Chapter 15-17:
Change Over
Time Notes
Early History
• Probably very hot from meteorites hitting
Earth
• Atmosphere lacked oxygen
• Gases from volcanic eruptions
– Water vapor, carbon dioxide, nitrogen,
methane, and ammonia
– Helped form an early atmosphere
• Oldest rocks formed 3.9 billion years ago
• Earth formed 4.6 billion years ago
Oparin’s Hypothesis
• Life began in the oceans
• Sun’s energy, lightning, and heat from
Earth triggered chemical reactions
– Produced small organic molecules from
elements in atmosphere
• Rain washed molecules into the oceans to
make primordial soup
Miller and Urey
• Simulated conditions of early
Earth in a lab
• Mixed water vapor with
ammonia, methane, and
hydrogen gases
• Sent an electric current through
mixture then cooled it
– Found amino acids, sugars, and
other small organic molecules
• Experiment supported Oparin’s
hypothesis
• Earth may have cooled around 4.4 billion
years ago
– Water in atmosphere condensed resulting
in a lot of rainstorms for millions of years
• Scientists estimated life began in the
oceans 3.9-3.4 billion years ago
Origin of Life
• Abiogenesis (spontaneous generation)
–Life comes from nonliving material
Francesco Redi (1668)
• Disproved spontaneous generation of larger
organisms
– Nonliving material cannot produce life
– Did an experiment involving meat and
maggots
Louis Pasteur (mid-1880’s)
• Disproved spontaneous generation of
microorganisms
– Completely isolated a culture medium with no
outside influence like spores or eggs
• Boiled culture several times
• Observed no living organisms appeared
• Biogenesis: living
organisms come only from
other living organisms
• Sidney Fox: heated solutions
of amino acids to produce
protocells (large, ordered
structure enclosed by a
membrane that carries out life
activities)
Origin of Cells
• First cells probably prokaryotes (anaerobic): 2
billion years ago
• Unicellular
• Heterotrophs
• Archaebacteria
– Live in harsh environments (deep sea vents
and hot springs)
• Development of photosynthesizing
bacteria
–Released oxygen from water
–Oxygen turned into ozone by sun’s
rays made ozone layer
Endosymbiont Theory
• Proposed by Lynn Margulis in the 1960’s
• Eukaryotic cells evolved from prokaryotic
cells through a symbiotic relationship
• Chloroplasts and mitochondria contain DNA
similar to DNA in prokaryotes
– Prokaryote ingested aerobic bacteria (produced
energy for the cell)
– Over time the aerobes became mitochondria
– Some prokaryotes also ingested cyanobacteria
(blue/green algae) that contain photosynthetic
pigments
– Cyanobacteria became chloroplasts when
ingested
Geologic Time Scale
• Divisions based on
organisms that lived
during that time
• Begins with the
formation of earth
• Calendar of Earth’s
history
• 4.6 billion years
• divided into eras and periods
–Precambrian: 87% of Earth’s history
• Paleozoic: Cambrian explosion of new
diversity
–Largest mass extinction 90% of life
disappeared
• Mesozoic: mammals 1st appeared and age
of the dinosaurs
– Extinction of the dinosaurs and 2/3 of all
living species
– Pangaea: 1 large land mass
• Was split apart due to plate tectonics:
continually moving land masses
• Cenozoic: era in which we live in today
Mass Extinction
• entire groups of organisms disappear
from the fossil record almost at once
Ch. 15-17 Bell Ringer #1:
1. Evidence shows that certain species have
disappeared, or become _____.
2. We are currently living in the _____ era.
3. Humans of today would not be able to
survive in Earth’s early atmosphere
because it contained little or no ______.
Evolution
• Thomas Malthus: proposed that the
human population grows faster
than Earth’s food supply
• Gradual change in populations
over time
• Proposed by Charles Darwin
–Observed plant and animal life on the
Galapagos Islands (ex: finches,
tortoises)
–Wrote On the Origin of Species
• Species evolve, not individual organisms
• Occurs by Natural Selection: “Survival of
the Fittest”
– Process by which individuals that are
better adapted to their environment are
more likely to survive and reproduce than
other members of the same species
3 Factors that Affect Natural
Selection
• Overproduction
• Species produce far more offspring
than can survive
• May not be enough resources
(food, water, living space)
• Competition
• Members of a species must compete
with each other to survive
• Does not usually involve direct physical
fighting (usually indirect)
• Lack of finding food
• Predation
• Variations
– Differences between individuals of
the same species
– Can make individuals better
adapted to their environment (more
likely to survive and reproduce)
– Offspring may inherit helpful
characteristics
– Environmental changes
• Can lead to selection
– Genetic variation
• Can result from the shuffling of
alleles during meiosis or
mutations
• Over time natural selection can lead to change in
populations
– some individuals have differences that permit them to
adapt and increase their chances for survival
– Organisms with favorable variations survive, reproduce,
and pass their variations to the next generation
– Organisms lacking favorable variations less likely to
survive and reproduce
– The ability to survive and reproduce in an environment
is an organism’s fitness.
Evidence for
Evolution
Adaptations
• any variation that aids an organism’s
chances of survival in its environment
– Develop over many generations
– Can be structural or behavioral
Mimicry
• one species can resemble another species
• Can provide protection from predators
• Can look harmful or look like another harmful
species
Camouflage
• Allows species to blend in with their
surroundings
• Used to avoid predators survive to
reproduce
Physiological Adaptations
• Changes in an organism’s metabolic processes
– Bacterial antibiotic resistance
– Resistance to pesticides
• Used to kill harmful insects
• Some insects have traits that protect them from the
pesticide and can survive
• Surviving offspring inherit the pesticide protection
• Pesticide becomes ineffective over several
generations
Fossils
• studied by paleontologists
– Used to learn the history of life
– Evidence of an organism that lived a long time
ago
– 99% of species have become extinct
• Can analyze structures of ancient
organisms
• Can also be used to find out about ancient
climate and geography
Fossil Formation
• Can form in many ways
– Organisms die and become
buried in sediments (particles
of soil and rock, mud, sand, or
clay)
– Become compressed over
time which hardens into rock
• Many found in sedimentary rock
– Oldest fossils in the deepest
layers
– Can show a gradual series of
changes in form of a species
through layers of sediment
Types of Fossils
• Petrified fossils: minerals replace
hard parts of an organism
• Trace fossils: footprints, trials,
burrows
• Molds: decayed organism leaving
an empty space
• Casts: minerals fill spaces
• Preserved remains
• Hard parts: bones, teeth, shells,
leaves
• Imprints
• Amber: resin from trees
• Tar pits
Relative Dating
• Used to determine age of
fossils in layers of rock
• Compares a fossil’s location
relative to other fossils in
nearby rock layers
• Cannot tell actual age
• Look at rock layers oldest
closer to the bottom
• Diagram:
Radiometric Dating
• Used to determine specific age of
rocks and fossils
• Radioactive isotopes in rocks (decay
over time giving off radiation)
• Half-life: decay rate of a radioactive
isotope
Homologous Structures
• Structural features with a common evolutionary
origin
• Similarity in body parts of different organisms due
to a common ancestor
• May differ in function but are similar in structure
• Ex: human hand, bat wing, amphibian leg, bird
wing, whale forelimb
Analogous Structures
• Body parts that do not
have a common
evolutionary origin but are
similar in function and
appearance
• Structures with different
anatomy but similar
function
• Ex: flippers of dolphin,
shark, and penguin, bird
and insect wings
Vestigial Structures
• No current function presently but are similar to
functional structures in related organisms
• No longer serves its original purpose but was
useful to an ancestor
• Still inherited even though it is no longer needed
• Ex: whale pelvic bone, snake leg bone, human
appendix and tail bone
Embryology
• Embryo: earliest stage of
growth and development of
plants and animals
• All embryos have similar
anatomy
• Comparing early
development of different
organisms
• Proceed through similar
stages of development
• Ex: fish, turtles, chickens,
mice, humans all look the
same
• Gill arches and tails
Biochemistry
• Cytochrome c sequence
• Amino Acid sequence similarities
• DNA Similarities
– Inherited similar genes from a common ancestor
– Compare the sequence of nitrogen bases in DNA of
different species to determine how closely related they
are
– Can compare the order of amino acids in a protein to
compare relatedness
Ch. 15-17 Bell Ringer #2:
1. A human’s appendix and snake legs are
examples of ___.
a. Vestigial organs
b. Fitness
c. Adaptation
d. Struggle for existence
2. Another phrase for natural selection is
“____”.
3. What conditions could force organisms to
compete in a struggle for existence?
Populations and Evolution
• Evolution occurs as a
population’s genes change
over time
– All genes together in a large
gene pool: all of the alleles
in a population’s genes
– Evolution occurs when
there is a change in the
gene pool
• Mutations
–Environmental or by
chance
• Genetic drift: the alteration of allelic
frequencies by chance events
– Can affect small populations
• Movement in and out of a population
– Transporting genes (Gene flow:
movement of genes in and out of the gene
pool)
• 3 different types of natural selection that
acts on variation
– Stabilizing selection
• Favors average individuals in a
population
• Diagram:
• Directional selection
– Favors one of the extreme variations of a
trait
– Diagram:
• Disruptive selection
– Individuals with either extreme of a traits
variation are selected for
– Tends to eliminate the intermediate
phenotypes
– Diagram:
Evolution of Species
• Species: group of organisms that look alike and
can interbreed
• Speciation: the evolution of a new species
– Members of similar populations can no longer
interbreed to produce fertile offspring
– Changes in allele frequencies that can result in the
formation of a new species from a parent species
– Ex: Darwin’s finches
• Creation of a new species
– Form when a group of individuals remains
isolated from the rest of its species long enough
to evolve different traits
– Isolation occurs when they are cut off from the
rest of the species
• Geographic Isolation: physical barrier
divides a population
– Bodies of water
– Volcanoes
– Mountain ranges
– Island formation
• Reproductive isolation: organisms can
no longer mate and produce fertile
offspring
–Influenced by different genetic
material and behavior patterns
Patterns of Evolution
• Charles Darwin observed different species
of finches
• Adaptive radiation
– An ancestral species evolves into a variety of
different species to fit a number of different
habitats
• Divergent evolution
– Species that once were similar to an
ancestral species become distinct or
different
– Populations change as they adapt to
new/different environmental conditions
– Results in new species
• Convergent evolution
–Distantly related organisms evolve
similar traits
–Occupy similar environments in
different parts of the world
Ch. 15-17 Bell Ringer #3:
1. The combined genetic information of all
members of a particular population is
called a (an) _____.
2. Genetic drift is more likely to occur in ___.
a. Large populations
b. Medium-sized populations
c. Small populations
d. One individual
3. What is the formation of a new species
called?