Download Descent with Modification

1/15/13
Descent with Modification
Darwin s voyage on the Beagle
•  The principle of Natural
Selection
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
1.  Variation
2.  Differential survival or
reproduction
3.  Inheritance
ATLANTIC
OCEAN
AFRICA
Pinta
Marchena
Santiago
Fernandina
Isabela
•  Evidence for Evolution
Santa
Santa
Cruz
Fe
PACIFIC
OCEAN
San
Cristobal
Española
Equator
SOUTH
AMERICA
Daphne
Islands
Pinzón
Florenza
–  Direct observations
–  Homology
–  Fossils
Genovesa
AUSTRALIA
Andes
The
Galápagos
Islands
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
New
Zealand
Fig. 22-5
Jan 16, 2013
Species are unique, but can also
be grouped.
(a) Cactus-eater
(c) Seed-eater
(b) Insect-eater
Fig. 22-6
(a) A flower mantid
in Malaysia
Hyracoidea
(Hyraxes)
Sirenia
(Manatees
and relatives)
Moeritherium
Barytherium
Deinotherium
Mammut
Platybelodon
(b) A stick mantid
in Africa
Stegodon
Mammuthus
Elephas maximus
(Asia)
Loxodonta
africana
(Africa)
Loxodonta cyclotis
(Africa)
34
24
Millions of years ago
5.5
2 104 0
Years ago
Fig. 22-8
Fig. 22-12
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The power of selective breeding
Terminal
bud
Cabbage
Lateral
buds
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Stem
Wild mustard
Flowers
and stems
Broccoli
Observation #1: Members of a population
often vary in their traits
Kohlrabi
Fig. 22-9
Observation #2: Traits are inherited from
parents to offspring
Kirk Douglas and Michael Douglas
Fig. 22-10
Observation #2: Traits are inherited from
parents to offspring
Observation #3: All species are capable of
producing more offspring than the
environment can support
F1 Generation
F2 Generation
Maple tree
seedlings
Spore
cloud
Fig. 15-4
Fig. 22-11
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Observation #4: Owing to lack of food or
other resources, many of these offspring do
not survive
•  Inference #2: This unequal ability of
individuals to survive and reproduce will lead
to the accumulation of favorable traits in the
population over generations.
Spore
cloud
Maple tree
seedlings
•  Inference #1: Individuals whose inherited
traits result in high survival and reproduction
in a given environment tend to leave more
offspring.
Fig. 22-11
R
S
Evolutionary Response = Selection Difference * heritability
Evidence supporting
evolution
Last paragraph of the Origin of Species
It is interesting to contemplate an entangled bank, clothed with
many plants of many kinds, with birds singing on the bushes, with
various insects flitting about, and with worms crawling through the damp
earth, and to reflect that these elaborately constructed forms, so
different from each other, and dependent on each other in so complex a
manner, have all been produced by laws acting around us. These laws,
taken in the largest sense, being Growth with Reproduction; Inheritance
which is almost implied by reproduction; Variability from the indirect and
direct action of the external conditions of life, and from use and disuse;
a Ratio of Increase so high as to lead to a Struggle for Life, and as a
consequence to Natural Selection, entailing Divergence of Character
and the Extinction of less-improved forms. Thus, from the war of nature,
from famine and death, the most exalted object which we are capable
of conceiving, namely, the production of the higher animals, directly
follows. There is grandeur in this view of life, with its several powers,
having been originally breathed into a few forms or into one; and that,
whilst this planet has gone cycling on according to the fixed law of
gravity, from so simple a beginning endless forms most beautiful and
most wonderful have been, and are being, evolved.
Percent of HIV resistant to 3TC
We can use these principles to predict change
100
Patient
No. 1
Patient No. 2
75
50
Patient No. 3
25
0
0
2
4
6
Weeks
Evolution
of Drug
Resistant
HIV
8
10
12
Fig. 22-14
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Rapid evolution in response to an introduced food plant
10
On native species,
southern Florida
8
Homologous structures reveal shared
ancestry
Number of individuals
6
4
2
0
Museum-specimen average
10
On introduced species,
central Florida
8
6
4
Human
2
0
6
7
8
9
Beak length (mm)
10
Cat
Whale
Bat
All are modifications of the forelimb
of their common ancestor
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Evolution by Natural Selection produces
adaptation to a particular environment
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Similarities can also
be the result of
Convergent Evolution
Fig. 22-20
Flying
squirrel
Natural selection: important
points
1.  Natural selection is an editing
mechanism, not a creative force.
2.  Natural selection favors traits that
increase fitness in the current,
local environment.
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