Ch. 15 Darwin

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Ch. 15 Darwins Theory of Evolution

• You can acquire new pants, but you cant change
  your GENES!

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Ch. 15 Outline

• 15-1 The Puzzle of Lifes Diversity
• The Voyage of the Beagle
• Darwins Observations
• The Journey Home

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151 The Puzzle of Life's Diversity

• What scientific explanation can account for the
  diversity of life?
• The answer is a collection of scientific facts,
  observations, and hypotheses known as the theory
  of evolution

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• Evolution is defined as change over time.
• Evolution describes the process by which modern
  organisms have descended from ancient organisms.
• A scientific theory is a well-supported testable
  explanation of phenomena that have occurred in
  the natural world.

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• What process is described by the Theory of
  Evolution?
• How modern organisms have descended from ancient
  organisms.

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15-1 Voyage of the Beagle

• Charles Darwin contributed more to our
  understanding of evolution than any other
  scientist
• Charles Darwin was born in England in 1809
• In 1831 Darwin joined the crew of the H.M.S.
  Beagle as the ships naturalist

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Voyage of the Beagle

• The voyage of the Beagle lasted five years

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15-1 Voyage of the Beagle

• Darwin made numerous observations and collected
  many plant, animal and fossil specimens
• This led Darwin to propose a hypothesis about
  the way life changes over time.
• This hypothesis is now called the theory of
  evolution.

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15-1 Darwins Observations

• Patterns of diversity
• Many plants and animals seemed well suited to
  their environment

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15-1 Darwins Observations

• Patterns of diversity
• Organisms survived and reproduced in many
  different ways
• Not all organisms lived everywhere

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• What three patterns of diversity did Darwin
  observe in organisms?
• The organisms were well suited to their
  environment, survived and reproduced in different
  ways, lived in a variety of places

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15-1 Darwins Observations

• Darwin collected fossils
• Fossil Are preserved remains of ancient
  organisms
• Some fossils Darwin collected resembled living
  organisms

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15-1 Darwins Observations

• Some fossils did not resemble any living organisms

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• As Darwin studied fossils, new questions arose.
• Why had so many of these species disappeared?
• How were they related to living species?

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15-1 Darwins Observations

• Darwins thoughts were greatly influenced by his
  collection and observation of species on his
  visit to the Galapagos Islands.

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15-1 Darwins Observations

• The Galapagos Islands
• Are off the west coast of South America
• Each Island has a different climate and different
  organisms

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• Darwin noticed that the birds had different
  shaped beaks on each island

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15-1 Darwins Observations

• Darwin noticed that the tortoises had different
  shaped shells on each island

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15-1 The Journey Home

• After returning to England, Darwin wondered if
  animals living on different islands had once been
  members of the same species.

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15-1 The Journey Home

• According to this hypothesis, these separate
  species would have evolved from an original South
  American ancestor species after becoming isolated
  from one another.
• This hypothesis challenged the accepted views on
  the age of the earth and the origin of different
  species.
• Darwin did not publish his thoughts until
  twenty-three years after his voyage on the
  Beagle.

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• What did Darwin hypothesize about the diversity
  of the species on the Galapagos Islands?
• The different species evolved from a common
  ancestor after they became isolated from each
  other.

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Ch. 15 Outline

• 15-2 Ideas that Shaped Darwins Thinking
• An Ancient, Changing Earth
• Lamarcks Evolution Hypotheses
• Population Growth

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152 Ideas That Shaped Darwin's Thinking

• About the same time Darwin was questioning the
  origin of life, other people were traveling
  around the world and making important
  discoveries.
• They also began to challenge established views
  about the natural world.

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152 Ideas That Shaped Darwin's Thinking

• Some people, however, found Darwin's ideas too
  shocking to accept.
• Most Europeans in Darwin's day believed that the
  Earth and all its forms of life had been created
  only a few thousand years ago.

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An Ancient, Changing Earth

• James Hutton and Charles Lyell were two
  geologists whose ideas influenced Darwin
• Hutton proposed that layers of rock form very
  slowly and others are pushed up from the sea
  floor to form mountains. (This takes a long time)

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Lyells Principles of Geology

• Lyell believed that the same processes that
  changed the Earth in the past still operate in
  the present.

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• Lyells and Huttons work influenced Darwin in
  two ways
• 1) If the Earth can change over time
  (earthquakes, volcanoes) maybe life can change
  over time!

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• 2) Life can change over time only if the earth is
  very old.

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• Why did Darwins, Huttons and Lyells view of
  the age of the earth was not accepted by some
  scientists?

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152 Ideas That Shaped Darwin's Thinking

• Jean-Baptiste Lamarck and Thomas Malthus were two
  other scientists who shaped Darwins thinking
• Lamarck proposed that new species changed over
  time by gaining or loosing certain traits in
  their lifetimes.

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152 Ideas That Shaped Darwin's Thinking

• Lamarck had two ideas
• Organisms can alter their bodies by use and
  disuse
• Use Use a structure and it will change
• Disuse Structures not used will disappear
• Acquired characteristics can be inherited.
• If you increase your muscle mass your children
  will inherit your big muscles

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Use and Disuse
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Lamarcks Evolution Hypotheses

• Although Lamarcks ideas were incorrect, he was
  one of the first ones to realize that organisms
  are adapted to their environments and propose a
  theory of evolution.

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• What are some acquired traits that are found in
  people today?

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152 Ideas That Shaped Darwin's Thinking

• Another influence of Darwin was Thomas Malthus.
• Malthus published a book in which he stated that
  babies were being born faster than people were
  dying. If the trend continued
• food and living space will run out.

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Population Growth

• Darwin thought this theory applied more to plants
  and other animals because humans usually only
  have one offspring at a time.

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• How did Lamarcks and Malthus theories influence
  Darwin?

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Ch. 15 Outline

• 15-3 Darwin Presents His Case
• Publication of On the Origin of Species
• Inherited Variation and Artificial Selection
• Evolution by Natural Selection
• Evidence of Evolution
• Summary of Darwins Theory

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15-3 Darwin Presents His Case

• When Darwin returned to England in 1836, he
  continued to study the specimens he collected
  from the Galapagos Islands.
• Darwin discovered that the birds, tortoises, and
  plants that he collected looked like similar
  species on the South American mainland.
• However, the island species were different from
  each other and the mainland species.

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Darwin Presents his Case

• Over 20 years later, Darwin published all his
  findings in a book called, On the Origin of
  Species.
• He didnt publish it earlier because it went
  against the common beliefs about organisms.

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Darwin Presents his Case

• Not only did Darwin propose the theory of
  evolution, he also proposed a mechanism of how
  evolution happens
• The mechanism for evolution is called natural
  selection

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Inherited Variation and Artificial Selection

• One of Darwins most important insights is that
  there is a lot of diversity within all species
• In inherited variation, organisms pass on their
  traits to their offspring. This randomly occurs
  in nature.

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Inherited Variation and Artificial Selection

• In artificial selection, humans select for
  variations in nature that are useful.
• The breeding of domestic animals and plant crops
  are examples.

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Evolution by Natural Selection

• Next, Darwin compared natural selection and
  artificial selection, and proposed his mechanism
  of how evolution occurs.
• Darwin realized that organisms competed for
  resources. This is called the struggle for
  existence.

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Evolution by Natural Selection

• Darwin noted that organisms better suited to
  their environment (ex. Run faster, hide from
  predators) survived to reproduce and pass on
  their genes.
• This is called survival of the fittest.

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Evolution by Natural Selection

• Fitness The ability of an animal to survive and
  reproduce
• Adaptation an inherited characteristic that
  increases an organisms chance of survival

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Evolution by Natural Selection

• Successful adaptations, Darwin enables organisms
  to survive and reproduce.
• Types of adaptations
• Structures
• Physiological processes
• Behavior

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Evolution of Natural Selection

• Survival of the fittest individuals that are
  better suited for their environment survive and
  reproduce most successfully. This is called
  Natural Selection
• Over time, natural selection results in changes
  in the inherited characteristics of a population.
  These changes increases a species fitness in
  its environment.

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Evolution of Natural Selection

• Darwin proposed that over long periods of time,
  natural selection produces organisms that have
  different structures. Species today look
  different than their ancestors
• Descent with Modification Each living species
  has descended, with changes from other species
  over time.

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Evolution of Natural Selection

• Descent with modification implies that all living
  species are related to each other
• All species, living and extinct were derived from
  a common ancestor

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15-3 Evidence of Evolution

• Fossil Record
• Geographic Distribution of Living Species
• Homologous Body Structures
• Embryology

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Fossil Cephalopods           Darwin argued that
the fossil record provided evidence that living
things have been evolving for millions of years.
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Evidence of Evolution

• Geographic Distribution of Living Species
• Similar organisms found in different places on
  Earth
• Ex Darwins Finches
• Organisms under the same environmental
  pressures in different locations had similar
  adaptations

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Homologous Body Structures

• Structures that have different mature forms but
  develop from the same embryonic tissues
• Ex. Wings and arms
• Help Scientist determine common ancestors
• Not all homologous structures serve important
  functions

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Homologous Structures
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish
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Homologous Body Structures

• Vestigial Organs Organs reduced in size (Traces
  of homologous organs in other species)
• Have little or no function

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Embryology

• Organisms that have similar developmental stages
  as embryos are more closely related to each other.

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Summary of Darwins Theory

1. Individual organisms differ, and some of this
   variation is inheritable
2. Organisms produced more offspring that can
   survive and there is competition for limited
   resources
3. Individuals best suited to environment survive
   and reproduce. Others die or leave fewer
   offspring. This process of natural selection
   causes species to change over time.
4. Species alive today are descended with
   modifications.