chapter 15: evolutionfriedsci.weebly.com/uploads/2/1/7/9/21791640/chapter_15...15-2 ideas that...
TRANSCRIPT
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Chapter 15Darwin’s Theory of Evolution
Essential Question:
What evidence did Darwin use to develop his theory of evolution?
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15-1 The Puzzle of Life’s Diversity
How did life change from a prokaryote
to all of this in
4.6 billion years?
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What is a theory? How does this relate to evolution?
• Theory is –– A well supported hypothesis.
There is A LOT of data and observation that supports a theory.
• Evolution is a theory – It is used to describe the
processes by which modern organisms have descended through time from ancient organisms.
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Charles Darwin
• born in 1809, the same birthday as Abraham Lincoln
• In 1832, after graduating from college, sailed around the world aboard the HMS Beagle working as an unpaid naturalist
• this voyage changed his thinking about natural history and changed the course of science
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Voyage of HMS Beagle1832 (technically Dec. 27, 1831) - HMS Beagle set sail to travel the world
– Aboard was Charles Darwin
– There to study plants and animals in South America, Africa, and Australia.
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Darwin’s Observations
1. Patterns of Diversity
2. Living Organisms and Fossils
3. The Galapagos Islands
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1. Patterns of Diversity• These
ladybugs are members of the same species yet their coloration varies.
• Why is this important?
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Diversity on Earth
• Many different kinds of organisms
• Each is suited for its environment
• These traits that make them well suited are called adaptions
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Variation can lead to diversity
• Cheetahs vary in speed.
• Can lead to starvation
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Darwin’s Influences?
Observations of Adaptations
• collected samples and
observed species in
their natural
environment.
• noticed that organisms
tended to be well
suited ( adapted) to
their environment.
http://www.terraquest.com/galapagos/wildlife/island/finch.html
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2. Living Organisms and Fossils
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Living Organisms and Fossils
• Darwin wondered why the animal species he saw in the fossil record had disappeared?
– What processes were leading to the loss and rise of species?
– Why did they look similar, but exhibit changes through the fossil record?
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3. The Galapagos Islands
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What are adaptations? How does variation lead to adaptation?
• Inherited traits that increase a population’s chances of survival and reproduction are called ADAPTATIONS
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Type of Adaptations Observed in Animals
• Physical– camouflage, mimicry
– Defense: spines, quills, armor
• Chemical– Smells, poisons, venom, sap, sprays
• Behavioral– Innate and learned
– Migration, hibernation (torpor)
– Courtship rituals
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Biodiversity: Global Village• The variety and abundance of
different species is called
BIODIVERSITY.
• Earth is estimated to have
5 million to 30 million different
living species.
• Estimates suggest that 99% of all
organisms that ever lived are now
extinct.
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Scientists over time began to ask questions
• Why is there such incredible Biodiversity?
• Why have so many species come and gone?
One man’s quest for an answer led to perhaps the most revolutionary theory in the history of science. . .
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15-2 Ideas That Shaped Darwin’s Thinking
Essential Question: How did past scientists thinking help with Darwin’s
idea of Evolution?
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How did Darwin develop his theory of
Evolution?
What were his 3 major influences?
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Influence 1: An Ancient Changing Earth
• James HuttonProposed
• Earth is shaped by geological forces
• These forces take millions of years
• Therefore Earth is millions of years old, not thousands
• Charles LyellPublished
• Principles of Geology which Darwin read while aboard the HMS Beagle
• Explained the mechanisms for geological change
• Insisted scientists must make modern observations to explain past events
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How did this influence Darwin?
Geology
• the geology work of Charles Lyell and James Hutton
• geological evidence suggested Earth was very old
• reasoned that if the Earth changed over time, these
changes would influence plant and animal life.
• fossil evidence seems to support this.
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Influence 2: Lamarkian Evolution
• Jean Baptiste Lamarck
– Developed one of the first evolutionary hypotheses in 1809
– Did not believe all creatures shared a common ancestor
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Lamarck’s Evolution Hypothesis
• 3 Parts
– Tendency towards Perfection
– Use and Disuse
– Inheritance of Acquired Traits
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Part 1. Tendency Towards Perfection
• Organisms strive to improve themselves throughout their lifetime
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Part 2. Use and Disuse
• Used body structures remain and develop: and unused body structures waste away
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Part 3. Inheritance of acquired traits
• Characteristics acquired during the lifetime of an organism could be passed to offspring.
tommee.glogster.com
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Darwin Didn’t Buy It• He questioned prior ideas and
sought a better explanation
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Influence 3: Thomas Malthus
• Economist Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone
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• All populations eventually exceed
the supply of resources (living
space and food)
• Populations would eventually be
limited by disasters such as
starvation, drought, war, etc.
• Remember what you learned in
Chapter 5!
http://www.rifpd.org/Family_Planning/Reproductive_Health/Infant-dying-starvation.jpg
Darwin Influences?
Population Control
http://www.design4effect.com/soc11/pop.htm
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Application to Darwin
• Darwin noticed species will over produce offspring.
• Most die off.
• What causes the death of so many individuals?
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15-3 Darwin Presents His Case
Essential Question:
What evidence of evolution did Darwin present?
How does natural selection lead to evolution?
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Charles Darwin’s
Theory of Evolution
published in 1859
On the Origin of Species
by Means of Natural
Selection
Portrait of Charles Darwinwww.lib.virginia.edu/science/parshall/darwinport.html
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The Origin of Species
• When Darwin returned from his voyage, he hesitated to publish work.
• Finally published his book in 1859 when learning colleague was working on the same topic.
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Sources of Heritable Variation
• 4 Sources of Variation
– 1. crossing over
– 2. independent assortment
– 3. recombining of egg and sperm
– 4. random mutations
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Fitness
• Species that are more adapted to their environment are have better ‘fitness’
• Which animal fitness is higher to live in the desert?
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Natural Selection
• The “survival of the fittest”
• The process where organisms that are better suited for their environment tend to survive and produce more offspring
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Natural Selection: 4 Steps
• 1. genetic variation must be present within a population
• 2. some variations must be more favorable and allow organisms to survive and reproduce
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Natural Selection: 4 steps
• 3. survival must be differential
• 4. favorable traits must be inherited by offspring
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So, what was Darwin’s Big Idea?
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• the theory that species descended from more ancient forms of life through structural and physiological modifications as a result of natural selection of traits
What evidence exists in support of this idea?
Evolution as a result of Natural Selection
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Types of Modern and Historical
Evidence for
the Theory of Evolution:
1. fossil record
2. chemical similarities
3. structural similarities
4. geographic distribution of species
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Evidence for Evolution:Fossils
• Fossil – Formed by ancient plants or animals
• Older fossils are found under newer fossils
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• Paleontologists study fossils for clues.
• FOSSILS are the preserved remains or imprints of ancient organisms.
/www.burgess-shale.bc.ca/gallery/gallery.htm
The Fossil Record
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• Remains of plants and animals found in sedimentary rocks
• Some extinct species had traits that were transitional between major groups of organisms
• Confirms that species are not fixed.
Evidence of change and extinction?
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Evidence of Habitat Change
• most common fossils
found in sedimentary
rocks are from the hard
parts of organisms,
including shells, bones,
teeth, and woody stems.
http://www.sdnhm.org/research/paleontology/images/otaywhale-rac26sept2001-2b.jpg
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Not just bones
• Fossils are not always the
body parts of an organism.
A mold is a type of fossil
in which an impression of
the shape or track of an
organism has survived
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Freezing
Amber
Impressions
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The Fossil Record
• Fossils can be dated using: – radioactive isotopes– relative dating based on
their position in the sedimentary rock
• Video Shorts you can watch at home!
http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html
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Structural Similarities
• Homologous Structures
– Structures that are embryologically similar, are called homologous structures.
– This suggests that these animals evolved from a common ancestor.
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Structural Similarities
• Structures that are similar in function but different in structural origin are called analogous structures
• They are not inherited from a common ancestor.
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Examples of analogous structures include:
• Insect wings and bird/bat wings – both are used for flying, but are not from the same genetic origin
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Similar in Appearance and Function
Homologous or Analogous?
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Similar in Appearance
BUT NO COMMON ANCESTOR !
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Structural Similarities
• The presence of structures that have a minimal purpose or no purpose at all are called Vestigial Structures
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Evidence for Evolution: Embryos
• The early stages, or embryos, of many animals with backbones are very similar
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Comparative Embryology
• Similarities in embryological development suggests a common ancestor and similar genetics.
http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html
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Evidence for Evolution: Geographic Distribution
• Animals found in the same geographic area tend to have multiple similarities
• Example: Marsupials in Australia
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Chemical Similarities• The genetic code is the
same for ALL organisms.
• similar DNA sequences in all organisms.
• Greater similarities in DNA sequences implies greater evolutionary relatedness.
http://web.mit.edu/esgbio/www/dogma/images/code.gif
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Evidence for Evolution: Molecular Biology
• All life on Earth shares at least SOME of the same DNA
• The more DNA you share, the more closely related on the evolutionary tree.