10.1: Early Ideas About Evolution

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10.1 Early Ideas About Evolution

• Objectives Examine early ideas about evolution.
• Identify three geological theories that
  influenced scientific debate over evolution.
• Warm Up Have you ever heard the expression,
  survival of fittest? What does it suggest to
  you? With evolution, what is it that survives?
• Words to Know Evolution, Species, Fossil,
  Catastrophism, Gradualism, Uniformitarianism.

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Early Scientists Proposed Ideas about Evolution

• Evolution is the process of biological change by
  which descendants come to differ from their
  ancestors.
• The concept had been discussed for more than 100
  years before Darwin proposed his theory.

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Carolus Linnaeus (1700s)

• Swedish botanist.
• Developed a classification system for all types
  of organisms known at the time.
• Did not believe that organisms were fixed and did
  not change.
• He proposed that they could change through
  hybridization.
• A Species is a group of organisms so similar to
  one another that they can reproduce and have
  fertile offspring.

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Georges Louis Leclerc de Buffon (1700s)

• French naturalist in the 1700s.
• He proposed that species shared ancestors instead
  of arising separately.
• He also suggested that the Earth was much older
  than the 6,000 years though by most.

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Erasmus Darwin (1700s)

• Charles Darwins grandfather.
• Respected English doctor and poet.
• Proposed all organisms evolved from a common
  ancestor and that more-complex forms of life
  arose from simpler forms of life.

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Jean-Baptiste Lamarck (1800s)

• French Naturalist (1809)
• Proposed that all organisms evolved toward
  perfection and complexity.
• Proposed changes in an environment caused an
  organisms behavior to change, leading to greater
  use or disuse of a structure or organ.
• The structure would become larger or smaller as a
  result.
• The organism could then pass these changes on to
  its offspring.
• Called the Inheritance of Acquired
  characteristics.
• Ex Giraffes had short necks ? They wanted to
  reach the leaves in the trees ? they stretched
  their necks long enough to reach the leaves ?
  over time their necks stayed long ? they passed
  these traits onto their offspring.
• HE WAS WRONG!!!
• What common ideas about organisms did these
  scientists share?

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Theories of Geologic Change Set the Stage for
Darwins Theory

• The early common view was that the Earth was
  about 6000 years old, and that neither the Earth
  or the species living on it had changed in that
  time.

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Georges Cuvier (1800s)

• Believed species could become extinct.
• Fossils are traces of organisms that existed in
  the past.
• He found that fossils in deeper layers of rock
  looked much different from those in the top
  layers.
• He explained is observations with the theory of
  Catastrophism.
• Catastrophism states that natural disasters such
  as floods and volcanic eruptions have happened
  often during Earths long history.
• These event shape landforms and caused species to
  become extinct.

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James Hutton (1700s)

• Scottish Geologist.
• Proposed the idea of Gradualism which states that
  landforms resulted from slow changes over a long
  period of time.
• Gradualism is a major component of evolutionary
  theory today.

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Charles Lyell (1800s)

• Published Principles of Geography in which he
  expanded on Huttons theory of gradualism into a
  theory of Uniformitarianism.
• Uniformitarianism states that the geologic
  processes that shape Earth are uniform through
  time.
• This soon replaced catastrophism as the favored
  theory of geologic change.
• What important concepts about Earth did Hutton
  and Lyell agree upon?

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Mining for Black Opal in the Desert that
used to be a Forest.
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10.2 Darwins Observations

• Objectives Describe how Darwin arrived at his
  idea about species variation.
• Recognize how Darwins discoveries supported
  Lyells ancient-Earth theory.
• Warm Up Thinking in terms of genetics, what is
  it about a cluster of islands that makes it a
  good laboratory for studying variation? What is
  it that the islands keep separate?
• Words to Know The Origin of Species, Variation,
  Adaptation

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Charles Darwin- the Father of Evolution

• He went on a voyage from 1831 1836 on the
  H.M.S. Beagle as the ships naturalist. The
  voyage went around the world and made a very
  important stop on the Galapagos Islands (a group
  of small islands off the west coast of South
  America). It was here that Darwin collected
  samples and observed the characteristics of many
  animals and plants varied noticeably among the
  different islands.
• Darwin began assembling his ideas upon his return
  from the voyage. However, he waited over twenty
  years (1859) before publishing his book On the
  Origin of Species. Because he was both stunned
  and disturbed by what he had observed/discovered
  as it challenged the fundamental scientific
  beliefs of that time (not to mention religious
  beliefs). Wallace, another scientist also had
  similar ideas.

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Darwin Observed Differences Among Island Species

• Darwin was struck by the variation in traits he
  observed on his travels.
• Variation is the difference in the physical
  traits of an individual from those of other
  individuals in the group to which it belong.
• Ex Different breeds of dogs.
• Darwin noted that the species found on one island
  looked different from those on nearby islands and
  that many of the species looked different from
  those on the mainland.
• The most notable differences he discovered were
  on the Galapagos islands, an island chain off the
  coast of Ecuador.

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Darwin Observed Differences Among Island Species

• Some difference seemed well suited to the
  animals environments and diets.
• Ex Saddle-back Tortoises, which have long
  necks and legs, lived in areas with a lot of tall
  plants.
• Domed tortoises, with their shorter neck
  and legs, lived in wet areas rich with mosses and
  short plants.

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Darwin Observed Differences Among Island Species

• Ex He noticed finches with strong, thick beaks
  lived in areas with a lot of large, hard-shelled
  nuts,while those species of
• finch with more delicate beaks were found where
  insects or fruit were widely available.
• What he noticed was adaptations.
• An Adaptation is a feature that allows an
  organism to better survive in its environment.
• Adaptations can lead to genetic change in a
  population over time.
• What adaptations did Darwin see in the finches of
  the Galapagos islands?

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Darwin Observed Fossil and Geologic Evidence
Supporting an Ancient Earth.

• Darwin found fossil evidence of species changing
  over time.
• He found large fossils in Argentina that looked
  like a larger version of current animals.
• He concluded that it must have taken a large
  amount of time in order for those changes to
  occur.
• Earth had to be more than 6000 years old.
• He also found marine fossils in the Andes
  mountains.
• He experienced an earthquake that showed him
  first hand how land underwater was forced above
  sea level.
• What could account for fossils of marine
  organisms being found on top of modern-day
  mountain ranges?

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10.3 Theory of Natural Selection

• Objectives Compare artificial selection to
  natural selection.
• Examine the factors Darwin considered in forming
  his theory of natural selection.
• Summarize the four principles of natural
  selection.
• Warm Up Why would Darwin turn to animal and
  plant breeders as a source of information in
  studying variation?
• Words to Know Artificial Selection,
  Heritability, Natural Selection, List 4 Main
  Principles to the Theory of Natural Selection,
  Fitness

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Artificial Selection

• Artificial selection is the process by which
  humans change a species by breeding it for
  certain traits.
• Humans then determine which traits are favorable
  and then breed individuals that show those
  traits.
• Heritability is the ability of a trait to be
  passed down from one generation to the next.
• Darwin compared what he learned about breeding to
  his ideas on adaptation.
• He concluded that those traits that were not
  beneficial could be selected out.
• Darwin applied his views to the Theory of
  Natural Selection.
• Natural Selection is a mechanism by which
  individuals that have inherited beneficial
  adaptations produce more offspring on average
  than do other individuals.
• In nature, the environment is the selecting agent.

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Struggle for Survival

• Thomas Malthus proposed that resources such as
  food, water, and shelter were natural limits to
  population growth.
• That is, human populations would grow
  geometrically if resources were unlimited.
• Instead disease and a limited food supply kept
  the population smaller.
• Darwin reasoned a similar situation took place in
  nature.
• Darwin proposed that these adaptations arose over
  many generations and called this process of
  evolution descent with modification.
• How did Malthuss economic theory influence
  Darwin?

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Natural Selection Explains how Evolution Can Occur

• There are 4 main principles to the theory of
  natural selection
• 1. Variation
• The heritable differences that exist in every
  population are the basis for natural selection.
• The differences among individuals result from
  differences in the genetic material of the
  organisms, whether inherited from a parent or
  resulting from a genetic mutation.

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Natural Selection Explains how Evolution Can Occur

• 2. Over-reproduction
• While having many offspring raises the chance
  that some will survive, it also result in
  competition between offspring for resources.

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Natural Selection Explains how Evolution Can Occur

• 3. Adaptation
• Certain variations allow some individuals to
  survive better than others.
• More successful individuals are naturally
  selected to live longer and to produce more
  offspring that share those adaptations for the
  environment.

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Natural Selection Explains how Evolution Can Occur

• 4. Descent with Modification
• Over time, natural selection will result in
  species with adaptations that re well suited for
  survival and reproduction in an environment.
• More individuals will have the trait in every
  following generation, as long as the
  environmental conditions stay the same.
• Examples Jaguars
• 11,000 years ago, many species faced extinction.
• Jaguars faced a shortage of food due to climate
  change. Mammals were less available, but
  reptiles were numerous.
• Jaguars with larger jaws and teeth were better
  able to survive and thus pass those traits onto
  their offspring.
• In Biology, the term Fitness is a measure of the
  ability to survive and produce more offspring
  relative to together member of the population in
  a given environment.
• What are the similarities and differences between
  natural selection and artificial selection?

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Changing Environments

• Ecologists observed an example of natural
  selection acting on existing traits within a
  population of medium ground finches on one of the
  Galapagos Islands.
• A drought in 1977 suddenly reduced the amount of
  small, soft seeds that the finches preferred.
• However there were still plenty of large,
  tough-shelled seeds.
• Because the large-beaked finches in the
  population were able to crack the large, tough
  seeds, they did not starve.
• The next year, they noticed a big increase in
  they number of large-beak hatchlings and most of
  the smaller beaked birds died.

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Adaptations as Compromises

• Not all adaptations result in individuals that
  are perfectly suited to their surroundings.
• Ex Pandas have a structure in their wrist that
  acts like a thumb. The thumb is actually an
  enlarged wrist bone that they use to help hold
  bamboo. It is not considered a true thumb
  though.
• Why is the pandas thumb considered an adaptive
  compromise?

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10.4 Evidence of Evolution

• Objectives Recognize the major sources of
  evidence for evolution.
• Examine the pattern of features that reveal the
  history of a species.
• Warm Up Why are the larger fossil organisms so
  different from the animals on Earth today?
• Words to Know List all 9 Evidence of Evolution
  with definitions.

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Evidence of Evolution1. Fossils

• In the late 1700s geologists wondered why
  certain types of fossils were found in some
  layers of rock and not others.
• Later studies suggested that the fossil organisms
  in the bottom, or older, layers were more
  primitive than those in the upper or newer layers.

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Evidence of Evolution2. Biogeography

• Recall that Darwin saw that island plants and
  animals looked like, but were not identical to,
  species on the South American continent...
• He hypothesized that at some point in the past,
  some individuals from the South American mainland
  had migrated to the islands.
• Different ecosystems favored different traits and
  there speciation occurred.
• Biogeography is the study of the distribution of
  organisms around the world.

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Evidence of Evolution3. Comparative Embryology

• A study proposing a relationship between crabs,
  which can walk, and barnacles, which are fixed in
  one place as adults, fascinated Darwin.
• He noticed that immature crabs and barnacles
  looked similar, but the adults were different.
• Comparative embryology now studies those
  similarities between organisms.
• Another example pharyngeal pouches and tails
  as embryos in a variety of chordates.

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Evidence of Evolution4. Homologous Structures

• Homologous structures are features that are
  similar in structure but appear in different
  organisms and have different functions.
• Ex forelimbs of tetrapod vertebrates (human
  hand, bat wing and mole foot).
• The limbs look very similar even though they have
  different functions.

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Evidence of Evolution5. Analogous Structures

• Analagous Structures are structures that perform
  a similar function but are not similar in origin.
• Ex Bat wings and insect wings are both used for
  flight, but are NOT similar in structure.
• Using the terms homologous and analogous,
  identify which group of structures provides
  evidence for a common ancestor? Explain.

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Evidence of Evolution6. Vestigial
StructuresStructural Patterns are Clues to the
History of a Species

• Some organisms have structures or organs that
  seem to lack any useful function, or at least are
  no longer used for their original purpose.
• Vestigial Structures are remnants of organs or
  structures that had a function in an early
  ancestor.
• Ex Snakes share a common ancestor with lizards
  and dogs. The tiny pelvic bones and hind limbs
  in many snakes are vestigial structures.
• Ex The appendix in humans. It is a remnant of
  part of the large intestine and was used to help
  digest cellulose.
• What are vestigial structures, and how do they
  demonstrate common ancestry?

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Evidence of Evolution7. Comparative
Biochemistry

• Comparative Biochemistry Study of an organism on
  a biochemical level for example the
  similarities of amino acids in hemoglobin of the
  blood of various vertebrates.

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Evidence of Evolution8. Genetic Evidence and 9.
Direct Observations

• Genetic Evidence for example DNA similarities
  between people in certain parts of the world
  compared to people in other parts of the world.
• Direct Observations observations of evolutionary
  changes that occur rapidly for example
  penicillin-resistant bacteria

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10.5 Evolutionary Biology Today

• Objectives Summarize different types of
  evidence that support evolution.
• Recognize the importance of evolution I unifying
  all branches of biological study.
• Warm Up What was Darwins mechanism for
  explaining the diversity of life? Mendels
  mechanism?
• Words to Know Paleontology

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Fossils Provide a Record of Evolution

• Paleontology is the study of fossils or extinct
  organisms.
• The fossil record is not complete because most
  living things do not become fossils after they
  die.
• NO fossil evidence has ever contradicted
  evolution.
• Many transitional fossils have been discovered
  since Darwins work to help support his theories.
• Why are fossils such as Basilosaurus isis
  considered transitional fossils?

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Transitional Fossil Evidence

• http//www.nature.com/nature/videoarchive/ancientw
  hale/

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Transitional Fossil Evidence

• What has the head of a crocodile and the gills of
  a fish?
• Tiktaalik of course, this 375 million year old
  fossil splashed across headlines as soon as its
  discovery was announced in April of 2006.
• It is technically a fish, complete with scales
  and gills but it has the flattened head of a
  crocodile and unusual fins.
• It has a combination of features that show the
  evolutionary transition between swimming fish and
  their descendents, the four-legged vertebrates
  a clade which includes amphibians, dinosaurs,
  birds, mammals, and of course, humans.

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Molecular and Genetic Evidence

• Because all living things have DNA, they share
  the same genetic code and make most of the same
  proteins from the same 20 amino acids.
• DNA or protein sequence comparisons can be used
  to show probable evolutionary relationships
  between species.

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DNA Sequence Analysis

• The sequences of nucleotides in a gene change
  over time due to mutations.
• DNA sequence analysis depends on the fact that
  the more related two organisms are, the more
  similar their DNA will be.
• Pseudogenes
• Sequences of DNA nucleotides known as pseudogenes
  also provide evidence of evolution.
• Pseudogenes are like vestigial structures.
• They no longer function but still are carried
  with functional DNA.

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Homeobox Genes

• Homeobox genes control the development of
  specific structures.
• These sequences are found in everything from
  fruit flies to humans.
• Protein Comparisons
• Similarities among cell types across organisms
  can be revealed by comparing their proteins, a
  technique called molecular fingerprinting.
• Cells from different species that have the same
  proteins most likely come from a common ancestor.
• Ex light-sensitive cells from an ancient marine
  worm were found to closely resemble those of
  cells in the vertebrate eye.
• How have protein comparisons helped determine
  ancestral relationships between organisms?

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Evolution Unites ALL Fields of Biology

• Scientists are still actively studying evolution.
• The theory of evolution combined with genetics is
  sometimes called the Modern Synthesis of
  Evolutionary Theory.
• The field of evolutionary biology is growing
  fast.
• The basic principles of evolution are used in
  fields such as medicine, geology, geography,
  chemistry, and ecology.
• How can the idea of a common ancestor help us
  understand new diseases?