Stage 1: Abiotic Synthesis of Organic Monomers Amino Acids Chains of nucleotides Chains of DNA bases Chains of RNA bases Building blocks of protein Sugars Lipids ATP
Stage 2: Abiotic Synthesis of Polymers Monomers, such as amino acids, spontaneously fused together to form proteins.
Stage 3: Origin of Self-Replicating Molecules inheritanceRibozyme: catalytic RNA used to fuel RNA replication
Stage 4: Formation of Pre-cells Molecular packages with some properties of life. The gap between pre-cells and true cells is enormous! Natural Selection
The origin of eukaryotic cellsEndosymbiotic Theory Membrane bound nuclear material Organelles More complex than prokaryotic cells Ancestors to fungi, plants and animals
Concept MapSection 17-2 Evolution of Life Early Earth was hot; atmosphere contained poisonous gases. Earth cooled and oceans condensed. Simple organic molecules may have formed in the oceans.. Small sequences of RNA may have formed and replicated. First prokaryotes may have formed when RNA or DNA was enclosed in microspheres. Later prokaryotes were photosynthetic and produced oxygen. An oxygenated atmosphere capped by the ozone layer protected Earth. First eukaryotes may have been communities of prokaryotes. Multicellular eukaryotes evolved. Sexual reproduction increased genetic variability, hastening evolution.
Evolution = “Descent with Modification” 1. ------------due to being spread over different habitats and therefore adapting and modifying themselves to fit the habitat. 2. Natural Selection • A population of organisms can change over generations if certain inheritable traits leave more offspring than others and those others get the chance to reproduce and continue the lineage. • Evolutionary Adaptation
Greek Philosophers• Plato’s Idealism• Aristotle’s scala naturae (scale of nature) special creation of each species organisms were created in their current form the earth was only a few thousand years old
THOMAS MALTHUS economist & clergyman published An Essay on the Principle of Population Populations had an inherent tendency to increasegeometrically, while the resources needed to support this growthincrease slowly or not at all. Because of the continued growth of a species would outstripneeded resources, growth would be limited.
JEAN-BAPTISTE de LAMARCK French biologist proposed that modern species descended from other species Lamarckism based on two theories:1. Inheritance of Acquired Characteristics - traits acquired by an individual during its life are passed to its offspring2. Use and Disuse - organs of the body that were used extensively to cope with the environment became larger and stronger, while organs that were not used deteriorated
THE ROAD TO EVOLUTIONARY THEORYExample: Evolution Before DarwinThe Evolution of the GiraffeGiraffes obtained their long necks fromprevious giraffes who stretched to eat theleaves of high tree branches.Stretching increased the length of theirnecks, and this acquired characteristicwas passed to the next generation.
Lamarckism first to present a unified theory that attempted to explain the changes in organisms from one generation to the next Although, mechanisms proposed for change was wrong, since acquired characteristics are not heritable!!! origin of species from preexisting species ability of organisms to adapt
GEORGES CUVIER French anatomist and naturalist and writer palaeontologist strongly opposed the concept of evolution history of living organisms recorded in layers of rock containing a succession of fossil species in chronological order fossils were organisms that had died in a series of catastrophes, after which extinct plants and animals were replaced by the immigration of distant species to the devastated region Catastrophism
CHARLES DARWIN voyage on the H.M.S. Beagle (1836) published (1859) The Origin of Species first person who proposed a mechanistic approach to evolutionary thought the father of synthetic evolution
Galapagos tortoise Darwin’s finches Most organisms on the islandswere endemic.
The birds were very similar (common ancestry). They all adapted to different Niches. Niche = Your job in nature. What you eat Where you live (on ground, in a tree) Reproductive Isolation resulted in speciation.
Fossils chronologicallyordered in rock layers
Geographic distribution of species: Australian marsupials
Notice that aChimp is moregeneticallyrelated to ahuman than toan Old WorldMonkey!
species not specially created in their present forms, but had evolved from ancestral species proposed a mechanism for evolution: Natural Selection A population of organisms can change over time as a result of individuals with certain heritable characteristics leaving more offspring than other individuals.
Darwinism in Historical Context
GREGOR MENDEL Austrian biologist discovered the basic principles of heredity father of Classical Genetics Individual characteristics determined by inherited factors transmitted from parent to offspring.
HUGO CARL ERICH VON DE VRIES CORRENS TSCHERMAK rediscovered Mendel’s laws of heredity the start of rediscovering evolution in terms of Mendel’s ideas
JAMES WATSONFRANCIS CRICK elucidated the structure of DNA (genetic material) DNA contains coded information which acts as a blueprint for the transfer of hereditary information from generation to generation mutation as the raw material for evolution
A population is the smallest unit of evolution. Natural selection acts on individuals. However the evolutionary impact of natural selection is only apparent in tracking how a population changes over time. Population Genetics emphasizes the extensive genetic variation within populations and tracks the genetic make-up of populations over time. Not all variation in a population is inheritable. Only the genetic component of variation is relevant to natural selection. Many variable traits in a population result from the combined effect of several genes.
Genetic equilibrium- allele frequenciesremain constant. Populations should be in a state of equilibrium assuming: 1. Large Population 2. Random Mating 3. No Migration 4. No Mutation 5. No natural selection occurs.
Speciation occurs relatively quickly with long periods of equilibrium in between. Speciation = The formation of a new species due to evolution.
Evolution can occur without natural selection. Genetic Drift is a change in the gene pool due to a random event. Example- Mount Saint Helens Eruption. If the event is catastrophic and all the organisms are killed off = Mass extinction.
= The formation of a new species due to evolution. Reproductive Isolation- Can result in speciation. It is the separation of members of a species due to some barrier. Islands Mountains Roads Oil Pipes
•Speciation occurs onlywith the evolution ofreproductive barriersbetween the isolatedpopulation and its parentpopulation.•If speciation occursduring geographicseparation, the newspecies will not breedwith its ancestralpopulation, even if thetwo populations shouldcome back into contact.
Allopatric Speciation A population forms a new species while geographically isolated from its parent population. Sympatric Speciation A small population becomes a new species in the midst of a parent population
Does not widely occur among animals but may account for over 25% of all plant species.
Notice how the hybrid bread wheat has a set of chromosomes from each of its ancestors: T. monococcum (AA), Triticum (BB), T. turgidum (AA BB), T. tauschii (DD)What can you notice aboutT. aestivum that mightmake it a good hybrid andthe most important wheatspecies today?
Convergent Evolution- Organisms of different ancestry adapting to a similar environment. Produces homologous Structures. Example: bats and Butterflies wings. Dolphin Penguin Shark Divergent Evolution- Organisms of common ancestry adapting to diverse environments. Produces analogous Structures. Example: Human Arm and Bird wing.
1. Genetic Drift Def: A change in the gene pool of a small population due to chance. The best measure of Darwinian fitness is the number of fertile offspring an individual leaves.
2. Gene Flow Def: The genetic exchange with another population.3. Mutations A change in an organism’s DNA sequence. Ultimate source of genetic variability.4. Natural Selection Directional Selection (selecting in favor of an extreme phenotype) Disruptive (Diversifying) Selection (leads to a balance between two or more contrasting phenotypic forms) Stabilizing Selection (maintains variation in a narrow range)
•Resistant Genes •Immediate Benefits •Long term Disaster •Evolution direct connection to daily lives
Def: Major biological changes evident in fossil record. CONTRAST: MICROEVOLUTION Speciation Nonbranching evolution (transform a population enough for it to be designated a new species.) Branching evolution (splits a lineage into two or more species)
Ernst Mayr Studied the diversity of birds in New Guinea (1927) Biological species concept Species = “groups of interbreeding natural populations that are reproductively isolated from other such groups.” Reproductive isolation blocks exchange of genes between species and keeps their gene pools separate.• Reproductive barriers between species • Zygote: fertilized egg • Pre-zygotic (factors that impede mating between species or hinder fertilization of eggs if mating is attempted) • Post-zygotic (mechanisms that operate should interspecies mating actually occur and form hybrid zygotes)
Isolating Mechanisms Courtship Sterile
Spurts ofSlow relativelyadaptations rapid change
Flowchart Section 17-4 Species that are Unrelated Related form in under under in in Similar IntenseInter-relationshiops Small Different environments environmental populations environments pressure can undergo can undergo can undergo can undergo can undergo Coevolution Convergent Punctuated Adaptive Extinction evolution equilibrium radiation
Systematics Reconstructing evolutionary history Radioactive dating = tool The study of biological diversity: past and present Taxonomy Identification, naming and classification of species Pioneer: Carolus Linnaeus (1707-1778) Binomial Nomenclature Homo sapien
Hierarchical Classification Which step is more specific? Class or Genus? How is DomainEukarya different fromBacteria and Archaea?
•Evolutionaryhistory of aspecies.•Tree is based onhomologousstructures, NOTanalogous.•Two species willhave morecommonnucleotidesequences basedon how recentlythey branchedfrom theircommon ancestor.