Transcript b) Directional Selection

Honors
Biology
Ch.15
The Theory
of Evolution
I. Darwin’s Theory of Evolution
by Natural Selection
Evolution:
hereditary change in populations of
organisms over time
A. Developing the Theory of
Evolution
1.Charles Darwin
(1809-1882)
- developed the
theory of
evolution by
natural selection
- traveled around the world as a
naturalist (1831-1836)
Galapagos wildlife
- Compared changes in species by
farmers through artificial selection
to what can happen in nature
Artificial
Selection
in the
Mustard
Family
‘Fancy Pigeon’ Bred by Artificial Selection
2. Natural Selection
- Natural Selection
is based on 4
principles:
a) Variation:
- All organisms produced sexually are
genetically unique.
Variation in Human Height
b) Heredity
- Variations are inherited
from parents.
c) Over Production:
- Populations produce more offspring
than can survive.
Female octopus with thousands
Thousands
of eggs
of dandelion
Dozens
seeds
of newly hatched sea turtles
d) Reproductive Advantage
- Those best suited will survive longer
and reproduce.
- Those less suited won’t survive or
reproduce
as often.
Peppered Moth
d) Reproductive Advantage
- Those best suited will survive longer
and reproduce.
- Those less suited won’t survive or
reproduce
as often.
Sandstone
Environment
Rock Pocket Mouse
10:25
Basalt
Environment
The Rock Pocket Mouse
10:25
3. The Origin of Species
- On the Origin of Species published
in 1859
- Darwin presented two main ideas:
(1) Descent with modification explains
life’s unity and diversity.
(2) Natural selection is
a cause of adaptive
evolution
II. Evidence of Evolution
- Evidence comes
from a wide variety
of observations.
Archaeopteryx Fossil
A. The Fossil
Record
- provides
direct
evidence for
evolutionary
relationships
A. The Fossil
Record
- provides
direct
evidence for
evolutionary
relationships
- many ‘missing
links’ have
been found
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)
B. Comparative Anatomy
1) Homologous Structures:
- organs in related organisms with a
similar underlying anatomy
- examples: forelimbs of humans,
bats, whales, etc.
Homologous Structures
Flying
Swimming Running
Grasping
2)Vestigial Structures:
- organs with no apparent function
that are homologous to functional
organs in related organisms
- examples: coccyx, appendix, ear
muscles, etc.
Salamander
Vestigial Structures
Gibbon Viper
Gray Whale
C. Comparative Embryology
- Organisms with common ancestors
share similarities in embryonic
development.
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo
D. Comparative Biochemistry
- All organisms contain
DNA, RNA, and
proteins made of the
same 20 amino acids.
- The more recent two
organisms share a
common ancestor, the
more similar their DNA
and proteins.
DNA Differences
in Cytochrome C
E. Biogeography
- Biogeography explains why certain
species are found in certain places.
- Islands have many endemic species
that are often closely related to
species on the nearest mainland or
island.
Biogeogaphy of a Group of
Pacific Island Monarchs
Biogeography
of Members
of the Camel
Family
F. Types of Adaptation
1. Camouflage
Leafy Sea Dragon
F. Types of Adaptation
1. Camouflage
Octopus near
Cayman Island
(1:15)
.
F. Types of Adaptation
1. Camouflage
Octopus
F. Types of Adaptation
1. Camouflage
Scorpionfish
Dead Leaf Butterfly
Walking Stick
Cheetah
Mantis
2. Mimicry
- A harmless species may imitate a
harmful species.
Milk Snake
Coral Snake
2. Mimicry
- A harmless species may imitate a
harmful species.
Hawkmoth larva
Green parrot snake
- 2 harmful species may reinforce each
other’s warning colors.
Spring Salamander
Gyrinophilus porphyriticus
Red Salamander
Pseudotriton ruber
Müllerian vs. Batesian Mimicry
Median
Wasp
Hoverfly
Hoverfly
Paper Wasp
Hoverfly
Longhorn
Beetle
III. Shaping Evolution Theory
A.Mechanisms of Evolution
1. Population Genetics
- Microevolution is a change in relative
frequency of alleles in the gene pool
of a population.
- A population is at genetic equilibrium
if 5 conditions are met:
Large size, No mutations,
No gene flow, Random mating, and
No natural selection.
2. Genetic Drift
- a random change in allele frequency
a) Founder Effect
- occurs when a new
population is established
from a small sample of a
population separated
from the rest of the
original population.
Ellis-van Creveld syndrome is more
common among the Amish and can be
traced back to a single family who
helped establish the colony in 1744.
2. Genetic Drift
Blue Iguana
Cyclura lewisi
Blue iguanas, endemic to
the Grand Cayman Island, is
believed to have originated
from a single pregnant
Cuban iguana 3 MYA.
Cuban Iguana
Cyclura nubila
2. Genetic Drift
Masai Giraffe
Reticulated Giraffe
Rothschild Giraffe
2. Genetic Drift
b) Bottleneck Effect
- occurs when a population is reduced in size
that no longer reflects the original
“King” Cheetah variation
population’s gene pool.
Cheetah populations
were nearly hunted
into extinction.
3. Mutation
- random change in DNA
- usually harmful or neutral, occasionally
advantageous (depends on environment)
- source of all
heritable
variation
3. Mutation
- random change in DNA
- usually harmful or neutral, occasionally
advantageous (depends on environment)
- source of all
heritable
variation
‘Blue eyes’ in humans
stem from a single genetic
mutation that occurred
6,000 - 10,000 years ago.
Evolving Lactase Persistence
14:30
4. Natural Selection
- acts on phenotypes and changes allele
frequency in a pop.
- favors individuals best adapted to
environment
a) Stabilizing Selection
- eliminates extreme
expressions of a trait
Original population
Phenotypes (fur color)
Original
population
Evolved
population
Phenotype
b) Directional Selection
- increases one
extreme expression
of a trait
Original population
Phenotypes (fur color)
Original
population
Evolved
population
Phenotypes (fur color)
b) Directional Selection
Rock Pocket Mouse:
One Species, Two Varieties
10:25
Sandstone
Environment
Basalt
Environment
b) Directional Selection
Rock Pocket Mouse:
One Species, Two Varieties
c) Disruptive Selection
- favors both extreme
expressions of a trait;
eliminates average
exp. of trait
Original population
Phenotypes (fur color)
Original
population
Evolved
populations
Phenotypes (fur color)
c) Disruptive Selection
Timema cristinae:
One Species, Two Varieties
Adenostoma
ecotype
Ceanothus ecotype
c) Disruptive Selection
5. Sexual Selection
- selection that favors the ability to attract
a mate
- produces differences between males and
females
5. Sexual Selection
A Bower of the
Satin Bower Bird
5. Sexual Selection
Male
Stalk-eyed Flies
African Elephant
Bird of Paradise
Gemsbok
Sandhills Crane
Intrasexual Selection
Intersexual Selection
5. Sexual Selection
Male Irish Elk
B. Speciation
- the origin of a new species
Phylogeny of
the Pig Family
1. Reproductive Isolation
- Members of a new
population of
organisms can no
longer produce
fertile offspring
with members of
the original
population.
Salamanders
in California
3:21
Salamanders
in California
a) Prezygotic Isolation
- prevents fertilization
Prezygotic barriers impede mating or hinder fertilization if mating does occur
Habitat
isolation
Behavioral
isolation
Temporal
isolation
Individuals
of different
species
Mechanical
isolation
Mating
attempt
HABITAT ISOLATION
TEMPORAL ISOLATION
BEHAVIORAL ISOLATION
(b)
MECHANICAL ISOLATION
(g)
(d)
(e)
(f)
(a)
(c)
2 Very Similar Species:
One in Eastern U.S., One in Eastern Asia
Liriodendron
tulipifera
Liriodendron
chinensis
2 Species of Southern Pine:
Time of Pollination Differs
Pinus taeda
April
Pollination
Pinus
palustris
February
Pollination
Behavioral Isolation
Eastern Meadowlark,
Sturnella magna
Western Meadowlark,
Sturnella neglecta
b) Postzygotic Isolation
- A hybrid offspring is born but is either not
viable or fertile.
Gametic
isolation
Reduce
hybrid
fertility
Reduce
hybrid
viability
Hybrid
breakdown
Viable
fertile
offspring
Fertilization
REDUCED HYBRID
VIABILITY
GAMETIC ISOLATION
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
(k)
(j)
(m)
(l)
(h)
(i)
2. Allopatric
Speciation
- speciation that occurs
when a physical barrier
separates a population
into 2 or more
populations
Allopatric Speciation
Kaibab Squirrel
Abert Squirrel
3. Sympatric Speciation
- speciation that occurs
without a physical
barrier that separates
a new population
C. Patterns of Evolution
1. Adaptive Radiation
(Divergent Evolution)
- when one species gives rise to several
new species
Hawaiian
Honeycreepers
2. Coevolution
- when 2 species evolve together forming
symbiotic relationships
Darwin’s Orchid and the Orchid Fly
2. Coevolution
- when 2 species evolve together forming
symbiotic relationships
California Newt
Coevolution of the Garter Snake
and the California Newt
Garter Snake
2. Coevolution
- when 2 species evolve together forming
symbiotic relationships
California Newt
Coevolution of the Garter Snake
and the California Newt
Garter Snake
3. Convergent Evolution
- When 2 unrelated species evolve similar
traits due to living in similar environments
Swordfish
Dolphin
Ichthyosaur
Shark
Convergent Evolution
Convergent Evolution
Convergent Evolution
American Cactus
African Euphorb
4. Rate of Speciation
a) Gradualism
- when evolutionary change occurs as a
series of small, gradual changes
b) Punctuated Equilibrium
- when evolutionary change occurs in rapid
spurts followed by longer periods of
little change
Gradualism
Punctuated Equilibrium
Triassic Landscape, Karen Carr
The End