The%20Theory%20of%20Evolution - PowerPoint PPT Presentation

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The%20Theory%20of%20Evolution

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Title: The Theory of Evolution Author: LHS-LIB-XP Last modified by: m_lewis Created Date: 4/19/2004 5:18:45 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: The%20Theory%20of%20Evolution


1
The Theory of Evolution
  • Natural Selection and the Evidence for Evolution

2
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.

3
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.

4
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

5
Section 15.1 Summary pages 393-403
Darwin on HMS Beagle
6
  • 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

7
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

8
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)

14
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.

15
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
18
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

19
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.

23
  • 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

26
Section 15.1 Summary pages 393-403
Embryology
Pharyngeal pouches
Pharyngeal pouches
Tail
Tail
Fish
Reptile
Bird
Mammal
27
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

28
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
57
29
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.
30
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.
31
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.
32
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.
33
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.
34
The Theory of Evolution
  • Mechanisms for Evolution

35
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

36
  • 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

37
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

38
  • 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

39
  • 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

40
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

41
  • 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

46
Disruptive Selection
47
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

50
  • 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

51
  • 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

52
Patterns of Evolution
  • Occur throughout the world
  • Support evolution
  • Divergent Evolution
  • Where species become different from each other
  • Based on needs of particular environment

53
  • Adaptive Radiation, example
  • An ancestral species evolves into an array of
    species to fit a number of diverse habitats
  • Ex Darwins finches, honeycreepers

54
Adaptive Radiation
55
  • Convergent Evolution
  • Distantly related organisms evolve similar traits
  • Share similar environmental pressures
  • Ex shark, penguin, dolphin
  • Fish, bird, mammal
  • Why do they look similar?

56
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
57
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
58
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.
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