleles these individuals have will determine the variation of new population (REDUCES) 5
b) Founder Effect – Effect – there is a change in allele frequencies DUE TO MIGRATION to a new area and creating a new population…the “founders” of the new population will determine the allele frequency frequency 5. Gene Flow – Flow – EXCHANGE of genes between individuals of DIFFERENT populations (individuals of species in same area) -> tend to decrease differences between populations I.e.: Neighboring populations of wild of wild flowers can pass (exchange) their pollen via wind 8.2 Macroevolution
Changes in species that is not based on genes (allele frequencies) -> this also increase diversity Speciation is a main focus of macroevolution – macroevolution – origin of new species RECALL: Biological species concept -> is a population/group of organisms that can o reproduce together and have FERTILE offspring (only applicable to organisms that reproduce sexually) HYBRID: offspring from mating of individuals of 2 different species (natural o hybrids are rare) Mechanisms of Macroevolution (specifically speciation) speciation) 1. Reproductive Barrier – Barrier – any factors that prevents 2 organisms from reproducing a. Geographical Barrier: geographic formation that prevents organism from being in close proximity to mate (I.e. Grand Canyon) b. Habitat Barrier – Barrier – different habitats but in general same location (no interbreeding) ex: fishes in low water like to mate with low water fishes, high with high c. Temporal Barrier – Barrier – different mating seasons that prevents interbreeding (Ie. Skunk -> western and eastern spotted) d. Behavioral Barrier – Barrier – different mating behaviors prevent interbreeding (Ie: Mating Calls) e. Mechanical Barrier – Barrier – different anatomical structure of reproductive organs (ie. 2 species of snails, don’t match) f. Gametic Barrier – Barrier – different gametes such as gametes don’t recognize each other (Ie. Sea Orchins) g. Hybrid Inviability – Inviability – hybrid don’t survive long enough to reproduce
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h. Hybrid Infertility – Infertility – hybrids mature BUT are unfertile (ie. Horse + Donkey = mule) 2. Adaptive Radiation (aka divergent evolution) – evolution) – common ancestors that result in different environment (I.e. Founder effect, natural selection + geographic, habitat and behavioral isolation – isolation – all result in adaptive radiation) 3. Convergent Evolution – Evolution – different species that live in similar environment that develop similar adaption -> these similar adaptations called analogous structures Rate of Speciation of Speciation 1. Gradualism: evolution of a species – species – due to gradual accumulation of small genetic changes over LONG period of time 2. Punctuated Equilibrium: species evolves “spontaneously” ->RAPID “spontaneously” ->RAPID evolutionary change (has very few intermediate forms) How do we find evidence for this? Fossil Records – Records – sedimentary rock o Grad – Grad – find intimidate species in the rock o PE – PE – since so fast, we don’t find fossils, We find last evolved species -> So o does not mean spontaneous just rapid that there weren’t many intermediate species to find in the fossils
8.3 Evolution on Ongoing Process
Co-evolution – Co-evolution – one species responds to changes in another species – usually there is a symbiotic relationship between the 2 organisms (but is not necessary) Flowering Plants and Pollinators (symbiotic) o 1. Ex: hawk moth and orchid; moth has a 40 cm tongue to access nectar inside orchid (moth gets nutrients, and flower sexually reproduces) Plants and Herbivorous Insects o 1. Some plants evolve to have toxic chemicals to protect itself from being eaten by insects but then insects evolve to tolerate or cope evolutionary change (ex: milkweed, and monarch) Mimicry o 1. One species resembles another species to protect itself (ex hoverfly looks like wasp, predator are scared it will sting) Evolution of Complex Features Darwin believes that gradual changes can account for breakthroughs in o form and function 7
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Camera-like eye is amazing structure, that come from a very simple structure Cumulative selection is the evolution of a simple structure into a more complex structure through a series of small adaptations
Adaptations of Existing structures to NEW functions Materials or structures that evolved as adaptation for certain functions that o later fulfilled different functions 1. Ex: the exoskeleton of a marine arthropod such as reef lobster helps protect the animals from predators, on land anthropoid exoskeleton of scorpion fulfills additional functions: resisting water loss, supporting body on dry land o Another example penguin flippers 1. Wings remodeled into flippers help swimming to hunt small fish and other prey
9.1 Origins of Life on Earth
Primary abiogenesis = life from non-living matter o Alexander Oparin + J.B.S Haldlane (came up with this theory independently in 1920s) EVIDENCE: Miller-Urey experiment by Stanley Miller at Urey University (part of Chicago uni) Recreated Earth’s early atmosphere in a flask: methane, carbon dioxide, carbon monoxide, hydrogen gas, ammonium, water vapor, and little oxygen (energy came from lightning, eruptions and UV light all which were very intense)
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Created a variety of organic molecules (contain Carbon -> building blocks for living things) Ie: they will form proteins, lipids, carbohydrates, nucleic acid (DNA/RNA) This experiment was done numerous times w/ different gas combinations which created a greater variety of organic molecules ***NOTE: these molecules are the basis for life and NOT living things HOW DID THESE MOLECULES FORM LIVING THINGS? o Hypothetical 4 Stage Sequence 1) Miller-Urey Experiment - inorganic to small organic molecules 2) Simpler molecules join to form large molecules (monomers to polymer -> I.e. Amino Acid to proteins, nucleotides to nucleic acid) 3) Molecules that could copy themselves formed the basis for inheritance (DNA) 4) Organic molecules became packed w/ membrane -> formed pre-cell WHERE DID LIFE BEGIN? Earlier – Earlier – shallow water, clay -> problems surface of earth too hot o wouldn’t allow the molecules to survive (will be broke down) = change according to the 4 step sequence Current – Current – deep sea hydrothermal vents (very hot -> energy chemical o composition provides basis for inorganic to organic) o Also they are prokaryotes that live there -> Archaebacteria (ancient) that resembles earliest cells Oldest Fossils STROMATOLITES = layered rock that form when certain prokaryotes o bind thin layers of sediment together EVIDENCE: Stromatolites are similar to modern Stromatolites o Found photosynthetic prokaryotes in Stromatolites that are 3.5 bya inferring that simpler prokaryotes (chemoautotroph) existed before this time which infers that life existed 3.5 bya Free Oxygen Changes Earth Chemoautotrophs (found in ocean floor vents +didn’t require light to o make energy) then came photosynthetic autotrophs that existed in low levels of o oxygen (anaerobe) -> environment change and more oxygen became
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present (b/c oxygen is byproduct byproduct of photosynthesis) -> oxygen and iron combine to form FeO which fell tot eh ocean floor causing oceans to change from brown to blue green highly reactive oxygen causes mass extinctions in prokaryotes -> ones o adapted to low oxygen (anaerobe) and few adapted to oxygen (aerobe -> led to more complex organisms) Eukaryotic Cells
Endosymbiotic Theory Ancestral eukaryotic cells lacked some organelles found in modern day eukaryotic cells: mitochondria and chloroplasts Mitochondria evolved from small aerobic prokaryotes that lived inside larger eukaryotic cells, they may have ingested some of these prokaryotes for food, instead of being digested they continued to live, forming a symbiotic relationship Chloroplast evolved in a similar way, some prokaryotes consumed these photosynthetic prokaryotes, making a symbiotic relationship, eventually they created a cell wall and because autotrophic Cells wall is an example of convergent evolution, cell wall in prokaryotes are made of peptioglycan and eukaryotic cell wall are made out of cellulose; thus they evolved independently Evolution of Sexual Reproduction and Multicellular Life Some eukaryotes reproduce sexually o Increasing variation o Variation good for natural selection and evolution to occur o o
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Million years later multicellular organisms develop and vary diversify to protists, plants, animals due to adaptive radiation Fossil Record and Geological time Scale Continental Drift: continuous movement of land masses WHAT HAPPENED? 2 events that had a MAJOR effect on life on earth o 1. PANGAEA (single land mass) – mass) – 250 myo Shoreline reduced Sea lvl dropped so coastal seas were drained Interior became dry Result: species in isolation brought together and forced to compete (b/c of limited resources) -> competition forces NATURAL SELETION to occur Marine organisms by coastal seas died -> mass extinctions 2. Breaking of Pangaea Aus. Broke off first Other continents that drifted off would now have their own “evolutionary arena” RESULT: in Aus. The marsupial mammals stayed on the continent only and remained isolated -> few placental mammals lived there AND - On other continents they were mostly placental and few marsupial - ALSO… there was evolution taking place that was unique to each area on each continent die to different pressures (NATURAL SELECTION) > speciation Mass Extinctions Great loss of a # of species o How does it affect species? Even though species go extinct, the species that do survive diversify by o ADAPTIVE RADIATION (DIVERGENTEVOLUTION) (DIVERGENTEVOLUTION) Ie: after mass xtinction at end of Cretaceous period -> mammals underwent huge change via adaptive radiation which leads to various species of mammals (evidence from fossils) EXAMPLES:Dinosaurs – EXAMPLES:Dinosaurs – only ones that evolved into birds continued CAUSES? o
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1) Climate Cooling -+ shallow seas receding receding -> temperature temperature change may have been drastic and seas reduce water availability 2) Crater in Mexico – Mexico – massive meteor hit Earth caused dust to build up in atmosphere and block out sun therefore reducing producers ability to photosynthesis (Therefore consumers had less food) (Evidence from fossil age and meteor age was equal) 9.2 Phylogeny and Human Evolution
Phylogeny: evolutionary development and history of group or species Information/evidence to create phylogenies come from fossil records, o morphology (i.e. homologous features) and genetics (sequencing) Cladistics: most widely accepted method of applying evidence METHOD: uses presence or absence of recently evolved traits (aka derived o traits) to determine how closely two groups are related the 2 groups are SYNAPHOMORPHLOGY: derived trait shared by 2 or more species of groups o Inference that if they share same (synaphymorplogy) trait they are more closely related Cladograms or phylogenic trees: illustration of evolutionary relationships Each branch is a Clade o There can be smaller clades embedded in larger clades o Each division of branches is called a junction o Derived traits (recent), primitive condition not derived o Human Evolution What makes humans a species? o Complex reasoning Exceptional ability to learn Make and use sophisticated tools Communicate using a complex language **Degree of evolution makes us different SKILLS Very large brain relative to body HANDS capable of manipulation and coordination BIPEDAL Primates o Have large brain Forward facing eyes
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Flexible hands and feet, opposable thumbs Arms that rotate Mostly have tails PROSIMIANS: a nocturnal lower primate with large eyes and ears, e.g. a lemur or bush ANTHROPOIDS: relating to the group of animals that includes monkeys (old and new world), Hominids: (gibbons, great apes, and humans(no tails))
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