Evolution€¦ · Lamarck’s Evolution Hypothesis •Jean-Baptiste Lamarck- proposed that by...

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EVOLUTION Chapters 15-17

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  • EVOLUTION Chapters 15-17

  • Warm Up Exercise

    • Please complete the evolution pretest that you

    picked up as you came in.

  • Darwin’s Theory of Evolution

    • Evolution- “change over time”- the process by

    which modern organisms have descended from

    ancient organisms.

    • Theory- a well-supported, testable explanation of

    phenomena that have occurred in the natural


    • Charles Darwin- joined the crew of the

    HMS Beagle and set sail for a voyage

    around the world. During his travels,

    Darwin collected evidence that led him

    to propose the theory of evolution.

  • Darwin’s Theory of Evolution

    • Galapagos Islands- Darwin observed that the

    characteristics of many animals and plants varied

    noticeably among the different islands of the


  • Exit Slip

    • Darwin found fossils of many organisms that were

    different from any living species. How would this

    finding have affected his understanding of life’s


  • Warm Up Exercise

    • Define evolution.

    • Why is evolution referred to as a theory?

  • An Ancient, Changing Earth

    • James Hutton- proposed that layers of rock form

    slowly and that rocks are shaped by natural

    forces that operate over millions of years.

    • Charles Lyell- wrote Principles of Geology,

    which explained that processes that changed

    Earth in the past are still operating in the present.

  • Lamarck’s Evolution Hypothesis

    • Jean-Baptiste Lamarck- proposed that by

    selective use or disuse of organs, organisms

    acquired or lost certain traits during their lifetime.

    These traits could then be passed on to their

    offspring. Over time, this process led to change

    in a species.

    • Lamarck’s hypothesis is now known to be incorrect.

    While organisms to adapt to their environment, an

    organism’s behavior has no effect on its heritable


  • Population Growth

    • Thomas Malthus- reasoned that if human

    population continued to grow unchecked, sooner

    or later there would be insufficient living space

    and food for everyone.

  • Darwin Presents His Case

    • Alfred Russel Wallace- a naturalist, like Darwin,

    who wrote an essay summarizing his thoughts on

    evolutionary change.

    • On the Origin of Species- Darwin’s book,

    published in 1859. Here he poses a mechanism

    for evolution that he called natural selection.

  • Exit Slip

    • What did Hutton, Lyell, Lamarck and Malthus

    teach us about evolution?

  • Warm Up Exercise

    • What did you observe about the different

    appendages in the lab from last class? What

    happened if one appendage didn’t serve its

    purpose very well?

    • Can you think of an example of evolution that you


  • Inherited Variation and Artificial Selection

    • Artificial Selection- nature provides the variation

    and humans select the variations that they find


  • Evolution By Natural Selection

    • Struggle for Existence- members of each species

    compete to obtain food, living space, and other

    necessities of life.

    • Fitness- the ability of an individual to survive and

    reproduce in its specific environment.

    • Adaptation- any inherited characteristic that increases an

    organism’s chance for survival.

    • Successful adaptations enable organisms to become better suited

    to their environment and thus better able to survive and reproduce.

  • Evolution By Natural Selection

    • Survival of the Fittest- individuals that are better

    suited to their environment and have adaptations

    that enable fitness, survive and reproduce most

    successfully. Individuals with characteristics that

    are not well suited to their environment have low

    levels of fitness, and either die or leave few


    • Darwin referred to this idea as natural selection.

    • Over time, natural selection results in changes in the

    inherited characteristics of a population. These

    changes increase a species’ fitness in its environment.

  • Descent with Modification

    • Descent With Modification- over time, natural

    selection produces organisms that have different

    structures and establish different niches. As a

    result, species today look different from their


    • Common Descent- all species- living and

    extinct- are derived from common ancestors,

    therefore a single “tree of life” links all living


  • Evidence of Evolution

    • The fossil record

    • Geographic distribution of

    living species

  • Evidence of Evolution

    • Homologous body structures

    • Homologous Structures- structures that have different

    mature forms but develop from the same embryonic


    • Vestigial Organs- organs that are reduced in size that

    they are traces of homologous organs in other species.

  • Evidence of Evolution

    • Similarities in embryology/early


  • Summary of Darwin’s Theory

    • Individual organisms differ and some of this variation is


    • Organisms produce more offspring than can survive and

    many that do survive do not reproduce.

    • Because more organisms are produced than can survive,

    they compete for limited resources.

    • Each unique species has different advantages and

    disadvantages in the struggle for existence.

    • Species alive today are descended with modification from

    ancestral species. They evolved from common ancestors

    which unites all organisms in a single tree of life.

  • Warm Up Exercise

    • Name three bits of evidence that scientists have

    provided to support the theory of evolution.

  • Genes and Variation

    • Changes in genes produce heritable variation on which

    natural selection can operate.

    • Gene Pool- consists of all genes, including all the

    different alleles that are present in a population.

    • Relative Frequency- the number of times an allele

    occurs in a gene pool, compared with the number of times

    other alleles for the same gene occur.

    • Typically expressed as a percentage.

    • Has nothing to do with dominant/recessive.

    • In genetic terms, evolution is any change in the relative

    frequency of alleles in a population.

  • Sources of Genetic Variation

    • Mutations

    • A mutation is any change in the DNA sequence, but mutations do

    not always affect an organism’s phenotype.

    • Mutations can be harmful, beneficial, or neutral.

    • Gene Shuffling (in sexual reproduction only)

    • The 23 pairs of chromosomes found in humans can form 8.4 million

    different combinations of genes- before crossing over.

    • Gene shuffling produces many different combinations of genes, but

    does not alter the relative frequencies of each type of allele in the


  • Single Gene and Polygenic Traits

    • The number of phenotypes produced for a given trait

    depends on how many genes control the trait.

    • Single Gene Trait- a trait controlled by a single gene with

    two alleles. (ex: widow’s peak)

    • Polygenic Trait- a trait controlled by two or more genes.

    Each of these genes often has two or more alleles. As a

    result, one polygenic trait can have many possible

    genotypes and phenotypes. (ex: height in humans)

  • Exit Slip

    • In genetic terms, what indicates that a poluation

    is evolving?

    • What two processes can lead to inherited

    variation in populations?

    • How does the range of phenotypes differ between

    single-gene traits and polygenic traits?

    • How does mutation affect genetic variation?

  • Warm Up Exercise

    • What are the two main sources of genetic variation?

    • What is the relationship between relative frequency and

    the gene pool?

  • Natural Selection on Single Gene Traits

    • Populations evolve, not individual organisms.

    • Natural selection on single-gene traits can lead to

    changes in allele frequencies and thus to evolution.

  • Natural Selection on Polygenic Traits

    • Directional Selection- when individuals at one end of the

    curve have higher fitness than individuals at another end

    of the curve, directional selection takes place.

  • Natural Selection on Polygenic Traits

    • Stabilizing Selection- when individuals near the center of

    the curve have higher fitness than individuals at either

    end of the curve, stabilizing selection takes place.

  • Natural Selection on Polygenic Traits

    • Disruptive Selection- when individuals at the upper and

    lower ends of the curve have higher fitness than

    individuals near the middle, disruptive selection takes


  • Genetic Drift

    • Genetic Drift- random change in allele frequencies that

    occurs in small populations

    • Founder Effect- allele frequencies change as a result of

    the migration of a small subgroup of a population.

  • Evolution vs. Genetic Equilibrium

    • Hardy-Weinberg Principle- allele frequencies in

    a population will remain constant unless one or

    more factors cause those frequencies to change.

    • Genetic Equilibrium- the situation in which allele

    frequencies remain constant.

  • Evolution vs. Genetic Equilibrium

    • Five conditions are required to maintain genetic


    • There must be random mating.

    • The population must be very large.

    • There can be no movement into or out of the


    • There can be no mutations

    • There can be no natural selection.

    If these conditions are not met, then equilibrium

    will be disrupted and the population will evolve.

  • Exit Slip

    • Draw a graph for each of the three types of

    natural selection.

  • Warm Up Exercise

    • What five statements must hold true in order to

    maintain genetic equilibrium- according to Hardy


  • Speciation

    • Speciation- the formation of new species.

    • As new species evolve, populations become

    reproductively isolated from each other.

    • Reproductive Isolation- when the members of

    two populations cannot interbreed and produce

    fertile offspring.

  • Types of Reproductive Isolation

    • Behavioral Isolation- occurs when two populations are

    capable of interbreeding but have differences in courtship

    rituals or other reproductive strategies that involve

    behavior. (ex: birds with different mating songs)

    • Geographic Isolation- two populations are separated by

    geographic barriers such as rivers, mountains, or bodies

    of water. (ex: Colorodo river separates two types of


    • Temporal Isolation- two or more species reproduce at

    different times. (ex: flowers releasing pollen at different

    times of year)

  • Testing Natural Selection in Nature

  • Speciation in Darwin’s Finches

    • Founders Arrive- finches from South American mainland (species

    A) populated the Galapagos.

    • Geographic Isolation- birds from species A crossed to another

    Galapagos island. The two populations became isolated from one

    another and had different gene pools.

    • Changes in the Gene Pool- populations on the new island adapted

    to their environment, forming population B.

    • Reproductive Isolation- because of their adaptations and different

    beaks, species A and B do not mate together if they come in


    • Ecological Competition- during dry season, individuals compete for

    food, and over time birds evolve better beaks (species C).

    • Continued Evolution- this process continues over several

    generations and over times produces the 13 species seen today.

  • Exit Slip

    • Suppose that drought on an island eliminates all

    but plants that produces large, tough seeds. All

    the finches on the island have very small beaks.

    How might this environment change impact the

    survival of this finch population?

  • Warm Up Exercise

    • Provide an example for each of the three types of

    reproductive isolation.

  • Fossils and Ancient Life

    • Paleontologists- scientists who study fossils.

    • Fossil Record- provides evidence about the

    history of life on Earth. It also shows how

    different groups of organisms, including species,

    have changed over time.

  • How Fossils Form

    • For a fossil to form, either

    the remains of the

    organism or some trace of

    its presence must be


  • Interpreting Fossil Evidence

    • Paleontologists determine the age of fossils using

    two techniques: relative dating and radioactive


    • Relative Dating- the age of a fossil is determined by

    comparing its placement with that of fossils in other

    layers of rock.

    • Radioactive Dating- scientists calculate the age of a

    sample based on the amount of remaining radioactive

    isotopes it contains.

  • Geologic Time Scale

    • Geologic Time Scale-

    divisions used to

    represent evolutionary


    • Geologists divide time into

    four major eras:

    precambrian, the paleozoic,

    the mesozoic, and the

    cenozoic eras.

    • Each era is subdivided into


  • Geologic Time Scale

    • Precambrian

    • 88% of Earth’s history.

    • Few multicellular fossils.

    • Paleozoic

    • Many vertebrates and invertebrates lived during the Paleozoic.

    • Mesozoic

    • “The Age of the Dinosaurs”

    • Mammals began to evolve during the mesozoic.

    • Cenozoic

    • “The Age of the Mammals”

    • The last 65 million years.

  • Exit Slip

    • What are the four eras on the geologic time


    • What is the difference between radioactive dating

    and relative dating?

  • Warm Up Exercise

    • On the half sheet of paper you picked up when

    you came in, tell me what you did on your spring

    break? Can you relate anything you did to

    science in any way?

  • FlashBack

    • What are the three parts of cell theory?

    • What is transcription/translation?

  • Formation of Earth

    • Geologic evidence shows that Earth is about 4.6

    billion years old and was created over many


    • Earth was formed from cosmic debris which

    compounded on one another over the course of

    millions of years.

    • Early Earth was extremely hot, and unsuitable for

    life because of violent earthquakes and asteroid


  • First Organic Molecules

    • 1950s- Stanley Miller and Harold Urey tried to

    simulate conditions of early Earth in the


    • Filled flask with fluids and gases similar to those in

    Earth’s early atmosphere. Passed electric sparks

    through this mixture to simulate lightning. Their

    experiments produced amino acids, the building blocks

    of _______?________.

  • The Puzzle of Life’s Origins

    • Insert figure 17.10

  • Free Oxygen

    • Microfossils of unicellular organisms resembling

    bacteria have been found in rocks more than 3.5

    byo, which means that they must have evolved in

    the absence of oxygen, because there was

    little/no oxygen in Earth’s early atmosphere.


    • Photosynthetic organisms evolved later, which

    created a rise in oxygen levels in the atmosphere.

    This change likely caused some organisms to

    become extinct, while others evolved more

    efficient respiration mechanisms which utilized


  • The Endosymbiotic Theory

    • One large prokaryotic cell, engulfed several other

    smaller prokaryotic cells with specialized

    functions. Together these cells lived symbiotically

    and were interdependent on one another.

    Collectively, they formed the first eukaryotic cell,

    which went on to divide and give rise to other

    eukaryotic cells.

  • The Endosymbiont Theory Plantsad



  • Warm Up Exercise

    • What were the first type of cells on earth?


    • How did early organisms breath?


    • Could humans have survived on early earth?

    Why or why not?

    • How old is Earth?

    • What does the endosymbiotic theory say?

  • Patterns of Evolution

    • Macroevolution- the large scale evolutionary

    patterns and processes that occur over long

    periods of time.

    • Extinction

    • More than 99% of all species that have ever lived are

    now extinct.

    • Several times in earth’s history, mass extinctions wiped

    out entire ecosystems.

    • Each mass extinction provides opportunities for

    organisms that survive and often results in a burst of

    evolution that produces many new species.

  • Patterns of Evolution

    • Adaptive Radiation- when a single species or

    small group of species evolves into several

    different forms that live in different ways.

  • Patterns of Evolution

    • Convergent Evolution- unrelated organisms

    independently evolve similarities when adapting

    to similar environments.

    • Analogous Structures- structures which look and

    function similarly but are made up of parts that do not

    share a common evolutionary history.

  • Patterns of Evolution

    • Coevolution- when two species evolve in

    response to changes in each other.

  • Patterns of Evolution

    • Punctuated Equilibrium- when long stable

    periods are interrupted by brief periods of more

    rapid change.

    • Gradualism- the idea that biological change is slow and

    steady. (supported by Darwin)

    • Scientists suggest that most new species are produced

    by periods of rapid change, because organisms evolve

    rapidly to fill available niches.

  • Patterns of Evolution

    • Developmental Genes and Body Plans

    • Hox Genes- guide development of major body

    structures in animals.

  • Exit Slip

    • Darwin's species of finches were very similar but different in beak size and feeding habits. This is an example of

    • convergent evolution.

    • coevolution.

    • adaptive radiation.

    • stabilizing selection.

    • A slow steady change in a particular line of descent is called

    • coevolution.

    • gradualism.

    • punctuated equilibrium.

    • convergent evolution.

    • Master control genes are called

    • hox genes.

    • developmental genes.

    • embryonic genes.

    • regulatory genes.

  • Exit Slip

    • Some evidence suggests that species do not change much over

    long periods of time and then undergo relatively short periods of

    rapid speciation. This kind of change is called

    • coevolution.

    • genetic equilibrium.

    • adaptive radiation.

    • punctuated equilibrium

    • Fossil evidence shows that mass extinctions

    • ended the existence of many species in a short period of time.

    • occurred mainly when the dinosaurs disappeared.

    • require an asteroid strike to occur.

    • caused convergent evolution among animals.