Descent with Descent with Modification: Modification: A Darwinian A Darwinian View of Life View of Life BIOL BIOL 102: 102: General Biology II General Biology II Chapter Chapter 22 22 Rob Rob Swatski Swatski Associate Professor Associate Professor of Biology of Biology HACC HACC-York York
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BIOL 102 Chp 22 Descent with Modification: A Darwinian View of Life
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Descent with Descent with Modification: Modification:
A Darwinian A Darwinian View of LifeView of Life
BIOL BIOL 102: 102: General Biology IIGeneral Biology II
Chapter Chapter 2222
Rob Rob SwatskiSwatski Associate Professor Associate Professor of Biologyof Biology
HACCHACC--YorkYork
2
1859: Charles Darwin 1859: Charles Darwin published published
The The Origin Origin of Species of Species
3
Main Ideas Main Ideas of Evolutionof Evolution
Current species are descendants
of ancestral species
“Descent with modification”
Natural selection
DescendantsDescendants
AncestorAncestor 4
5
Evolution accounts Evolution accounts for the unity & for the unity & diversity of lifediversity of life
Theodosius Theodosius DobzhanskyDobzhansky
“Nothing in biology makes sense
except in the light of evolution.”
6
7
8
1809
1798
1812
1795
1830
1790 1809 183136
1844
1859 1870
Lamarck publishes his hypothesis of evolution.
Malthus publishes “Essay on the Principle
of Population.”
Hutton proposes his principle of
gradualism.
Charles Darwin
is born.
Darwin travels around the world on HMS
Beagle.
The Galápagos Islands
Darwin writes his essay on descent with modification.
On the Origin of Species is published.
While studying species in
the Malay Archipelago,
Wallace (shown in 1848)
sends Darwin his hypothesis
of natural selection.
1858 Cuvier publishes his extensive studies of vertebrate fossils.
Lyell publishes
Principles of Geology.
Ancient ViewsAncient Views
Aristotle
Species are fixed & arranged on a scala
naturae
Old Testament
Species were individually designed
by God and, therefore, perfect
9
ScalaScala NaturaeNaturae God in
Heaven
Angels
Humans
Animals
Plants
Rocks
Devil in Hell 10
TaxonomyTaxonomy
Branch of biology that classifies organisms
into taxa
1700’s: Carl Linne, the “father of modern
taxonomy”
Viewed adaptations as evidence that the
Creator had designed each species for a specific purpose
“The state of the natural world is the result “The state of the natural world is the result of a long succession of events.”of a long succession of events.” -- Charles LyellCharles Lyell
29
JeanJean--BaptisteBaptiste LamarckLamarck
Species evolve through the use & disuse of body
parts
Characteristics acquired during life are inherited
Unsupported by evidence
30
Lamarck’s HypothesisLamarck’s Hypothesis
31
32
Aren’t you glad Aren’t you glad Lamarck Lamarck was wrong?was wrong? 33
Darwin’s Darwin’s ResearchResearch
Darwin always had a deep
interest in science & nature
Was a student of medicine & theology at Cambridge
5-year voyage on the Beagle after
graduation 34
Don’t Listen to Don’t Listen to Your ParentsYour Parents
Adaptation to the environment & speciation are closely related
Strongly supported by
modern biology
Galápagos finches
40
CactusCactus--eatereater
41
InsectInsect--eatereater
42
SeedSeed--eatereater 43
Adaptive Radiation of Galápagos FinchesAdaptive Radiation of Galápagos Finches
44
If you had an idea thatIf you had an idea that was going to outragewas going to outrage
society…society…
would you keep would you keep it to yourself?it to yourself? 45
46
47
Darwin’s Two Main Ideas Darwin’s Two Main Ideas on Evolutionon Evolution
Descent with Descent with modification modification
Explains the unity &
diversity of life
Natural Natural SelectionSelection
Results in adaptive radiation
48
Descent with Descent with ModificationModification
Darwin never used the word “evolution” in the 1st edition of Origin of
Species
“Descent with modification”
summarized his view of the unity of life
All organisms are related through descent from an ancestor that lived in the
distant past 49
50
The “Tree of The “Tree of Life”Life”
Branches represent life’s
diversity
Darwin’s theory meshed well with
Linnaeus’s hierarchy
Ex: elephants
51
52
Hyracoidea
(Hyraxes)
Sirenia (Manatees and relatives)
†Deinotherium
†Mammut
†Platybelodon
†Stegodon
†Mammuthus
Elephas maximus
(Asia)
Loxodonta africana
(Africa)
Loxodonta cyclotis
(Africa)
†Moeritherium
†Barytherium
60
Millions of years ago
34 24 5.5 2 104 0
Years ago
53
Artificial Artificial SelectionSelection
Darwin noted that humans have
modified other species
Select & breed individuals with
desired traits
Selective breeding =
artificial selection 54
55
56
57
Brussels
sprouts
Kale
Selection
for leaves
Selection for
axillary (side)
buds
Selection for
apical (tip) bud
Cabbage
Broccoli
Kohlrabi Wild mustard
Selection
for stems
Selection
for flowers
and stems
Four Four Observations Observations
of Nature of Nature Made by Made by DarwinDarwin
58
1.1. Members of a Members of a population often vary population often vary
greatly in their traitsgreatly in their traits 59
60
2.2. Traits are Traits are inheritedinherited from from parents to offspringparents to offspring 61
3.3. All species are All species are capable of producing capable of producing moremore offspring than offspring than the environment can the environment can supportsupport
62
4.4. Many offspring don’t surviveMany offspring don’t survive due to lack of food or predationdue to lack of food or predation 63
Two Inferences Two Inferences Made Made by Darwinby Darwin
64
1. Individuals whose inherited traits give them
a higher probability of surviving & reproducing in an environment tend to leave more offspring
than others
65
2. This unequal ability of individuals to survive & reproduce will lead to the accumulation of favorable traits in the
population over generations 66
Thomas Thomas MalthusMalthus
Another major influence on Darwin
Malthus wrote about the potential for
human population to increase faster than
food supplies & other resources
67
68
Value of Value of Beneficial Beneficial
TraitsTraits
Traits that provide advantages will
accumulate in the population
This increases the frequency of
individuals having these adaptations
Explains the match between
organisms & their environment
69
Natural Natural SelectionSelection
Individuals with certain traits
survive & reproduce at a
higher rate than others
This increases the adaptation of
organisms to their environment over
time 70
71
72
Limits of Limits of Natural Natural
SelectionSelection
Can only increase or decrease heritable
traits in a population
Individuals do not evolve…
Populations evolve
73
Evolution is supported by Evolution is supported by an overwhelming amount an overwhelming amount of scientific evidenceof scientific evidence 74
Tiktaalik the fishapod! 75
76
Direct Observations of Direct Observations of Evolutionary ChangeEvolutionary Change
Natural selection in response to
introduced plant species
The evolution of drug-resistant
bacteria
77
78
Soapberry bug with beak inserted in balloon vine fruit
FIELD STUDYFIELD STUDY Can a change in a Can a change in a population’s food population’s food source result in source result in evolution by evolution by natural selection?natural selection?
On native species,
southern Florida
Museum-specimen average
On introduced species,
central Florida
Nu
mb
er
of
ind
ivid
ua
ls
10
8
6
4
2
0
10
8
6
4
2
0
Beak
Beak length (mm)
6 7 8 10 11 9
79
RESULTSRESULTS
80
1 2,750,000
2,500,000
2,250,000
2,000,000
1,750,000
1,500,000 1,250,000
1,000,000
750,000
500,000
250,000 base pairs
Chromosome map
of S. aureus clone USA300
Key to adaptations
Methicillin resistance
Ability to colonize hosts
Increased disease severity
Increased gene exchange
(within species) and
toxin production
MRSAMRSA
Mosquito Resistance to DDTMosquito Resistance to DDT
81
Summary of Summary of Natural Natural
SelectionSelection
It does not create new traits
It edits or selects for traits already present in
a population
The local environment determines which traits will be selected for or
against in a population 82
Fossils as Fossils as EvidenceEvidence
Species extinction
Origin of new taxonomic
groups
Changes within groups over time
83
Bristolia insolens
10
8
0
De
pth
(m
ete
rs)
4
Bristolia bristolensis
2
4
6
3
4
3
Latham Shale dig site, San Bernardino County, CA 84