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Biologists believe that organic evolution by natural selection accounts for the major steps in evolution. macroevolution – PowerPoint PPT presentation

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Title: Chapters

  • Chapters

Intro to Evolution
  • the process of cumulative change in the
    heritable characteristics of a population

Players in Evolution
  • Jean Baptiste de Lamarck (1744-1829)
  • Russel Wallace (1823-1913) and Charles Darwin

Natural Selection
  • A process in nature in which organisms possessing
    certain genotypic characteristics that make them
    better adjusted to an environment tend to
    survive, reproduce, increase in number or
    frequency, and therefore, are able to transmit
    and perpetuate their essential genotypic
    qualities to succeeding generations.

Evidence for Natural Selection
  • Fossil Records
  • Artificial Selection
  • Homologous Structures

Mechanisms of Evolution
  • Too many offspring
  • over production of offspring leads to
    intra-species competition and survival of the
    individuals best suited to that particular
  • competition can also lead to adaptive behaviours.
  • Natural Variation in a Population 
  • random assortment of chromosomes
  • crossing over of segments of chromosomes result
    in new combinations of genes, different than the
    parental combinations
  • random fusion of gametes in sexual reproduction
  • additional variations arise due to mutations,
    either chromosomal or gene

Natural Selection Summarized
  • The favourable characteristics are expressed in
    the phenotypes of some of the offspring
  • These offspring may be better able to survive and
    reproduce in a particular environment others
    will be less able to compete successfully to
    survive and reproduce.
  • Examples
  • Antibiotic Resistant Bacteria
  • Peppered Moth
  • Heavy Metal Tolerance in Plants

Evolution and the Origin of Life
  • Biologists believe that organic evolution by
    natural selection accounts for the major steps in
  • macroevolution major developments such as the
    origin of the eukaryotic cell, the origin of
    multicellular organisms, and the origin of
    vertebrates from non-vertebrates
  • microevolution the relatively minor changes
    that arise and lead to the appearance of new, but
    closely related species.
  • Theory of evolution - the Big Bang.

Four Processes for the Spontaneous Origin of Life
  • Chemical Reactions to produce simple organic
    molecules, from inorganic molecules
  • Assembly of the molecules into polymers
  • Self Replication of Polymers
  • Development of Membranes to enclose the polymer

Chemical Reactions to Produce Simple Organic
  • Heat, Temperature and Lightning Miller and Urey
  • Recreated ancient atmosphere (nitrogen, water
    vapour and carbon dioxide, smaller amounts of
    methane, ammonia, carbon monoxide, sulphur
    dioxide, hydrogen sulphide and hydrogen cyanide.
  • Lightning and UV radiation to provide energy

Chemical Reactions to Produce Simple Organic
  • Other Possibilities
  • In Space Panspermia
  • Alternating Wet and Dry Environments
  • Near Volcanos
  • Deep Sea and Ocean Vents

Formation of Polymers and Self-replication - RNA
  • As the organic compounds are made, they arrange
    themselves in lines polymers (Using the Clay
    Lattice as a template)
  • Lines of molecules form early enzymes (ribozymes)
  • Catalyse reactions, such as peptide bond
  • RNA strand is made and due to enzymes, a
    complementary strand can be made, and then copies
    are made
  • Longer and longer double stranded pieces are
    made, forming , now DNA
  • DNA more useful as it is longer and can hold more
    information (RNA 1500 nucleotides max)

Development of Membranes - Protobionts
  • Membranes were needed to separate the external
    environment from the internal environment
  • Phospholipids would have formed and due to
    hydophilic and hydrophobic properties, would form
    spheres in water (called coacervate)
  • Due to the bilayers, an internal environment
    would form, and if the early molecules (RNA to
    DNA) were trapped in the membrane, protobionts
    would have formed

Prokaryotes and the Oxygen on the Atmosphere
  • Early cells were anaerobic and heterotrophs
  • As nutrients decreased in amount, some evolved to
    become chemoautotrophic, using the gases in the
  • Since there was a large amount of CO2, some early
    prokaryotes used the gas, to produce early
    carbohydrate. The waste product was O2, which
    went into the atmosphere

Prokaryotes and the Oxygen on the Atmosphere
  • The formation of an ozone layer in the upper
    atmosphere commenced
  • The ozone layer began to reduce the incidence of
    UV light reaching the Earths surface.
  • Terrestrial existence (rather than life
    restricted to below the water surface) became a
  • Other prokaryotes, simply fed on the organic
    molecules available in their environment.
  • The bacteria had evolved aerobic respiration and
    so had the enzymes not only of glycolysis, but
    also of the Krebs cycle and terminal oxidation.

Endosymbiotic Theory
Species and Speciation
Definitions Neo - Darwinism
  • Gene Pool all of the genetic information
    present in the reproducing members of a
    population at a given time
  • Allele Frequency is a measure of the proportion
    of a specific variation of a gene in a
  • The allele frequency is expressed as a proportion
    or a percent, and can be calculated by the
    Hardy-Weinberg equation (more later).
  • For example, it is possible that a certain
    allele if present in 25 of the chromosomes
    studied in a population. One quarter of the loci
    for that gene are occupied by that allele. Keep
    in mind it is not the same as the number of
    people who show a particular trait.

Evolution Change in Allele Frequency
Species and Speciation
  • Species
  • Morphological Definition
  • A type of organism that has fixed characteristics
    that distinguish it from all other species
  • Biological Definition
  • Group of actually or potentially interbreeding
    populations, with a common gene pool, which are
    reproductively isolated from other such groups

Species and Speciation
  • Speciation
  • the evolution of new species, requires that
    allele frequencies change with time in
  • Mechanisms Isolation
  • Geographic (Allopatric)
  • Temporal (Sympatric)
  • Behavioral (Sympatric)

Species and Speciation (Animation)
  • Geographical Isolation (Allopatric)
  • Ex. Galapagos Islands
  • Ex. Snails
  • Lizards

Species and Speciation
  • Temporal (Sympatric)
  • Ex. Plants and Apple Maggot Fly
  • Behavioral (Sympatric)
  • Ex. Konrad Lorenz and the Gwan
  • Movie
  • Hybrid Infertility

Species and Speciation Trends in Evolution
  • Adaptive Radiation
  • many similar but distinctive species evolve
    relatively rapidly from a single species or from
    a small number of species.

Species and Speciation Trends in Evolution
  • When the species evolves different ways, this is
  • The new species is different than the first, in
    terms of the adaptations that have taken place

Species and Speciation Trends in Evolution
  • Living organisms often find the same solution to
    particular physiological problems, and as a
    result the organisms, in response to their
    environment, can become morphologically similar,
    even though they are not related to a common

Species and Speciation Rates of Evolution
  • Gradualism
  • Punctuated Equilibrium

Species and Speciation
  • Transient Polymorphisms
  • When there are two alleles for a gene in the gene
    pool, it is called polymorphic.
  • If one allele is gradually replacing the other,
    based upon environmental pressures, this is
    called balanced polymorphism
  • Ex. Peppered Moth (Biston betularia)

Species and Speciation
  • Balanced Polymorphism
  • When two alleles of a gene can persist
    indefinitely in the gene pool of a population
  • Ex. Sickle Cell Anemia
  • HbN HbN normal
  • Hbn Hbn - Sickle Cell anemic but immune to
  • HbN Hbn heterozygous, slight anemia, but
    resistant to malaria

Human Evolution and Origins
Human Evolution
  • Humans are known as Homo sapiens (modern man).
    The full classification is
  • Kingdom Animalia
  • Phylum Chordata
  • Subphylum Vertebrata
  • Class Mammalia
  • Subclass Eutheria
  • Order Primates
  • Suborder Anthropoids
  • Family Hominidae
  • Genus Homo
  • Species Sapiens

Human Evolution
  • Use Fossil Records as evidence
  • Use Carbon 14 Dating to see how old the fossil
    or artefact is.
  • For C14, the half-life is 5730 years.
  • For fossils and rocks older than 60 000 years, we
    use K40 dating.

Human Evolution Humans as Primates
  • What defines humans as primates?
  • Opposable Thumbs for grasping
  • Mobile arms with shoulder joints allowing
    movement in three planes and the bones of the
    shoulder allowing force to be applied to the
  • Stereoscopic vision
  • Skull Modified for upright posture Magnum

Trends in Hominid Fossils
  • Ardipithecus ramidus
  • Lived approximately 5.8 4.4 mya in Ethiopia

Trends in Hominid Fossils
  • Australopithecines
  • A. afarensis from the Afar desert (4-2.8 mya)
  • A. africanus (3-2 mya) found in South Africa.
  • A. robustus (2-1.4 mya) in South Africa.

Trends in Hominid Fossils
  • A. Africanus

Trends in Hominid Fossils
  • Homo genus.
  • They were from around 2 mya and had larger brains
    (600 cm3) and walked upright.
  • H. habilis (handy man). thought he arose from A.
    afarensis 2 mya in East Africa and used simple
  • Homo erectus was from Africa. It is thought it
    migrated to other parts of the world and had a
    larger brain than H. habilis.
  • H. neanderthalensis, which lived in Eurasia from
    200 000 to 30 000 years ago
  • Next was H. sapiens, which came to Europe.

Trends in Hominid Fossils
  • H. Habilis

Trends in Hominid Fossils
  • H. Erectus

Trends in Hominid Fossils
  • H. Neadrathalis

Trends in Hominid Fossils
Trends in Hominid Development
  • Hominid Diets and Brain Size
  • Australopithecus brains were only slightly larger
    in relation to body size than the brains of apes.
  • Powerful jaws meant a largely vegetarian diet.
  • 2.5 mya, Africa became drier, led to an evolution
    for survival, as there were less plants
  • Tools to hunt, increased supply of protein
    correspond to the changes in brain size

Trends in Hominid Development
  • Hominid Diets and Brain Size
  • The correlation between the change in diet and
    the increases in brain size can be explained in
    two ways
  • 1. Eating meat increases the supply of protein,
    fat and energy in the diet, making it possible
    for the growth of larger brains
  • 2. Catching and killing prey on the savannas is
    more difficult than gathering plant foods, so
    natural selection will have favoured hominids
    with larger brains and greater intelligence.

Trends in Hominid Development
  • Genetic and Cultural Evolution
  • In the recent evolution of humans, cultural
    evolution has been very important and has been
    responsible for most of the changes in the lives
    of humans over the last few thousand years.
  • This is much too short a period for genetic
    evolution to cause much change.
  • Some aspects of cultural evolution, ex. Medicine,
    have reduced natural selection between different
    genetic types and therefore, genetic evolution.

Taxonomy and Classification
Classification and the Binomial System
  • Classification
  • The process of classification involves giving
    every organism an agreed name and arranging
    organisms into groupings of apparently related
  • Scheme of the overall diversity of living things.
  • Classification attempts to reflect evolutionary

Classification and the Binomial System
  • The Binomial System
  • Carolus Linnaeus in the 18th Century
  • The first part of the name is the genus or the
    generic name based upon a noun.
  • The second name is the species, or the specific
    name, based upon an adjective.
  • Ex. Canis lupis dog / wolf and grey /brindled

Classification and the Binomial System
  • Scheme of Classification
  • Kingdom largest and most inclusive grouping
  • Phylum / division organisms constructed on a
    similar plan
  • Class a grouping of orders within a phylum
  • Order a group of apparently related families
  • Family- a group of apparently related genera
  • Genus - a group of similar and closely related
  • Species a group of organisms capable of
    interbreeding to produce fertile offspring

Classification and the Binomial System
  • Kingdoms
  • Prokaryotes Examples are bacteria and
  • Protista Examples are Euglena and Paramecium
  • Fungi Examples are yeasts and mushrooms.
  • Plantae Examples are mosses, ferns, flowering
  • Animalia - Examples are humans and jellyfish.

Classification and the Binomial System
  • Plantae Phyla
  • Bryophytes (mosses, liverworts)
  • Filicinophyta (ferns and horsetails)
  • Coniferophyta (cedars, junipers, fir, pine trees)
  • Angiospermophyta

Classification and the Binomial System
  • Animalia Phyla
  • Porifera (sponges)
  • Cnidaria (corals, sea anemones, jellyfish, sea
    jellies, hydra)
  • Platyhelminthes (flatworms)
  • Annelida (earthworms, leeches and polychaetes)
  • Mollusca (snails, clams, and octopi)
  • Arthropoda (insects, spiders, scorpions, and
    crustaceans (crabs, shrimp))

Classification and the Binomial System
  • Dichotomous Key

Mathematics of Population at EquilibriumHardy-We
inberg Principle
Hardy-Weinberg Principle
  • A mathematical formula to detect change or
    constancy in gene pools
  •  The formula
  • For 2 alleles of a gene
  • Use B for dominant, and its frequency in the
    population is p (a number between 0 1)
  • Use b for recessive, and its frequency in the
    population is q (a number between 0 1)
  • A gene must have an allele, with the options
    either B or b. No other options are available,
    so if B is present, it frequency is 1, and b is
    0, therefore p q 1 (10)
  • Each gene has two alleles, so if the frequency of
    B is p, then BB is p2
  • If the frequency of b is q, then bb is q2
  • If you have Bb, the frequency is 2pq

Hardy-Weinberg Principle
  • Since genotypes must be one of the three, the
    percentage in a population will be
  • p2 2pq q2 1
  • In order to be used, the following conditions
    need to be observed.
  • Large population
  • Random mating occurs
  • No directional selection (no advantage)
  • No allele specific mortality
  • No mutations
  • No immigration or emigration

Hardy-Weinberg Principle
Phylogeny and Systematics
Phylogeny and Systematics
  • One of the objectives of classification is to
    represent how living and extinct organisms are
    connected, which means natural classification.
  • Phylogeny
  • is the study of the evolutionary past of a
  • Species which are the most similar are most
    likely to be closely related
  • Species which show a higher degree of difference
    are considered less likely to be closely related.

Phylogeny and Systematics
  • Values to classifying this way.
  • Identify unknown organisms, as other similar
    organisms are grouped together using a key.
  • We can see how organisms are related in and
    evolutionary way. By looking at organisms, which
    have similar anatomical features, it is possible
    to see relationships on their phylogenetic tree.
    DNA evidence confirms the anatomical evidence for
    placing organisms in the same group.
  • It allows for the prediction of characteristics
    shared by members of a group.

Phylogeny and Systematics
  • Biochemical Evidence for Common Anscestry
  • Every known living organism on Earth uses DNA as
    its main source of genetic information
  • All the proteins found in living organisms use
    the same 20 amino acids to forms their
    polypeptide chains
  • All the living organisms on Earth have
    left-handed amino acids and none are
    right-handed, leading to the belief that there is
    a common ancestor.

Phylogeny and Systematics
  • If we compare the amino acid sequences of
    haemoglobin in humans, cats and earthworms, we
    see that cats and humans have greater
    similarities that humans and earthworms.
  • This shows several trends
  • The more similar the biochemical evidence, the
    more interrelated the species are
  • The more similar the evidence, there is less time
    since the two species had a common ancestor (ie.
    The ancestor of earthworms lived a longer time
    ago than the ancestor of cats and human.)
  • Changes in the DNA sequences of genes from one
    generation to another are partly due to mutations
    and the more differences there are between two
    species, the les closely related they are.

Phylogeny and Systematics

1 and 2 have the fewest differences in their DNA
and are more closely related
Phylogeny and Systematics
  • Cladogram

Phylogeny and Systematics
  • Cladistics
  • Clades
  • Need to classify, taking into account
  • Homologous Characteristics
  • Analogous Characteristics

Phylogeny and Systematics
Phylogeny and Systematics - Dinosaur
  • Birds
  • Reptiles
  • Fused clavicle (wishbone)
  • Flexible wrists
  • Hollow bones
  • Characteristic egg shell
  • Hip and leg structure, notably with backward
    pointed knees
  • Shoulder girdle
  • Strong skeletal system
  • Lay eggs
  • Lateral leg and hip structure