Download Chapter 15 Darwin`s Theory of Evolution

Chapter 15
Darwin’s Theory of Evolution
15.1 The Puzzle of Life’s Diversity
15.2 Ideas that shaped Darwin’s
Thinking
15.3 Darwin Presents his case
15.1 The Puzzle of Life’s Diversity
I. Voyage of the Beagle
II. Darwin’s Observations
III. The Journey Home
• Variety / diversity
• Evolution – changes over time
• Theory – well supported
Voyage of the Beagle
• Charles Darwin – England, 1809- , 1831
set sail, observations, collected evidence,
documented, theory of evolution,
explanation of diversity of life.
Darwin’s Observations
• Patterns of Diversity
• Living organisms and fossils
• The Galapagos Islands
• Observed beak varieties on island
• Seeds, worms, bugs, tree insects, fish
Patterns of Diversity
• Impressed by how well-suited plants and
animals were to environment
• Why were some animals and plants in
areas but other others of the same habitat
had none? No rabbits in Australia, No
kangaroos in England.
Living organisms and fossils
• Geology influences
• Extinct organisms
• Why did they become extinct?
The Galapagos Islands
• Most influential of stops
• Different climates: dry, hot, wet, desert,
rainforest, etc.
• Tortoises, iguanas, birds, seeds
The Journey Home
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Examined specimen
Reread notes/journal
Characteristic varied from island to island
Could these animals and plants come from
an original parent and changed?
15.2 Ideas that shaped Darwin’s
Thinking
• I. An Ancient, Changing Earth
• II. Lamarck’s Evolution Hypotheses
• III. Population Growth
• Times of Darwin: explosion of knowledge, not
easy to share, earth was only a few thousand
years old, no continental drift, natural disasters
caused most land, theory of creation, too much
change for most to accept
I. An Ancient, Changing Earth
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Earth is older than 3 thousand years
Bible
Family stories
evidences
James Hutton
• 1795 layers of rock slowly moved up to
form earth
• Natural forces formed valleys
• For this to take place the earth must be
millions of years old
Hutton
Lyell’s principles of Geology
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Book Darwin read on voyage
Earth is millions of years old
Volcanoes make more land
Floods and rains cause erosion that
makes valleys and canyons
• Darwin witnessed volcanic eruptions and
earthquakes.
Lyell
II. Lamarck’s Evolution
Hypotheses
• Selective usage – use it or lose it
• Traits passed on to offspring if you use
• Traits lost if not used
Lamarck
Tendency toward perfection
• All organisms tend to try to improve their
existence
• It took many generations for birds to fly,
but it was necessary for survival
• If some trait give you an advantage, you
keep it
• Ex. Skin color, HIV resistance, cilia in
bronchioles, aposable thumbs
Use and disuse
• If trying to fly, develop stronger pectorial
muscles, feather, wing structure
• If not trying to fly, each generation
develops weaker pectorial, less feathers,
smaller wing structures
Inheritance of acquired traits
• Acquired characteristics were inherited
• If I jumped and have big legs, so would my
children
• Not quite right because of exercise and
working out, and weight lifting
Evaluating Lamarck’s hypotheses
• Did not know how traits were inherited
• Did not know organism’s behaviors had
effect
• Hypothesis of evolution and organisms
adapt to environment
III. Population Growth
• Malthus 1798 economist
more babies than people dying
• Populations unchecked will run out of food and space in
time
• War, famine, and disease
• Darwin viewed this as more important for plants and
animals because human’s have so few offspring
• Ex. Oak tree – 25,000 seeds a year, oyster – million
eggs per year
• Most die – who survives is key to Darwin’s thinking
Thomas Malthus
15.3 Darwin Presents his case
• I. Publication of On the origin of Species
• II. Inherited variation and artificial
selection
• III. Evolution by Natural Selection
• IV. Evidence of Evolution
• V. Summary of Darwin’s Theory
• VI. Strengths and Weaknesses of
• VII. Evolutionary Theory
• 1836 Darwin returns to England
• Discovers many specimens are not same
species > cannot reproduce a fertile
offspring
• Most of these are not found anywhere in
the world
I. Publication of On the origin of
Species
• Diversity > becomes evolution
• Scared to publish > too extreme and
controversial
• After 25 yrs. 1858 needs to publish to help
support Wallace Essay
• Puts out On the Origin of Species 1859
• Abe Lincoln is running for President
II. Inherited variation and artificial
selection
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Variation was good for plants and animals
“gene pool”
Artificial selection – most useful traits stay
Best milking cows, plants bear the most fruit,
fastest horse, biggest pigs, etc.
• Artificial selection – humans breed what nature
provides
• Ex. horses
III. Evolution by Natural Selection
• Populations increases
• Struggle for existence – compete for
resources – food, shelter, mates, etc.
• Camouflaged, protections, anything that
give an advantage
Survival of the fit
• Suited to environment – antibacterial soap ex.
• Plants getting leaves for photosynthesis, fighting
for the top or first leaves
• Behaviors in animals
• Feathers for flying
• Fitness is the key for natural selection
• Meaning (survival of the fittest)
• Ex. Speed, protection, scents, quills, sight,
smell, strength
modification
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Adaption
Changing niche/habitat
“descent with modification”
Common ancestors over years
Ex. Cat family, dogs
Common descent
Ex. Trees showing characteristics of
extinct and present species
IV. Evidence of Evolution
• Over millions of years – big break from
their thinking, only thought the earth was a
couple of thousand years old
• Fossil record starts to take off
• Deeper the layer, the older the fossil
• Still some gaps but can tell what was
around with what
The fossil record
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Proof of extinct species
Proof of age of earth
Proof of transitional species
(Still some gaps)
Geographic distribution of living
species
• Species adapt to habitat
• Beaks, feet, color, diet
• Natural selection – keep the best traits
Homologous body structures
• Similar structure – different functions
• Arms, wings, legs, flippers – same bones
• Embryology the same cells are making
these
• Share a common ancestor
• Vestigial organs – reduced in size, not
important: resemble miniature legs, tails,
other structures
• Dolphin not a fish, in has lungs, not gills
Similarities in embryology
• Formation is similar in embryos
• Not identical embryos, misleading
V. Summary of Darwin’s Theory
• Individual organisms differ, and some of this variation is heritable
• 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 organism has different advantages and disadvantages
in the struggle for existence. Individuals best suited to their
environment survive and reproduce most successfully. These
organisms pass their heritable traits to their offspring. Other
indidividuals die or leave fewer offspring. This process of natural
selection causes species to change over time.
• Species alive today are descended with modification from ancestral
species that lived in the distant past. This process, by which diverse
species evolved from common ancestors, unites all organisms on
Earth into a single tree of life
VI. Strengths and Weaknesses of
Evolutionary Theory
• New advances in geology, embryology,
physics have supported theory
• Virus evolves
• The grand theory interdisciple of all
science?
• Origin of life? Big bang, just chemicals,
how did they combine?
VII.
• Darwinists claim that the reptile-to-mammal evolution is
well documented. But for reptiles to evolve into
mammals at least some of these transformations must
have happened:
• • Scales had to have mutated into hair.
• • Breasts had to have evolved from nothing.
• • Externally laid eggs had to evolve into soft-shelled eggs
that were nourished by an umbilical cord and placenta in
a womb.
• religion