Transcript Theory of Evolution

Key Terms
 Biogenesis:
 All living things come from other living things
 Makes sense to us, but prior to the 17th century they had
other ideas
 Spontaneous Generation:
 Living things could arise from nonliving things
Ideas from the Past
 Francesco Redi (1626-1697):
 Observed fundamental forms of flies

Found that they form from maggots
 Previously thought that flies spontaneously generated
from rotten meat
Ideas from the Past
 During this time scientists using microscopes thought
that microorganisms arose spontaneously from a “vital
force” in the air
 Lazzaro Spallanzani (1729-1799): text p. 280
 Found that microorganisms come from other
microorganisms
 Used broth: Control group & Experimental Group
 Many scientists did not accept his conclusions
Ideas from the Past
 Mid-1800s, controversy over spontaneous generation
raged on
 Prize was offered to who ever could clear up the issue
 Louis Pasteur (1822-1895):
 Answered Spallanzani’s experiment
 Used broth and curved-necked flask
Section 14.2
Earth’s History
 Formation of the Earth
 5 billion years ago our solar system formed
 Age of the earth is more than 4 billion years
Radiometric Dating
 Determines the age of materials
 Use radioactive isotopes and their rate of decay
 Carbon 12 – STABLE
 Carbon 14 – UNSTABLE – decays at a certain rate


Half-life = length of time it takes for one-half of any size
sample of an isotope to decay to a stable form
Measured against the amount of another stable substance
(Carbon – 12)
 How?


When an organism dies, its uptake of carbon stops
Carbon-14 decay continues & Carbon-12 remains constant
Radiometric Dating & Half-Lives
 Carbon-14 = 5,730 years
 Uranium-235 = 704,000,000 years
 Potassium-40 = 1,250,000,000 years
 Uranium-238 = 4,500,000,000 years
Earth’s History
 Miller-Urey Experiment: tested the hypothesis
 Some molecules, including amino acids, did form
 However: now know that the early atmosphere was CO2,
N, water vapor, & high O2…this prevents organic
molecule production
First Cells
 Lack evidence, and can only make inferences
 Anaerobic, heterotrophic prokaryotes
First Eukaryotes
 Formed from prokaryotic cells that formed a
mutually beneficial relationship
 Endosymbiosis: smaller aerobic prokaryote was
engulfed by and began to live and reproduce inside
of a larger, anaerobic prokaryote
 Later evolved into mitochondria and chloroplasts
 Evidence for this: replicate independently, circular DNA
Idea of Evolution
 Charles Darwin (1809-1882)
 Traveled the world & noticed similarities & differences
among many organisms
 Was convinced that organisms changed over time
Idea of Evolution
 Evolution: development of new types of organisms
from preexisting types of organisms over time
 Heritable change in characteristics w/in a pop. from one
generation to the next
 Darwin’s Theory
 Developed to explain how evolution occurs
Idea of Evolution
 Ideas of Darwin’s Time
 Species were permanent & unchanging
 Earth’s age only 1000’s of years old
Idea of Evolution
 Ideas About Geology
 Studied Strata, or rock layers
 Lower strata=older rock/ Higher strata=younger
 Different strata holds different organisms
 Georges Cuvier: Catastrophism, idea that sudden
geologic catastrophes caused extinctions
 Charles Lyell: Uniformitarianism, processes that have
changed the shape of the Earth’s surface in the past
continue to work
Sedimentary Rock
Idea of Evolution
 Lamarck’s Ideas on Evolution
 Supported Darwin
 Idea that simple organisms could arise from nonliving
matter
 Life developed from simple to complex
 Acquire traits during lifetime as a result of experience or
behavior––> offspring

Inheritance of acquired characteristics
Darwin’s Ideas
 Darwin & Alfred Wallace formed new theory on how
evolution take’s place
 Presented to scientists in London after voyage around
the Earth
 Published: On the Origin of Species by Means of Natural
Selection


Evidence for evolution
Explain variety & distribution of organisms
Darwin’s Ideas
 Descent w/ Modification
 Species descend by reproduction from preexisting
species
 Argued that ALL species had descended from only ONE
or a FEW original kinds of life

Example: Galapagos Islands
 Finches: 13 species descended from 1 common ancestor
Darwin’s Ideas
 Natural Selection
 4 Main Parts of Darwin’s Reasoning
 Overproduction: More offspring produced than survive
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
Genetic Variation: Individuals have different traits


Occasionally new traits may appear in a population
Struggle to Survive: individuals compete to survive &
reproduce



Thomas Malthus: environment limits populations
Variations improve or reduce chances
Adaptation = trait that makes an individual successful
Differential Reproduction:


Best adaptations = survival
Adaptations become more frequent & populations differ
Darwin’s Ideas
 Natural Selection
 Accounts for descent w/ modification, as species
become better adapted to different environments
 Nature changes species by selecting traits
 Fitness = measure of an individual’s hereditary
contribution to the next generation

Ability to survive and reproduce
Evidence of Evolution
15-2 Questions
1.
The wing of a bat and the foreleg of an alligator are
A.
B.
C.
D.
2.
Analogous features.
Homologous features
Vestigial features.
Artificially selected features.
Features that were useful to an ancestral organism but are not useful to a
modern organisms that inherited them are said to be?
A.
B.
C.
D.
Analogous.
Homologous.
Vestigial.
Artificially selected.
15-2 Questions
3.
According to the principle of superposition, the lowest layer in a cross
section of a rock sequence
A.
B.
C.
D.
4.
Which of the following is an impediment to understanding the evolutionary
history of all organisms?
A.
B.
C.
D.
5.
Is the most recent
Is the oldest
Has the fewest fossils
Contains only the fossils of burrowing animals
Presence of vestigial structures
Lack of transitional fossils
Lack of homologous structures
Presence of analogous structures
Fossils are
A.
c.
Remains or traces of preexisting organisms
Deeply buried sedimentary rock strata
All extinct organisms
D. From animals, not plants
B.
The Fossil Record
 What is a fossil?
 Remains or traces of an organism that died long ago
 Formed under many different conditions
 Different organisms, different times & places
 Some of the most powerful evidence for evolution
The Fossil Record
 Age of Fossils
 Nicolaus Steno (1638-1686)
 Principle of superposition:
 Rock strata at a location have not been disturbed, the lowest
stratum was formed before the strata above it
 Geologists in 1700s & 1800s compared strata from
different places & compared fossils found in different
strata

Put together the geologic time scale – timeline for the order of
organisms
The Fossil Record
 Age of Fossils
 Fossil’s relative age: age compared to that of other fossils
 Determined by referring to the geologic time scale and to records
of known fossils
 Absolute age: time since the formation of the rock
 Determined by radiometric dating
 Use relative and absolute dating to make the history of
life on earth as precise as possible

Fossil record is incomplete––not ALL organisms have left fossil
evidence, only form by rare events
The Fossil Record
 The Distribution of Fossils
 4 Inferences that can be made




Different organisms lived at different times
Today’s organisms are different from those in past
Fossils found in adjacent layers are more similar than fossils
found higher or lower in strata
By comparing fossils from all over the world, we can infer when
and where organisms existed
The Fossil Record
 Transitional Species
 Infer that species have differed in a gradual sequence of
forms over time


Based on Transitional Species, which have features that are
intermediate b/w those of hypothesized ancestors and later
descendent species
 Hypothesis of whale evolution is an example
Other groups of organisms for which no transitional species
have been found as fossils
Biogeography
 Study of the locations of organisms around the world
 Darwin & Wallace saw evidence of evolution in
distribution of organisms



Closely related organisms, but occupied different habitats
Unrelated organisms, but had similar adaptations in similar
environments that were far apart
Example: Australian Mammals
Anatomy & Embryology
 Anatomy: study of the body structure of
organisms
 Embryology: study of how organisms develop
 Descent w/ modification also predicts the findings
of anatomy & embryology
 Bones in the forelimbs of humans, penguins, alligators,
and bats
 Explanation: early ancestor shared by all these
organisms had a forelimb w/ a similar bone structure
Anatomy & Embryology
 What happened?
 Generations passed, & diff. populations of descendents
adapted to diff. envirn.
 Bones inherited from ancestors became modified for
different tasks
 Homologous Structures: anatomical structures that
occur in diff. species & that originated by heredity
from the most recent common ancestor
Anatomy & Embryology
 Analogous Structures: closely related functions
but do not derive from the same ancestral
structure
 Ex: birds, bats and moths have wings, but they have
very diff. underlying structures

Wings evolved independently in these animals
 Vestigial Structures: structures that seem to
serve no function , but that resemble structures
w/ functional roles in related organisms
 Ex: human tailbone––animal tail; whale pelvic bone;
human appendix
Anatomy & Embryology
 Development of Animal Embryos
 Some stages of vertebrate embryo development are very
alike
 Similarities fade as development proceeds
 Possible answer––vertebrates share a common ancestor
Biological Molecules
 Organisms that share many traits––>more recent
common ancestor than those that share fewer
traits
 Darwin predicted this through anatomy
 Modern studies of biological molecules support this
 DNA & RNA are molecular basis for inheritance of traits
 DNA affects traits encoding the amino acid sequences that form
proteins
Developing Theory
 Hypotheses & theories of evolution are continually
being formed, challenged, and revised
 Many aspects are poorly understood & some
observations remain unexplained
 Can never be “proven”, but is widely accepted &
applied by scientists b/c it explains the broadest
range of observations & makes useful predictions
Convergent Evolution
Divergent Evolution
Artificial Selection
Chapter 16
Genetic Equilibrium
 Variation of Traits w/in a Population
 Population Genetics: genetic study of evolution
 Microevolution: evolution at the genetic level, where a
change in the collective genetic material of a population
occurs
 Vary in observable traits
Genetic Equilibrium
 Variation arises from:
 Mutation
 Recombination
 Random pairing of gametes
Genetic Equilibrium
 Gene Pool: total genetic info available in a population
 Allele frequency: how often an allele will show up

Certain allele number / total number of alleles
 Phenotype frequency: how often a phenotype shows

Number of indiv. w/ phenotype / total number of indiv. in the
population
Genetic Equilibrium
 Hardy-Weinberg Genetic Equilibrium
 Genotype frequencies in a population tend to remain
the same from generation to generation UNLESS acted
on by outside influences





No mutations
No individuals enter or leave the population
Large population
Random mating
Natural selection does not occur
Disruption of Genetic Equilibrium
 Mutations
 Exposed to mutagens…increase mutations
 Creates new alleles for a trait
 Most are harmful…some beneficial
Disruption of Genetic Equilibrium
 Gene Flow
 Size of population needs to remain constant
 Immigration: movement into a pop.
 Emigration: movement out of a pop.
 Process of genes moving from one population to another

Migration, dispersal of seeds/spores
Disruption of Genetic Equilibrium
 Genetic Drift
 Allele frequencies in a population change as a result of
random events, or chance
 Mechanism for evolution of a new species
 Graph page 322
Disruption of Genetic Equilibrium
 Nonrandom Mating
 Sexual Selection


Females choose the males based on certain traits
Ex: birds
 Natural Selection
 Stabilizing Selection: average form of a trait have the
highest fitness – medium fish
 Disruptive Selection: either extreme variation have
greater fitness – very small/very large fish
 Directional Selection: more extreme form has greater
fitness – very large fish
Question #1
 Scientists
have
estimated the age
of Earth to be
a.
b.
c.
d.
about 10 billion years old.
100,000 years old.
about 4.6 billion years old.
about 4.6 million years old.
Question #2
 What
theory
proposes a method
for the evolution
of photosynthetic
eukaryotic
organisms from
prokaryotes?
a)Chemosynthesis
b) RNA replication
c) radioactive decay
d) endosymbiosis
Question #3
 What
is the idea
developed by
Charles Lyell
stating that the
geologic processes
that shaped the
Earth in the past
continue to operate
today?
a)Catastrophism
b) uniformitarianism
c) inheritance of acquired
characteristics
Question #4
 What
is the process
called by which
different species
evolve similar
traits?
a)adaptive
radiation
b) divergent evolution
c) Coevolution
d) convergent evolution
Question #5
 Strong
evidence
for evolution
comes from:
a)phylogenetic
trees.
b) nuclear physics.
c) the fossil record.
d) works of philosophy.
Question #6
 Eukaryotes
may
have evolved
from:
a)prokaryotes
and
engulfed small
anaerobic prokaryotes.
b) eukaryotes and
engulfed small aerobic
prokaryotes.
c) cyanobacteria.
Question #7
 The
evolutionary
pattern
illustrated by
the
finch species on
the Galapagos
Islands is an
example of:
a)coevolution.
b) convergent evolution.
c) divergent evolution.
d) artificial selection.
Question #8

a.
b.
c.
d.
According to Darwin, evolution occurs
In response to use or disuse of a characteristic
Because of catastrophic geologic events
By natural selection
Within an individual’s lifetime
Question #9

a.
b.
c.
d.
The inference that evolution occurs gradually
over time,
Is not supported by any fossil evidence
Is know as coevolution
Is supported by many transitional forms in the fossil
record
Was proposed by Lyell
Question #10

a.
b.
c.
d.
Natural selection causes
Changes in the environment
Plants and animals to produce more offspring than
can survive
Changes in the frequency of certain adaptations in a
population
Genetic variation w/in populations
Question #11

a.
b.
c.
d.
The similarity in the body shape of a whale and
of a fish is an example of
Divergent evolution
Convergent evolution
Coevolution
Vestigial structures
Question #12

a.
b.
c.
d.
Which of the following must exist in a
population in order for natural selection to act?
Genetic variation
Overproduction
Struggle to survive
All of the above
Question #13

a.
b.
c.
d.
The scientist who proposed that individuals
could pass on traits acquired during their
lifetime was
Lamarck
Darwin
Cuvier
Lyell
Question #14

a.
b.
c.
d.
Which of the following is an acquired human
characteristic?
Number of bones in the hand
Eye color
The presence of a tailbone in humans
Large muscles from weight lifting
Question #15

a.
b.
c.
d.
Which of the following is an impediment to
understanding the evolutionary history of all
organisms?
Presence of vestigial structures
Lack of transitional fossils
Lack of homologous structures
Presence of analogous structures