Download Unit 8: Evolution Notes

Unit 8: Biological Change Over Time
Name __________________________ Hour ____
I. Origin of Life on Earth (approximate age in bya or billions of years ago)
sun’s age – 4.75 bya
5bya
1st Eukaryotes – 2 bya
oceans formed on earth – 3.8 bya
4bya
3bya
2bya
1bya
Present
oldest fossils on earth (1st Prokaryotes - bacteria|) – 3.5 bya
planet formation (including earth) - 4.6 bya
These notes
were written
Mixture of gases
simulating
atmospheres of
early Earth
solar system age – 5 bya
A. Oparin’s Theory (Russia, 1923) - From physical and empirical data,
Oparin noted that the early atmosphere consisted of several gases:
Ammonia (NH3), Hydrogen Gas (H2), Water Vapor (H2O), Hydrogen
cyanide (HCN), CO2, H2S, CO, N2, and Methane (CH4). These gases in
the presence of a large energy source (lightning) may have caused a
chemical reaction that produced organic molecules.
Spark simulating
lightning storms
Cold
water
cools
chamber,
causing
droplets
to form
Condensation
chamber
Water
vapor
B. Miller & Urey Experiment (USA, 1953) - Put the molecules from Oparin’s
theory into an airtight chamber, ignited a spark (lightning). Amino acids,
ATP, and nucleic acids were made. Since 1953 other scientists have
performed similar experiments adding gases thought to have been emitted
by volcanoes. These experiments produced more organic molecules.
Liquid containing
amino acids and
other organic
compounds
Living cells have never been made in a laboratory. New data, including
locating a meteorite with 90+ amino acids (19 of which can be found in
nature on earth) add to the list of ingredients for early molecules as well possible sources for the origins of life on earth.
C. The first life forms were probably anaerobic (no atmospheric oxygen existed), heterotrophic (could not make their own
food via photosynthesis) and prokaryotic (no nucleus).
Q: Where on Earth did the first cells probably live and why? ____________________________________________
_____________________________________________________________________________________________________________________
D. Endosymbiosis – Theory proposed by Lynn Margulis in 1970 that suggested how the evolution of prokaryotes (no
nuclei) into eukaryotes (true nucleus) took place. Mitochondria and chloroplasts were engulfed by
large bacteria for a mutually beneficial relationship (bacteria received energy from the mitochondria
and chloroplasts; they in turn received protection from the bacteria).
Evidence
Chloroplast
1. Cells can still live in other cells (parasites).
2. Chloroplasts & mitochondria have their
own DNA that is circular like bacteria.
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Photosynthetic
bacteria
Mitochondrion
3. Chloroplasts & mitochondria reproduce
independently of the cell, similar to
bacteria (binary fission).
Primitive Photosynthetic
Eukaryote
4. Chloroplasts & mitochondria both have
bilpid membranes like the cell does.
5. Chloroplasts & mitochondria have their
own ribosomes to make proteins.
Plants and
plantlike
protists
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
Animals, fungi, &
non-plantlike protists
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II.
Theories of Evolution
A. Definitions
Evolution – ____________________________________________________________________________________
Species – Group of freely interbreeding organisms that are similar in structure and can produce fertile offspring.
Phylogeny – Evolutionary history of an organism, a phylogenetic tree can show relationships between organisms.
B. Natural Selection (Darwin & Wallace – 1800s) - Individuals that are better suited to their environment survive and
reproduce most successfully. This is often referred to as________________________________________________.
1. Within every species there is variation of traits/characteristics (color, size, etc…). Some of this variation is inherited.
2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce
3. Because more organisms are produced than can survive, members of each species must compete for limited
resources. Q: What resources do organisms compete for?
_____________________________________________________________________________________________________
4. Because each organism is unique, each has different advantages and disadvantages in the struggle for
existence (to stay alive and have the ability to breed a next generation).
5. Individuals best suited to their environment survive and reproduce the most successfully. The characteristics that
make them best suited to their environment are passed on to their offspring.
The Far Side. Gary Larson.
Q: What happens to individuals that are
not as well suited to their environment?
a.) _______________________________
b.) _______________________________
c.) _______________________________
6. The offspring of the organisms that reproduce with this advantageous trait pass
down this trait to their offspring, who themselves will out compete other members
of their species to reproduce. This trend continues until all or most of the members
of the group now possess the positive trait.
7. Species change over time. Over long periods of time, natural selection causes
changes in the characteristics of a species. New species arise, and other species
disappear.
8. Species alive today have descended with modifications from species that lived in the past.

All organisms on Earth are united into a single phylogenetic tree of life by common descent.
d) ____________________
e) ____________________
f) __________________
Protista
b) ________________________________
c) ______________________________
a) ___________________________
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III. Types of Natural Selection
A. Directional – When individuals with one of the extreme forms of a trait out compete those with the moderate and
other extreme form of the trait (white or black).
B. Stabilizing – When the middle/moderate form of a trait out competes the two extremes (gray).
C. Disruptional – When both extreme forms of a trait out-compete the moderate form (white and black outcompete grey).
D. Sexual – Having a particular trait that gives an organism a better opportunity to reproduce and pass on its genes
(and therefore the beneficial trait). Examples include singing, nesting, color, size, dance, etc.
Bell curve of phenotypes
_______________________
_______________________
_______________________
IV. How Populations Evolve
A. Definitions

Gene pool – All the genes in a population or every gene possessed by each member of a population.

Allele frequency – How often a form of a trait appears in a population.

Genetic equilibrium – When allele frequencies are the same from generation to generation.
B. Hardy-Weinberg Principle

In 1908 G. H. Hardy & G. Weinberg developed the solution to why allele frequencies occur in the manner they
do. Hardy & Weinberg proposed conditions under which biological change (evolution) will or will not occur.
They used a mathematical formula to gauge changes in any allele frequency.
C. Causes of Allele Frequency Changes or Evolution (Text book pps. 397-402)

Mutations – Any change in the number and/or sequence of DNA bases which cause a change in the number
and/or sequence of amino acids, which in turn changes the size and/or shape of a protein. A change in the
shape and/or size of a protein can cause a change in the proteins function. The change in a proteins function
within an organisms is usually negative (DMD, CF, etc.). But some mutations (a change in an organisms
size, color, or ability to live in dry conditions, etc.) can be positive.

Migration – The movement of individuals (thus their genes) from one population to another.
Q: How can immigration (in) or emigration (out) affect allele frequency within a given population?
______________________________________________________________________________________
______________________________________________________________________________________
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
Genetic Drift – A change in allele frequency in a population due to chance (natural selection not involved).
Examples: natural disaster, bottlenecks, founder effect
Define founder effect - ___________________________________________________________________
__________________ __________________________________________________________________________
Describe one example of a bottleneck occurring due to
the founder effect: ____________________________
___________________________________________
___________________________________________
____________________________________

Nonrandom Mating – Mating partners with particular traits, inbreeding, or self-fertilization can alter allele
frequencies (how often a form of a trait appears in a population).

Natural Selection – An organism has a survival or sexual advantage over another within a population.

Small Population – In a small population, changes in allele frequency are amplified. (Occurs in a short time.)
D. Hardy-Weinberg Principles for maintaining genetic equilibrium
(What must be true in order for a population to remain at genetic equilibrium?)
* ______________________________________________
* _________________________________________________
* ______________________________________________
* _________________________________________________
* ______________________________________________
* _________________________________________________
V. Patterns of Evolution (Text pages436-438)

Adaptive radiation - A species or a small group of a species
evolves into several different forms that become less and less
like each other as time passes.
Examples:___________________________________________
___________________________________________________

Convergent evolution – Unrelated organisms come to
resemble each other more and more as time passes.
Examples:__________________________________________
__________________________________________________

Coevolution – Two species evolve in response to changes in each other over time.
Examples:______________________________________________________________
______________________________________________________________________
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 Mass Extinction
 Extinction – ______________________________________________________________________
 More than 99% of all the species that have ever inhabited Earth are now extinct.
 Extinctions appear at a fairly constant rate in the fossil record much of the time.
 B. Mass Extinction – Disappearance of a huge number of different species in a relatively short
amount of time. Fossil evidence suggests that there have been multiple mass extinctions
throughout the history of Earth.
Q: What is the most accepted hypothesis for the extinction of the dinosaurs?
Q: How have mass extinctions actually contributed to diversity of species that we observe today (and
throughout history)?
VI. Species Formation – How do new species form? (Text book pps. 404-405)
 Developmental Genes and Body Plans – master control genes called hox genes control development of body
parts in organisms. Small mutations in these genes can cause large change in body parts such as number,
size, or placement of arms, legs, and wings.
Q: How might hox genes contribute to speciation?
_____________________________________________
_______________________________________________________________________________________
Isolating Mechanisms – as new species evolve, populations become reproductively isolated from each other.
 Geographic Isolation – Physical
separation and isolation of a species
caused by land bridges, earth
quakes, volcanic eruptions, floods,
droughts, fire, ice age, etc.
Examples:____________________
_____________________________
_____________________________
_____________________________
_____________________________
 Behavioral Isolation – Different populations are capable of interbreeding, but they do not due to differences
in their courtship rituals or other sexual behaviors. Examples: ______________________________________
_______________________________________________________________________________________
 Temporal Isolation – Different populations that do not interbreed because they reproduce at different times.
Examples: ______________________________________________________________________________
_______________________________________________________________________________________
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VII.
Evidence of Evolution
A. Fossils – Mineral traces of once living organisms buried in sedimentary rocks where O2 and bacteria will not
destroy them.
 Fossils may also be found frozen in ice, trapped in amber (tree sap), and in peat bogs (low nutrient & rain fed).
 When fossils are arranged in order of their age, a progressive series of changes are seen.
 The fossil record shows that life on Earth has changed over time.
Dating Sedimentary Fossils

Relative Dating – Based on uniformitarianism, the oldest fossils are found in the oldest/deepest rock. The age of
a fossil is determined by comparing its placement with that of fossils found in other layers.

Radioisotopes – Using known half-lives of radioactive elements to determine age of fossils (Half-life is the
length of time required for half of the radioactive atoms in a sample of fossil or rock to decay).
Examples:
C-14 = 5,730 years
K-40 = 1.3 billion years
U-238 = 4.5 billion years
Example Problem:
A sample of a 300 kg fossil contained 225 kg of decayed
potassium-40. How old is the fossil sample?
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B. Homologous Structures – Vertebrates contain a similar pattern of organs or body parts; these body parts may or may
not perform the same function.
C. Embryonic Development – During development, embryos & fetuses of different species exhibit similar characteristics
which grow & change into pre-programmed (genetically) organisms as gestation continues.
Examples:____________________________________________________________________________________
_____________________________________________________________________________________
Big Idea: Local Rules control development. Life of all kinds essentially follows the same “recipe” using DNA.
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D. Biochemistry – The longer organisms have diverged from a common ancestor, the more differences are seen in the
sequence and structures of their DNA and proteins. This correlates with the fossil record.
First 50 Amino Acids in Cytochrome C
1
Human
Turtle
Shark
Fruit Fly
5
10
15
20
25
30
35
40
45
50
GDVEKGKKIFIMKCSQCHTVEKGGKHKTGPNLHGLFGRKTGQAPGYSYTA
GDVEKGKKIFVQKCAQCHTVEKGGKHKTGPNLNGLIGRKTGQAEGFSYTE
GDVEKGKKVFVQKCAQCHTVENGGKHKTGPNLSGLFGRKTGQAQGFSYTP
GDVEKGKKLFVQRCAQCHTVEAGGKHKVGPNLHGLIGRKTGQAAGFAYTN
Amino acid key:
G- Glycine; A- Alanine; V- Valine; L- Leucine; I – Isoleucine;
M – Methionine; F – Phenylalinine; W – Tryptophan; P – Proline; S- Serine;
T – Threonine; C – Cysteine; Y – Tyrosine; N – Asparagine; Q – Glutamine;
K – Lysine; R – Arginine; H – Histidine; D – Aspartic Acid; E – Glutamic Acid
E. Vestigial Structures – Body parts that have no apparent function but resemble useful parts of another organism.
Examples: _________________________________________________________________________________
__________________________________________________________________________________
F. Parallel adaptation – Natural selection of similar traits by organisms living in similar climates in different
geographic locations. Examples:________________________________________________________________
___________________________________________________________________________________________
G. Geographic Patterns of Distribution – Inhabitants of ocean islands resemble organisms on the nearest mainland
with some differences. Example: Darwin found different finches on some of the Galapagos Islands that all shared
some resemblance, yet were all distinctly different. They all resembled a species of finch found on the mainland of
South America. Darwin suggested that they all shared the same ancestor, but because each island had its own
unique environmental pressures, they all developed different characteristics.
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Q: How is it possible that organisms that are very closely genetically related are found geographically far apart
(even in the fossil record)?
VIII.
Geological Change Over Time
A. Plate Tectonics – The movement of large plates (parts of the earth’s crust) across the surface of the earth. This is the
proposed mechanism by which continental drift takes place.
 As hot magma rises from the mantle of the earth, it cools and forms new additions to already existing plates.
This causes the plates to move and shift on the surface of the earth.
B. Continental Drift – Hypothesis proposed by Alfred Wegener stating that throughout time the earth’s continents had,
and continue to, move or drift. This has been substantiated through science and satellite imagery.
Q: List and explain evidence that supports plate tectonics and continental drift.
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