The%20Theory%20of%20Evolution

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The Theory of Evolution

• Natural Selection and the Evidence for Evolution

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15.1 Section Objectives page 393
Section Objectives

• Summarize Darwins theory of natural selection.

• Explain how the structural and physiological
  adaptations of organisms relate to natural
  selection.

• Distinguish among the types of evidence for
  evolution.

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Section 15.1 Summary pages 393-403
Charles Darwin and Natural Selection

• The modern theory of evolution is the fundamental
  concept in biology.

• Recall that evolution is the change in
  populations over time.

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Charles Darwin and Natural Selection

• Evolution
• Change in populations over time
• Charles Darwin
• H.M.S. Beagle
• Naturalist study nature
• Galapagos Islands
• First started to realize that organisms change
  over time

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Section 15.1 Summary pages 393-403
Darwin on HMS Beagle
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• Worked on his ideas for over 2 decades
• Used Malthus idea that the human population
  would grow too large for the food supply
• Must struggle to compete for supplies
• Pigeon-breeding
• Artificial selection similar to nat.selec.
• Breeding organisms w/ specific traits in order to
  produce offspring w/ desired traits

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Natural Selection

• Organisms w/ favorable variations survive,
  reproduce, and pass their variations to the next
  generation
• Alfred Wallace had similar ideas
• Advent of genetics further supports evolution

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Adaptations Evidence for Evolution

• Adaptations develop over time
• Thorns or no thorns
• Distinctive coloring or plain
• Ex mole-rats
• Those that live underground are blind have large
  teeth and claws

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• Mimicry
• Enables one species to resemble another species
• Harmless species mimics a harmful species
• Ex harmless fly and wasp Fig. 15.4
• Camouflage
• Blend w/ surroundings Fig. 15.4C

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• Most structural adaptations take millions of
  years to develop
• Physiological adaptations can be quicker
• Ex Antibiotic resistant bacteria
• Penicillin no longer kills as many bacteria as it
  once did
• Also observed in insects and weeds (insecticides
  and pesticides)

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Section 15.1 Summary pages 393-403
Physiological adaptations can develop rapidly
The resistant bacteria live and produce more
resistant bacteria.
When the population is exposed to an antibiotic,
only the resistant bacteria survive.
The bacteria in a population vary in their
ability to resist antibiotics.

• Today, penicillin no longer affects as many
  species of bacteria because some species have
  evolved physiological adaptations to prevent
  being killed by penicillin.

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Other Evidence of Evolution

• Fossils
• Provide a record of early life and evolutionary
  history
• Ex ancestors of whales were probably
  land-dwelling dog-like animals
• Record is incomplete
• Like a puzzle -gt still understand the picture
• Table 15.1 evolution of camel

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Section 15.1 Summary pages 393-403
Camel Evolution
Paleocene 65 million years ago
Eocene 54 million years ago
Oligocene 33 million years ago
Miocene 23 million years ago
Age
Present
Organism
Skull and teeth
Limb bones
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Other Evidence of Evolution, contd

• Anatomy
• Homologous structures
• Structural features w/ a common evolutionary
  origin
• Ex Fig. 15.6 forelimbs of crocodile, whale, and
  bird
• Analogous structures
• Structures that do not have a common evolutionary
  origin , but are similar in function
• Ex bird wing and insect wing

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Crocodile forelimb
Whale forelimb
Bird wing
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Section 15.1 Summary pages 393-403
Analogous Structures

• For example, insect and bird wings probably
  evolved separately when their different ancestors
  adapted independently to similar ways of life.

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• Vestigial Structures
• Structure in a present day organisms that no
  longer serves its original purpose
• Ex appendix, eyes of blind mole-rats, pelvic
  bones of whales

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Other Evidence of Evolution, contd

• Embryology
• Most embryos of different species look similar to
  each other
• Fig. 15.9

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Section 15.1 Summary pages 393-403
Embryology
Pharyngeal pouches
Pharyngeal pouches
Tail
Tail
Fish
Reptile
Bird
Mammal
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Other Evidence of Evolution, contd

• Biochemistry
• Nearly all organisms share DNA, ATP, and many
  enzymes (cytochrome c found from bacteria to
  bison to humans)
• Organisms that are more closely related have more
  similar cytochrome c Fig. 15.10

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Section 15.1 Summary pages 393-403

• Organisms that are biochemically similar have
  fewer differences in their amino acid sequences.

Biochemical Similarities of Organisms
Percent Substitutions of Amino Acids in
Cytochrome c Residues
Comparison of Organisms
Two orders of mammals
5 and 10
Birds vs. mammals
8-12
Amphibians vs. birds
14-18
Fish vs. land vertebrates
18-22
Insects vs. vertebrates
27-34
Algae vs. animals
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Section 1 Check
Question 1
_______ is considered to be the fundamental
concept of biology.
A. genetics
B. the modern theory of evolution
C. artificial selection
D. structural adaptation
The answer is B.
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Section 1 Check
Question 2
Breeding organisms with specific traits in order
to produce offspring with identical traits is
called _______.
A. natural selection
B. adaptation
C. mutation
D. artificial selection
The answer is D.
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Section 1 Check
Question 3
What is the difference between artificial
selection and natural selection?
Answer
Artificial selection is the intentional breeding
of organisms with specific traits in order to
produce offspring with identical traits. Natural
selection occurs when organisms with favorable
variations of traits survive in nature,
reproduce, and pass these favorable variations to
offspring.
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Section 1 Check
Question 4
Mimicry and camouflage are NOT examples of
_________.
A. adaptation
B. natural selection
C. evolution
D. artificial selection
The answer is D.
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Section 1 Check
Question 5
How does mimicry differ from camouflage?
Answer
Mimicry is an adaptation that allows one species
to resemble another species. Camouflage is an
adaptation that allows one species to resemble
its surroundings.
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The Theory of Evolution

• Mechanisms for Evolution

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Populations Genetics and Evolution

• Populations evolve, not individuals
• Natural selection acts on the range of phenotypes
• Gene pool
• All of the alleles in a pop
• Allelic frequency
• percentage of any specific allele in the gene
  pool

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• Calculating Allelic Frequency
• Same way a baseball player calculates batting
  average
• Add up all of the alleles/by total alleles
• Genetic Equilibrium
• Frequency of alleles remains the same over
  generations

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Changes in Genetic Equilibrium

• Any factor that affects the genes in a gene pool
  can change allelic frequencies disruption in
  equilibrium evolution
• Mutations can be harmful or beneficial
• Radiation
• Genetic drift
• The alteration of allelic frequencies by chance
  events

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• Can greatly affect small populations
• Only genes available to pass on to offspring
• Found in humans that have become isolated
• Amish population in Lancaster County,
  Pennsylvania
• Pop 12,000
• One of the original founders had the recessive
  allele for short arms and legs and extra fingers
  and toes. Fig. 15.12
• Today 1 in 14, general pop of US 1 in 1000

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• Gene Flow
• Migration of individuals into and out of a
  populations
• Leave a pop loss of genes in gene pool
• Enter a pop gain genes in gene pool

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Natural Selection acts on Variations

• Traits have variations
• Eye color, height, skin color
• Some variations increase or decrease an
  organisms chance of survival in an environment
• 3 types of natural selection that act on variation

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• Stabilizing Selection
• Favors average individuals in a pop
• Ex spider size
• Too big predators can find easily
• Too small cant get to food
• Average more likely to survive, reproduce and
  pass on genes

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• 2. Directional selection
• Favors one of the extreme variations of a trait
• Ex woodpecker beak size
• Only those w/ long beaks can reach the bugs that
  live deep in the tree
• Long beaks would be an advantage over short beaks
  or average size beaks

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• Disruptive Selection
• Individuals w/ either extreme of a traits
  variation are selected.
• Ex marine limpets
• Color from white, to tan, to dark brown
• Live attached to rocks which are light and dark
• Both the white and dark brown are camouflaged
• Birds easily see tan

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Disruptive Selection
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The Evolution of Species

• Speciation
• Occurs when members of similar populations no
  longer interbreed to produce fertile offspring
• Creates new species
• Geographic Isolation
• Physical barrier divides a population
• Examples?

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• Reproductive Isolation
• Occurs when formerly interbreeding organisms can
  no longer mate and produce fertile offspring
• Genes are so different that fertilization or the
  production of a fertile offspring does not occur
• Mating times differ

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• Polyploidy
• Individual or species contains a multiple of the
  normal set of csomes
• Caused by mistakes during cell division
• May result in immediate reproductive isolation

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• Speciation Rates
• Rate at which new species arise
• Gradualism
• Gradual change of adaptations
• Ex sea lilies
• Punctuated Equilibrium
• Occurs quickly, in rapid bursts
• Long periods of genetic equilibrium in between

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Patterns of Evolution

• Occur throughout the world
• Support evolution
• Divergent Evolution
• Where species become different from each other
• Based on needs of particular environment

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• Adaptive Radiation, example
• An ancestral species evolves into an array of
  species to fit a number of diverse habitats
• Ex Darwins finches, honeycreepers

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Adaptive Radiation
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• Convergent Evolution
• Distantly related organisms evolve similar traits
• Share similar environmental pressures
• Ex shark, penguin, dolphin
• Fish, bird, mammal
• Why do they look similar?

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Section 2 Check
Question 1
Which type of natural selection does NOT
favor the evolution of new species?
A. divergent
B. disruptive
C. stabilizing
D. directional
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Section 2 Check
Question 2
Which type of natural selection does NOT
favor the evolution of new species?
A. divergent
B. disruptive
C. stabilizing
D. directional
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Section 2 Check
Question 3
Why are the Galapagos Islands rich in
unique species of organisms?
A. The islands are an area exhibiting an
abnormal number of mutations.
B. The islands are geographically isolated.
C. The island species have been subjected to
increased gene flow.
D. The island species have been subjected to
stabilizing selection.