Download Chapter 16 - Microevolution

Chapters 14-16
Evolution
College Prep Biology
Mr. Martino

Concept 16.1- Prokaryotic Life
◦ Early Earth contained carbon monoxide, carbon
dioxide, and water vapor; little oxygen
 The introduction of lightening created small
organic molecules.
◦ Amino acids, sugars, lipids, nitrogen bases found in
DNA, RNA, and ATP
 RNA molecules have been observed to self-replicate w/o
enzymes in solutions containing nucleotides
 Led to the formation of DNA
 The Oxygen Revolution
◦ Cyanobacateria are photosynthetic prokaryotic bacteria
that live in water that give of oxygen as a waste product
I. Introduction
- 50,000 years ago began to domesticate
dogs
 - 14,000 years ago started to develop
different varieties
(subspecies or breeds)

◦ Used artificial selection –
choosing desired traits
◦ Evolution: genetic
change in a line of
descent through
successive generations
Early Beliefs & Discoveries
•
“It seems to me the disease
called sacred…has a natural
cause, as other diseases have.
Men think it divine merely
because they do not
understand it. But if they
called everything divine that
they did not understand, there
would be no ending to divine
things!…If you watch these
fellows treating the disease,
you see them use all kinds of
incantations and magic – but
they are also careful in
regulating diet. Now if food
makes the disease better or
worse, how can they say it is
the gods who do this?…It does
not really matter whether you
call such things divine or not.
In Nature, all things are alike
in this, in that they can be
traced to preceding causes.” –
On The Sacred Disease (400
B.C.)



2000 years ago it was
believed disease came
from “angry gods”
Aristotle attempted to
find explanations for
natural occurrences
15th century naturalists
attempted to describe
& catalog all organisms
14.2 Early Evidence for Evolution
1) Biogeography: study of world distribution of organisms
Australian
Emu
African ostrich
South American Rhea
2)Comparative morphology: study of body plans between
major groups of organisms
Ex. Bones of human arm, whale flipper, bat wing
Ex. Why are there hind limb bones in pythons, tail bones in
humans, etc?
Late 1600’s – geologists began
mapping layers of rocks and
found
 3) Fossils: preserved remains
or markings

◦ Identified patterns and specific
sequences of life in layers
◦ Noticed similarities yet differences
with living organisms

4) Molecular Biology
◦ The study of the genetic code and protein
sequences of species
 If sequences are similar, than species are
closely related

5) Comparative Embryology – embryos of
closely related species follow similar
developmental stages
◦ All vertebrates have an embryonic stage where
pouches form on the this side of the throat

6) Taxonomy –
the classification
of organisms
14.1 A Flurry of New Theories




A. Catastrophism: Georges Cuvier (anatomist) who felt life was
created at one time - many destroyed by catastrophe
B. Acquired Traits: Jean Baptist Lamarck – organisms develop
characteristics if needed & lose what is not needed
C. Natural Selection: Charles Darwin 1831 – Charles Darwin began 5 yr voyage on HMS Beagle
◦ Theology degree from Cambridge University
◦ Ship’s naturalist – collected samples
◦ Observed:
 Fossils resembled living species
 Earthquakes and volcano eruptions
 Marine animal fossils high up in mountains
 Galapagos Island species were similar yet different
◦ Read (and influenced by) Charles Lyell’s Principles of Geology
- Earth is old and changing

D. Galapagos Islands volcanic islands in Pacific
◦ Many very unique species
◦ Darwin spent many
years studying there

Aristotle believed species were
unchanging and did not evolve
◦ Western Judeo-Christian culture
adopted Aristotle’s views
 Earth and all species are perfect and
A Young
unchanging
Charles Darwin
 Earth +/- 6000 years old
 All life designed as is by creator

Mid 1700’s Georges Buffon
suggested Earth was old
◦ E. Theory of Uniformity: Earth is
gradually, uniformly, and repetitively
changing
 Directly challenged catastrophism &
current beliefs of the time
Darwin’s Theory

1836 – Darwin returned, did
many years research - had many
questions
◦ Ex. Fossils of 10’ long armadillo-like
glyptodonts only in regions where
armadillos are now found
 Descent with modification?
◦ Read Thomas Malthus –
clergyman/economist who observed
struggles for existence in humans as
result of populations growing faster
than resources
 If environment restricts # of
reproducing individuals - which are
chosen to repro.?
A. Darwin’s main ideas:
◦ 1. Overproduction of offspring
◦ 2. Variety among individuals of a
population
◦ 3. Varying traits passed to offspring
◦ 4. Natural Selection: individuals of
a population who were genetically fit
for their environment are most likely
to survive and reproduce
 Based on artificial selection of farmers
& breeders
 reproductive fitness - best suited
individuals tend to leave more
offspring
5. Populations must remain stable in
size.
Fossils of giant sloth
and glyptodont

1840’s Darwin developed an
essay with all the main points
of his theory
◦ Delayed publishing due to fear
of results
◦ Mid – 1850’s Alfred Wallace
developed a similar theory
◦ 1858 – colleagues presented
Wallace’s paper and some of
Darwin’s essay to scientists
◦ B. 1859 – On the Origin of
Species by Means of Natural
Selection was published
 Descent with modification
 Fueled further research
 Unity within diversity
Video: Who was Charles Darwin?
Video:
Darwin –
The
Reluctant
Rebel
What About God?
Video:
Scopes
Monkey Trial
Is it possible to be religious
and still consider the theory
of evolution to be viable?
 Must scientists be atheists
just by choice of profession?

 Darwin believed in both a
Devine power AND natural
selection…
 Your opinion is for YOU to
decide….
Video:
Courtroom
Controversy
Video: Why is
Evolution
Controversial
Anyway?
Video: Personal
Stories
Video: Biblical
Literalist
14.3 Individuals Don’t Evolve –
Populations Do

A. Darwin presented
evidence
to convince many scientists
evolution occurs w/out
supernatural intervention
◦ - Later discoveries and
DNA tech further support
◦ - Fossils still a rich source
of evolutionary evidence
◦ - Individuals don’t evolve
populations do
Video: Isn’t Evolution Just A Theory?
Wild Mustard and Descendants
14.4 – Darwin’s Natural Selection at Work

B. Population: group of same species living
together in same place at same time that reproduce
◦ - All have same basic –
 Morphological traits (body plan)
 Physiological traits (metabolic, growth, & repro. traits)
 Behavioral traits (respond to stimuli in the same ways)
◦ 1) Gene pool: sum total of all genes present within a
population; genes are passed on within population
◦ Darwin did not know about genetics- now genetics
explains his ideas as population genetics: science of
genetic change of a population
 All of above traits vary in either qualitative or quantitative
ways - two or more different morphs (polymorphisms)
 Ex. White or purple flowers
◦ 2) Species: group of populations whose individuals can
interbreed and produce fertile offspring
Do we know this guy?!
Do we know this
lady?
Same Species, different forms of a trait!!!

C. Sexually reproduced offspring are unique:
◦ 1. Mutations (produce new alleles in gene pool)
◦ 2. Crossing over during meiosis – new gene combinations
◦ 3. Independent assortment during meiosis – new random
mixtures of maternal and paternal chromosomes
◦ 4. Fertilization – combines alleles of 2 parents
◦ 5. Changes in chromosome number or structure
Human gametes have one of 10600 possible allele
combinations…not even 1010 are alive today!
 You are one of a kind!
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D. Allele Frequencies:
how often certain alleles
occur in population
E. Hardy-Weinberg
Equilibrium: frequency
of alleles in gene pool
remains same unless
acted upon
F. Microevolution:
small changes in gene
pool over many
generations

G. Five conditions for HardyWeinberg equilibrium
◦
◦
◦
◦
◦
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1.
2.
3.
4.
5.
Population is large
Population is isolated
Mutations do not occur
Mating must be random
No natural selection
Rarely met in nature
Each gene has a specific
mutation rate
◦ Some mutations are lethal or
neutral (doesn’t help or harm – Ex.
Human fingerprint)
◦ Advantageous mutations are
passed on to offspring
16.7 3 Forms of Natural
Selection

A. Directional Selection: favors one
extreme
◦ Environmental change (peppered moth)
B. Stabilizing Selection: favors
intermediate individuals, reducing
extremes (human birth weight)
 C. Disruptive Selection: favors both
extremes, reducing intermediates
(incomplete dominant phenotype fails)

Directional Selection


Video: Evolution of
Antibiotic Resistance
Results in resistant pests,
parasites, and bacteria
◦ Kills off weak, strong and
immune survive
◦ Results in more strong and Dies Lives Dies Dies Dies
immune pests & parasites
When exposed to problems,
organisms either adapt,
move, or die
◦ According to fossil record,
most die - those that
survive often change
enough to become new
All survive!
species
Video: Why Does
Evolution Matter
Now?
Video: Hygiene
Hypothesis
Video: Evolution of Drug
Resistant Aids

D. Peppered Moths –
19th century England
◦ - Industrial
revolution caused
moth population to
change from light
to dark
◦ - Soot from
factories settled on
the trees
16.8 Stabilizing &
Disruptive Selection

A. Stabilizing seems to
counteract effects of
mutations, etc. and
preserve phenotype
◦ Reduces variation
◦ Ex. Human birth weight
Stabilizing
Selection
Ginkgo Leaf

Living fossils, like the coelacanth, ginkgo,
and horseshoe crab, are examples of
organisms that are relatively unchanged
(stabilized) from their distant ancestors

Disruptive selection
16.9 Special Selections


A. Sexual Selection: occurs in
organisms
that have
distinct male and female traits
B. Sexual Dimorphism: secondary
sexual characteristics
◦ Visible differences between males
and females
◦ Darwin’s sexual selection
 Competitions for harem or females
 Individuals of one sex are choosy
about mate
Video:
Importance
of sex
Video:
Polyandry
Video:
Songbird
Infidelity
Video: Tale of
the Peacock
Video: Asexual Repro
Would mates select….
Video: Sweaty T-Shirts
16.10 Gene Flow

A. Gene Flow: physical
flow of alleles
◦ 1) Immigration: moving
into population
◦ 2) Emigration: moving
out of population
◦ Reduces genetic variation
◦ Enables separated
populations to be
genetically similar
16.11 Genetic Drift

A) Genetic Drift: change in
small gene pool due to
chance
◦ Greatest effect in small
populations
◦ 1) Bottleneck Effect:
disaster
greatly reduces gene pool
 Unselective
 Ex. Elephant seals –
reduced to 20 & now
have no variation in 24
genes
◦ 2) Founder Effect:
colonization of new location
 Galapagos Islands

B. Inbreeding: nonrandom mating
between closely related individuals
◦ - Leads to homozygyotes

Endangered species have low
genetic variability
◦ Cheetahs, elephants, gorillas,
rhinocerouses, Florida panther
◦ Lower populations # = lower gene pool
diversity
◦ Ex. Cheetahs have 3 small populations
 E. Africa – 1.4% heteros.
 S. Africa - .04% heteros.
◦ Reduced capability to adapt
◦ Usually due to reduced habitat