Transcript Chapter 15 - TeacherWeb

How did life begin?
Miller and Urey’s
Experiment
 Passed sparks
through a mixture of
hydrogen methane
ammonia and water
 This produced
amino acids – the
building blocks of life
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Theory of Life cont.
Endosymbiotic theory
eukaryotic cells
arose from living
communities formed
by prokaryotic
organisms
Ancient prokaryotes
entered primitive
eukaryotic cells and
remained there as
organelles
Lamark
Theory of acquired
characteristics

Lamark said
organisms acquired
traits by using their
bodies in new ways

These new
characteristics were
passed to offspring

Lamark was totally
wrong!
Geologists:
Hutton and Lyell
Fundamentalists said that the
earth was around 6000 years
old
Hutton and Lyell argued that
the earth is many millions of
years old b/c
 layers of rock take time to
form
 processes such as
volcanoes and earthquakes
shaped the earth and still
occur today
Malthus
 Reasoned that if the
human population
continued to grow
unchecked, sooner or
later there would be
insufficient living space
and food for everyone
Charles Darwin (1809-1882)
Sailed around the world 1831-1836
2. What did
Darwin’s
Travels reveal
 The diversity of living
species was far greater
than anyone had
previously known!!
 These observations led
him to develop the
theory of evolution!!
3.How did tortoises and birds
differ among the islands of
the Galapagos?
Warbler finch
Cactus finch
Woodpecker finch
Sharp-beaked finch
Small insectivorous
tree finch
Small ground
finch
Large
insectivorous
tree finch
Cactus
eater
Medium
ground finch
Insect eaters
Seed eaters
Vegetarian
tree finch
Bud eater
Large
ground
finch
Galapagos
Tortoises
Evolution is when organisms change
over time. So, modern organisms
descended from ancient ones
Evolution is a Theory –
Just like Gravity!
• Evolution is a well
supported
explanation of
phenomena that have
occurred in the
natural world
• A theory in science
must be supported by
facts, it can’t be
based on supposition.
Darwin finally
published his
ideas in 1859
 Only when other
naturalists were
developing the
same theory that
he had did Darwin
finally publish his
findings.
Artificial Selection
 nature provides variation, humans select
variations that are useful.
 Example - a farmer breeds only his best
livestock
Natural
Selection
 The traits that
help an organism
survive in a
particular
environment are
“selected” in
natural selection
What color genes are in the beetle gene pool?
What’s happening to the color genes in the
beetle gene pool?
Why is this happening?
Explain why we say green beetles have been
selected against while brown beetles have
been selected for?
Natural Selection and
Species Fitness
 Overtime, natural selection results in
changes in the inherited
characteristics of a population.

 These changes increase a species
fitness (survival rate)
Bottom line:
Those that are best adapted to their
environment survive to reproduce.
Evidence of Evolution
1. Fossil Record
2. Geographic Distribution of Living
Species
3. Homologous Body structures
4. Similarities in Embryology
5. Vestigial organs
Evidence of
Evolution
Fossil Record provides
evidence that living
things have evolved
Fossils show the history
of life on earth and
how different groups
of organisms have
changed over time
Primate Fossils
Australopithecus
Homo erectus
Homo sapien
Remember PANGEA?
Evidence of
Evolution
2. Geographic
Distribution of Living
Species
Similar animals in
different locations
were the product of
different lines of
descent
Evidence of Evolution
Geographic Distribution of
Living Species
Analogous Structures
are the result of
convergent evolution
-
Similar animals in
different locations exhibit
analogous structures due
to similar environmental
pressures.
Eg. North American flying
squirrel and the
Australian sugar glider
More evidence for adaptations
wings of birds wings of damselflies
what about wings
of butterflies?
wings = adaptations for flight (similar by function not
descent) This means they are analogous structures.
unrelated organisms adapt independently to a common
environment.
Convergent evolution – natural selection pressure
has selected for best adaptation.
Convergent evolution
 Fish: aquatic vertebrates
 Dolphins: aquatic mammals
similar adaptations to
life in the sea
 not closely related

Those fins & tails
& sleek bodies are
analogous structures!
Evidence of
Evolution
Adaptive radiation leads to
Homologous Body
Structures thru
divergent evolution

Turtle
Alligator
Structures that have
different mature forms
but develop from the
same embryonic
tissues
e.g. Wing of bat, leg of
turtle & human arm,
are similar by descent not function.
Bird
Convergent evolution
 Fish: aquatic vertebrates
 Dolphins: aquatic mammals
similar adaptations to
life in the sea
 not closely related

Those fins & tails
& sleek bodies are
analogous structures!
Homologous Body Structures…………
…………are the result of divergent evolution
13. Evidence of
Evolution
Similarities in
Embryology

In their early
stages of
development,
chickens,
turtles and rats
look similar,
providing
evidence that
they shared a
common
ancestry.
Embryological development
Vestigial organs
 Modern animals may have structures
that serve little or no function
 remnants of structures that were functional
in ancestral species
 evidence of change over time
 some snakes & whales show remains of
the pelvis & leg bones of walking
ancestors
 eyes on blind
cave fish
 human tail bone
This is not
LaMarck’s loss
from “disuse”!
Vestigial Structures
in snakes
Vestigial Structures
in whales
Molecular record
 Comparing DNA & protein structure
 universal genetic code!
 DNA & RNA
 compare common genes
 cytochrome C (respiration)
 hemoglobin (gas exchange)
Why compare
these genes?
Human/kangaroo
Closely related species have
sequences that are more similar
than distantly related species
 DNA & proteins are a molecular
record of evolutionary
relationships
Nucleotide substitutions
100
Dog/
cow
75
Human/
cow
Rabbit/
rodent
50 Horse/
donkey
Llama/
cow
Horse/cow
Sheep/
goat
25
Human/rodent
Pig/
cow
Goat/cow
0
0
25
50
75
100
Millions of years ago
125
Comparative hemoglobin structure
Human Macaque
Dog Bird
Frog
Lamprey
32 45
67
125
Why does comparing
amino acid sequence
measure evolutionary
relationships?
8
0 10 20 30 40 50 60 70 80 90 100 110 120
Number of amino acid differences between
hemoglobin (146 aa) of vertebrate species and that of humans
Descent with Modification
 Each living
species has
descended
with changes
from other
species over
time
Summary of Darwin’s Theory
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than
survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass
those advantages to their children
5. Species alive today are descended with
modifications from common ancestors
Variation in
Populations
2 processes can
lead to this:
Mutations change in DNA
sequence
Gene Shuffling –
from sexual
reproduction
Gene Pool
Combined genetic
info. of all
members
Allele frequency is #
of times alleles
occur
Genetic Drift changes populations…
Random change in allele frequency
causes an allele to become common
 Founder Effect:
a cause of genetic
drift attributable to
colonization by a
limited number of
individuals from a
parent population
Evolution of Populations
Occurs when there is a
change in relative
frequency of
alleles……….
in other words – a
change in the contents
of the gene pool
 Gene Flow:
genetic exchange
due to the
migration of fertile
individuals or
gametes between
populations
(reduces
differences
between
populations)
 Nonrandom mating aka artificial
selection: inbreeding and assortive
mating (both shift frequencies of
different genotypes)
 Natural Selection:
differential success
in reproduction;
only form of
microevolution that
adapts a
population to its
environment
Single-Gene vs. Polygenic
Traits
Single-Gene:
2 Distinct Phenotypes (EG: tongue rolling)
Polygenic:
Many Phenotypes
Natural Selection on Polygenic
Traits
 Shifts to
middle range
 Shifts to
2 extremes
 Shifts to
1 extreme
Are you more closely related to a turtle or a frog?
Natural selection in action
 Insecticide &
drug resistance
 insecticide didn’t
kill all individuals
 resistant survivors
reproduce
 resistance is inherited
 insecticide becomes less
& less effective