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WHAT IS EVOLUTION?
General definition: a change or modification
through time (e.g., galaxies and language
evolves)
biological or organic evolution: change in the
properties of organisms that transcend the
lifetime of a single individual
: in biology, more specifically,
changes that are heritable
: changes in allele frequency
HISTORICAL DEVELOPMENT OF EVOLUTION
I. Classical Thinking
Greeks thought that the world changes, but by
Plato’s time the idea of a static world came into
prominence
A. Static World by Plato (427 to 347 BC)
-there is the “essence” or “form” that
doesn’t change, and things on earth
are a reflection of this
-so things on earth can show variation, but
the form never changes.
B. Purpose in Life: Natural Order "Will of God"
Scala Naturae or “the ladder of life”
HISTORICAL DEVELOPMENT OF EVOLUTION
II. Pre-Darwinian Thinking
A. (1500-1700) No purpose in physical world: Newton and Copernicus
B. Geologist: Earth is old!!
James Hutton (1788): uniformitarianism
Charles Lyell (1830)
Based on rocks, earth is billions of years old (about 4.6), not 5668,
according to Archbishop James Usher, who used lineages in the Old
Testament to estimate this.
HISTORICAL DEVELOPMENT OF EVOLUTION
II. Pre-Darwinian Thinking
C. Jean Baptiste de Lamarck (1744-1829): evolve to be better by design
of God (in his book Philosophie Zoologie, 1809); use and disuse of
traits, then passed on to the next generation
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
1. Homology: the study of likeness
a) ontogeny: development of embryo to adult
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
1. Homology
b) Structural:
so why similar? Creator or because of common descent
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
2. Change Through Time:
a) fossil record: old things resembled new and transitional animals
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
2. Change Through Time:
b) vestigial parts: parts that are now useless were once useful
other examples: whale femur, human appendix
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
2. Change Through Time:
c) extinction in fossil records
-creationist: extinct due to
flooding
-biologist: extinct species are
relatives of extant species
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
A. Basic types of evidence that challenged old paradigm
2. Change Through Time:
d) marine fossils in arid areas: earth itself is dynamic! (grand canyon,
see figure)
coral fossil in AnzaBorrego State Park
(desert in CA)
3. Age of the earth: Geology – earth is old (4.6 by)
Evolution was really accepted, but the mechanisms is what was
controversial (and the idea of no design!)
HISTORICAL DEVELOPMENT OF EVOLUTION
III. Darwin's time:
B. Darwin
Charles Darwin: 1809-1882
1831-1836 joined the crew of the HMS Beagle to
travel around the world as the ship's
naturalist.
1844: he wrote an essay on Natural Selection
1858: another biologist, Alfred Wallace (18231913), sent Darwin a manuscript outlining
natural selection, identical to his!
So at the urging of his colleagues, Darwin
presented his work, along with Wallace's, at a
meeting of the Linean Soceity of London in
1858. In 1858, he published his seminal
“abstract” -- On the Origin of Species.
HISTORICAL DEVELOPMENT OF EVOLUTION
C. Natural Selection
a. Darwin proposed 4 steps, how Natural Selection drives evolution:
1.
2.
3.
4.
individuals need to be variable
traits that are variable are heritable -- passed on to next generation
excess offspring is produced
differential production or survival – linked to specific traits (see 2)
HISTORICAL DEVELOPMENT OF
EVOLUTION
IV. Neo-Darwinian
How are traits passed on?
A.Lamarckism
B. Mendelian Genetics: Gregor Mendel, in
1854 carried out breeding experiments
in a monastery using the garden pea
Pisum sativum
In 1865 he reported his results, but his
results were not widely read until the
1900's
HISTORICAL DEVELOPMENT OF
EVOLUTION
IV. Neo-Darwinian
How are traits passed on?
B. Mendelian Genetics
Experiment:
smooth x wrinkled seeds.
The f1: all smooth
The f2: 3/4 smooth and 1/4 wrinkled.
One of Mendel’s basic outcomes:
inheritance of genes is discrete, no
mixing
NATURAL SELECTION
V. Example of Evolution by Natural Selection
A. Observations: Galapagos Finches by
Grants and colleagues
-
Galapagos Archipelago, dramatic
differences among finch “species”’’
Is this evolution in action?
1. Individuals need to be variable
- Medium ground finch (Geospiza fortis) on Isla Daphne Major
2. Traits that are variable are heritable
3. Excess offspring is produced
4. Differential reproduction or survival
V. Example of Evolution by NS
A. Observations: Galapagos
Finches by Grants and
colleagues
Remember, NS works:
3. Excess offspring is produced
4. Differential reproduction or
survival
– linked to specific characters
V. Example of Evolution by NS
A. Observations: Galapagos
Finches by Grants and
colleagues
Remember, NS works:
3. Excess offspring is produced
4. Differential reproduction or
survival
– linked to specific characters
V. Example of Evolution by NS
A. Observations: Galapagos
Finches by Grants and
colleagues
Are populations evolving??
V. Example of Evolution by NS
B. Type of Natural Selection
1. DIRECTIONAL SELECTION
w = fitness (how well an animal does)
e.g., larger trait results in higher fitness
w
trait
f = frequency of animal
with specific trait
f
trait
V. Example of Evolution by NS
B. Type of Natural Selection
2. STABILIZING SELECTION
w
trait
f
trait
V. Example of Evolution by NS
B. Type of Natural Selection
2. STABILIZING SELECTION:
EXAMPLE
BIRTH WEIGHT IN HUMANS
By Karn and Penrose
•13,730 birth records at University
College Hospital between 1935-1946
•7037 males and 6693 females
•Survivorship (to 28 days), weight,
gestation time and mother
•Stabilizing Selection for birth weight
•Stabilizing Selection for gestation time and age of mother (not
shown)
MORE RECENT SURVEY IN ITALY (1954-1985) FOUND A
4-FOLD DECREASE IN INTENSITY OF SELECTION
V. Example of Evolution by NS
B. Type of Natural Selection
3. DISRUPTIVE SELECTION
w
trait
f
trait
V. Example of Evolution by NS
B. Type of Natural Selection
3. DISRUPTIVE SELECTION
Seedeater Finches, Pyerenestes ostrinus
•Two forms: large and small billed
•Feed on two species of sedge: hard and soft
shelled (10 fold difference in hardness)
•Consumption of seeds (handling time)
related to bill morphology
•Two rainy seasons, split by dry season –
survival across dry season is low
-- By T. B. Smith
•Banded and measured > 2500 birds
•Found (in general) 20% survival across seasons
•Bill morphology heritable
VI. Forces that Drive Evolution
A.
Natural Selection
B.
Genetic Drift: changes in gene frequencies occur because of
chance events (sampling errors) that occur when populations
are finite in size (small).
Population could be small due to founder event or bottle neck
VI. Forces that Drive Evolution
A.
Natural Selection
B.
Genetic Drift
e.g., Clegg and colleagues work
on Silvereyes (Zosterops lateralis)
-populations have colonized islands off
Australia
-founder populations lose alleles
VI. Forces that Drive Evolution
A.
Natural Selection
B.
Genetic Drift
C.
Mutation
D.
Gene Flow
VII. SOURCES OF GENETIC VARIATION
A.
MUTATION
“TRUE” SOURCE OF VARIATION
MISTAKES DURING REPLICATION OF
DNA RESULTS IN MUTATIONS
THAT ARE HERITABLE
1.
TYPES OF MUTATIONS
a)
Point Mutation: Substitution of
single base pair
VII. SOURCES OF GENETIC VARIATIONa) POINT MUTATION
b) DELETION: REMOVAL OF 1 OR MORE NUCLEOTIDES IN A DNA
SEQUENCE
c) INSERTION: ADDITION OF ONE OR MORE NUCLEOTIDES IN A
DNA SEQUENCE
VII. SOURCES OF GENETIC VARIATION
MECHANISMS OF DELETION AND INSERTION
1. unequal crossing over during recombination
2. transposition: jumping of genetic material from one position to
another chromosome (transposable elements)
VII. SOURCES OF GENETIC VARIATION
MECHANISMS OF DELETION AND INSERTION
1) unequal crossing over during recombination
2) transposition
3) slippage
VII. SOURCES OF GENETIC VARIATION
d) INVERSION: 180 DEGREE ROTATION OF DNA
e) POLYPLOIDY: INHERITING EXTRA COPIES OF
CHROMOSOMES
-COMMON IN PLANTS, RARE IN ANIMALS
(WE’LL COVER THIS IN THE NEXT LECTURE)
VII. SOURCES OF GENETIC
VARIATION
A. MUTATION
B. RECOMBINATION
-DURING METAPHASE,
HOMOLOGOUS
CHROMOSOMES
EXCHANGE
C. GENE FLOW
Copyright © 2002 Pearson Education, Inc.
VIII. Sexual Selection
Peahen and chick drab and cryptic
Peacock elaborate
Peacocks highly conspicuous and vulnerable to predators
Why does this evolve?
Sexual Selection: Differential Reproduction Related to Elaborate Male Display
Traits
VIII. Sexual Selection
A. Causes of Sex Differences
1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES
Male Birds:
Female Birds:
Fairywren: 8 billion
sperms at one time
One egg = 15-20% of
body weight
In Kiwi, it’s 25%, 1 lbs
SALMON: FEMALES LAY 3500 EGGS DURING SPAWNING,
MALES FERTLIZE THEM WITH 400,000,000,000 SPERM!
HUMANS: FEMALES PRODUCE ONE VIABLE EGG PER MONTH
MALES CAN FERTILIZE THE ENTIRE WORLD WITH 1 EJACULATION
VIII. Sexual Selection
A. Causes of Sex Differences
1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES
2. Parental Investment (post gametes)
-females typically invest more than males
e.g., mammals:
females nourish and carry embryo, nurse offspring
vs.
males fertilize eggs and leave
VIII. Sexual Selection
B. Effects of Sex Differences
1. Reproductive Potential – Bateman’s Rule
males
reproductive success
9
8
8
7
7
6
6
5
5
4
4
3
3
2
2
1
1
0
0
0
2
4
6
females
9
8
10
0
2
4
6
8
number of mates
-males increase their mating success with more females
-females do not necessarily increase their mating success with more
males
10
VIII. Sexual Selection
B. Effects of Sex Differences
2. Operational Sex Ratio (by Emlen and Oring)
The ratio of available males to available females NOT just the
ratio of males to females
-note: if a female is mated, she is no longer available for mating
while males after being mated are still available for mating
-as season progresses, skew towards more males than
available females
FEMALES ARE CHOOSY SEX BECAUSE OF THESE TWO
FACTORS!
VIII. Sexual Selection
C. Test
Differential Parental Investment Dictates Which Sex is Choosy
1. Mormon Cricket Observations
By D. Gwynne
MALES PRODUCE SPERMATOPHORES:
NUTRIENT RICH PRODUCTS
SPERMATOPHORE IS UP TO 25% OF MALES
WEIGHT!
IN AREAS WHERE FOOD IS SCARCE AND OSR
IS FEMALE BIASED, MALES ARE THE CHOOSY
SEX
VIII. Sexual Selection
Differential Parental Investment Dictates Which Sex is Choosy
2. Australian Katydids Lab Experiment By D. Gwynne
•Different food quality:
Shaded = high quality
Unshaded = low quality
-FEMALES MATED MORE OFTEN WHEN
FOOD QUALITY IS LOW; MALES MATED
MORE OFTEN WHEN FOOD QUALITY IS
HIGH
-WITH HIGH QUALITY FOOD,
SPERMATOPHORE PRODUCTION IS
EASY (LOW PI FOR MALES), SO
FEMALES BECOME MORE VALUABLE
AND CHOOSY
-WITH LOW QUALITY FOOD, MALES
BECOME CHOOSY
VIII. Sexual Selection
C. Test Differential Parental Investment Dictates Which Sex is Choosy
3. Australian Katydids Field Experiment By D. Gwynne and L. Simmons
CAGE
MEAN NO. OF
CALLING ♂
MEAN NO. OF
MATINGS PER
♀
%
INTERACTION
S WITH ♀-♀
COMPETITION
CONTROL 1
0.4
1.4
15
CONTROL 2
0.7
1.2
22
CONTROL 3
0.1
1.4
27
CONTROL 4
0.3
1.3
30
EXTRA FOOD
1
8.1
0.6
0
EXTRA FOOD
2
4.7
0.7
0
EXTRA FOOD
3
5.7
0.8
0
EXTRA FOOD
4
7.9
0.6
0
•Placed 8
fiberglass cages
in the field
•Four – extra
food, Four –
intact/control
•24 males, 24
females released
in each cage
IX. Modes of Sexual Selection
A. Intrasexual Competition
B. Intersexual Choice
- Differential Mating Success Among Individuals
IX. Modes of Sexual Selection
A. Intrasexual Competition:
Elephant Seals
•Size dimorphic: Males 3x > Females
IX. Modes of Sexual Selection
A. Intrasexual Competition:
Elephant Seal
© Stan Russell
•Size dimorphic: Males 3x > Females
•Females gather at beaches for 3 months – breed
IX. Modes of Sexual Selection
A. Intrasexual Competition:
Elephant Seal
www.saintbrendan.com
•Size dimorphic: Males 3x > Females
•Females gather at beaches for 3 months – breed
•Males fight to dominate these “harems”
IX. Modes of Sexual Selection
A. Intrasexual Competition:
Elephant Seal work by T. S. McCann
(also B. LeBoeuf)
1. Combat:
* Largest and oldest males win
male-male combats
*Winner of combats are the
dominant males in a harem: 8
most dominant males
inseminated 348 females
2. Endurance Rivalry
- Males stay on the beach for 90 days without
feeding = lose over 40% of body weight by end
IX. Modes of Sexual Selection
B. Intersexual Choice:
1. Precopulatory Choice
-dimorphic, males with long tails and red
epaulet
- males defend territories for female nesting
IX. Modes of Sexual Selection
B. Intersexual Choice:
1. Premating Female Choice
e.g. widowbird work by Andersson
-alter tail length
-longer tails = more females
-shorter tails = lost females
IX. Modes of Sexual Selection
B. Intersexual Choice:
2. Postcopulatory Female Choice
e.g. jungle fowl work by
Pizzari and
Birkhead
-dimorphic
-females prefer males with
redder comb
-females prefer dominant
males
-force copulations are
common
-female preferentially eject
sperm low ranking males
X. MALE MATE CHOICE – SEX ROLE REVERSAL
e.g., fish family Syngnathidae – seahorses and
pipefish, where male “pregnancy” occurs
Rosenqvist’s work on broad-nosed pipefish
-male provide all of parental care
-males have brood pouches where females deposit
eggs, and male provide oxygen, nutrients, protection
until they hatch
-females can produce eggs much quicker than males
rearing eggs to hatchling, so PI greater in males
X. MALE MATE CHOICE – SEX ROLE
REVERSAL
Rosenqvist’s work on broad-nosed pipefish
Drosophila
a) Bateman’s Principle
comparing Bateman’s Drosophila work in
1948 with current work on pipefish
pipefish test by Jones, Rosenqvist,
Berglund and Arnold 2000
-in barrels: 4 males and 4 females or 2
male and 6 females (results same, so
pooled)
As predicted, female reproductive success
increases more steeply with more
mates than for males
open, solid line=male
filled, dashed line=female
Pipefish
X. MALE MATE CHOICE – SEX ROLE REVERSAL
e.g., pipefish by Rosenqvist and colleagues
two species: Syngnathus typhle and Nerophis ophidion
-In both species, male provide all of parental care
-not energetically costly, but time is the key cost
-males more valuable, so females should compete over males, and males should be
choosy
N. ophidion: females are larger and
have dark blue stripes and skin
folds on their bellies
S. typhle: same size, but females
court (zigzag)
X. MALE MATE CHOICE – SEX ROLE REVERSAL
e.g., pipefish by Rosenqvist and colleagues
two species: Syngnathus typhle and Nerophis ophidion
in both species, males choose
in Nerophis, use female
traits
in Syngnathus, use “parasite”
infestation