Biology Chapter 14 Evolution: How Change Occurs

1
Biology - Chapter 14Evolution How Change Occurs

• Charles Page High School
• Stephen L. Cotton

2
Section 14-1 Developing a Theory of Evolution

• OBJECTIVES
• Discuss the importance of evolutionary theory.

3
Section 14-1 Developing a Theory of Evolution

• OBJECTIVES
• Identify the basic assumptions of Lamarcks
  theory of evolution.

4
Section 14-1 Developing a Theory of Evolution

• OBJECTIVES
• Explain some of the major ideas that helped shape
  Darwins theory of evolution.

5
Section 14-1 Developing a Theory of Evolution

• Evolutionary theory is the foundation on which
  the rest of biological science is built
• Theodor Dobzhansky wrote that nothing in biology
  makes sense, except in the light of evolution

6
Section 14-1 Developing a Theory of Evolution

• Observing that evolution has occurred is
  relatively simple, because we can see changes
• Explaining how and why evolution occurs is more
  difficult

7
Section 14-1 Developing a Theory of Evolution

• Certain parts of Darwins original theory have
  been revised in the years since he proposed it
• Evolutionary change is undeniable it does
  happen.
• it is a collection of carefully reasoned and
  tried hypothesis

8
Section 14-1 Developing a Theory of Evolution

• Consider the fact that we have no doubt that
  gravity exists, but we do not completely
  understand how it works
• Jean Baptiste de Larmarck (1744-1829) was among
  the first to recognize change over time

9
Section 14-1 Developing a Theory of Evolution

• Lamarck also called this change to the attention
  of other scientists
• He realized that organisms adapted to their
  environments
• Lamarck relied on three assumptions (which we now
  know are incorrect)

10
Section 14-1 Developing a Theory of Evolution

• 1. A desire to change. Lamarck thought that
  organisms change because they have an inborn urge
  to better themselves
• -birds had an urge to fly, and their constant
  efforts led to the development of wings

11
Section 14-1 Developing a Theory of Evolution

• 2. Use and Disuse. He said that organisms could
  alter their shape by using their bodies in new
  ways
• -also that if a body part was not used, that
  body part would decrease

12
Section 14-1 Developing a Theory of Evolution

• 3. Passing on Acquired Traits. The belief of
  Lamarck, and many other scientists at that time,
  was that acquired characteristics could be
  inherited
• -Figure 14-2, page 292 about cropped ears in
  dogs

13
Section 14-1 Developing a Theory of Evolution

• Even though many of Lamarcks ideas were
  incorrect, he did pave the way for Darwins
  theory of evolution
• Darwin (1809-1882) came after Lamarck (1744-1829)

14
Section 14-1 Developing a Theory of Evolution

• Lamarcks ideas may seem strange to us now, but
  was consistent with knowledge of that time
• a later understanding of genetics and heredity
  showed his ideas to be false

15
Section 14-1 Developing a Theory of Evolution

• Darwin was greatly influenced by his personal
  experiences on the Beagle, books he read, and
  people he talked with
• Charles Lyell, a geologist, affected Darwins
  thinking by presenting information about the age
  of the earth

16
Section 14-1 Developing a Theory of Evolution

• The long periods of time it would have taken for
  millions of species to evolve from a common
  ancestor- can only be explained if the Earth was
  very old
• Darwin also observed changes in the earth- such
  as volcanoes

17
Section 14-1 Developing a Theory of Evolution

• And if the Earth itself could change over time,
  so too could life on Earth!
• Darwin talked with many plant and animal breeders
• they could not cause variation it happened
  naturally or not

18
Section 14-1 Developing a Theory of Evolution

• Once the variations did occur, they could use it
  to their advantage- selective breeding
• Darwin called this artificial selection- only the
  best organisms were allowed to produce offspring

19
Section 14-1 Developing a Theory of Evolution

• Darwin was convinced that a process similar to
  artificial selection must be at work in nature
• Another important influence on Darwin was the
  economist Thomas Malthus (1766-1834)

20
Section 14-1 Developing a Theory of Evolution

• Malthus observed that babies were being born at a
  faster rate than people were dying
• sooner or later there wouldnt be enough food or
  space
• to prevent human growth famine, disease, and war

21
Section 14-1 Developing a Theory of Evolution

• In time, these unpleasant observations were
  called the Malthusian Doctrine
• Darwin realized this applied even more to plants
  and animals than humans, because most other
  species produce more offspring

22
Section 14-1 Developing a Theory of Evolution

• Marine animals, such as the common mussel,
  produce millions of eggs
• if they all survived, the oceans would be overrun
  with them
• but, only a few survive Why?

23
Section 14-2 Evolution by Natural Selection

• OBJECTIVES
• Describe the process of natural selection.

24
Section 14-2 Evolution by Natural Selection

• OBJECTIVES
• Provide an example of natural selection in action.

25
Section 14-2 Evolution by Natural Selection

• Finally, Darwin recognized a process similar to
  artificial selection- but this happened in nature
• he called it natural selection
• this was based on many observations he made

26
Section 14-2 Evolution by Natural Selection

• Those individuals with characteristics best
  suited to their environment survive the struggle
  for existence
• survival of the fittest
• the fact that many do not survive keeps numbers
  down

27
Section 14-2 Evolution by Natural Selection

• An example of natural selection in action is the
  peppered moth
• Fig. 14-8, page 297
• spend time resting on tree bark
• some light in color, some dark
• which ones seen easier?

28
Section 14-2 Evolution by Natural Selection

• When the Industrial Revolution began in England,
  the soot stained the trees
• which was easier to see now?
• Birds are the major predators
• However, more testing is needed to reach any
  conclusions

29
Section 14-2 Evolution by Natural Selection

• Kettlewell, a British ecologist, did such a test
  for this hypothesis
• showed that in each environment the moths that
  were better camouflaged had the higher survival
  rate

30
Section 14-3 Genetics and Evolutionary Theory

• OBJECTIVES
• Explain how genes affect natural selection.

31
Section 14-3 Genetics and Evolutionary Theory

• OBJECTIVES
• Define evolution in genetic terms.

32
Section 14-3 Genetics and Evolutionary Theory

• OBJECTIVES
• Relate genes to fitness and adaptation.

33
Section 14-3 Genetics and Evolutionary Theory

• Darwin worked under a serious handicap-
• he had no idea how the inheritable traits were
  passed from one generation to the next
• Mendel made his ideas in Darwins lifetime- went
  unknown

34
Section 14-3 Genetics and Evolutionary Theory

• Genetics and evolutionary theory are inseparable!
• Today we define fitness, adaptation, species, and
  the process of evolutionary change in genetic
  terms

35
Section 14-3 Genetics and Evolutionary Theory

• Genes, the carriers of inheritable
  characteristics, are also the source of random
  variation and genetic interaction
• mutations cause variation
• variation occurs as chromosomes are shuffled

36
Section 14-3 Genetics and Evolutionary Theory

• Variation does not occur because an animal needs
  to or wants to evolve
• no way for an organism to cause a particular
  change
• no way for them to prevent the variations that do
  occur

37
Section 14-3 Genetics and Evolutionary Theory

• Entire organisms, NOT individual genes, either
  survive and reproduce or do not
• Natural selection can operate only on the
  phenotypic variation among individuals that is
  already present

38
Section 14-3 Genetics and Evolutionary Theory

• Today, evolutionary biologists study populations-
  a collection of individuals of the same species
  in a given area, whose members can breed with one
  another
• since they can interbreed, they share a common
  group of genes, called a gene pool

39
Section 14-3 Genetics and Evolutionary Theory

• The number of times an allele occurs in a gene
  pool compared with the number of times other
  alleles for the same gene occur is called the
  relative frequency of the allele
• sexual reprod. alone doesnt change the relative
  frequency

40
Section 14-3 Genetics and Evolutionary Theory

• Cards? Shuffling produces an enormous variety of
  different hands, but does not change the relative
  number of aces, kings, fours, etc.
• Evolution is any change in the relative
  frequencies of alleles in the gene pool of a
  population

41
Section 14-3 Genetics and Evolutionary Theory

• Each time an organism reproduces, it passes
  copies of its genes to its offspring
• Thus, evolutionary fitness is the success an
  organism has in passing these genes on
• adaptation increases fitness

42
Section 14-3 Genetics and Evolutionary Theory

• In the past, biologists defined a species as a
  group of organisms that looked alike
• but there are exceptions

43
Section 14-3 Genetics and Evolutionary Theory

• Now, a species is a group of similar-looking
  (though not identical) organisms that breed with
  one another and produce fertile offspring in the
  natural environment

44
Section 14-3 Genetics and Evolutionary Theory

• Thus, they share a common gene pool
• Horse donkey mule, which is usually sterile
  males

45
Section 14-4 The Development of New Species

• OBJECTIVES
• Define niche.

46
Section 14-4 The Development of New Species

• OBJECTIVES
• Relate the availability of niches to speciation.

47
Section 14-4 The Development of New Species

• OBJECTIVES
• Describe the process of speciation.

48
Section 14-4 The Development of New Species

• We are now nearly ready to explain HOW new
  species evolve from old ones- a process
  biologists call speciation
• A niche is the combination of an organisms
  profession and the place in which it lives

49
Section 14-4 The Development of New Species

• If two species try to occupy the same niche, they
  will compete for food and space
• one species will not survive
• No two species can occupy the same niche in the
  same location for a long period of time

50
Section 14-4 The Development of New Species

• If the two species occupy different niches,
  however, they will not compete with each other as
  much
• With less competition, there is less chance that
  one species will cause the other to become extinct

51
Section 14-4 The Development of New Species

• Scientists have learned that new species usually
  form only when populations are isolated, or
  separated
• they need reproductive isolation, or the two
  species gene pools intermix

52
Section 14-4 The Development of New Species

• Reproductive isolation can occur in many ways
• geographic barriers such as rivers, mountains,
  and even roads differences in courtship behavior
  or fertile time periods

53
Section 14-4 The Development of New Species

• Once reproductive isolation occurs, natural
  selection usually increases the differences
  between the separated populations
• As they become better adapted to their new
  environment, gene pools become more dissimilar

54
Section 14-4 The Development of New Species

• If the populations remain separated for a long
  time, their gene pools eventually become so
  different that their reproductive isolation
  becomes permanent
• not just separate populations, but separate
  species now

55
Section 14-4 The Development of New Species

• We can use this understanding of evolution to
  explain the variety of a bird that Darwin saw-
  finches of 14 different varieties on the
  Galapagos Islands
• Fig. 14-18, page 306 shows adaptations for
  feeding differently (different niches!)

56
Section 14-4 The Development of New Species

• How did so many strange and unusual finch species
  evolve?
• Shows how geographic and behavioral barriers and
  reproductive isolation eventually lead to the
  formation of new species

57
Section 14-4 The Development of New Species

• Step 1 Founding fathers and mothers
• Step 2 Separation of populations
• Step 3 Changes in the gene pool (adapt to their
  environment)
• Step 4 reproductive isolation

58
Section 14-4 The Development of New Species

• Step 5 Sharing the same island
• 3 possibilities
• coexistence (need to occupy a different niche)
• extinction (too similar niche)
• further evolution (exhibiting enough genetic
  variation

59
Section 14-4 The Development of New Species

• When one species gives rise to many species, this
  is called adaptive radiation (also known as
  divergent radiation)
• Fig. 14-20, page 309
• a number of different species diverge (move away)
  from a common ancestral form

60
Section 14-4 The Development of New Species

• They must evolve a variety of characteristics
  that enable them to survive in different niches
• Adaptive radiation has occurred many times
  throughout history
• Hawaiian honeycreepers (birds), dinosaurs,
  todays mammals

61
Section 14-4 The Development of New Species

• Evidence of past adaptive radiation can be easily
  observed
• the homologous structures seen in Chapter 13 are
  evidence in which similar body parts of related
  organisms evolved to perform different tasks

62
Section 14-4 The Development of New Species

• From Fig. 14-20, page 309 we can also see
  different organisms produce species that are
  similar in appearance and behavior
• called convergent evolution
• has produced many of the analogous structures
  seen today bird and butterfly wings

63
Section 14-5 Evolutionary Theory Evolves

• OBJECTIVES
• Discuss how gene pools can change in the absence
  of natural selection.

64
Section 14-5 Evolutionary Theory Evolves

• OBJECTIVES
• Explain why some gene pools may change very
  little over time.

65
Section 14-5 Evolutionary Theory Evolves

• OBJECTIVES
• Describe the theory of punctuated equilibria.

66
Section 14-5 Evolutionary Theory Evolves

• It should be apparent that evolutionary theory
  has been modified over the years
• even today it continues to evolve as scientists
  formulate theories about the details of
  evolutionary change

67
Section 14-5 Evolutionary Theory Evolves

• Natural selection is not always necessary for
  genetic change to occur
• gene pools can change (evolution can occur) in
  the absence of natural selection
• by CHANCE!

68
Section 14-5 Evolutionary Theory Evolves

• Random change in the frequency of a gene is
  called genetic drift
• occurs most efficiently in a small population
• does not have to necessarily contribute to its
  fitness
• Fig. 14-23, page 311 - Horns?

69
Section 14-5 Evolutionary Theory Evolves

• The powerful forces of change (natural selection
  and genetic drift) do not cause genetic
  alterations in all species all the time under all
  conditions
• one form may remain nearly unchanged for a long
  period of time

70
Section 14-5 Evolutionary Theory Evolves

• One example is the horseshoe crab, Limulus, who
  is identical to ancestors that lived hundreds of
  millions of years ago
• such organisms are often called living fossils

71
Section 14-5 Evolutionary Theory Evolves

• Darwin thought that change was slow and steady
• known as gradualism
• Fig. 14-25, page 313
• Some hardly change at all, and this is called
  equilibrium

72
Section 14-5 Evolutionary Theory Evolves

• Every now and then, something upsets the
  equilibrium
• some changes occurred over relatively short
  periods of time (relatively short in the geologic
  time scale can be millions of years)

73
Section 14-5 Evolutionary Theory Evolves

• Rapid evolution after equilibrium can occur
• 1. A small population becomes isolated from the
  main body
• 2. Small group of organisms migrates to a new
  environment
• 3. Dramatic changes in Earth

74
Section 14-5 Evolutionary Theory Evolves

• Some species have vanished in a short period of
  time- mass extinction
• may be caused by global climate changes
• many niches are left unoccupied

75
Section 14-5 Evolutionary Theory Evolves

• Punctuated equlibria - the pattern of long stable
  periods interrupted by brief periods of change
• Summary Biological science is based on
  evolutionary theory